reversible fuel cell, module and reversible fuel cell system

专利摘要:
FUEL CELL AND REVERSIBLE FUEL CELL SYSTEM A reversible fuel cell includes a positive electrode containing manganese dioxide, a negative electrode containing a hydrogen storage material, a separator disposed between the positive electrode and the negative electrode and an electrolyte. Each of the negative electrode and the positive electrode is an energy generation electrode and is also an electrode that applies electrolysis to the electrolyte through an electric current to be fed from the outside. This cell is capable of storing electrical energy to be provided at the time of overload by converting electrical energy into gas, and is also capable of converting gas into electrical energy in order to use electrical energy. In this way, a reversible fuel cell and a reversible fuel cell system are provided, each of which is excellent in terms of energy use efficiency, energy density and load segment capacity.
公开号:BR112014024288B1
申请号:R112014024288-7
申请日:2012-12-18
公开日:2020-06-30
发明作者:Atsushi Tsutsumi；Kaduo Tsutsumi
申请人:The University Of Tokyo；Exergy Power Systems, Inc.；
IPC主号:

专利说明:

[0001] [001] The present invention relates to a reversible fuel cell, capable of storing electrical energy at the time of charging as chemical energy and using the chemical energy stored by reconversion to electrical energy. The present invention also relates to a reversible fuel cell system, a reversible fuel cell module and a reversible fuel cell bank each including the reversible fuel cell. TECHNICAL FUNDAMENTALS
[0002] [002] Fuel cells and secondary batteries are highly efficient clean energy sources. In recent years, electric vehicles, fuel cell vehicles and trains equipped with such fuel cells and secondary batteries as power supplies are already in development on a worldwide basis.
[0003] [003] Attention has been paid to a fuel cell as an energy source with high energy conversion efficiency and a small environmental load. A fuel cell is unable to accumulate electrical energy. However, it is possible to build a particular energy storage system by combining a fuel cell with, for example, a device that produces hydrogen for the production of hydrogen by electrolysis of water. Such an energy storage system is called a reversible fuel cell (reference to Patent Literature 1 and Patent Literature 2). The reversible fuel cell built by combining fuel cells with the water electrolyser performs the electrolysis of water, which is an inverse reaction of energy generation, using natural energy or electric power at night, while the reversible fuel cell is not generating electricity. Thus, this energy generation system produces fuel for its own use.
[0004] [004] On the other hand, a secondary battery has been used as a power source for an electrical or electronic device that requires large current discharge, such as an electrical tool. In recent years, in particular, attention has been paid to a secondary nickel-metal hydride battery and a secondary lithium-ion battery as a battery for a hybrid vehicle to be powered by an engine and battery.
[0005] [005] A typical secondary battery is charged with electricity, thus storing electricity. Patent Literature 3 discloses a secondary battery, which is rechargeable with gas. In addition, Patent Literature 4 discloses a new type of fuel cell, which is a combination of a fuel cell and a secondary battery, and which contains manganese hydroxide as an active material of the positive electrode and a storage alloy of hydrogen as an active material of the negative electrode. LIST OF QUOTES Patent Literature
[0006] [006] Patent Literature 1: JP 2002-348694 A Patent Literature 2: JP 2005-65398 A Patent Literature 3: JP 2010-15729 A Patent Literature 4: JP 2010-15783 A SUMMARY OF THE INVENTION Technical problem
[0007] [007] A secondary battery is capable of storing electrical energy. However, an amount of an active material from the negative electrode and an amount of an active material from the positive electrode depends on the volume of a battery. Therefore, the battery's electrical capacity is limited. In addition, it is difficult to increase the energy density of the secondary battery considerably.
[0008] [008] On the other hand, a fuel cell generates (discharges) electric energy using hydrogen gas or oxygen gas to be supplied from the outside. Unlike a secondary battery, therefore, a fuel cell has no problem with limiting energy density. In order to use a fuel cell, there is usually a need to provide apparatus or members for supplying hydrogen gas and oxygen gas to the electrode portions. In addition, a fuel cell is smaller than a secondary battery in an ability to track a load change. Therefore, it is difficult to use a fuel cell only as a power source for an appliance that requires a large load change, such as a vehicle.
[0009] [009] In addition, the gas to be produced by a hydrogen production apparatus (see, for example, Patent Literature 1) is hydroxygen gas in which a hydrogen to oxygen ratio is 2: 1. Therefore, there is a need to ensure security carefully.
[0010] [010] The "fuel cell battery" disclosed in Patent Literature 4 contains manganese hydroxide as an active material for the positive electrode. Therefore, trimanganese tetroxide that does not contribute to loading and unloading reactions is generated by repeated loading and unloading. Thus, the present fuel cell has a weak life-time problem.
[0011] [011] The primary zinc-manganese battery has been widely known as an aqueous solution-based battery including a positive electrode made of manganese dioxide. A zinc-manganese battery is used as a primary battery, exclusively, and is not used as a secondary battery. The reasons for this are mentioned below. In a positive electrode of a manganese battery, the manganese dioxide MnO ₂ is changed to manganese oxyhydroxide MnOOH, and then it is changed to manganese hydroxide, Mn (OH) ₂ , during the discharge. Here, when the discharge is continued until manganese hydroxide is generated, Mn ₃ O ₄ trimanganese tetroxide is disadvantageously generated to inhibit positive electrode recharge. In other words, there is a problem in which an irreversible substance to be generated on the positive electrode, that is, trimanganese tetroxide increases in repetitions of discharge (manganese oxy-hydroxide → manganese hydroxide) and charge (manganese hydroxide → oxy- manganese hydroxide).
[0012] [012] Trimanganese tetroxide has a low electrical conductivity characteristic. Low electrical conductivity causes the following disadvantage. That is, it takes hard for the battery to be charged satisfactorily, because it takes a long time to charge. In addition, the battery which is of low electrical conductivity also becomes poor in terms of charging efficiency. As a result, when trimanganese tetroxide increases, a fuel cell is degraded in performance, and ultimately becomes unusable. For these reasons, manganese dioxide is used for a primary battery exclusively, but is not used as an active electrode material for a secondary battery as of now.
[0013] [013] The present invention was designed taking into account the aspects described above, and an objective of it is to provide a reversible fuel cell, which is of high energy density, excellent in load segment capacity and also excellent in characteristic of life span. Solution to the problem
[0014] [014] In order to solve the problems described above, the inventors have eagerly carried out studies and completed a reversible fuel cell according to the present invention.
[0015] [015] The reversible fuel cell according to the present invention (hereinafter, referred to as the fuel cell) includes a positive electrode that contains manganese dioxide, a negative electrode that contains a hydrogen storage material, a separator disposed between the positive electrode and the negative electrode, an oxygen storage chamber and a hydrogen storage chamber to store hydrogen generated from the positive electrode and oxygen generated from the negative electrode, independently of each other, and an electrolyte. In this fuel cell, the oxygen storage chamber is charged with the electrolyte, in which the oxygen dissolves.
[0016] [016] In this fuel cell, discharge reactions on positive and negative electrodes can be represented by formulas (1) and (3), respectively, and charge reactions on positive and negative electrodes can be represented by formulas (2) and ( 4), respectively. MH → M + H ⁺ + e ^- (1) M + ½ H ₂ → MH (2) MnO ₂ + H ⁺ + e ^- → MnOOH (3) MnOOH + O ₂ → MnO ₂ + H ₂ O (4)
[0017] [017] In formulas (1) and (2), M represents a hydrogen storage material.
[0018] [018] As shown in formulas (2) and (4), each representing the fuel cell charging process, the negative electrode and the positive electrode are chemically charged with hydrogen and oxygen, respectively.
[0019] [019] As shown in reaction formulas (3) and (4), the active material of the positive electrode is repeatedly taken up to manganese dioxide and changed to manganese oxy-hydroxide during loading and unloading.
[0020] [020] When the discharge is continued until the manganese dioxide is changed to manganese hydroxide, trimanganese tetroxide is disadvantageously generated. Thus, the inventors considered it as follows. That is, if the discharge is not continued until the manganese dioxide is changed to manganese hydroxide, trimanganese tetroxide is not generated, so the positive electrode is not degraded. In addition, the inventors demonstrated this consideration for experience. This experience is described below.
[0021] [021] The inventors have experimented with the transition of a characteristic of the manganese dioxide loading and unloading cycle sensitive to the depth of a discharge reaction. Figs. 13A and 13B illustrate the results of the experiment. In Figs. 13A and 13B, the vertical geometric axis indicates an electrode potential, and the horizontal geometric axis indicates the amount of discharge. The discharge curves shown in FIG. 13A are obtained when the charge and discharge in an electron reaction are repeated 30 times. The discharge curves shown in FIG. 13B are obtained when the charge and discharge in a reaction of two electrons are repeated 30 times. As shown in Fig. 13A, the discharge curves differ little from each other, even when loading and unloading are repeated. As shown in Fig. 13B, on the other hand, the amount of discharge decreases as the loading and unloading are repeated. Here, an electron reaction refers to a discharge reaction in which the manganese dioxide is changed to manganese oxyhydroxide. The two electron reaction refers to a discharge reaction in which the manganese dioxide is changed to manganese oxy-hydroxide, and then it is changed to manganese hydroxide. It is evident from the results of the experiment illustrated in Figs. 13A and 13B that a discharge characteristic remains almost homogeneously as long as the discharge reaction is an electron reaction. It is also evident that when the reaction of two electrons occurs, the discharge characteristic gradually deteriorates as the charge and discharge are repeated. Thus, it is evident that the electrode is gradually degraded.
[0022] [022] In order to pursue the cause of this degradation, the inventors performed the XRD measurement on the electrode after charging and discharging. Fig. 14 illustrates the results of this measurement. As illustrated in a graph (a) of fig. 14, when the charge and discharge are repeated in the reaction of an electron, a new peak is hardly found except for a peak corresponding to a crystal structure of the electrode before the experiment. For comparison, a graph (s) in Fig. 14 illustrates the results of measurements made on the electrode before the experiment. As illustrated in a graph (b) of Fig. 14, however, when the charge and discharge are repeated in the reaction of two electrons, a characteristic peak derived from manganese dioxide is hardly found, but a peak from a tetroxide derivative trimanganese is found. It is evident from this result that it is possible to contain the generation of trimanganese tetroxide by stopping the discharge at the stage where the manganese dioxide is changed to the manganese oxyhydroxide.
[0023] [023] Even when the manganese dioxide is subjected to hydroxylation by the discharge, the contact of the electrode with oxygen allows a return to the manganese dioxide. Thus, manganese dioxide is not changed to manganese hydroxide, so that irreversible trimanganese tetroxide is not generated. That is, the inventors have been successful in using manganese dioxide as a material for the positive electrode, such that the positive electrode is charged by contact with oxygen in the hydroxylation phase of manganese dioxide.
[0024] [024] Figs. 15A and 15B illustrate the results of the experiment, indicating that the positive electrode can be charged while being put in contact with oxygen gas.
[0025] [025] As illustrated in Figs. 15A and 15B, with respect to one half of the battery configured with a positive electrode made of manganese oxy hydroxide, a silver reference electrode (Ag), and an alkaline electrolyte, changing a potential on the positive electrode in the moment when charging and discharging are carried out with oxygen gas under pressure provided to the battery is plotted in relation to time. In Figs. 15A and 15B, the vertical geometric axis indicates the potential (V vs Ag / AgCl) of the positive electrode, and the horizontal geometric axis indicates the elapsed time (minutes). In the battery half including the positive electrode made of manganese dioxide and the silver reference electrode, a cutting potential at the moment when the manganese dioxide in the positive electrode is changed to the manganese oxy-hydroxide by discharge is - 0.5 V. It is evident from Figs. 15A and 15B, that the manganese dioxide on the positive electrode is changed to manganese oxyhydroxide, because the potential on the positive electrode is - 0.5 V before charging (at a point in time zero).
[0026] [026] In fig. 15A, (i) indicates a graph that illustrates a potential at the reference electrode after the pressurized oxygen gas is supplied to the positive electrode. In Fig. 15A, (ii) indicates a graph at a time when the supply of oxygen gas is stopped and then a 0.2 C discharge is made. As shown in Fig. 15A, at a time when that the positive electrode is put in contact with oxygen gas (a solid line), the positive electrode is almost fully charged after a 60-minute lapse and is then discharged at 0.2 C. On the other hand, in a moment where the positive electrode is not in contact with oxygen gas (a dashed line), the positive electrode is hardly charged. Thus, it was confirmed that a fuel cell cathode reaction (oxidation-reduction reaction) occurs by oxygen gas and that the discharge through a secondary battery reaction occurs after the interruption of the oxygen gas. Fig. 15B illustrates a state of charge using oxygen gas, in the state discharged at 0.2 C. It is evident from this figure that charging using oxygen gas can be performed even during discharge. It was confirmed from the test results illustrated in the figures. 15A and 15B that the positive electrode can be charged by supplying oxygen gas to the positive electrode.
[0027] [027] In the fuel cells according to the present invention, an amount of oxygen that dissolves in the electrolyte is 0.02 to 24 g / L. In the fuel cells according to the present invention, on the other hand, a electrolyte pressure is 0.2 MPa to 278 MPa.
[0028] [028] When the electrolyte pressure is not greater than 0.2 MPa, the positive electrode may not be sufficiently charged with oxygen that dissolves in the electrolyte. In addition, when the electrolyte pressure is not less than 278 MPa, separation of oxygen and hydrogen by electrolysis is difficult to occur. Preferably, the electrolyte pressure is 0.95 MPa to 100 MPa. When the pressure is not greater than 1 MPa, the fuel cell can be easily manipulated, because there is no need to use a high pressure tank. When the pressure is not less than 100 MPa, the main body of the fuel cell must be configured with an ultra-high pressure vessel. Preferably, the amount of oxygen that dissolves in the electrolyte is 0.08 to 8.6 g / L.
[0029] [029] According to this configuration, the manganese dioxide in the positive electrode is temporarily changed to the manganese oxyhydroxide by discharge. However, the positive electrode is charged with the oxygen that dissolves in the electrolyte, so that the manganese oxy-hydroxide is taken up with the manganese dioxide. Therefore, the positive electrode is not discharged to such a degree that the manganese dioxide changed to manganese oxy hydroxide is further changed to a different substance. By charging and discharging, the active material of the positive electrode is changed between manganese dioxide and manganese oxyhydroxide. Therefore, trimanganese tetroxide that does not contribute to loading and unloading is not generated. In addition, since trimanganese tetroxide is not generated, the reduction in electrical conductivity is also restricted.
[0030] [030] In the fuel cells according to the present invention, each of the positive electrode and the negative electrode is an electrode for the generation of energy and is also an electrode for the electrolysis of the electrolyte fed through electric current from the outside.
[0031] [031] According to this configuration, each of the positive and negative electrodes contains an active material. Therefore, this fuel cell serves as a battery. In other words, this fuel cell can generate electrical energy without a gas supply and can be charged with electrical current. In this fuel cell, when the electric current is additionally fed to this fuel cell in a fully charged state, the electrolyte undergoes water decomposition. Thus, hydrogen and oxygen are generated from the respective electrodes.
[0032] [032] According to this configuration, when the electrodes in the fully charged state are still charged with electric current, hydrogen is generated from the active material of the negative electrode by the electrolysis of water (hereinafter referred to simply as electrolysis). This hydrogen can be stored inside the hydrogen storage chamber. In addition, the oxygen generated from the positive electrode dissolves in the electrolyte. Therefore, this oxygen can be stored as the electrolyte dissolved in oxygen in the oxygen storage chamber. In addition, the positive electrode and the negative electrode serve not only as electrodes to generate electrical energy using oxygen and hydrogen as fuel, respectively, but also electrodes for decomposing water. In addition, the hydrogen and oxygen generated from the negative electrode and the positive electrode by electrolysis can be stored in the respective storage chambers independently of each other, without contact and reaction between them.
[0033] [033] The hydrogen stored in the hydrogen storage chamber and oxygen stored in the oxygen storage chamber can be used by conversion to electrical energy at the time of cell discharge. In particular, the oxygen generated from the positive electrode dissolves in the electrolyte and is not stored in the gaseous state. This increases safety when handling oxygen. At the time of discharge, the cell serves as a secondary battery, so that electrical energy can be extracted from it. This allows for quick unloading and also allows for improvement in the load segment capacity.
[0034] [034] As described above, an electrical capacity of a secondary battery depends on an amount of an active material contained in an electrode. Therefore, it is difficult to increase the energy density of the secondary battery. According to this fuel cell, however, the available electrical energy can be stored as chemical energy in each storage chamber.
[0035] [035] As a result, it becomes possible to increase the amount of chemical energy to be stored per volume and to improve the energy density in volume of the fuel cell, improving the pressure-resistant and sealing performance of each storage chamber and the cell including the storage chambers.
[0036] [036] Each of the oxygen storage chambers and the hydrogen storage chambers configured as described above, is not necessarily an independent dedicated space. These storage chambers can be provided in a gap formed in, for example, a mixture of the active materials of the positive or negative electrode, or can be provided in a gap formed in the cell.
[0037] [037] In this fuel cell, the oxygen storage chamber and the hydrogen storage chamber can be separated from each other by a moving element or a flexible member.
[0038] [038] According to this configuration, the oxygen storage chamber and the hydrogen storage chamber can be provided to join one another. The two chambers are separated by the movable member. Therefore, when a pressure in the hydrogen storage chamber increases because of the hydrogen gas generated by overload, the movable member deforms under the influence of pressure. Due to this deformation, the electrolyte in the oxygen storage chamber is compressed, and the electrolyte pressure and pressure in the hydrogen storage chamber are equalized, so that the electrolyte pressure is increased. A coefficient of volumetric elasticity of liquid is considerably higher than that of gas. Therefore, the movable member is very little deformed. The movable member can be a flexible member, or it can contain an elastic material. The movable member may have a sheet or film structure. In addition, the movable member can be the positive electrode or the negative electrode. The moving element can be a film made of rubber or synthetic resin, such as polypropylene, or it can be a film made of thin metal.
[0039] [039] The communication passage can be provided between the oxygen storage chamber and the hydrogen storage chamber. In this example, a pressure in the hydrogen storage chamber can be transferred to the electrolyte in the oxygen storage chamber via a movable member over the communication passage. In this example, the moving element can be a piston. In addition, this fuel cell can be separated by a flexible member. In addition, the flexible member can be the positive electrode, the negative electrode and the separator.
[0040] [040] In this fuel cell, preferably in a tubular case, the negative electrode formed in the form of a tube is arranged with a radial space interposed between the negative electrode and the tubular case, the positive electrode formed in the form of a tube is arranged inside the negative electrode with the separator interposed between the positive electrode and the negative electrode, the hydrogen storage chamber is formed in the radial space, and the oxygen storage chamber is formed inside the positive electrode, or in a case tubular, the positive electrode formed in the form of a tube is disposed with a radial space interposed between the positive electrode and the tubular case, the negative electrode formed in the form of tube is disposed inside the positive electrode with the separator interposed between the negative electrode and the positive electrode, the oxygen storage chamber is formed in the radial space, and the hydrogen storage chamber is formed inside the electrode the negative. In this configuration, the case serves as an external enclosure.
[0041] [041] This fuel cell also includes a negative electrode terminal provided at one axial end of the case and electrically connected to the negative electrode, a positive electrode terminal provided at the other axial end of the outer housing and electrically connected to the positive electrode, a projection provided with one between the positive electrode terminal and the negative electrode terminal, and a recess provided on the other positive electrode terminal and the negative electrode terminal. Here, the projection can be fitted inside the recess so that two reversible fuel cells are connected in series. In this configuration, the case serves as an external enclosure.
[0042] [042] A fuel cell module according to the present invention includes a plurality of cell units connected in series. In the fuel cell module, each of the cell units may include a plurality of reversible fuel cells, and a pair of current collector plates provided to oppose the other such that the plurality of reversible fuel cells is sandwiched between them. The positive electrode terminal is connected to one of the current collecting plates and the negative electrode terminal is connected to the other current collecting plate, so that the reversible fuel cells can be connected in parallel with the current collecting plate.
[0043] [043] Preferably, this fuel cell also includes an outer covering that includes a part of the tubular body, and projecting parts provided in openings formed at two ends of the body part to protrude out of the openings and cover the openings, oxygen storage chambers formed in the interior spaces of the protruding parts of the external coating, and a tubular current collector housed in the external coating in an axial direction and which has two open ends in the oxygen storage chambers. In this fuel cell, the positive electrode is placed on an external periphery of the current collector. The separator covers around the positive electrode. The hydrogen storage chamber is formed between the separator and the outer shell. The negative electrode is charged in the hydrogen storage chamber. The electrolyte is stored in the oxygen storage chambers and can be drained between the oxygen storage chambers through the current collector.
[0044] [044] This fuel cell also includes an external casing that includes a part of the tubular body, and a rod-shaped current collector that passes through the positive electrode, the negative electrode and the separator. In this fuel cell, the positive electrode, the negative electrode and the separator can be stacked in an axial direction of the body part and are housed in the outer shell. The positive electrode may have a notch to be formed by cutting a part of an outer periphery thereof, and the outer periphery of the positive electrode may be in contact with an internal surface of the body part except the notch. The positive electrode may not be in contact with the current collector. The negative electrode can have a U-shaped section open in the inner circumferential direction and be in contact with the current collector. A space surrounded with the negative electrode and the current collector can form the hydrogen storage chamber. An external dimension of the negative electrode can be smaller than an internal dimension of the body part, and an electrolyte reservoir can be provided between the negative electrode and the body part to communicate with the notch. The oxygen storage chamber may include the notch and the electrolyte reservoir.
[0045] [045] In this configuration, the outer shell may include a tubular body part and a cover member to cover an opening of the body part. Alternatively, the outer shell may include a closed cylindrical can at one end and a lid member to be provided in an opening of the cylindrical can.
[0046] [046] When the outer shell is shaped into a cylindrical shape, the positive electrode is in contact with the outer shell because an outer diameter of the positive electrode is greater than the inner diameter of the body part. In addition, the positive electrode is not in contact with the current collector, because the size of an orifice, through which the current collector passes, in the positive electrode is larger than an external diameter of the current collector. Likewise, the negative electrode is in contact with the current collector, because the size of a hole in the negative electrode is smaller than the external diameter of the current collector.
[0047] [047] A reversible fuel cell system according to the present invention includes the fuel cell, an oxygen storage source and a hydrogen storage source each connected to this fuel cell. In this reversible fuel cell system, the oxygen storage source can supply oxygen that dissolves in the electrolyte to the reversible fuel cell, and can store oxygen generated from the reversible fuel cell in a state where the oxygen dissolves in the electrolyte. The hydrogen gas storage source can supply hydrogen gas to the reversible fuel cell and can store the hydrogen gas generated from the reversible fuel cell.
[0048] [048] A reversible fuel cell system according to the present invention can include that fuel cell, a salt concentration adjustment device connected to this fuel cell to remove the water contained in the electrolyte, and an adjustment device concentration of oxygen connected to this fuel cell to supply oxygen to the electrolyte, thereby adjusting a concentration of dissolved oxygen.
[0049] [049] In this fuel cell, manganese dioxide serves as a catalyst for a positive electrode charge reaction, and the hydrogen storage material serves as a catalyst for a negative electrode charge reaction.
[0050] [050] According to this configuration, at the time of discharge, the negative electrode is charged with hydrogen gas stored in the hydrogen storage chamber and the positive electrode is charged with oxygen stored in the first or second oxygen storage chamber, so that the charge compensates for the reduced electricity by the discharge. More specifically, at the negative electrode, protons are emitted from the hydrogen storage alloy (MH), in the charged state, as represented by the Reaction Formula (1) indicating the discharge reaction. As represented by the Reaction Formula (2), then the hydrogen gas compensates for the protons emitted. Thus, the negative electrode is kept in a charged state.
[0051] [051] On the other hand, on the positive electrode, manganese dioxide (MnO ₂ ) in the charge state is reduced, so that manganese oxyhydroxide (MnOOH) is generated, as represented by the Reaction Formula (3 ) indicating the discharge reaction. This manganese oxy-hydroxide is oxidized with oxygen again as represented by the Reaction Formula (4). Thus, the positive electrode is kept in a charged state. As described above, hydrogen gas and oxygen gas in the respective storage chambers are consumed.
[0052] [052] In other words, as long as hydrogen gas and oxygen gas are provided for this fuel cell, this fuel cell can be readily charged with hydrogen gas and oxygen gas, even when electricity is lost at the time of discharge. Thus, this fuel cell is almost always maintained in an almost fully charged state. Since the negative electrode is almost always in the hydrogen gas storage state, the expansion and contraction of the negative electrode volume due to the charge and discharge are contained. As a result, the negative electrode has an excellent lifetime characteristic. In addition, even when the amount of active material is small, the negative electrode has the functions described above. Therefore, it is possible to decrease an amount of heavy and expensive hydrogen storage alloy. As a result, it becomes possible to achieve weight reduction and cell cost reduction.
[0053] [053] In this fuel cell, the positive electrode may contain, in addition to manganese dioxide, superior manganese oxide. Here, examples of higher manganese oxide Mn ₂ O ₅ can include Mn ₂ O ₇ and MnO ₅ . The upper manganese oxide described above is temporarily generated in the positive electrode, when the positive electrode is overloaded at the moment of the decomposition of the electrolyte water.
[0054] [054] In this fuel cell, preferably a content of trimanganese tetroxide (Mn ₃ O ₄ ) in the positive electrode is not greater than 5% by weight in relation to the weight of the positive electrode. Trimanganese tetroxide is not generated since hydrogen gas and oxygen are almost always provided. However, there is a possibility that trimanganese tetroxide will be generated if hydrogen gas or oxygen gas becomes temporarily short. The amount greater than 5% of the weight can cause a problem. The amount not greater than 5% by weight is permissible depending on the use of the cell. The weight of the positive electrode to be defined here excludes the weight of the current collector.
[0055] [055] In this fuel cell, the manganese dioxide contained in the positive electrode can be subjected to a carbon coating.
[0056] [056] Cobalt can be used in electroconductive treatment. However, cobalt is expensive. Typically, carbon is used as an electrically conductive material. However, carbon is oxidized to generate carbon dioxide. Therefore, it is difficult to maintain electrical conductivity. The interior of this fuel cell is under an atmosphere of hydrogen. Therefore, carbon is not oxidized, so that electrical conductivity can be maintained.
[0057] [057] In this fuel cell, the hydrogen storage material contains a hydrogen storage alloy or at least one type of metal selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co and Ni. In addition, on the negative electrode of this fuel cell, a surface in contact with the separator may contain a hydrophilic material, and a surface in contact with the hydrogen storage chamber may contain a hydrophobic material. ADVANTAGE EFFECT OF THE INVENTION
[0058] [058] The reversible fuel cell according to the present invention is characterized by high energy density, excellent load segment capacity and excellent life span characteristic. BRIEF DESCRIPTION OF THE DRAWINGS
[0059] [059] [Fig. 1] Fig. 1 is a sectional view schematically illustrating a reversible fuel cell structure according to a first embodiment of the invention, which illustrates an example that oxygen dissolves in the electrolyte.
[0060] [060] [Fig. 2A] Fig. 2A is a sectional view illustrating a fuel cell structure according to a second embodiment of the invention.
[0061] [061] [Fig. 2B] Fig. 2B is a sectional view taken along line D-D in Fig. 2A.
[0062] [062] [Fig. 3] Fig. 3 is a sectional view illustrating a fuel cell structure according to a second example of modifying the second embodiment of the invention.
[0063] [063] [Fig. 4A] Fig. 4A is a view that illustrates a structure of a battery module configured with the fuel cell according to the modification example illustrated in Fig. 3, in which a circled portion is an enlarged view that illustrates main parts .
[0064] [064] [Fig. 4B] Fig. 4B is a front view showing a current collector plate in Fig. 4A.
[0065] [065] [Fig. 5] Fig. 5 is a diagram illustrating the configuration of a process using the fuel cell according to the second embodiment.
[0066] [066] [Fig. 6A] Fig. 6A is a partial sectional side view illustrating a reversible fuel cell structure according to a third embodiment of the invention.
[0067] [067] [Fig. 6B] Fig. 6B is a sectional view taken along line A-A in fig. 6A.
[0068] [068] [Fig. 7] Fig. 7 is a horizontal section view, which schematically illustrates a structure of a portion of the electrode in the reversible fuel cell according to the third embodiment of the invention.
[0069] [069] [Fig. 8] Fig. 8 is a system diagram showing an energy generation process using the reversible fuel cell according to the third embodiment of the invention.
[0070] [070] [Fig. 9] Fig. 9 is a horizontal sectional view, illustrating a reversible fuel cell structure according to a fourth embodiment of the invention.
[0071] [071] [Fig. 10A] Fig. 10A is a sectional view taken along line BB in Fig. 9.
[0072] [072] [Fig. 10B] Fig. 10B is a sectional view taken along line C-C in fig. 9.
[0073] [073] [Fig. 11] Fig. 11 is a system diagram that illustrates a relationship between the reversible fuel cell according to the fourth embodiment of the invention and an external system.
[0074] [074] [Fig. 12] Fig. 12 is a system diagram illustrating an electrolyte treatment process using the reversible fuel cell according to the fourth embodiment of the invention.
[0075] [075] [Fig. 13A] Fig. 13A is a graph that illustrates a discharge characteristic of a positive manganese dioxide electrode (in an electron reaction).
[0076] [076] [Fig. 13B] Fig. 13B is a graph that illustrates the discharge characteristics of the positive manganese dioxide electrode (in a reaction of two electrons).
[0077] [077] [Fig. 14] Fig. 14 is a graph illustrating the XRD measurement results for examining a change in composition of the positive manganese dioxide electrode according to the difference in discharge depth.
[0078] [078] [Fig. 15A] Fig. 15A is a graph illustrating the results of the test in which the manganese dioxide electrode is charged with oxygen gas.
[0079] [079] [Fig. 15B] Fig. 15B is a graph that illustrates the results of another experiment in which the manganese dioxide electrode is charged with oxygen gas.
[0080] [080] [Fig. 16] Fig. 16 is a characteristic graph that schematically illustrates a relationship between the composition of a positive electrode and a terminal voltage.
[0081] [081] [Fig. 17] Fig. 17 is a graph that illustrates the influence of a pressure to be exerted by free energy, the influence of being obtained through thermodynamic calculations. DESCRIPTION OF THE PERFORMANCE
[0082] [082] Before describing the embodiments, first, a description of a common electrolyte in these embodiments will be given. <Electrolyte>
[0083] [083] Preferably, an electrolyte to be used in the present invention is an electrolyte dissolved in oxygen corresponding to an electrolyte in which the oxygen dissolves within a range of 0.02 to 24 g / L. When a dissolution concentration of oxygen in the electrolyte is less than 0.01 g / L, it takes a long time for the oxidation of an active material of the positive electrode, because of this low oxygen concentration. On the other hand, when the oxygen concentration is greater than 24 g / L, the life span of a negative electrode is reduced because the corrosivity of the electrolytes increases. More preferably, the electrolyte is an electrolyte dissolved in oxygen corresponding to an electrolyte in which the oxygen dissolves in the range of 0.08 to 8.6 g / L. The concentration of dissolved oxygen can be adjusted by increasing a pressure of electrolyte fluid. In this case, preferably, the fluid pressure of the electrolyte is from 0.2 MPa to 278 MPa. Most preferably, an electrolyte pressure is 0.95 MPa to 100 MPa. The use of high-pressure or ultra-high-pressure electrolyte is allowed to increase the concentration of dissolved oxygen and dissolve oxygen to be generated at the time of overloading the electrolyte. In addition, use is also permitted to increase an operating voltage of a cell.
[0084] [084] The electrolyte contacts dissolved in oxygen with a positive electrode, thereby oxidizing an active material of the positive electrode (the positive electrode is charged). When the electrolyte dissolved in oxygen is under high pressure or ultra-high pressure, the oxygen to be generated at the time of charging dissolves in the electrolyte. Thus, the concentration of oxygen dissolved in the electrolyte can be increased.
[0085] [085] With respect to the electrolyte pressure fluid range, it becomes difficult to increase the concentration of oxygen that dissolves in the electrolyte when the electrolyte pressure fluid is less than 0.2 MPa. Therefore, it takes a long time to oxidize the active material of the positive electrode, and it becomes difficult to effectively dissolve oxygen to be generated at the time of charging the electrolyte. The definition of the fluid pressure of the electrolyte at an ultra-high pressure greater than 278 MPa, takes a load on the cell structure.
[0086] [086] The electrolyte to be used in the present invention can be an aqueous alkaline solution typically used. In order to restrict the elution of an alloying component in the electrolyte, alkaline materials such as lithium hydroxide (LiOH), sodium hydroxide (NaOH) and potassium hydroxide (KOH) can be used alone or in combination. The concentration of the alkaline material in the electrolyte is preferably 1 to 10 mol / L, more preferably 3 to 8 mol / L.
[0087] [087] A thickener can dissolve in the electrolyte. The thickener that dissolves in the electrolyte has a high viscosity and therefore has a low rate of oxygen diffusion. Due to the low oxygen diffusion rate, since the negative electrode is difficult to come into contact with oxygen, the self-discharge reaction of the negative electrode can be suppressed. In addition, as the viscosity of the electrolyte becomes greater, spill resistance is also improved. A material for the thickener can be water-absorbing materials, which increase the viscosity of the electrolyte. Examples of the material can include polyacrylate, polystyrene sulfonate, polyvinyl sulfonate, gelatin, starch, polyvinyl alcohol (PVA), and resin, such as fluororesin.
[0088] [088] Hereinafter, a more detailed description of the present invention will be given based on more specific embodiments. However, the present invention is not intended to be limited to those embodiments. (First embodiment)
[0089] [089] Fig. 1 is a sectional view that schematically illustrates a structure of a C1 reversible fuel cell (hereinafter, simply referred to as a C1 cell) according to a first embodiment, cell C1 has a basic configuration of a fuel cell. The C1 cell uses chemical energy, including hydrogen and oxygen by converting chemical energy into electrical energy. In addition, the C1 cell is capable of storing electrical energy by converting electrical energy into chemical energy. Cell C1 includes as main elements a negative electrode 4, a positive electrode 6, an electrolyte 3, a negative electrode case 1 and a positive electrode case 2. Negative electrode 4 and positive electrode 6 are opposite each other with a separator 5 interposed between them. The negative electrode case 1 has a hydrogen storage chamber 8. The positive electrode case 2 has an oxygen storage chamber 7.
[0090] [090] The negative electrode 4 contains, as an active negative electrode material, a hydrogen storage alloy having the composition La _0.54 Pr ₀ , ₁₈ Nd ₀ , ₁₈ Mg _0.1 Ni _4.5 Al _0.1 . Negative electrode 4 is produced as follows. First, a pasty mixture is prepared from acetylene black (AB), carboxymethyl cellulose (CMC) and styrene-butadiene rubber in a 97: 1: 1: 1 weight ratio. In addition, this mixture Pasty is applied on a perforated metal sheet made of a nickel-plated steel material. The negative electrode 4 has a surface in contact with the separator 5 and containing a hydrophilic material, and a surface in contact with the hydrogen storage chamber 8 and containing a hydrophobic material.
[0091] [091] Positive electrode 6 contains manganese dioxide as an active positive electrode material. Positive electrode 6 is produced as follows. First, a pasty mixture is prepared from AB, CMC and polytetrafluoroethylene in a 97: 0.5: 2: 0.5 weight ratio. In addition, this pasty mixture is introduced on a nickel foam substrate. Here, the active material of the positive electrode, that is, manganese dioxide is loaded into a rotary kiln (at 700 ° C, for 1 hour, under an atmosphere of butane gas) in advance. Thus, a thin electroconductive film is formed in manganese dioxide. A cover of an electroconductive coating film (carbon coated film) is obtained by subjecting the resulting manganese dioxide to a heat treatment under an oxygen atmosphere and calculating the difference between the weight of the manganese dioxide before the heat treatment and a weight of manganese dioxide after heat treatment. The carbon-coated film coverage is 0.9% by weight relative to 100% by weight of manganese dioxide.
[0092] [092] The separator 5 includes a microporous film (thickness: 20 μm, average pore diameter: 0.2 μm) of polypropylene. Electrolyte 3 is retained in separator 5.
[0093] [093] Electrolyte 3 contains a 6 mol / L aqueous solution of potassium hydroxide. Electrolyte 3 contains more than 5% by weight of sodium polyacrylate as a thickener. The oxygen storage chamber 19 is charged with electrolyte 3. Even when a void is formed in the upper part of the oxygen storage chamber 19, a void ratio is at most 5 in relation to the volume of the oxygen storage chamber oxygen 19, the volume being set to 100. In other words, an electrolyte ratio 3 to charge the oxygen storage chamber 19 is 95 to 100% relative to the volume of the oxygen storage chamber 19, the volume being set like 100%. When the void is large, an amount of oxygen to be effectively stored decreases.
[0094] [094] As shown in Fig. 1, separator 5 is sandwiched between negative electrode 4 and positive electrode 6. In negative electrode 4, in addition, the surface that is not in contact with separator 5 is hermetically covered with the negative electrode case in the form of a box 1. An interior space to be formed by the negative electrode 4 and the negative electrode case 1 corresponds to the hydrogen storage chamber 8. The hydrogen storage chamber 8 directly stores hydrogen gas to be generated from the negative electrode, without the need to provide an additional member such as a reinforcer. In addition, the hydrogen storage chamber 8 is provided in contact with the negative electrode 4. Therefore, the hydrogen gas can be supplied directly to the negative electrode 4, without a need to provide a communication passage or an additional member.
[0095] [095] On the positive electrode 6, the surface that is not in contact with the separator 5 is covered with the positive electrode case in the form of a box 2. An interior space to be formed by the positive electrode 6 and the positive electrode case 2 corresponds to the oxygen storage chamber 7 to store oxygen. The oxygen storage chamber 7 stores electrolyte 3 with a high pressure fluid (for example, 10 MPa). Therefore, the oxygen to be generated from the positive electrode 6 dissolves in the electrolyte, and is stored as the dissolved oxygen in the oxygen storage chamber 7. In other words, the oxygen to be generated from the positive electrode 6 is directly stored in the oxygen storage chamber 7, without the need to provide an additional element, such as a reinforcement. In addition, the oxygen storage chamber 7 is provided in contact with the positive electrode 6. Therefore, the oxygen can be fed directly to the positive electrode 6, without the need to provide a communication passage or an additional member. Preferably, the oxygen storage chamber 7 has an internal surface coated with nickel or chromium. The oxygen storage chamber 07 can have an internal surface deposited with nickel or deposited with chromium.
[0096] [096] The hydrogen storage chamber 8 and the oxygen storage chamber 7 are separated from each other by a movable wall member 9. The wall member 9 includes positive electrode 4, negative electrode 6 and separator 5 The wall member 09 can be a flexible member.
[0097] [097] On the negative electrode 4, the surface that is in contact with the hydrogen storage chamber 8 contains the hydrophobic material in a large amount. Thus, the hydrogen storage alloy on negative electrode 4 can be brought into contact with hydrogen gas without being moistened. On the negative electrode 4, on the other hand, the surface that is in contact with the separator 5 has a hydrophilic property. Thus, this surface prevents hydrogen gas from passing through the negative electrode 4. This surface is maintained in a state where the surface is almost always moistened with the electrolyte. Thus, the ionic conductivity of negative electrode 4 is ensured. Specifically, carbon, Teflon (trademark) or the like which has a hydrophobic property can be applied on, or sprayed on, the side surface of the hydrogen storage chamber 8 of negative electrode 4 In addition, modified nylon having the hydrophilic property can be applied on or sprayed on the surface, which is in contact with the separator 5, of the negative electrode 4 '. In addition, vinyl acetate which has both hydrophilic and hydrophobic properties can be granulated and used as a binder.
[0098] [098] From now on, the description of the configuration of cell C1 will be given. Cell C1 includes positive electrode 6 containing the active material of the positive electrode and negative electrode 4 containing the active material of the negative electrode. Therefore, electrical energy is stored in the electrodes of cell C1 at the time of the initial charge. Then, charge exceeding an electrical capacity of the electrode's active material is occasionally referred to as overload for convenience of description. In an overload state, oxygen gas and hydrogen gas are generated.
[0099] [099] In cell C1, when electric current is supplied to the electrodes after the initial charge, hydrogen gas is generated from the negative electrode and oxygen gas 4 is generated from the positive electrode 6. The hydrogen gas is stored in the chamber of hydrogen storage 8. When charging is continued, a pressure in the hydrogen storage chamber 8 increases. Consequently, the hydrogen storage chamber 8 expands under the influence of the pressure of the hydrogen gas. The hydrogen storage chamber 8 and the oxygen storage chamber 7 are separated from each other by the movable wall member 9. Therefore, when the hydrogen storage chamber 8 expands, the wall member 9 is displaced or deformed. , so that the electrolyte 3 in the oxygen storage chamber 7 is compressed. The deformation of the wall element 9 is continued until the pressure in the hydrogen storage chamber 8 and the pressure in the oxygen storage chamber 7 become almost equal to each other. Thus, electrolyte 3 in the oxygen storage chamber 7 is highly pressurized. As a result, the oxygen generated from the positive electrode 6 dissolves in electrolyte 3. In this way, electrolyte 3 is changed to an electrolyte dissolved in oxygen.
[0100] [100] In cell C1 according to this embodiment, electrolyte 3 has a fluid pressure of 0.95 MPa. In cell C1 according to this embodiment, electrolyte 3 can have a fluid pressure within a range from 0.2 MPa to 278 MPa.
[0101] [101] At the time of discharge from cell C1, a discharge reaction like a secondary battery occurs between negative electrode 4 and positive electrode 6. Thus, the electric current is fed into a charge. Here, an amount of electrical energy at the negative electrode 4 and an amount of electrical energy at the positive electrode 6 decrease by the discharge. The charge using the hydrogen gas stored in the hydrogen storage chamber 8 and the oxygen gas stored in the oxygen storage chamber 7 compensates for the electricity corresponding to the decrease in electrical energy in negative electrode 6 and positive electrode 4. That is, the reaction represented by the chemical formula (2) occurs at the negative electrode 4. As a result, the hydrogen gas compensates for the protons emitted from the hydrogen storage alloy (MH) in the charged state. Thus, the negative electrode is kept in a charged state. On the other hand, the reaction represented by the chemical formula (4) occurs at the positive electrode 6. As a result, manganese oxy-hydroxide generated by the reduction of manganese dioxide (MnO ₂ ), in the charged state is oxidized again by oxygen. Thus, the positive electrode is kept in a charged state. That is, manganese dioxide serves as a catalyst for a positive electrode reaction. On the other hand, the hydrogen storage alloy serves as a catalyst for a reaction on the negative electrode.
[0102] [102] Manganese dioxide at positive electrode 6 is reduced to manganese oxy hydroxide by discharge. Manganese oxy-hydroxide is oxidized by oxygen in the electrolyte and is therefore taken up with manganese dioxide. In this way, manganese dioxide almost always exists in the positive electrode 6. Therefore, a SOC (charge state) of the positive electrode is maintained at about 100%. In addition, the positive electrode 6 faces the oxygen storage chamber 7, and is always in contact with oxygen. With regard to the manganese dioxide discharge reaction, therefore, manganese dioxide is not changed to manganese hydroxide, so that trimanganese tetroxide (Mn ₃ O ₄ ), which is an irreversible component, is not generated . Therefore, since the degradation of the positive electrode 6 is contained, its lifetime characteristic is considerably improved.
[0103] [103] The hydrogen storage alloy on negative electrode 4 emits protons at the time of discharge. Therefore, an amount of hydrogen in the hydrogen storage alloy decreases. However, the negative electrode 4 faces the hydrogen storage chamber 8 and is always in contact with the hydrogen gas. Therefore, hydrogen gas compensates for protons emitted from the hydrogen storage alloy (MH). As a result, the hydrogen storage alloy, from which hydrogen was released, stores hydrogen again. Thus, the alloy contained in negative electrode 4 almost always stores hydrogen. As a result, the SOC of the negative electrode is maintained at around 100%.
[0104] [104] Fig. 16 is a graph that schematically illustrates a relationship between the potential of the manganese dioxide electrode (vertical geometric axis) and S (horizontal geometric axis). As shown in Fig. 16, the potential of the C1 cell is in the vicinity of a high potential represented by manganese dioxide (MnO ₂ ). In other words, the discharge potential of cell C1 is maintained at a high level.
[0105] [105] In cell C1 according to this embodiment, each of the storage chambers 7 and 8 stores as electrical energy, the electrical energy to be supplied at the time of overload. The C1 cell is able to use the stored chemical energy by converting the chemical energy into electrical energy. Unlike a conventional secondary battery, therefore, the electrical capacity of the C1 cell has no limitations due to an amount of active material. In this way, it is possible to increase an amount of hydrogen gas to be stored by volume and an amount of dissolved oxygen by increasing the pressure-resistant and sealing performance of storage chambers 7 and 8 and cell C1. Thus, it is possible to considerably improve the energy density of the C1 cell, compared to that of a conventional secondary battery (for example, up to several dozen times). In addition, the hydrogen gas generated from the negative electrode 4 is directly stored in the storage chamber 8 and oxygen generated from the positive electrode 6 is directly stored in the storage chamber 7, at the time of overload. Therefore, there is no need to provide an additional reinforcement or communication path for the gas. Therefore, cell C1 has a simple structure, and therefore can be manufactured and distributed at low cost. Particularly, oxygen is stored in such a way as to dissolve in the electrolyte. Therefore, safety regarding oxygen handling is drastically improved.
[0106] [106] As described above, even more, electrical energy is produced from cell C1, at the time of discharge by the reactions represented by formulas (1) and (3). In comparison with a conventional fuel cell, therefore, the C1 cell is considerably improved in energy and tracking capacity in relation to a load. Thus, the C1 cell is applicable to a use in which a high instantaneous output is required and a change in load is large, such as a vehicle. In this, cell C1 can be used exclusively without a need to provide an additional secondary battery or an energy storage device, such as a capacitor. (Second embodiment)
[0107] [107] Next, a description of a C2 cell will be given according to a second embodiment of this fuel cell. The C2 cell has a structure that is excellent in pressure resistant performance and can be easily handled. Figs. 2A and 2B are seen from each section that illustrates the structure of cell C2. Here, Fig. 2B is a sectional view taken along line D-D in Fig. 2A. Cell C2 has a basic configuration similar to cell Cl according to the first embodiment illustrated in Fig. 1. As shown in Fig. 2A, however, cell C2 has a tubular outer shell 10. Thus, the cell C2 has excellent pressure-resistant performance and handling performance. In addition, the C2 cell has a higher energy density and is easily manipulated. With respect to the C2 cell according to this embodiment, a negative electrode, a positive electrode, a separator and an electrolyte, which are the basic elements of a battery, can have substances and structures similar to those of the C cell according to with the first embodiment, except for the aspects to be particularly described below.
[0108] [108] As illustrated in Fig. 2A, more specifically, the tubular outer shell 10 has a cylindrical portion 10a and a lower portion 10b. The lower portion 10b follows one end of the cylindrical portion 10a and corresponds to the lower portion of the outer shell 10. Negative electrode 14, positive electrode 16 and separator 15, arranged between negative electrode 14 and positive electrode 16 are housed inwardly of the lower portion 10b. Each of the negative electrode 14 and the positive electrode 16 is formed in a closed cylindrical shape at one end. The negative electrode 14 has a cylindrical peripheral wall 14a and a lower portion 14b, and the positive electrode 16 has a cylindrical peripheral wall 16a and a lower portion 16b. The positive electrode 16 is disposed inside the outer shell 10 with a space formed between the positive electrode 16 and the outer shell 10 in the radial direction. The negative electrode 14 is disposed inside the positive electrode 16 with the separator 15 interposed between the negative electrode 14 and the positive electrode 16. In cell C2, the space (radial space) formed between the outer shell 10 and the positive electrode 16 serves as an oxygen storage chamber 19. On the other hand, the space formed inside the negative electrode 14 serves as a hydrogen storage chamber 18.
[0109] [109] The outer shell 10 is made of an electroconductive material, specifically, the iron deposited in nickel. An outer surface of the lower portion 16b of the positive electrode 16 is connected to an inner surface of the lower portion 10b of the outer shell 10. Thus, the outer shell 10 serves as a positive electrode terminal of cell C2. On the other hand, a disc-shaped negative electrode terminal 11 is connected to a right end 14c (to the right in Fig. 2A) opposite the lower portion 14b of negative electrode 14. Specifically, the right end 14c of negative electrode 14 is arranged to project to the right from a right end surface 10c of the outer casing 10 and a right end surface 16c of the positive electrode 16. an inner diameter surface 17 of a ring-shaped insulating member 17 is provided with an outer peripheral surface of the right end 14c. The surface 10c of the right end of the outer housing 10 and the surface 16c of the right end of the positive electrode 16 are covered with the insulating member 17. In addition, an internal surface (to the left in fig. 2A), which is one of the surfaces of the negative electrode terminal 11 is connected to the right end 14c of the negative electrode 14.
[0110] [110] Electrodes 14 and 16 each have flexibility. Therefore, when the hydrogen storage chamber 18 is pressurized with hydrogen gas generated by overload, the pressure in the hydrogen storage chamber 18 is transferred to the oxygen storage chamber 19. As a result, electrolyte 13 in the oxygen storage chamber. oxygen 19 is compressed, so that their pressure increases. The high-pressure electrolyte allows oxygen to dissolve there in a greater amount.
[0111] [111] On the negative electrode 14, a surface in contact with the hydrogen storage chamber 18 contains a large amount of hydrophobic material. Thus, a hydrogen storage alloy on the negative electrode 14 can be brought into contact with hydrogen gas without being moistened. Also on the negative electrode 14, a surface in contact with the separator 15 has a hydrophilic property, and therefore must be kept in a state where this surface is almost always moistened with the electrolyte. Thus, the hydrogen gas is prevented from passing through the negative electrode 14, and the ion conductivity of the negative electrode 14 is ensured.
[0112] [112] The description of dimensions of the outer shell 10 will be given. An outer diameter of the outer shell 10 can encompass a range of 13.5 mm to 14.5 mm. In addition, the length of the outer shell 10 can encompass a range of 49.0 mm to 50.5 mm. The outer diameter of the outer shell 10 can also encompass a range of 10.5 mm to 9.5 mm. The length of the outer shell 10 can also encompass a range of 42.5 mm to 44.5 mm. The dimensions, which fall within the ranges described above, of the outer housing 10 allow for dimensional compatibility with a commercially available R6 or R03 battery.
[0113] [113] Cell C2 according to the second embodiment produces the following advantageous effects, in addition to the beneficial effects produced by cell C1 according to the first embodiment.
[0114] [114] As illustrated in Figs. 2A and 2B, the outer shell 10 of cell C2 has a tubular structure. This facilitates the achievement of excellent pressure resistance and increased energy density. In addition, a battery module having a large charge and discharge capacity can be easily configured by connecting a large number of C2 cells, in parallel and in series. In cell C2 according to this embodiment, in particular, the oxygen storage chamber 19 is formed in the radial space. In addition, the hydrogen storage chamber 18 is formed within the negative electrode 14. Therefore, there is no need to provide additional members for the formation of the hydrogen storage chamber 18 and the oxygen storage chamber 19. Thus, the cell C2 has a simple structure, and therefore can be formed using only the minimum members. Therefore, cell C2 is small in size and therefore has high resistance to pressure and energy density. Regardless of this configuration, cell C2 is easily assembled, because the parts count is small. (Example of Modification of the Second Embodiment)
[0115] [115] Next, a description of a C3 cell will be given according to a modification of the example of the second embodiment of this fuel cell. Fig. 3 is a partial section view showing a connection structure of cell C3. Cell C3 corresponds to cell C2 according to the second embodiment in which the outer structure is partially altered. From now on, the description of mainly the modification will be given. Cell C3 has a negative electrode terminal 11 electrically connected to a negative electrode 14, at one of its ends, in an axial direction (axial direction of an outer shell 10). In addition, cell C3 has a positive electrode terminal corresponding to the outer casing 10 electrically connected to a positive electrode 16, on the other end, in the axial direction. As shown in Fig. 3, a projection 11d is formed in the center of the negative electrode 11 terminal. In addition, a lower recess 10d is formed in the center of a lower portion 10b of the outer shell 10. The projection 11d and the lower recesses 10d are formed to fit together. Thus, two C3 cells can be connected in series.
[0116] [116] According to this configuration, it is possible to connect a plurality of C3 cells in series, without the need to supply wires. In the example illustrated in Fig. 3, a rib is formed on an external periphery of the projection, in the axial direction. On the other hand, a notch is formed on an internal circumferential surface of the lower recess. In addition, the projection rib can be fitted within the notch of the lower recess. However, the shape of this fitted portion is not limited to these.
[0117] [117] Each of the positive electrode terminals (outer casing 10) and the negative electrode terminal 11 may have a thread portion. More specifically, the projection 11d of the negative electrode 11 terminal can be formed as a male thread, and the recess 10d formed in the lower portion 10b of the outer shell 10 can be formed as a female thread. Thus, the two C2 cells can be connected to each other reliably.
[0118] [118] In cell C3, an oxygen storage chamber (not shown) can be charged with an electrolyte, in which the oxygen dissolves. Alternatively, the oxygen storage chamber can be charged with the electrolyte dissolved in oxygen and oxygen gas.
[0119] [119] Figs. 4A and 4B each show a structure of a battery module B3 that includes a plurality of C3 cells connected to each other. The battery module B3 includes a pair of electrically conductive current collector plates 25 that oppose each other. The plurality of C3 cells are disposed between the current collecting plates 25. The outer shell 10 that serves as a positive electrode terminal is in contact with one of the current collecting plates 25. The negative electrode terminal 11 is in contact with the other current collecting plate 25. To maintain this state, C3 cells are arranged in parallel. In battery module B3, groups of cells, each including a plurality of C3 cells connected in parallel, are connected in series (Fig. 4A).
[0120] [120] This configuration is allowed to eliminate the need for wires for the connection of C3 cells. This facilitates the assembly of the B3 battery module. As shown in the enlarged view of the main part that corresponds to a portion of a circle in fig. 4A, a through hole 25a can be formed in the current collecting plate 25. In this example, the projection 11d of the cell C3 is fitted into the lower recess 10d of the different cell C3 through the through hole 25a. This makes mounting the B3 battery module even easier. According to this structure, the plurality of cell C3 is supported by current collectors 25. Consequently, battery module B3 has a monoblock structure, like a battery. Here, the cell of the battery module B3 is not limited to cell C3, but it can be cell C2.
[0121] [121] An air fan 27 can be provided for supplying cooling air in a parallel direction to the current collecting plates 25. Heat generated from cell C3 is transferred to the current collecting plate 25. The air collecting plate 25 current 25 functions as a radiation fin, so that the C3 cell is indirectly cooled. The collecting plate current 25 plays a role of an electroconductive member and a role of a radiation member. Therefore, the current collecting plate 25 can be made of a material with high thermal conductivity and electrical conductivity. In this regard, aluminum has relatively low electrical resistance and relatively high thermal conductivity. Therefore, aluminum has preferable characteristics as a material for the current collecting plate 25. However, since aluminum is prone to oxidation, the contact resistance of the current collecting plate 25 tends to increase. Accordingly, an aluminum plate forming the current collecting plate 25 can be deposited with nickel. This achieves a reduction in contact resistance. The current collecting plate 25 is provided with a plurality of coolant fluid passages 26 for the insulating oil passage for cooling (see Fig. 4B). In addition, C3 cells (through holes 25a) can be arranged in a staggered manner (see fig. 4B). Thus, the cooling air from the air fan 27 is blown directly over the side surface of cell C3. As a result, a cooling effect is increased. If the battery module is cold, the air fan 27 can blow heated air through a heater (not shown). Thus, the battery module can be heated. (Battery system, including the fuel cell of the second embodiment)
[0122] [122] Next, a description of a battery system, including the fuel cell according to the second embodiment, will be given. Fig. 5 is a diagram illustrating the configuration of a process using a C4 fuel cell according to the present invention. Cell C4 corresponds to cell C3, which is partially altered. Cell C4 has a lower portion provided with an oxygen circulation port 32 that communicates with an oxygen storage chamber 19, and a projection 11d provided with a hydrogen circulation port 28, which communicates with a storage chamber of hydrogen 18. The oxygen circulation port 32 is connected to a cooling device 34 via a duct 33. The cooling device 34 cools a heated electrolyte by operating cell C4. The electrolyte of the cooling device 34 is fed with an electrolyte storage source 36. The electrolyte in the electrolyte storage source 36 is stirred by an agitator 37, so that the oxygen gas generated is provided from the top of the source of electrolyte. electrolyte storage 36 to an oxygen source 38, and then it is stored in oxygen source 38. On the other hand, the hydrogen circulation port 28 is connected to a cooling device 30 through a duct 29. The cooling device 30 cools the hydrogen gas. The hydrogen gas from the cooling device 30 is stored in a hydrogen source 31.
[0123] [123] The electrolyte dissolved in high concentration oxygen in the electrolyte storage source 36 can be supplied to the oxygen storage chamber 19 by a pump 35. In addition, high pressure hydrogen gas can be supplied from the source of hydrogen 31 to the hydrogen storage chamber 18. (Third embodiment)
[0124] [124] Figs. 6A and 6B are section views, each illustrating a structure of a reversible fuel cell C10 according to a third embodiment of this fuel cell (hereinafter, simply referred to as a C10 cell). More specifically, Fig. 6A is a partial section view in the longitudinal direction. Fig. 6B is a sectional view taken along line A-A in Fig. 6A. Cell C10 has a structure covered with an outer sheath 100. In the outer sheath 100, a plurality of tubular positive electrodes 110 are in an axial direction of the outer sheath 100 (direction X in Fig. 6A). In addition, a negative electrode 120 is charged and disposed around the positive electrode 110 with a separator 130 interposed between the negative electrode 120 and the positive electrode 110. The negative electrode, the positive electrode, the separator and an electrolyte, which are the basic elements of cell C10 according to this embodiment, may have substances, compositions and structures similar to those of cell C1 according to the first embodiment, except for cases to be particularly described below.
[0125] [125] The outer casing 100 has a cylindrical body part 101 and protruding parts 102. The protruding parts 102 are provided in openings formed at both ends of the body part 101. The protruding part 102 protrudes out of the opening, so away from the opening, and covers the opening. A gasket 103 is arranged between the body part 101 and the protruding part 102, in order to maintain fluid tightness inside the outer shell 100. Each of the body part 101 and the protruding part 102 can be made of steel, preferably high tensile strength steel. Thus, the body part 101 is cylindrical in shape, and the projecting part 102 projects outwardly. In this way, the outer sheath 100 is capable of structurally resisting ultra-high pressure.
[0126] [126] In the outer shell 100, oxygen storage chambers 136a and 136b are provided in interior spaces of the projecting parts 102, respectively. Each of the right and left oxygen storage chambers 136a and 136b is defined by a partition 135. Oxygen storage chambers 136a and 136b can be connected to an external device via flanges 211 and 212 each connected to the outer shell 100 The positive electrode 110, the negative electrode 120, the separator 130 and a current collector 134 are arranged in a space formed between the oxygen storage chambers 136a and 136b and surrounded with the dividers 135 and the body part 101.
[0127] [127] Fig. 7 is a partial section view that illustrates an electrode structure of cell C10. The current collector 134 is a perforated steel tube deposited in nickel. Positive electrode 110 is formed in such a way that a pasty mixture containing manganese dioxide is applied around the current collector 134. Positive electrode 110 can be formed in such a way that the mixture is applied directly to the current collector 134 Alternatively, the positive electrode 110 can be formed in such a way that a positive electrode sheet obtained by applying the mixture on a nickel foam substrate is wound around the current collector 134. The separator 130 is interposed between the electrode positive 110 and the negative electrode containing 120 an oxygen storage alloy. The separator 130 prevents contact between the positive electrode 110 and the negative electrode 120. The oxygen storage chambers 136ae 136b located on the right and the left ends of the outer shell 100 communicate with each other through the current collector 134. Electrolyte 137 in each of the oxygen storage chambers 136a and 136b can flow in a direction shown with an arrow in Fig. 7.
[0128] [128] A space formed between the right and left partitions 135 and located to the outside of the separator 130 is loaded with a hydrogen storage alloy having an average particle diameter of 20 µm. According to this configuration, a porosity is about 35%. Porosity varies, depending on a method for loading the hydrogen storage alloy. The porosity can be greater than 35%. When the average particle diameter is 5 to 50 µm, the porosity is about 30 to 60%. A void formed as described above serves as a hydrogen storage chamber 138. Here, the average particle diameter value is obtained using an equivalent sphere diameter based on the light scattering of JIS Z 8910, as in the other embodiments .
[0129] [129] As shown with a dotted line in Fig. 6A, a hydrogen gas storage source 121 and a storage passageway 122 are connected to the hydrogen storage chamber 138 in cell C10. Negative electrode 120 can be charged with hydrogen gas provided from the outside.
[0130] [130] The current collector 134 of the positive electrode passes through partitions 135 of steel deposited in nickel. The two ends of the current collector 134 are supported by the dividers 135. Therefore, the protruding portion 102 is electrically connected to the positive electrode 110 through partition 135. Thus, the protruding portion 102 serves as a positive electrode terminal of cell C10. In addition, the body part 101, which is in direct contact with the negative electrode 120 serves as a negative electrode terminal. Gasket 103 not only has a sealing property, but also an insulating property. Thus, gasket 103 prevents a short circuit between positive electrode 110 and negative electrode 120.
[0131] [131] Next, the description of the operations of cell C10 configured as described above will be given. The electrolyte 137 in which the oxygen dissolves is fed to cell C10 through one of the flanges 211 (the right side of fig. 6A). Electrolyte 137 is an electrolyte in which oxygen dissolves at a high concentration, and can be referred to as an electrolyte dissolved in high concentration oxygen. The electrolyte dissolved in high concentration oxygen 137 flows to the tube-shaped current collector 134, passes through the perforation formed over the current collector 134, and comes into contact with the positive electrode 110. Thus, manganese oxy-hydroxide on the positive electrode it is oxidized with the oxygen that dissolves in the electrolyte and is changed to manganese dioxide. As a result, the positive electrode is charged. Thus, the oxygen that dissolves in the electrolyte is consumed to generate H ₂ O, so that the oxygen concentration in the electrolyte is reduced. Electrolyte 137 in which the oxygen concentration is reduced (electrolyte dissolved in low concentration oxygen) is drained into the left oxygen storage chamber 136b and finally released from flange 212 to the outside of the system. On the other hand, the negative electrode 120 is charged with hydrogen gas to be provided from the external hydrogen gas storage source 121.
[0132] [132] Cell C10 is discharged in such a way that an electrical charge is connected between the protruding part 102 that serves as the positive electrode terminal and the body part 101 that serves as the negative electrode terminal via a wire cable (not shown). Thus, the electric current is fed to the electrical charge. The electric charge current can be made from both of the two protruding parts 102. Therefore, the electric current flowing through the current collector 134 is divided into two, one of which is fed to the right and the other of which is fed to the left, so that the loss of Joule is reduced to about a quarter.
[0133] [133] Next, a case will be given where the C10 cell is charged by converting electrical energy into chemical energy. In cell C10, the hydrogen storage chamber 138 is capable of storing hydrogen gas generated by overload. Also in cell C10, each of the oxygen storage chambers 136a and 136b is capable of storing oxygen in a state where oxygen dissolves in the electrolyte. That is, the C10 cell according to this embodiment is capable of storing electrical energy by converting electrical energy into chemical energy. In addition, the C10 cell is capable of producing electrical energy as appropriate, converting chemical energy into electrical energy. Unlike a conventional secondary battery, therefore, the C10 cell has no limitation on an energy storage capacity, due to an amount of active material.
[0134] [134] As in cell C1 according to the first embodiment, cell C10 according to this embodiment is discharged through the reaction of the battery at the time of discharge and is charged with hydrogen gas and oxygen gas. At the time of loading and unloading described above, manganese dioxide serves as a catalyst for a positive electrode reaction. On the other hand, the hydrogen storage alloy serves as a catalyst for a reaction on the negative electrode.
[0135] [135] Fig. 8 illustrates a process of generating energy using cell C10 according to the fourth embodiment. A duct 220 is connected to cell C10 through flange 212. Electrolyte 137 degraded by the discharge of cell C10 is drained into a first chamber 231 of a salt concentration adjustment apparatus 230 through duct 220. A reverse osmosis membrane 233 it is connected to the salt concentration adjustment device 230. The salt concentration adjustment device 230 is divided into the first chamber 231 and a second chamber 232 by the reverse osmosis membrane 233. The reverse osmosis membrane 233 has a function of allow water in electrolyte 137 to pass selectively through it. Passing water is retained as a drain in the second chamber 232, and is released from a drain outlet 234 to the outside of the system. Electrolyte 137 in the salt concentration adjustment apparatus 230 is taken to an oxygen concentration adjustment apparatus 250 through a duct 221. The oxygen concentration adjustment apparatus 250 has a bottom in which an oxygen storage source 251 and a storage passageway of 252 are connected. Oxygen gas is in contact with electrolyte 137, so that the concentration of oxygen dissolved in the electrolyte is increased. Here, the oxygen concentration adjustment device 250 is provided with a separate storage passage 253, so that the oxygen generated by the overload can be stored in the oxygen storage source 251. Thus, the electrolyte dissolved in high concentration oxygen from the oxygen storage source 251 can be returned to the oxygen concentration adjustment device 250. This electrolyte can be used to adjust the oxygen concentration reduced by the discharge.
[0136] [136] The temperature of electrolyte 137 from the oxygen concentration adjustment device 250 increases due to the use of the cell. The electrolyte 137 is cooled by a cooling device 260 in order to reach a predetermined temperature. After that, electrolyte 137 is pressed by a pump 270, and is returned to cell C10, through a duct 222. (Fourth embodiment)
[0137] [137] Fig. 9 is a sectional view that schematically illustrates, in an axial direction, a reversible fuel cell according to a fourth embodiment of this fuel cell (hereinafter, simply referred to as a C30 cell) . A negative electrode, positive electrode, a separator and an electrolyte, which are the basic elements of the C30 cell according to this embodiment, may have substances, compositions and structures similar to those of the C1 cell according to the first embodiment, except for the aspects to be particularly described below. As illustrated in Fig. 9, cell C30 includes, as main constituent elements, an outer casing 300, a current collector 310, and the electrodes housed in the outer casing. The outer casing 300 includes a round tube 301 and the disk-shaped cap members 302. The cap members 302 are provided in openings formed at both ends of the round tube 301. Each of the round tubes 301 and the cover 302 is made of iron deposited in nickel.
[0138] [138] The current collector 310 is made of iron deposited in electrically conductive nickel in the form of a rod. The chain collector 310 has two ends that pass through holes formed over the centers of the cover members 302. The two ends of the chain collector 310 are threaded on nuts 311. These nuts 311 secure the chain collector 310 to the cover members 302. Each of the 311 nuts is shaped into a pocket shape. This prevents the electrolyte from being leaked from the cell. A seal 312 that has an insulating property is provided between nut 311 and cover member 302. Gasket 312 prevents electrical contact between the current collector 310 and cover member 302. A gasket 303 for the cell seal it is provided between the round tube 301 and the cap member 302. The gasket 303 has an insulating property. Therefore, the gasket 303 prevents electrical contact between the round tube 301 and the cap member 302. The current collector 310 is subjected to nickel deposition, and therefore is prevented from being corroded by the electrolyte.
[0139] [139] Positive electrode 320 and negative electrode 330 are stacked in an axial direction of round tube 301 (the X direction in Fig. 9) with separator 340 interposed between them. The positive electrode 320 and negative electrode 330 are housed in the outer shell 300. The separator retains the electrolyte. The separator 340 allows the isolation between the positive and negative electrodes, and also allows the ions to pass through it. Positive electrode 320 is made of a foam nickel substrate loaded with manganese dioxide. Negative electrode 330 is made of a foam nickel substrate loaded with a hydrogen storage alloy. Thus, the hydrogen gas is able to pass through the negative electrode. Positive electrode 320 is formed in a substantially disk shape and has an outer diameter that is slightly larger than the inner diameter of round tube 301. Positive electrode 320 is partially cut 180 degrees away from each other on an outer periphery the same. The outer periphery of the positive electrode 320 is in contact with an internal surface of the round tube 301, with the exception of the cutting portions (see fig. 10A). A notch 321 is formed between the cutting part of the positive electrode 320 and a round tube 301. A gasket of PP 351 that is made of polypropylene and has the same thickness as the positive electrode 320 is interposed between the positive electrode 320 and the collector current 310 at positive electrode 320. This PP 351 gasket allows insulation between positive electrode 320 and current collector 310.
[0140] [140] Fig. 10A illustrates a section of cell C30, taken along line B-B, and Fig. 10B illustrates a section of cell C30, made by line CC.
[0141] [141] Negative electrode 330 has a disk shape. Negative electrode 330 has a U-shaped section and is opened in an internal circumferential direction. Current collector 310 passes through a hole formed in the center of negative electrode 330. This through hole has a diameter that is slightly smaller than the outer diameter of current collector 310. Therefore, the internal diameter portion of the negative electrode 330 and the external diameter portion of the current collector 310 are in contact with each other. A space surrounded with the negative electrode 330 and the current collector 310 forms a hydrogen storage chamber 380. The separator 340 is interposed between the positive electrode 320 and the negative electrode 330. In the negative electrode 330, an outer peripheral surface, in radial direction it is covered with a PP 352 gasket. An outer diameter of the PP 351 gasket is less than an internal diameter of the round tube 301. Therefore, a gap (gap) 331 is formed between the PP 351 gasket and the round tube 301 (see Fig. 10B). In the negative electrode 330, in addition, the portion that is not facing the separator 340 and the hydrogen storage chamber 380 is covered with a PP 353 gasket.
[0142] [142] Cap member 302 has a hydrogen gas supply port 373. Positive electrode 320 has an opening 351a, and the PP gasket 353 has an opening 353a. Each of the openings 351 a and 353a forms a hydrogen gas passage 370 communicating with the hydrogen storage chamber 380. As shown in Fig. 11, a high pressure hydrogen gas storage source 371 is connected to the power port of hydrogen gas 373 through a storage passage 372. High pressure hydrogen gas can be provided to each of the hydrogen storage chambers 380 through the passage of hydrogen gas 370.
[0143] [143] An electrolyte inlet 365 and an electrolyte outlet 366 corresponding to an inlet and outlet for the electrolyte dissolved in oxygen are provided on the cap member 302, in positions spaced 180 degrees apart. Electrolyte inlet 365 and electrolyte outlet 366 communicate with notches 321, respectively. In addition, the notch 321 communicates with the gap 331 formed between the PP 351 gasket and the round tube 301. Therefore, the electrolyte that enters through the electrolyte inlet 365 circulates through cell C30 along the inner surface of the round tube 301, and then is released from the electrolyte outlet 366. As illustrated in Fig. 11, a power supply of high concentration of oxygen dissolved in electrolyte 361 is connected to the electrolyte inlet 365 through a supply 362. On the other hand, an electrolyte adjustment chamber 363 is connected to the electrolyte outlet 366 through a release passage 364. An electrolyte containing a low oxygen concentration is treated in the electrolyte adjustment chamber 363.
[0144] [144] Fig. 12 is a system diagram illustrating an electrolyte treatment process related to the C30 cell according to a fifth embodiment. The electrolyte from the electrolyte outlet 366 of the C30 cell is fed to a cooling device 326 through a duct 364a. The electrolyte heated through the use of the cell is cooled by the cooling device 326 to reach a certain temperature. Thereafter, the electrolyte is pressed by a 327 pump, and is transported to the electrolyte adjustment chamber 363 through duct 364b. Here, the water is partially and selectively removed from the electrolyte. In addition, the electrolyte receives oxygen supply from the 361 electrolyte power supply. Thus, the oxygen concentration of the electrolyte is adjusted. After that, the electrolyte is returned to cell C30 through a duct 364c.
[0145] [145] Next, the description of the functions of cell C30 will be given. As described above, the hydrogen gas provided from the hydrogen gas supply port 373 is conducted to the hydrogen storage chamber 380, so that the negative electrode 330 is charged. On the other hand, the electrolyte dissolved in high concentration oxygen from the electrolyte inlet 365 is fed from the notch 321 to the positive electrode 320, so that the positive electrode 320 is charged. When the positive electrode 320 is charged, H ₂ O is generated. This H2O is mixed into the electrolyte, and then released from electrolyte outlet 366 to the outside of cell C30.
[0146] [146] As with charging and discharging cell C1 according to the first embodiment, at the time of discharge, cell C30 according to this embodiment is discharged by the function of a secondary battery, and is chemically charged with hydrogen gas and oxygen gas. That is, the C30 cell is discharged as a secondary battery and, at the same time, it is charged with gas. Here, manganese dioxide serves as a catalyst for a positive electrode reaction. On the other hand, the hydrogen storage alloy serves as a catalyst for a reaction on the negative electrode. In addition, the C30 cell can be charged with electrical current. The hydrogen gas generated by overload can be stored in the hydrogen gas storage source 371 through the hydrogen gas passage 370 and the storage passage 372. In addition, oxygen gas can be stored in the state in which the oxygen gas dissolves in the electrolyte. In other words, the C30 cell according to this embodiment is capable of storing electrical energy by converting electrical energy into chemical energy. Unlike a conventional secondary battery, therefore, the C30 cell has no limitation on an energy storage capacity, due to an amount of active material.
[0147] [147] In C30 cells, hydrogen gas is supplied to the negative electrode. Therefore, the negative electrode is not oxidized even by discharge. Consequently, the life span of the negative electrode is not degraded because of the expansion and contraction of volume. The positive electrode is charged by oxidation using oxygen in the electrolyte dissolved in oxygen. Therefore, the positive electrode is not degraded by the discharge. <Reversible fuel cell energy efficiency>
[0148] [148] In the case where electrical energy is generated through a chemical reaction, a relationship of Δ H = Δ G + T Δ S is established, where Δ H represents the energy to be obtained from the chemicals used, Δ G represents an amount of electricity generated and T Δ S represents the heat generated.
[0149] [149] In the case where hydrogen is converted to electrical energy in a fuel cell, heat (T Δ S) occupies 17% of the chemical energy A H obtained from hydrogen. In order to decrease the amount of heat generated, electricity is generated by supplying high pressure hydrogen to the fuel cell. Thus, it is possible to restrict heat generation and increase energy generation efficiency. In the case where hydrogen is produced from electrical energy in the fuel cell, the heat (T Δ S) corresponding to 17% of the energy Δ H obtained from hydrogen is used. Here, when hydrogen and oxygen are generated at atmospheric pressure, the work is done against an atmosphere, which leads to a loss. For this reason, electrolysis is performed in an enclosed space. Thus, the heat used T Δ S can be less than 17% of the energy A H. Fig. 17 illustrates the results of thermodynamic calculation. This figure indicates that, as the pressure becomes higher, the heat T Δ S becomes lower.
[0150] [150] In this fuel cell, oxygen and hydrogen obtained by applying electrolysis to the electrolyte are stored and used under high pressure, without returning to atmospheric pressure. Thus, it is possible to achieve high energy generation efficiency η.
[0151] [151] In addition, a potential V is proportional to the free energy Δ G. That is, a relationship of V = Δ G / FM is established (here, F, Faraday coefficient, M, molecular weight). More specifically, as the potential V becomes greater, the free energy Δ G becomes greater and the energy generation efficiency η is also increased. As shown in Fig. 16, the fuel cell is almost always kept at a high potential, and maintains the high energy generation efficiency η.
[0152] [152] The terminal voltage for a fuel cell at the moment of open circuit encompasses a range of 0.8 to 1.48 V. When the discharge of the positive electrode is continued, manganese oxy hydroxide occupies almost the entire composition, and the electrolyte pressure is 0.1 MPa, so the terminal voltage becomes 0.8 V. When the positive electrode charge is continued, manganese dioxide occupies almost the entire composition, and the electrolyte pressure is greater than 10 MPa and in addition, the terminal voltage becomes 1.48 V. INDUSTRIAL APPLICABILITY
[0153] [153] The fuel cell can be properly used as an industrial energy storage device and a consumer energy storage device. REFERENCE SIGN LIST
[0154] [154] 1 Negative electrode case
[0155] [155] 2 Positive electrode case
[0156] [156] 3 Electrolyte
[0157] [157] 4 Negative electrode
[0158] [158] 5 Separator
[0159] [159] 6 Positive electrode
[0160] [160] 7 Oxygen storage chamber
[0161] [161] 8 Hydrogen storage chamber
[0162] [162] 9 Wall member
[0163] [163] 10 External housing
[0164] [164] 11 Negative electrode terminal
[0165] [165] 13 Electrolyte
[0166] [166] 14 Negative electrode
[0167] [167] 15 Separator
[0168] [168] 16 Positive electrode
[0169] [169] 17 Isolation member
[0170] [170] 18 Hydrogen storage chamber
[0171] [171] 19 Oxygen storage chamber
[0172] [172] 25 Current collecting plate
[0173] [173] 26 Coolant flow
[0174] [174] 27 Air fan
[0175] [175] 28 Hydrogen circulation port
[0176] [176] 29 Duct
[0177] [177] 30 Cooling device 30
[0178] [178] 31 Hydrogen source 31
[0179] [179] 32 Oxygen circulation port
[0180] [180] 33 Duct
[0181] [181] 34 Cooling device 34
[0182] [182] 35 Bomb
[0183] [183] 36 Electrolyte storage source
[0184] [184] 37 Agitator
[0185] [185] 38 Oxygen source
[0186] [186] 100 Outer sheath
[0187] [187] 101 Body part
[0188] [188] 102 Protruding part
[0189] [189] 103 Gasket
[0190] [190] 110 Positive electrode
[0191] [191] 120 Negative electrode
[0192] [192] 121 Hydrogen gas storage source
[0193] [193] 130 Separator
[0194] [194] 134 Current collector
[0195] [195] 135 Partition
[0196] [196] 136a, 136b Oxygen storage chamber
[0197] [197] 137 Electrolyte
[0198] [198] 138 Hydrogen storage chamber
[0199] [199] 211,212 Flange
[0200] [200] 220,221,222 Duct
[0201] [201] 230 Salt concentration adjustment device
[0202] [202] 233 Reverse osmosis membrane
[0203] [203] 250 Oxygen concentration adjustment device
[0204] [204] 251 Oxygen storage source
[0205] [205] 260 Cooling device
[0206] [206] 270 Pump
[0207] [207] 300 outer casing
[0208] [208] 301 Round tube
[0209] [209] 302 Cover member
[0210] [210] 310 Current collector
[0211] [211] 311 Nut
[0212] [212] 320 Positive electrode
[0213] [213] 321 Notch
[0214] [214] 330 Negative electrode
[0215] [215] 331 Slack
[0216] [216] 340 Separator
[0217] [217] 351, 352, 353 PP gasket
[0218] [218] 365 Electrolyte intake
[0219] [219] 361 Electrolyte power supply
[0220] [220] 363 Electrolyte adjustment chamber
[0221] [221] 364 Release passage
[0222] [222] 366 Electrolyte outlet
[0223] [223] 371 Hydrogen gas storage source
[0224] [224] 372 Hydrogen gas storage passage
[0225] [225] 373 Hydrogen gas supply port
[0226] [226] 380 Hydrogen storage chamber

权利要求:
Claims (19)
[0001]
Reversible fuel cell, characterized by the fact that it comprises: a positive electrode containing manganese dioxide; a negative electrode containing a hydrogen storage material; a separator disposed between the positive electrode and the negative electrode; an electrolyte, a hydrogen storage chamber for storing hydrogen generated from the negative electrode by electrolyte electrolyte, and an oxygen storage chamber to store oxygen generated from the positive electrode by electrolyte electrolyte, where oxygen is oxygen dissolved in the electrolyte; and where 95 to 100% of the volume of the oxygen storage chamber is filled with the electrolyte.
[0002]
Reversible fuel cell according to claim 1, characterized by the fact that the amount of oxygen that dissolves in the electrolyte is 0.02 to 24 g / L.
[0003]
Reversible fuel cell according to claim 1, characterized by the fact that an electrolyte pressure is from 0.2 MPa to 278 MPa.
[0004]
Reversible fuel cell, according to claim 1, characterized by the fact that each of the positive electrode and the negative electrode is an electrode for the generation of energy and is also an electrode for the electrolyte of the electrolyte using electric current fed to from the outside.
[0005]
Reversible fuel cell according to claim 1, characterized by the fact that the oxygen storage chamber and the hydrogen storage chamber are separated from each other by a moving element or a flexible element.
[0006]
Reversible fuel cell, according to claim 1, characterized by the fact that in a tubular case, the negative electrode formed in the tube form is disposed with a radial space interposed between the negative electrode and the tubular case, the positive electrode formed in the tube form is disposed inside the negative electrode with the separator interposed between the positive electrode and negative electrode, the hydrogen storage chamber is formed in the radial space, and the oxygen storage chamber is formed inside the positive electrode, or in a tubular case, the positive electrode formed in the tube shape is disposed with a radial space interposed between the positive electrode and the tubular case, the negative electrode formed in the tube shape is disposed inside the positive electrode with the separator interposed between the negative electrode and positive electrode, the oxygen storage chamber is formed in the radial space, and the hydrogen storage chamber is formed in the negative electrode.
[0007]
Reversible fuel cell, according to claim 6, characterized by the fact that it also comprises: a negative electrode terminal provided at an axial end of the case and electrically connected to the negative electrode; a positive electrode terminal provided at the other axial end of the outer shell and electrically connected to the positive electrode; a projection provided in one between the positive electrode terminal and the negative electrode terminal; and one recess provided in the other between the positive electrode terminal and the negative electrode terminal, in which the projection can be fitted inside the recess so that two reversible fuel cells are connected in series.
[0008]
Reversible fuel cell module, characterized by the fact that it comprises a plurality of cell units connected in series, in which each cell unit includes: a plurality of reversible fuel cells defined in claim 7; and a pair of current collecting plates provided to oppose each other in such a way that the plurality of reversible fuel cells are sandwiched between them, and the positive electrode terminal is connected to one of the current collecting plates and the negative electrode terminal is connected to the other current collecting plate, so that the reversible fuel cells are connected in parallel with the current collecting plate.
[0009]
Reversible fuel cell, according to claim 1, characterized by the fact that it also comprises: an outer covering that includes a tubular body part, and projecting parts provided in openings formed at two ends of the body part to protrude out of the openings and cover the openings; the oxygen storage chambers formed inside the protruding parts of the outer covering; and a tubular current collector housed in the outer shell in an axial direction and which has two open ends in the oxygen storage chambers, in which the positive electrode is disposed on an external periphery of the current collector, the separator covers around the positive electrode, the hydrogen storage chamber is formed between the separator and the outer shell, the negative electrode is charged in the hydrogen storage chamber, and the electrolyte is stored in the oxygen storage chambers and can be drained between the oxygen storage chambers through the current collector.
[0010]
Reversible fuel cell, according to claim 1, characterized by the fact that it also comprises: an outer shell, including a tubular body part; and a rod-shaped current collector that passes through the positive electrode, the negative electrode and the separator, where the positive electrode, the negative electrode and the separator are stacked in the axial direction of the body part and are housed in the outer shell, the positive electrode has a notch to be formed by cutting a part of an outer periphery of it, and the outer periphery of the positive electrode is in contact with an internal surface of the body part except the notch, the positive electrode is not in contact with the current collector, the negative electrode has a U-shaped section, opened in an internal circumferential direction and is in contact with the current collector, a space surrounded with the negative electrode and the current collector forms the hydrogen storage chamber, an external dimension of the negative electrode is less than an internal dimension of the body part, and an electrolyte reservoir is provided between the negative electrode and the body part to communicate with the notch, and the oxygen storage chamber includes the notch and the electrolyte reservoir.
[0011]
Reversible fuel cell system, characterized by the fact that it comprises: a reversible fuel cell defined in claim 6, 9 or 10; and an oxygen storage source and a hydrogen storage source each connected to the fuel cell, where the oxygen storage source can supply oxygen that dissolves in the electrolyte to the reversible fuel cell, and can store oxygen generated from the reversible fuel cell in a state where oxygen dissolves in the electrolyte, and the hydrogen gas storage source can supply hydrogen gas to the reversible fuel cell and can store the hydrogen gas generated from the reversible fuel cell.
[0012]
Reversible fuel cell system, characterized by the fact that it comprises: a reversible fuel cell defined in claim 6, 9 or 10; a salt concentration adjustment device connected to the reversible fuel cell to remove water contained in the electrolyte; and an oxygen concentration adjustment device connected to the reversible fuel cell to supply oxygen to the electrolyte, thereby adjusting the dissolved oxygen concentration.
[0013]
Reversible fuel cell according to claim 1, characterized by the fact that manganese dioxide serves as a catalyst for a positive electrode charge reaction, and the hydrogen storage material serves as a catalyst for a charge reaction on the negative electrode.
[0014]
Reversible fuel cell, according to claim 1, characterized by the fact that the positive electrode contains, in addition to manganese dioxide, superior manganese oxide.
[0015]
Reversible fuel cell, according to claim 1, characterized by the fact that a content of trimanganese tetraoxide (Mn ₃ O ₄ ) in the positive electrode is not more than 5% by weight relative to the weight of the positive electrode.
[0016]
Reversible fuel cell, according to claim 1, characterized by the fact that the manganese dioxide contained in the positive electrode is coated with carbon.
[0017]
Reversible fuel cell according to claim 1, characterized by the fact that the hydrogen storage material contains a hydrogen storage alloy or at least one type of metal selected from the group consisting of Sc, Ti, V , Cr, Mn, Fe, Co and Ni.
[0018]
Reversible fuel cell according to claim 1, characterized by the fact that in the negative electrode, a surface in contact with the separator contains a hydrophilic material, and a surface in contact with the hydrogen storage chamber contains a hydrophobic material.
[0019]
Reversible fuel cell according to claim 1, characterized by the fact that the oxygen storage chamber has an internal surface coated with nickel or chromium.

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法律状态:
2018-03-27| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2018-04-03| B25G| Requested change of headquarter approved|Owner name: THE UNIVERSITY OF TOKYO (JP) , EXERGY POWER SYSTEM |

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2019-08-20| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2020-04-14| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2020-06-30| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 18/12/2012, OBSERVADAS AS CONDICOES LEGAIS. |

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2020-11-10| B16C| Correction of notification of the grant|Free format text: REF. RPI 2582 DE 30/06/2020 QUANTO A QUALIFICACAO DOS TITULARES. |

优先权:

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申请号 | 申请日 | 专利标题

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JP2012-083294|2012-03-30|

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JP2012083294|2012-03-30|

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PCT/JP2012/082849|WO2013145468A1|2012-03-30|2012-12-18|Reversible fuel cell and reversible fuel cell system|

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