Charging system for flow-type metal-air battery and flow-type metal-air battery

Abstract

The invention provides a charging system for a flow-type metal-air battery and a flow-type metal-air battery, which can peel off negative electrode active material particles from a negative electrode without consuming a large amount of power and are not liable to deteriorate. A charging system for a flow-type metal-air battery includes a first layer in which a first flow path is formed, a positive electrode facing the first flow path, a second layer in which a second flow path is formed, a negative electrode facing the second flow path, a separator that separates the first flow path and the second flow path from each other, and a positive electrode liquid flowing through the first flow path. A negative electrode liquid flowing through the second flow path; and a control device that controls the flow path of the negative electrode liquid on the basis of at least one selected from the group consisting of a voltage applied between the positive electrode and the negative electrode and a liquid supply pressure of the negative electrode liquid. At least one selected from the group consisting of the flow rate of the negative electrode solution and the current flowing between the positive electrode and the negative electrode is controlled.

Description

Technical Field

[0001] This disclosure relates to a charging system for a flowable metal-air battery and a flowable metal-air battery. Background Technology

[0002] U.S. Patent No. 7,470,351 discloses a system for generating metal particles. In this system, metal particles are generated on the surface of a cathode by electrolyzing a solution containing dissolved metal.

[0003] When the formed metal particles are of sufficient size, they are removed from the surface of the cathode by a scraper or other appropriate means (paragraphs 0014 and 0057). Summary of the Invention

[0004] In the system disclosed in U.S. Patent No. 7,470,351, a scraper or other suitable means must be moved along the surface of the cathode in order to remove metal particles from the cathode surface. Therefore, the power consumption required to move the scraper or other suitable means, and the system degradation caused by moving the scraper or other suitable means along the cathode surface, become problems. For example, wear degradation of the scraper or other suitable means, wear degradation of the cathode, and system degradation due to blockage by metal particles that cannot be removed from the cathode surface become problems.

[0005] One aspect of this disclosure was made in view of this problem. The object of one aspect of this disclosure is to provide, for example, a charging system for a flow-type metal-air battery that can strip negative electrode active material particles from the negative electrode without consuming a large amount of electricity and is not easily degraded, and a flow-type metal-air battery.

[0006] The first aspect of the charging system for a flow-type metal-air battery disclosed herein includes: a first layer having a first flow path; a positive electrode facing the first flow path; a second layer having a second flow path; a negative electrode facing the second flow path; a separator separating the first flow path and the second flow path from each other; a positive electrode liquid flowing through the first flow path; and a negative electrode liquid flowing through the second flow path, and having a period in which hydrogen evolution occurs in the negative electrode.

[0007] A flow-type metal-air battery according to a second aspect of this disclosure includes: a charging system for a flow-type metal-air battery according to a first aspect of this disclosure; a discharge section for a flow-type metal-air battery; and a control device that controls at least one selected from the group consisting of the flow rate and the current based on the discharge depth of the discharge section for the flow-type metal-air battery. Attached Figure Description

[0008] Figure 1 This is a schematic diagram illustrating the flow-type metal-air battery of the first embodiment. Figure 2 This is a schematic diagram showing an exploded perspective view of the charging unit included in the flow-type metal-air battery of the first embodiment. Figure 3 This is a schematic diagram showing a cross-sectional view of the charging unit of the flow-type metal-air battery according to the first embodiment. Figure 4A This is a diagram showing an example of how the current flowing between the positive electrode and the negative electrode of the charging unit in the first and fourth embodiments of the flow-type metal-air battery changes over time. Figure 4B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the flow-type metal-air battery of the first and fourth embodiments changes over time. Figure 5 This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery of the first embodiment. Figure 6A This is a diagram illustrating an example of how the current flowing between the positive electrode and the negative electrode of a charging unit in a flow-type metal-air battery of the first embodiment and the first embodiment of the fourth embodiment changes over time. Figure 6B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the first modified example of the first embodiment and the first modified example of the fourth embodiment of the flow-type metal-air battery changes over time. Figure 7A This is a diagram illustrating an example of how the current flowing between the positive electrode and the negative electrode of the charging unit in the second and fifth embodiments of the flow-type metal-air battery changes over time. Figure 7B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid changes over time in the second flow path of the second layer of the charging unit of the flow-type metal-air battery provided in the second and fifth embodiments. Figure 8 This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery of the second embodiment. Figure 9A This is a diagram illustrating an example of how the current flowing between the positive and negative terminals of a charging unit in a flow-type metal-air battery according to the third embodiment changes over time. Figure 9B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid changes over time in the second flow path of the second layer of the charging unit of the flow-type metal-air battery according to the third embodiment. Figure 10This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery according to the third embodiment. Figure 11A This is a diagram showing an example of how the current flowing between the positive electrode and the negative electrode of the charging unit in the first variation of the third embodiment and the first variation of the sixth embodiment of the flow-type metal-air battery changes over time. Figure 11B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the first variation of the third embodiment and the first variation of the sixth embodiment changes over time. Figure 12A This is a diagram showing an example of how the current flowing between the positive electrode and the negative electrode of the charging unit in the second variation of the third embodiment and the second variation of the sixth embodiment of the flow-type metal-air battery changes over time. Figure 12B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the second variation of the third embodiment and the second variation of the sixth embodiment changes over time. Figure 13 This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery of the second variation of the third embodiment. Figure 14 This is a schematic diagram illustrating the flow-type metal-air battery of the fourth embodiment. Figure 15 This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery according to the fourth embodiment. Figure 16 This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery according to the fifth embodiment. Figure 17 This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery according to the sixth embodiment. Figure 18 This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery of the second variation of the sixth embodiment. Figure 19 This diagram shows details of the processing performed by the control unit of the flow-type metal-air battery according to the seventh embodiment. Figure 20 This diagram illustrates the processing performed by the control unit of the flow-type metal-air battery according to the seventh embodiment. Figure 21This diagram illustrates the processing performed by the control unit of the flow-type metal-air battery according to the seventh embodiment. Figure 22 This diagram illustrates the processing performed by the control unit of the flow-type metal-air battery according to the seventh embodiment. Detailed Implementation

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Furthermore, in the drawings, the same or equivalent elements are labeled with the same reference numerals, and repeated descriptions are omitted.

[0010] 1 First Implementation Method 1.1 Flow-type metal-air battery Figure 1 This is a schematic diagram illustrating the flow-type metal-air battery of the first embodiment.

[0011] Figure 1 The flow-type metal-air battery 1 of the first embodiment illustrated absorbs oxygen 11 from the air surrounding the flow-type metal-air battery 1 during discharge. During charging, the flow-type metal-air battery 1 releases oxygen 12 into the air surrounding the flow-type metal-air battery 1.

[0012] The flowing metal-air battery 1 is a flowing zinc-air battery. Therefore, the negative electrode active material in the flowing metal-air battery 1 is zinc. However, the flowing metal-air battery 1 can also be a flowing metal-air battery other than a flowing zinc-air battery. Therefore, the negative electrode active material in the flowing metal-air battery 1 can also be a metal other than zinc. Metals other than zinc include, for example, cadmium, lithium, sodium, magnesium, lead, tin, aluminum, or iron. The metal constituting the metal can consist solely of the metal as the main component, or it can consist of an alloy of the metal as the main component and secondary components. The metal can be any of metals and oxides. Which metal or oxide is the metal depends on the extent of the discharge or charging reaction.

[0013] like Figure 1 As shown, the flow-type metal-air battery 1 includes a positive electrode liquid 21, a negative electrode liquid 22, a storage section 23, a discharge section 24, a charging section 25, and a control device 26.

[0014] 1.2 Positive Electrode Liquid like Figure 1 As shown, the positive electrode liquid 21 includes a first electrolyte 31.

[0015] The first electrolyte 31 is an aqueous solution of potassium hydroxide. The first electrolyte 31 can be an aqueous solution other than potassium hydroxide aqueous solution, or an electrolyte other than an aqueous solution.

[0016] The water contained in the first electrolyte 31 is a reactant in the charging reaction that occurs in the charging section 25.

[0017] 1.3 Negative Electrode Fluid like Figure 1 As shown, the negative electrode liquid 22 includes negative electrode active material particles 41a in a reduced state, negative electrode active material particles 41b in an oxidized state, negative electrode active material ions 42, and a second electrolyte 43.

[0018] As described above, the flowing metal-air battery 1 is a flowing zinc-air battery. Therefore, the reduced-state negative electrode active material particles 41a, the oxidized-state negative electrode active material particles 41b, and the negative electrode active material ions 42 are zinc. The reduced-state negative electrode active material particles 41a are metallic zinc (Zn) particles, and the oxidized-state negative electrode active material particles 41b are zinc oxide (ZnO) particles. The reduced-state and oxidized-state negative electrode active material particles 41a and 41b are dispersed in the second electrolyte 43. Therefore, the negative electrode liquid 22 has a slurry-like consistency. The reduced-state negative electrode active material particles 41a, for example, have a particle size of several μm, and the oxidized-state negative electrode active material particles 41b, for example, have a particle size of tens to hundreds of nm. The negative electrode active material ions 42 are zinc oxide ions (Zn(OH)4). 2- ), and dissolved in the second electrolyte 43.

[0019] The second electrolyte 43 is an aqueous solution of potassium hydroxide. The second electrolyte 43 can be an aqueous solution other than potassium hydroxide, or an electrolyte other than an aqueous solution.

[0020] The negative electrode active material ions 42 are reactants in the charging reaction that occurs in the charging section 25. The reduced negative electrode active material particles 41a are products of the charging reaction that occurs in the charging section 25.

[0021] 1.4 Storage Department The storage section 23 stores the negative electrode solution 22. The storage section 23 is formed with an outlet 23a, an inlet 23b, an outlet 23c, and an inlet 23d. Outlets 23a and 23c allow the negative electrode solution 22 to flow out. Inlets 23b and 23d allow the negative electrode solution 22 to flow in.

[0022] 1.5 Discharge Section The discharge section 24 absorbs oxygen 11 from the air surrounding it. Negative electrode liquid 22 flows into the discharge section 24 from the storage section 23. The discharge section 24 causes the absorbed oxygen 11 and the flowing-in negative electrode liquid 22 to participate in a discharge reaction that generates electrical discharge, causing the negative electrode liquid 22 involved in the discharge reaction to flow out of the storage section 23. The discharge section 24 also causes the oxygen 11 and the reduced-state negative electrode active material particles 41a contained in the negative electrode liquid 22 to participate in the discharge reaction, causing the reduced-state negative electrode active material particles 41a to disappear and generating negative electrode active material ions 42.

[0023] like Figure 1 As shown, the discharge unit 24 includes piping 51, pump 52, piping 53, discharge unit 54, and piping 55.

[0024] Piping 51 guides the negative electrode liquid 22 from the outlet 23a of the storage section 23 to the inlet 52a of the pump 52. Thus, piping 51 causes the negative electrode liquid 22 flowing out of the outlet 23a to flow into the inlet 52a.

[0025] Pump 52 causes the negative electrode liquid 22 flowing into the inlet 52a of pump 52 to flow out from the outlet 52b of pump 52. Pump 52 generates the flow of negative electrode liquid 22 at this time. Thus, pump 52 delivers negative electrode liquid 22 from storage section 23 to discharge unit 54.

[0026] Piping 53 guides the negative electrode liquid 22 from the outlet 52b of pump 52 to the inlet 54a of discharge unit 54. Thus, piping 53 causes the negative electrode liquid 22 flowing out of outlet 52b to flow into inlet 54a.

[0027] The discharge unit 54 absorbs oxygen 11 from the air surrounding it. The discharge unit 54 causes the negative electrode liquid 22 flowing into its inlet 54a to flow out from its outlet 54b. During this process, the absorbed oxygen 11 and the flowing negative electrode liquid 22 participate in a discharge reaction, and the negative electrode liquid 22 participating in the discharge reaction flows out from its outlet 54b. The discharge unit 54 outputs discharge electricity generated by the discharge reaction.

[0028] Piping 55 guides the negative electrode liquid 22 from the outlet 54b of the discharge unit 54 to the inlet 23b of the storage section 23. Thus, piping 55 causes the negative electrode liquid 22 flowing out of the outlet 54b to flow into the inlet 23b.

[0029] 1.6 Discharge Unit like Figure 1 As shown, the discharge unit 54 includes a layer 61, a negative electrode liquid 62, a positive electrode 63, a separator 64, and a negative electrode 65.

[0030] A flow path 61a is formed in layer 61. The flow path 61a extends from the inlet 54a of the discharge cell 54 to the outlet 54b of the discharge cell 54. Therefore, the flow path 61a allows the negative electrode liquid 22 flowing into the inlet 54a to pass through and allows the passed negative electrode liquid 22 to flow out from the outlet 54b.

[0031] The negative electrode liquid 62 flows in the flow path 61a of the layer 61. The negative electrode liquid 62 is part of the negative electrode liquid 22 in the flow-type metal-air battery 1.

[0032] The positive electrode 63 comes into contact with the air surrounding the discharge unit 54. As a result, oxygen 11 contained in the air surrounding the discharge unit 54 is supplied to the positive electrode 63. As a result, an oxygen reduction reaction represented by formula (1) occurs in the positive electrode 63.

[0033] O2 + 2H2O + 4e - →4OH - (1)

[0034] The positive electrode 63 faces the flow path 61a of the layer 61 through the separator 64. Thus, the positive electrode 63 transfers the product of the oxygen reduction reaction, represented by equation (1), OH to the negative electrode liquid 62 flowing through the flow path 61a via the separator 64. - .

[0035] The negative electrode 65 faces the flow path 61a of the layer 61. Thus, the negative electrode 65 comes into contact with the negative electrode liquid 62 flowing through the flow path 61a. Thus, in the negative electrode 65, the oxidation reaction of metallic zinc, represented by equations (2) and (3), occurs.

[0036] Zn + 4OH - →Zn(OH)4 2- +2e - (2) Zn(OH)4 2- →ZnO + H₂O + 2OH⁻ - (3)

[0037] Through the reduction reaction of oxygen in the positive electrode 63 and the oxidation reaction of metallic zinc in the negative electrode 65, all the reactions represented by equation (4) occur in the discharge unit 54.

[0038] 2Zn + O2 → 2ZnO (4)

[0039] Therefore, the discharge unit 54 discharges when metallic zinc changes into zinc oxide.

[0040] 1.7 The negative electrode liquid 22 flows from the storage section 23 into the charging section 25. The charging section 25 causes the incoming negative electrode liquid 22 to participate in the charging reaction of regenerating the negative electrode liquid 22, and causes the negative electrode liquid 22 participating in the charging reaction to flow out into the storage section 23. The charging section 25 causes the negative electrode active material ions 42 contained in the negative electrode liquid 22 to participate in the charging reaction, causing the negative electrode active material ions 42 to disappear and generating negative electrode active material particles 41a in a reduced state.

[0041] like Figure 1 As shown, the charging unit 25 includes piping 71, pump 72, piping 73, piping 74, pump 75, piping 76, power supply 77, charging unit 78, piping 79 and piping 80.

[0042] Piping 71 directs the positive electrode liquid 21 from the supply source of the positive electrode liquid 21 (not shown) to the inlet 72a of the pump 72. Thus, piping 71 allows the positive electrode liquid 21 flowing out from the supply source of the positive electrode liquid 21 to flow into the inlet 72a.

[0043] Pump 72 causes the positive electrode liquid 21 flowing into the inlet 72a of pump 72 to flow out from the outlet 72b of pump 72. In this process, pump 72 generates the flow of positive electrode liquid 21. Thus, pump 72 delivers positive electrode liquid 21 from the supply source of positive electrode liquid 21 to charging unit 78.

[0044] Piping 73 guides the positive electrode liquid 21 from the outlet 72b of pump 72 to the inlet 78a of charging unit 78. Thus, piping 73 allows the positive electrode liquid 21 flowing out of outlet 72b to flow into inlet 78a.

[0045] Piping 74 guides the negative electrode liquid 22 from the outlet 23c of the storage section 23 to the inlet 75a of the pump 75. Thus, piping 74 allows the negative electrode liquid 22 flowing out of the outlet 23c to flow into the inlet 75a.

[0046] Pump 75 causes the negative electrode liquid 22 flowing into the inlet 75a of pump 75 to flow out from the outlet 75b of pump 75. Pump 75 generates the flow of negative electrode liquid 22 at this time. Thus, pump 75 delivers negative electrode liquid 22 from storage section 23 to charging unit 78. The outflow and inflow directions of pump 75 can also be changed to reverse the flow.

[0047] Piping 76 guides the negative electrode liquid 22 from the outlet 75b of the pump 75 to the inlet 78b of the charging unit 78. Thus, piping 76 allows the negative electrode liquid 22 flowing out of the outlet 75b to flow into the inlet 78b.

[0048] Power supply 77 inputs charging power to charging unit 78.

[0049] The charging unit 78 causes the positive electrode liquid 21 flowing into the inlet 78a of the charging unit 78 to flow out from the outlet 78c of the charging unit 78, and causes the negative electrode liquid 22 flowing into the inlet 78b of the charging unit 78 to flow out from the outlet 78d of the charging unit 78. During this process, the charging unit 78 involves the incoming positive electrode liquid 21 and negative electrode liquid 22 in the charging reaction generated by the charging power, causing the positive electrode liquid 21 participating in the charging reaction to flow out from the outlet 78c, and the negative electrode liquid 22 participating in the charging reaction to flow out from the outlet 78d, while discharging the oxygen 12 generated by the charging reaction into the air surrounding the charging unit 78.

[0050] Pipe 79 guides the positive electrode liquid 21 from the outlet 78c of the charging unit 78 to the supply source of the positive electrode liquid 21. Thus, pipe 79 causes the positive electrode liquid 21 flowing out of the outlet 78c to flow into the supply source of the positive electrode liquid 21.

[0051] Piping 80 guides the negative electrode liquid 22 from the outlet 78d of the charging unit 78 to the inlet 23d of the storage section 23. Thus, piping 80 allows the negative electrode liquid 22 flowing out of the outlet 78d to flow into the inlet 23d.

[0052] 1.8 charging unit Figure 2 This is an exploded perspective view schematically illustrating the charging unit of the flow-type metal-air battery according to the first embodiment. Figure 3 This is a schematic cross-sectional view showing the charging unit of the flow-type metal-air battery according to the first embodiment.

[0053] like Figure 2 and Figure 3 As shown, the charging unit 78 includes: a first layer 91, a positive electrode liquid 92, a positive electrode 93, a power board 94, a pad 95, a second layer 96, a negative electrode liquid 97, a negative electrode 98, a power board 99, a pad 100, a separator 101, a pad 102, and a pad 103.

[0054] The first layer 91 has a rectangular frame shape. Therefore, the first layer 91 has an opening surface 91p, an opening surface 91q, an end surface 91a, and an end surface 91c. The opening surfaces 91p and 91q are located on opposite sides of each other. The end surfaces 91a and 91c are located on opposite sides of each other. The first layer 91 may also have a frame shape other than a rectangular frame shape.

[0055] A first flow path 91e is formed on the first layer 91.

[0056] The first flow path 91e of the first layer 91 is exposed at the opening surface 91p and the opening surface 91q, and the opening surface 91p and the opening surface 91q have openings 91pe and 91qe respectively.

[0057] The first flow path 91e of the first layer 91 is exposed at end faces 91a and 91c, and each end face 91a and 91c has an inlet 78a and an outlet 78c, respectively. Therefore, the first flow path 91e extends from the inlet 78a to the outlet 78c. Thus, the first flow path 91e allows the positive electrode liquid 92 flowing into the inlet 78a to pass through, and allows the passed positive electrode liquid 21 to flow out from the outlet 78c.

[0058] The inlet 78a and outlet 78c of the charging unit 78 are respectively disposed on the lower side and the upper side. Therefore, the first flow path 91e of the first layer 91 guides the positive electrode liquid 92 from the lower side to the upper side. The inlet 78a can be disposed in a position other than the lower side, and the outlet 78c can also be disposed in a position other than the upper side.

[0059] The positive electrode liquid 92 flows in the first flow path 91e of the first layer 91. The positive electrode liquid 92 is a part of the positive electrode liquid 21. As described above, the inlet 78a and outlet 78c of the charging unit 78 are respectively disposed on the lower side and the upper side. Therefore, the flow direction of the positive electrode liquid 92 in the first flow path 91e is from the lower side to the upper side.

[0060] When the flow direction of the positive electrode liquid 92 is from top to bottom, the positive electrode liquid 92 will flow down the first flow path 91e before it is completely filled. Therefore, it is possible that the first flow path 91e may not be completely filled with the positive electrode liquid 92. Conversely, when the flow direction of the positive electrode liquid 92 is from bottom to top, the positive electrode liquid 92 overflows from the first flow path 91e after it is completely filled. Therefore, the first flow path 91e can be completely filled with the positive electrode liquid 92.

[0061] The oxygen 12 generated in the positive electrode 93 moves not only from bottom to top due to buoyancy, but also from bottom to top with the flow of the positive electrode liquid 92. This facilitates the discharge of oxygen 12 from the charging unit 78.

[0062] The positive electrode 93 has a rectangular plate shape. The positive electrode 93 is disposed on the opening surface 91p of the first layer 91. Thus, the positive electrode 93 closes the opening 91pe of the first layer 91 and faces the first flow path 91e of the first layer 91. Thus, the positive electrode 93 comes into contact with the positive electrode liquid 92 flowing to the first flow path 91e. Thus, the oxidation reaction of water represented by formula (5) occurs in the positive electrode 93.

[0063] 4OH - →O2 + 2H2O + 4e - (5)

[0064] Therefore, the charging unit 78 generates oxygen 12 through the oxidation reaction of water in the positive electrode 93. The generated oxygen 12 is discharged from the charging unit 78.

[0065] The positive electrode 93 is composed of metals, spinel-based conductive oxides, perovskite-based conductive oxides, etc. The metals include foamed nickel. The spinel-based conductive oxides contain nickel, cobalt, etc.

[0066] The energizing plate 94 has a rectangular plate shape. The energizing plate 94 is disposed overlapping the positive electrode 93 on the opening surface 91p of the first layer 91. Thus, the energizing plate 94 is in contact with the positive electrode 93, forming an energizing path to the positive electrode 93.

[0067] The gasket 95 is sandwiched between the opening surface 91p of the first layer 91 and the positive electrode 93 and the energized plate 94, thus liquid-tightly sealing the opening surface 91p of the first layer 91 with the positive electrode 93 and the energized plate 94.

[0068] The second layer 96 has a rectangular frame shape. Therefore, the second layer 96 has an opening surface 96p, an opening surface 96q, an end surface 96b, and an end surface 96d. The opening surfaces 96p and 96q are located on opposite sides. The end surfaces 96b and 96d are located on opposite sides.

[0069] A second flow path 96e is formed on the second layer 96.

[0070] The second flow path 96e of the second layer 96 is exposed at the opening surface 96p and the opening surface 96q, and the opening surface 96p and the opening surface 96q have openings 96pe and 96qe respectively.

[0071] The second flow path 96e of the second layer 96 is exposed at end faces 96b and 96d, and each end face 96b and end face 96d has an inlet 78b and an outlet 78d, respectively. Therefore, the second flow path 96e extends from the inlet 78b to the outlet 78d. Thus, the second flow path 96e allows the negative electrode liquid 97 flowing into the inlet 78b to pass through, and allows the passed negative electrode liquid 97 to flow out from the outlet 78d.

[0072] The inlet 78b and outlet 78d of the charging unit 78 are respectively located on the lower side and the upper side. Therefore, the second flow path 96e of the second layer 96 guides the negative electrode liquid 97 from the lower side to the upper side.

[0073] The negative electrode liquid 97 flows in the second flow path 96e of the second layer 96. The negative electrode liquid 97 is a part of the negative electrode liquid 22. As described above, the inlet 78b and outlet 78d of the charging unit 78 are respectively disposed on the lower side and the upper side. Therefore, the flow direction of the negative electrode liquid 97 in the second flow path 96e is from the lower side to the upper side.

[0074] When the flow direction of the negative electrode liquid 97 is from top to bottom, the negative electrode liquid 97 will flow down the second flow path 96e even before it is completely filled. Therefore, it is possible that the second flow path 96e cannot be completely filled with the negative electrode liquid 97. Conversely, when the flow direction of the negative electrode liquid 97 is from bottom to top, the negative electrode liquid 97 overflows from the second flow path 96e after it is completely filled. Therefore, the second flow path 96e can be completely filled with the negative electrode liquid 97.

[0075] The negative electrode 98 has a rectangular plate shape. The negative electrode 98 is disposed on the opening surface 96p of the second layer 96. Thus, the negative electrode 98 blocks the opening 96pe of the second layer 96 and faces the second flow path 96e of the second layer 96. Thus, the negative electrode 98 comes into contact with the negative electrode liquid 97 in the second flow path 96e. Thus, the negative electrode 98 is supplied with zinc oxide ions Zn(OH)4 generated by the oxidation reaction of metallic zinc represented by formulas (2) and (3). 2- And / or zinc oxide (ZnO) as the negative electrode solution. Thus, in the negative electrode 98, a reduction reaction to metallic zinc occurs as represented by formulas (6) and (7).

[0076] ZnO + H₂O + 2OH⁻ - →Zn(OH)4 2- (6) Zn(OH)4 2- -+2e - →Zn+4OH - (7)

[0077] Therefore, the charging unit 78 generates reduced negative electrode active material particles 41a through the reduction reaction of zinc in the negative electrode 98. The generated reduced negative electrode active material particles 41a adhere to the negative electrode 98.

[0078] The negative electrode 98 is made of conductive material. The conductive material is composed of carbon material and resin.

[0079] The energizing plate 99 has a rectangular plate shape. The energizing plate 99 is disposed overlapping the negative electrode 98 on the opening surface 96p of the second layer 96. Thus, the energizing plate 99 is in contact with the negative electrode 98, forming an energizing path to the negative electrode 98.

[0080] The gasket 100 is sandwiched between the opening 96p of the second layer 96 and the negative electrode 98 and the energized plate 99, thereby liquid-tightly sealing the opening 96p of the second layer 96 with the negative electrode 98 and the energized plate 99.

[0081] The separator 101 has a sheet-like shape. The separator 101 is flexible. The separator 101 is disposed on the opening surface 91q of the first layer 91. Thus, the separator 101 closes the opening 91qe of the first layer 91, facing the first flow path 91e of the first layer 91. Furthermore, the separator 101 is disposed on the opening surface 96q of the second layer 96. Thus, the separator 101 closes the opening 96qe of the second layer 96, facing the second flow path 96e of the second layer 96.

[0082] The separator 101 is sandwiched between the first layer 91 and the second layer 96. Thus, the separator 101 separates the first flow path 91e of the first layer 91 from the second flow path 96e of the second layer 96. The separator 101 does not allow reduced-state negative electrode active material particles 41a and oxidized-state negative electrode active material particles 41b to pass through. Therefore, the separator 101 inhibits the movement of reduced-state negative electrode active material particles 41a and oxidized-state negative electrode active material particles 41b from the negative electrode liquid 97 to the positive electrode liquid 92.

[0083] The separator 101 has high ionic conductivity. Therefore, the separator 101 allows hydroxide ions (OH-) to pass through it. - Therefore, the hydroxide ion OH - It can move from negative electrode liquid 97 to positive electrode liquid 92.

[0084] In the reduction reaction to metallic zinc in the negative electrode 98, i.e., the electrodeposition reaction of metallic zinc, dendritic zinc grows from the negative electrode 98 due to the non-uniformity of current distribution. The separator 101 has high dendrite resistance. Therefore, the separator 101 prevents dendritic zinc from growing beyond the separator 101. This suppresses short circuits between the positive electrode 93 and the negative electrode 98 via the dendritic zinc.

[0085] The gasket 102 is sandwiched between the opening surface 91q of the first layer 91 and the separator 101, thereby liquid-tightly sealing the opening surface 91q of the first layer 91 and the separator 101.

[0086] The gasket 103 is sandwiched between the opening surface 96q of the second layer 96 and the separator 101, thereby liquid-tightly sealing the opening surface 96q of the second layer 96 and the separator 101.

[0087] 1.9 Theoretical Voltage of Flow-Type Metal-Air Batteries Through the oxidation reaction of water in the positive electrode 93 and the reduction reaction to metallic zinc in the negative electrode 98, the total reaction represented by equation (8) occurs in the charging unit 78.

[0088] 2ZnO→2Zn+O2 (8)

[0089] Therefore, the charging unit 78 converts zinc oxide into metallic zinc during charging.

[0090] During the discharge and charging reactions, the potentials of the positive and negative electrodes, relative to the standard hydrogen electrode, are -1.25V and 0.40V, respectively. Therefore, the theoretical voltage of the flow-type metal-air battery 1 is 1.65V.

[0091] 1.10 Control Device like Figure 1 As shown, the control device 26 includes a voltage measuring unit 111 and a control unit 112. The charging unit 25 and the control device 26 constitute a charging system.

[0092] Power supply 77 causes current I to flow between positive terminal 93 and negative terminal 98.

[0093] The voltage measuring unit 111 measures the voltage V between the positive terminal 93 and the negative terminal 98. When performing the measurement, it is not necessary to directly measure between the positive terminal 93 and the negative terminal 98; the measurement can be performed using a current-carrying plate that is approximately at the same potential as each terminal.

[0094] The control unit 112 controls the pump 75 and the flow rate VL of the negative electrode liquid 22 in the second flow path 96e of the second layer 96. In addition, the control unit 112 controls the power supply 77 and the current I flowing between the positive electrode 93 and the negative electrode 98.

[0095] The control unit 112 controls the flow rate VL based on the voltage V.

[0096] The control unit 112 includes a microcontroller and peripheral circuitry. The microcontroller includes a processor and memory. The processor executes a program stored in memory to cause the microcontroller and peripheral circuitry to function as the control unit 112. All or part of the processing performed by the microcontroller can be executed by dedicated electronic circuitry.

[0097] 1.11 Control of current value and flow rate Figure 4A This is a diagram showing an example of how the current flowing between the positive and negative terminals of a charging unit in a flow-type metal-air battery according to the first embodiment changes over time. Figure 4B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the flow-type metal-air battery of the first embodiment changes over time.

[0098] exist Figure 4A In the diagram, the horizontal axis represents time T, and the vertical axis represents current I. Figure 4B In the diagram, the horizontal axis represents time T, and the vertical axis represents flow velocity VL.

[0099] like Figure 4A As shown, the control unit 112 maintains the current I at a constant current I1. Therefore, the control unit 112 sets the current I to a constant current I1 during the period T0 to T4.

[0100] In addition, such as Figure 4B As shown, the control unit 112 switches the flow rate VL between a first flow rate VL1 and a second flow rate VL2. Therefore, during periods T0 to T1, the control unit 112 sets the flow rate VL to the first flow rate VL1; during periods T1 to T2, it sets the flow rate VL to the second flow rate VL2; during periods T2 to T3, it sets the flow rate VL to the first flow rate VL1; and during periods T3 to T4, it sets the flow rate VL to the second flow rate VL2. The second flow rate VL2 is slower than the first flow rate VL1.

[0101] The first flow rate VL1 is such that the amount of negative electrode active material ions 42 supplied to the negative electrode 98 becomes sufficient, and a reduction reaction occurs in the negative electrode 98 where the negative electrode active material ions 42 are reduced to the negative electrode active material particles 41a in a reduced state. However, no hydrogen evolution reaction, which competes with the reduction reaction, occurs in the negative electrode 98. The second flow rate VL2 is such that the amount of negative electrode active material ions 42 supplied to the negative electrode 98 becomes insufficient, and no reduction reaction occurs in the negative electrode 98, but a hydrogen evolution reaction occurs in the negative electrode 98.

[0102] Hydrogen gas produced by the hydrogen evolution reaction adheres to the reduced-state negative electrode active material particles 41a. As a result, the buoyancy acting on the reduced-state negative electrode active material particles 41a increases. Consequently, the force acting on the reduced-state negative electrode active material particles 41a increases.

[0103] Furthermore, the hydrogen gas generated by the hydrogen evolution reaction increases the internal pressure of the second flow path 96e in the second layer 96. As a result, the flow rate of the negative electrode liquid 97 in the second flow path 96e locally increases. Consequently, the force acting on the reduced-state negative electrode active material particles 41a increases.

[0104] Therefore, in the event of a hydrogen evolution reaction, the reduced-state negative electrode active material particles 41a are easily stripped from the negative electrode 98 and discharged from the charging unit 78. If a hydrogen sensor of the electrode method, semiconductor type, thermoelectric type, etc., intermittently detects hydrogen gas for a period of 10 seconds or more in the storage section 23 or the outlet 78d of the charging unit 78, it can be considered that a period of hydrogen evolution is occurring in the negative electrode. For example, a hydrogen sensor for alkaline water electrolysis that can be inserted between the discharge paths can be used. The hydrogen sensor is placed in the path of the outlet 78d of the charging unit 78 and the piping 80 for measurement.

[0105] However, the electricity used for the hydrogen evolution reaction is not used for the reduction reaction. Therefore, when the hydrogen evolution reaction occurs, the charging efficiency, which represents the ratio of the electricity consumed by the reduction reaction to the electricity consumed by the charging unit 25, becomes lower. Therefore, the hydrogen evolution reaction is suppressed to a minimum necessary level, which is the minimum necessary level required to strip the reduced state negative electrode active material particles 41a from the negative electrode 98 and discharge the stripped reduced state negative electrode active material particles 41a from the charging unit 78.

[0106] During the hydrogen evolution reaction, from T1 to T2 and from T3 to T4, the voltage V increases as the hydrogen evolution reaction proceeds and also increases over time.

[0107] Based on the voltage V, the control unit 112 controls the timing T2 and timing T4 for switching the flow rate VL from the second flow rate VL2 to the first flow rate VL1. Therefore, based on the voltage V, the control unit 112 varies the lengths of the periods T1-T2 and T3-T4 during the hydrogen evolution reaction. This allows the hydrogen evolution reaction to be suppressed to a minimum necessary level, which is the minimum necessary level required to strip the reduced-state negative electrode active material particles 41a from the negative electrode 98 and discharge the stripped reduced-state negative electrode active material particles 41a from the charging unit 78. This improves charging efficiency.

[0108] In response to the rise rate ΔV of voltage V becoming greater than the set rise rate ΔVs, the control unit 112 switches the flow rate VL from the second flow rate VL2 to the first flow rate VL1.

[0109] During the hydrogen evolution reaction periods T1–T2 and T3–T4, the voltage V strongly depends on the current I, but the rate of rise of the voltage V, ΔV, does not strongly depend on the current I. Therefore, the flow rate VL is switched not in response to the voltage V becoming greater than a set voltage, but in response to the rate of rise of the voltage V, ΔV, becoming greater than a set rate of rise, ΔVs. This ensures that the timing T2 and T4 for switching the flow rate VL are appropriate, regardless of the current I.

[0110] When the durations of the hydrogen evolution reaction (T1-T2 and T3-T4) are longer than appropriate, the amount of hydrogen generated by the reaction is greater than appropriate. Therefore, the generated hydrogen remains in the second flow path 96e of the second layer 96. This results in an abnormal voltage (V) due to dry burning. Conversely, when the durations of the hydrogen evolution reaction (T1-T2 and T3-T4) are shorter than appropriate, the amount of hydrogen generated is less than appropriate. Therefore, it is difficult to strip the reduced-state negative electrode active material particles 41a from the negative electrode 98 and discharge them from the charging unit 78. This can cause the second flow path 96e to become blocked by the reduced-state negative electrode active material particles 41a. Therefore, the time rise rate ΔVs, set by comparing it with the time rise rate ΔV of the voltage V, is set such that the durations of the hydrogen evolution reaction (T1-T2 and T3-T4) are appropriate, for example, 1.35V / s.

[0111] In the first embodiment, the current I is maintained at a constant current I1 during the period T0 to T4. However, during the period T0 to T4, the current I can also be varied within a range above a specific current. Furthermore, in the first embodiment, the flow velocity VL is maintained at a constant first flow velocity VL1 during the periods T0 to T1 and T2 to T3, and at a constant second flow velocity VL2 during the periods T1 to T2 and T3 to T4. However, the flow velocity VL can be varied within a range above the first flow velocity VL1 during the periods T0 to T1 and T2 to T3, or it can be varied within a range below the second flow velocity VL2 during the periods T1 to T2 and T3 to T4.

[0112] In the first embodiment, the charging system includes a charging unit 78. However, the charging system may also include a stack comprising multiple charging units 78 connected in series. When the charging system has a stack, the voltage measurement unit 111 measures the overall voltage V of the stack and returns the value of voltage V / n, obtained by dividing the measured voltage V by the number n of the multiple charging units 78. Based on the value of voltage V / n, the control unit 112 controls timing T2 and timing T4 for switching the flow rate VL from the second flow rate VL2 to the first flow rate VL1.

[0113] 1.12 Processing Flow Figure 5 This is a flowchart illustrating the processing flow performed by the control unit of the flow-type metal-air battery of the first embodiment.

[0114] Control Unit 112 Execution Figure 5 Steps S101 to S104 are shown.

[0115] In step S101, the control unit 112 sets the flow rate VL to a first flow rate VL1. This ensures that the amount of negative electrode active material ions 42 supplied to the negative electrode 98 becomes sufficient. Consequently, a reduction reaction occurs in the negative electrode 98 where the negative electrode active material ions 42 reduce the negative electrode active material particles 41a to a reduced state. As a result, the reduced negative electrode active material particles 41a attach to the negative electrode 98 and grow.

[0116] In the next step S102, the control unit 112 determines whether the time t elapsed after the flow velocity VL reaches the first flow velocity VL1 is longer than the set time ts. If the control unit 112 determines that the time t is longer than the set time ts, it executes step S103. If the control unit 112 determines that the time t is shorter than the set time ts, it executes step S101.

[0117] Through steps S101 and S102, the flow rate VL remains at the first flow rate VL1 until a set time ts elapses. Furthermore, the state of the flow rate VL being at the first flow rate VL1 ends synchronously with the set time ts elapsed after the flow rate VL reaches the first flow rate VL1.

[0118] In step S103, the control unit 112 sets the flow rate VL to a second flow rate VL2. As a result, the amount of negative electrode active material ions 42 supplied to the negative electrode 98 becomes insufficient. Consequently, a hydrogen evolution reaction occurs in the negative electrode 98. As a result, the reduced-state negative electrode active material particles 41a attached to the negative electrode 98 are stripped away.

[0119] In the next step S104, the control unit 112 determines whether the rate of rise of voltage V ΔV is greater than a set rate of rise ΔVs. If the control unit 112 determines that the rate of rise of voltage V ΔV is greater than the set rate of rise ΔVs, it executes step S101. If the control unit 112 determines that the rate of rise of voltage V ΔV is less than the set rate of rise ΔVs, it executes step S103.

[0120] Through steps S103 and S104, the flow rate VL remains at the second flow rate VL2 until the rate of increase of voltage V ΔV reaches the set rate of increase ΔVs. Furthermore, the state of flow rate VL being at the second flow rate VL2 ends synchronously with the rate of increase of voltage V ΔV reaching the set rate of increase ΔVs.

[0121] From steps S101 to S104, the flow rate VL switches between a first flow rate VL1 and a second flow rate VL2. Furthermore, the time during which the flow rate VL is at the first flow rate VL1 is a set time ts. Conversely, the time during which the flow rate VL is at the second flow rate VL2 is a variable time, varying according to the progress of the hydrogen evolution reaction.

[0122] 1.13 Variation Example Figure 6A This is a diagram showing an example of how the current flowing between the positive electrode and the negative electrode of the charging unit in a first variation of the first embodiment of the flow-type metal-air battery changes over time. Figure 6B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the first modified example of the first embodiment of the flow-type metal-air battery changes over time.

[0123] exist Figure 6A In the diagram, the horizontal axis represents time T, and the vertical axis represents current I. Figure 6B In the diagram, the horizontal axis represents time T, and the vertical axis represents flow velocity VL.

[0124] In the first embodiment, such as Figure 4B As shown, the second flow rate VL2 is greater than 0. Therefore, even during the period when the flow rate VL is the second flow rate VL2, the control unit 112 keeps the pump 75 in the open state, causing the pump 75 to generate the flow of negative electrode liquid 22.

[0125] In contrast, in a first variation of the first embodiment, such as Figure 6B As shown, the second flow rate VL2 is 0. A flow rate within ±0.5 for 5.0 seconds is considered 0. Therefore, during the period when the flow rate VL is the second flow rate VL2, the control unit 112 keeps the pump 75 in a closed state, preventing the pump 75 from generating the negative electrode liquid 22. Thus, the control unit 112 switches the flow rate VL between the first flow rate VL1 and the second flow rate VL2 by switching the state of the pump 75 between the open and closed states. When the second flow rate VL2 is 0, compared to when the second flow rate VL2 is greater than 0, the lengths of the hydrogen evolution reaction periods T1-T2 and T3-T4 can be shortened, reducing the power consumed by the pump 75 and other auxiliary equipment. The flow rate of the pump 75 depends on the voltage input to the pump 75; the microcomputer sends signals to control VL1, VL2, and 0 (pump off). Therefore, by monitoring the voltage on the input side of the pump 75, if the voltage on that input side is 0V, the flow rate can be considered 0. Regarding exceeding the threshold, as long as it exceeds the threshold by only 0.01 seconds within a period of 0.01 seconds, it is considered to have exceeded the threshold.

[0126] 2. Second Implementation Method The differences between the second embodiment and the first embodiment will be explained below. Regarding the parts not described, the second embodiment also employs the same configuration as the first embodiment.

[0127] In the second embodiment, the control unit 112 controls the current I based on the voltage V.

[0128] Figure 7AThis is a diagram showing an example of how the current flowing between the positive and negative terminals of a charging unit in a flow-type metal-air battery according to the second embodiment changes over time. Figure 7B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the flow-type metal-air battery of the second embodiment changes over time.

[0129] exist Figure 7A In the diagram, the horizontal axis represents time T, and the vertical axis represents current I. Figure 7B In the diagram, the horizontal axis represents time T, and the vertical axis represents flow velocity VL.

[0130] In the second embodiment, such as Figure 7A As shown, the control unit 112 switches the current I between a first current I1 and a second current I2. Therefore, the control unit 112 sets the current I to the first current I1 during the period T0 to T1, sets the current I to the second current I2 during the period T1 to T2, sets the current I to the first current I1 during the period T2 to T3, and sets the current I to the second current I2 during the period T3 to T4. The second current I2 is greater than the first current I1.

[0131] In addition, such as Figure 7B As shown, the control unit 112 maintains the flow velocity VL at a constant flow velocity VL1. Therefore, the control unit 112 maintains the flow velocity VL at a constant flow velocity VL1 during the period T0 to T4.

[0132] The first current I1 is less than the current Ih at which the hydrogen evolution reaction begins, and it is the current at which the reduction reaction of the negative electrode active material ions 42 to the reduced state of the negative electrode active material particles 41a occurs in the negative electrode 98, but the hydrogen evolution reaction, which competes with the reduction reaction, does not occur in the negative electrode 98. The second current I2 is greater than the current Ih, and it is the current at which the hydrogen evolution reaction occurs in the negative electrode 98 without the reduction reaction.

[0133] The control unit 112 controls the timing T2 and timing T4 for switching the current I from the second current I2 to the first current I1 based on the voltage V. Therefore, the control unit 112, based on the voltage V, changes the lengths of the periods T1-T2 and T3-T4 during the hydrogen evolution reaction. This allows the hydrogen evolution reaction to be suppressed to a minimum necessary level, which is the minimum necessary level required to strip the reduced-state negative electrode active material particles 41a from the negative electrode 98 and discharge the stripped reduced-state negative electrode active material particles 41a from the charging unit 78. This improves charging efficiency.

[0134] For example, in response to the rise rate ΔV of voltage V becoming greater than the set rise rate ΔVs, control unit 112 switches current I from second current I2 to first current I1.

[0135] Figure 8 This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery of the second embodiment.

[0136] In the second embodiment, the control unit 112 performs... Figure 8 Steps S111 to S114 are shown.

[0137] In step S111, the control unit 112 sets the current I to a first current I1. As a result, a reduction reaction occurs in the negative electrode 98 where the negative electrode active material ions 42 are reduced to the reduced state negative electrode active material particles 41a. Consequently, the reduced state negative electrode active material particles 41a attach to the negative electrode 98 and grow.

[0138] In the next step S112, the control unit 112 determines whether the time t elapsed since the current I became the first current I1 is longer than the set time ts. If the control unit 112 determines that the time t is longer than the set time ts, it executes step S113. If the control unit 112 determines that the time t is shorter than the set time ts, it executes step S111.

[0139] Through steps S111 and S112, the state in which the current I is the first current I1 continues until a set time ts elapses. Furthermore, the state in which the current I is the first current I1 ends synchronously with the elapsed time ts from the time I becomes the first current I1.

[0140] In step S113, the control unit 112 sets the current I to the second current I2. This causes a hydrogen evolution reaction to occur in the negative electrode 98. Consequently, the reduced-state negative electrode active material particles 41a attached to the negative electrode 98 are stripped away.

[0141] In the next step S114, the control unit 112 determines whether the rate of rise of voltage V ΔV is greater than a set rate of rise ΔVs. If the control unit 112 determines that the rate of rise of voltage V ΔV is greater than the set rate of rise ΔVs, it executes step S111. If the control unit 112 determines that the rate of rise of voltage V ΔV is less than the set rate of rise ΔVs, it executes step S113.

[0142] Through steps S113 and S114, the current I remains in the state of the second current I2 until the rate of rise of voltage V, ΔV, reaches the set rate of rise, ΔVs. Furthermore, the state of the current I remaining in the second current I2 ends synchronously with the rate of rise of voltage V, ΔV, reaching the set rate of rise, ΔVs.

[0143] From steps S111 to S114, the current I switches between a first current I1 and a second current I2. Furthermore, the time during which the current I is the first current I1 is a predetermined time ts. The time during which the current I is the second current I2 is a variable time, varying depending on the progress of the hydrogen evolution reaction.

[0144] 3. The differences between the third embodiment and the first embodiment will be explained below. For parts not described, the third embodiment also adopts the same configuration as that adopted in the first embodiment.

[0145] In the third embodiment, the control unit 112 controls the current I and the flow rate VL based on the voltage V.

[0146] Figure 9A This is a diagram illustrating an example of how the current flowing between the positive and negative terminals of a charging unit in a flow-type metal-air battery according to the third embodiment changes over time. Figure 9B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the flow-type metal-air battery of the third embodiment changes over time.

[0147] exist Figure 9A In the diagram, the horizontal axis represents time T, and the vertical axis represents current I. Figure 9B In the diagram, the horizontal axis represents time T, and the vertical axis represents flow velocity VL.

[0148] In the third embodiment, such as Figure 9A As shown, the control unit 112 switches the current I between a first current I1 and a second current I2. Therefore, the control unit 112 sets the current I to the first current I1 during the period T0 to T1, sets the current I to the second current I2 during the period T1 to T2, sets the current I to the first current I1 during the period T2 to T3, and sets the current I to the second current I2 during the period T3 to T4. The second current I2 is greater than the first current I1.

[0149] In addition, such as Figure 9B As shown, the control unit 112 switches the flow rate VL between a first flow rate VL1 and a second flow rate VL2. Therefore, the control unit 112 sets the flow rate VL to the first flow rate VL1 during the period T0 to T1, sets the flow rate VL to the second flow rate VL2 during the period T1 to T2, sets the flow rate VL to the first flow rate VL1 during the period T2 to T3, and sets the flow rate VL to the second flow rate VL2 during the period T3 to T4. The second flow rate VL2 is slower than the first flow rate VL1.

[0150] The first current I1 is less than the current Ih at which the hydrogen evolution reaction begins, and it is the current at which the reduction reaction of the negative electrode active material ions 42 to the reduced state of the negative electrode active material particles 41a occurs at the negative electrode 98, but the hydrogen evolution reaction, which competes with the reduction reaction, does not occur at the negative electrode 98. The second current I2 is greater than the current Ih, and it is the current at which the hydrogen evolution reaction occurs at the negative electrode 98 without the reduction reaction.

[0151] The first flow rate VL1 is the flow rate at which the amount of negative electrode active material ions 42 supplied to the negative electrode 98 becomes sufficient, resulting in a reduction reaction of the negative electrode active material ions 42 to the reduced negative electrode active material particles 41a in the negative electrode 98, but no hydrogen evolution reaction competing with this reduction reaction occurs in the negative electrode 98. The second flow rate VL2 is the flow rate at which the amount of negative electrode active material ions 42 supplied to the negative electrode 98 becomes insufficient, resulting in no reduction reaction in the negative electrode 98, but a hydrogen evolution reaction occurs in the negative electrode 98.

[0152] When the current I is switched to the second current I2 and the flow rate VL is switched to the second flow rate VL2, compared to the case where the current I is switched to the second current I2 but the flow rate VL is maintained at the first flow rate VL1, and the case where the current I is maintained at the first current I1 and the flow rate VL is switched to the second flow rate VL2, a large amount of hydrogen is generated in a short time. Thus, with a large amount of hydrogen generated in a short time, it becomes easier to strip the reduced-state negative electrode active material particles 41a from the negative electrode 98 and discharge the stripped reduced-state negative electrode active material particles 41a from the charging unit 78. Therefore, charging efficiency can be further improved.

[0153] Based on voltage V, control unit 112 controls timing T2 and timing T4 for switching the flow rate VL and current I from the second flow rate VL2 and second current I2 to the first flow rate VL1 and first current I1. Thus, based on voltage V, control unit 112 varies the lengths of the periods T1-T2 and T3-T4 during the hydrogen evolution reaction. This allows the hydrogen evolution reaction to be suppressed to a minimum necessary level, which is the minimum necessary level required to strip the reduced-state negative electrode active material particles 41a from the negative electrode 98 and discharge the stripped reduced-state negative electrode active material particles 41a from the charging unit 78. This improves charging efficiency.

[0154] In response to the rise rate ΔV of voltage V becoming greater than the set rise rate ΔVs, the control unit 112 switches the flow rate VL and current I from the second flow rate VL2 and the second current I2 to the first flow rate VL1 and the first current I1.

[0155] Figure 10 This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery of the third embodiment.

[0156] In the third embodiment, the control unit 112 performs... Figure 10 Steps S121 to S124 are shown.

[0157] In step S121, the control unit 112 sets the current I to a first current I1 and the flow rate VL to a first flow rate VL1. As a result, a reduction reaction occurs in the negative electrode 98 where the negative electrode active material ions 42 move to the reduced state of the negative electrode active material particles 41a. Consequently, the reduced state of the negative electrode active material particles 41a adheres to the negative electrode 98 and grows. During the period when the current I is the first current I1 and the flow rate VL is the first flow rate VL1, the power consumed by the charging unit 25 is minimized.

[0158] In the next step S122, the control unit 112 determines whether the time t elapsed since setting the current I to the first current I1 and the flow rate VL to the first flow rate VL1 is longer than a set time ts. If the control unit 112 determines that the time t is longer than the set time ts, it executes step S123. If the control unit 112 determines that the time t is shorter than the set time ts, it executes step S121.

[0159] Through steps S121 and S122, the state in which the current I is the first current I1 and the flow rate VL is the first flow rate VL1 continues until a set time ts has elapsed since the current I is the first current I1 and the flow rate VL is the first flow rate VL1. Furthermore, synchronously with the set time ts elapsed since the current I is the first current I1 and the flow rate VL is the first flow rate VL1, the state in which the current I is the first current I1 and the flow rate VL is the first flow rate VL1 ends.

[0160] In step S123, the control unit 112 sets the current I to the second current I2 and the flow rate VL to the second flow rate VL2. As a result, a hydrogen evolution reaction occurs in the negative electrode 98. Consequently, the reduced-state negative electrode active material particles 41a attached to the negative electrode 98 are stripped away.

[0161] In the next step S124, the control unit 112 determines whether the rate of rise of voltage V ΔV is greater than a set rate of rise ΔVs. If the control unit 112 determines that the rate of rise of voltage V ΔV is greater than the set rate of rise ΔVs, it executes step S121. If the control unit 112 determines that the rate of rise of voltage V ΔV is less than the set rate of rise ΔVs, it executes step S123.

[0162] Through steps S123 and S124, the current I remains at the second current I2 and the flow rate VL remains at the second flow rate VL2 until the rate of rise of voltage V ΔV reaches the set rate of rise ΔVs. Furthermore, synchronously with the rate of rise of voltage V ΔV reaching the set rate of rise ΔVs, the state where the current I is the second current I2 and the flow rate VL is the second flow rate VL2 ends.

[0163] From steps S121 to S124, the current I and flow rate VL switch between a first current I1 and a first flow rate VL1 and a second current I2 and a second flow rate VL2. Furthermore, the time during which the current I and flow rate VL are the first current I1 and the first flow rate VL1 is set to a specific time ts. Conversely, the time during which the current I and flow rate VL are the second current I2 and the second flow rate VL2 is a variable time, varying according to the progress of the hydrogen evolution reaction.

[0164] Figure 11A This is a diagram illustrating an example of how the current flowing between the positive and negative terminals of a charging unit in a first variation of the third embodiment of a flow-type metal-air battery changes over time. Figure 11B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the first modified example of the third embodiment of the flow-type metal-air battery changes over time.

[0165] exist Figure 11A In the diagram, the horizontal axis represents time T, and the vertical axis represents current I. Figure 11B In the diagram, the horizontal axis represents time T, and the vertical axis represents flow velocity VL.

[0166] In the third embodiment, such as Figure 9B As shown, the second flow rate VL2 is greater than 0. Therefore, even during the period when the flow rate VL is the second flow rate VL2, the control unit 112 keeps the pump 75 in the open state, causing the pump 75 to generate the flow of negative electrode liquid 22.

[0167] In contrast, in the first variation of the third embodiment, such as Figure 11B As shown, the second flow rate VL2 is 0. Therefore, during the period when the flow rate VL is the second flow rate VL2, the control unit 112 keeps the pump 75 in a closed state, preventing the pump 75 from generating the negative electrode liquid 22. Therefore, the control unit 112 switches the flow rate VL between the first flow rate VL1 and the second flow rate VL2 by switching the state of the pump 75 between the open and closed states. When the second flow rate VL2 is 0, compared with the case where the second flow rate VL2 is greater than 0, the lengths of the hydrogen evolution reaction periods T1 to T2 and T3 to T4 can be shortened, and the power consumed by the pump 75 and other auxiliary equipment can be reduced.

[0168] Figure 12AThis is a diagram illustrating an example of how the current flowing between the positive and negative terminals of a charging unit in a second variation of the third embodiment of a flow-type metal-air battery changes over time. Figure 12B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the second modified example of the third embodiment of the flow-type metal-air battery changes over time.

[0169] exist Figure 12A In the diagram, the horizontal axis represents time T, and the vertical axis represents current I. Figure 12B In the diagram, the horizontal axis represents time T, and the vertical axis represents flow velocity VL.

[0170] In the second variation of the third embodiment, if the rate of increase of voltage V ΔV1 during the current hydrogen evolution reaction T3 to T4 is not lower than the rate of increase of voltage V ΔV2 during the previous hydrogen evolution reaction T1 to T2, then even after the timing T4, the control unit 112 continuously switches between the first current I1 and the first flow rate VL1 and the second current I2 and the second flow rate.

[0171] However, if the rate of increase of voltage V ΔV1 during the current hydrogen evolution reaction period T3-T4 is lower than the rate of increase of voltage V ΔV2 during the previous hydrogen evolution reaction period T1-T2, the control unit 112 performs maintenance processing during the following period T4-T5. When maintenance processing begins, if... Figure 12A As shown, the control unit 112 maintains the current I at the second current I2, as... Figure 12B As shown, the flow velocity VL is switched from the second flow velocity VL2 to the third flow velocity VL3. The third flow velocity VL3 has a sign opposite to that of the second flow velocity VL2. The third flow velocity VL3 can have the same absolute value as the second flow velocity VL2, or it can have a different absolute value than the second flow velocity VL2.

[0172] When maintenance is performed, a hydrogen evolution reaction occurs. Therefore, it becomes easy to strip the reduced-state negative electrode active material particles 41a from the negative electrode 98 and discharge the stripped reduced-state negative electrode active material particles 41a from the charging unit 78.

[0173] Based on this, after maintenance treatment, the negative electrode liquid 97 flows countercurrently in the second flow path 96e of the second layer 96. As a result, a force having the opposite direction to the force acting on the reduced state negative electrode active material particles 41a before maintenance treatment is applied to the reduced state negative electrode active material particles 41a. Therefore, it becomes easier to peel off the reduced state negative electrode active material particles 41a from the negative electrode 98 and discharge the peeled reduced state negative electrode active material particles 41a from the charging unit 78.

[0174] The reduced-state negative electrode active material particles 41a grow along the flow direction of the negative electrode liquid 97. Therefore, when the flow direction of the negative electrode liquid 97 is constant, the reduced-state negative electrode active material particles 41a continue to grow along this direction. Conversely, when the flow direction of the negative electrode liquid 97 is not constant, the continuous growth of the reduced-state negative electrode active material particles 41a along this direction can be suppressed. Therefore, when a force with the opposite direction acts on the reduced-state negative electrode active material particles 41a, it becomes easier to peel off the reduced-state negative electrode active material particles 41a from the negative electrode 98.

[0175] Figure 13 This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery of the second variation of the third embodiment.

[0176] In a second variation of the third embodiment, the control unit 112 performs... Figure 13 Steps S131 to S136 are shown.

[0177] In steps S131 to S133, respectively, the following steps are performed: Figure 10 The same process is performed as shown in steps S121 to S123.

[0178] In the next step S134, the control unit 112 determines whether the rate of rise of voltage V ΔV is greater than the set rate of rise ΔVs. If the control unit 112 determines that the rate of rise of voltage V ΔV is greater than the set rate of rise ΔVs, it executes step S135. If the control unit 112 determines that the rate of rise of voltage V ΔV is less than the set rate of rise ΔVs, it executes step S133.

[0179] In step S135, the control unit 112 determines whether the rate of increase of voltage V ΔV1 during the period when the current I and flow rate VL are the second current I2 and the second flow rate VL2 is lower than the rate of increase of voltage V ΔV2 during the previous period when the current I and flow rate VL were the second current I2 and the second flow rate VL2. If the control unit 112 determines that the rate of increase of voltage V ΔV1 is lower than the rate of increase of voltage V ΔV2, it executes step S136, and then executes step S131. If the control unit 112 determines that the rate of increase of voltage V ΔV1 is not lower than the rate of increase of voltage V ΔV2, it executes step S131 without executing step S136.

[0180] In step S136, the control unit 112 performs maintenance processing.

[0181] Following steps S135 and S136, if the rate of rise of voltage V ΔV1 is not lower than the rate of rise of voltage V ΔV2, the control unit 112 continues the alternation of current I and flow rate VL without performing maintenance processing. If the rate of rise of voltage V ΔV1 is lower than the rate of rise of voltage V ΔV2, maintenance processing is performed and the alternation of current I and flow rate VL resumes. The control unit 112 may also perform maintenance processing under conditions other than the condition that the rate of rise of voltage V ΔV1 is lower than the rate of rise of voltage V ΔV2.

[0182] 4. Fourth Implementation Method The differences between the fourth embodiment and the first embodiment will be explained below. For parts not described, the fourth embodiment also uses the same configuration as the first embodiment.

[0183] Figure 14 This is a schematic diagram illustrating the flow-type metal-air battery of the fourth embodiment.

[0184] In the fourth embodiment, such as Figure 14 As shown, the control device 26 includes a pressure measuring unit 113 and a control unit 112. The pressure measuring unit 113 and the control unit 112 constitute a charging system.

[0185] The pressure measuring unit 113 is connected to the piping 76 and measures the delivery pressure P of the negative electrode liquid 22 guided by the piping 76. The measured delivery pressure P represents the pressure applied to the second flow path 96e of the second layer 96.

[0186] In the fourth embodiment, the control unit 112 controls the flow rate VL based on the liquid delivery pressure P.

[0187] Figure 4A It is also a diagram showing an example of how the current flowing between the positive electrode and the negative electrode of the charging unit in the fourth embodiment of the flow-type metal-air battery changes over time. Figure 4B This is also a diagram showing an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the flow-type metal-air battery of the fourth embodiment changes over time.

[0188] In the fourth embodiment, such as Figure 4A As shown, the control unit 112 maintains the current I at a constant current I1.

[0189] In addition, such as Figure 4B As shown, the control unit 112 switches the flow rate VL between a first flow rate VL1 and a second flow rate VL2. The second flow rate VL2 is slower than the first flow rate VL1.

[0190] The first flow rate VL1 is the flow rate at which the reduction reaction of negative electrode active material ions 42 to reduced negative electrode active material particles 41a occurs in negative electrode 98, but the hydrogen evolution reaction, which competes with the reduction reaction, does not occur in negative electrode 98. The second flow rate VL2 is the flow rate at which the hydrogen evolution reaction occurs in negative electrode 98 without the reduction reaction.

[0191] During the hydrogen evolution reaction, from T1 to T2 and from T3 to T4, the liquid delivery pressure P increases as the hydrogen evolution reaction proceeds and also increases over time.

[0192] In the fourth embodiment, the control unit 112 controls timing T2 and timing T4 for switching the flow rate VL from the second flow rate VL2 to the first flow rate VL1 based on the liquid delivery pressure P. This suppresses the hydrogen evolution reaction to a minimum necessary level, which is the minimum necessary level required to strip the reduced-state negative electrode active material particles 41a from the negative electrode 98 and discharge the stripped reduced-state negative electrode active material particles 41a from the charging unit 78. This improves charging efficiency.

[0193] In response to the rise rate ΔP of the liquid delivery pressure P becoming greater than the set rise rate ΔPS, the control unit 112 switches the flow rate VL from the second flow rate VL2 to the first flow rate VL1.

[0194] The time rise rate ΔPs, which is set by comparing it with the time rise rate ΔP of the delivery pressure P, is set to an appropriate time for the hydrogen evolution reaction period T1~T2 and the period T3~T4, for example, 10.4 kPa / s.

[0195] Figure 15 This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery according to the fourth embodiment.

[0196] Control Unit 112 Execution Figure 15 Steps S141 to S144 are shown.

[0197] From steps S141 to S143, execute the steps from... Figure 5 The processes shown in steps S101 to S103 are the same.

[0198] In the next step S144, the control unit 112 determines whether the rate of increase of the liquid delivery pressure P, ΔP, is greater than a set rate of increase, ΔPs. If the control unit 112 determines that the rate of increase of the liquid delivery pressure P, ΔP, is greater than the set rate of increase, ΔPs, then it executes step S141. If the control unit 112 determines that the rate of increase of the liquid delivery pressure P, ΔP, is less than the set rate of increase, ΔPs, then it executes step S143.

[0199] Through steps S143 and S144, the flow rate VL remains at the second flow rate VL2 until the rate of increase of the delivery pressure P, ΔP, reaches the set rate of increase ΔPs. Furthermore, the state of flow rate VL at the second flow rate VL2 ends synchronously with the rate of increase of the delivery pressure P, ΔP, reaching the set rate of increase ΔPs.

[0200] Figure 6A This is also a diagram illustrating an example of how the current flowing between the positive and negative terminals of the charging unit in the first variation of the fourth embodiment of the flow-type metal-air battery changes over time. Figure 6B This is also a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the first modified example of the fourth embodiment of the flow-type metal-air battery changes over time.

[0201] In the first variation of the fourth embodiment, such as Figure 6B As shown, the second flow rate VL2 is 0. When the second flow rate VL2 is 0, compared with the case where the second flow rate VL2 is greater than 0, the lengths of the hydrogen evolution reaction periods T1 to T2 and T3 to T4 can be shortened, and the power consumed by pump 75 and other auxiliary equipment can be reduced.

[0202] 5. Fifth Implementation Method The differences between the fifth embodiment and the fourth embodiment will be explained below. Regarding the parts not described, the fifth embodiment also employs the same configuration as the fourth embodiment.

[0203] In the fifth embodiment, the control unit 112 controls the current I based on the liquid delivery pressure P.

[0204] Figure 7A It is also a diagram showing an example of how the current flowing between the positive electrode and the negative electrode of the charging unit in the fifth embodiment of the flow-type metal-air battery changes over time. Figure 7B This is also a diagram showing an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the flow-type metal-air battery of the fifth embodiment changes over time.

[0205] In the fifth embodiment, such as Figure 7A As shown, the control unit 112 switches the current I between a first current I1 and a second current I2. The second current I2 is greater than the first current I1.

[0206] In addition, such as Figure 7B As shown, the control unit 112 maintains the flow velocity VL at a constant flow velocity VL1.

[0207] The first flow rate VL1 is the flow rate at which the reduction reaction of negative electrode active material ions 42 to reduced negative electrode active material particles 41a occurs in negative electrode 98, but the hydrogen evolution reaction, which competes with the reduction reaction, does not occur in negative electrode 98. The second flow rate VL2 is the flow rate at which the hydrogen evolution reaction occurs in negative electrode 98 without the reduction reaction.

[0208] In the fifth embodiment, the control unit 112 controls timing T2 and timing T4 for switching the current I from the second current I2 to the first current I1 based on the liquid delivery pressure P. This suppresses the hydrogen evolution reaction to a minimum necessary level, which is the minimum necessary level required to strip the reduced-state negative electrode active material particles 41a from the negative electrode 98 and discharge the stripped reduced-state negative electrode active material particles 41a from the charging unit 78. This improves charging efficiency.

[0209] In response to the rise rate ΔP of the liquid delivery pressure P becoming greater than the set rise rate ΔPs, the control unit 112 switches the flow rate VL from the second flow rate VL2 to the first flow rate VL1.

[0210] Figure 16 This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery according to the fifth embodiment.

[0211] Control Unit 112 Execution Figure 16 Steps S151 to S154 are shown.

[0212] In steps S151 to S153, respectively, the following steps are performed: Figure 8 The processes performed in steps S111 to S113 shown are the same.

[0213] In the next step S154, the control unit 112 determines whether the rate of increase of the liquid delivery pressure P, ΔP, is greater than a set rate of increase, ΔPs. If the control unit 112 determines that the rate of increase of the liquid delivery pressure P, ΔP, is greater than the set rate of increase, ΔPs, then it executes step S151. If the control unit 112 determines that the rate of increase of the liquid delivery pressure P, ΔP, is less than the set rate of increase, ΔPs, then it executes step S153.

[0214] Through steps S153 and S154, the current I remains in the state of the second current I2 until the rate of increase of the liquid delivery pressure P, ΔP, reaches the set rate of increase ΔPs. Furthermore, synchronously with the rate of increase of the liquid delivery pressure P, ΔP, reaching the set rate of increase ΔPs, the state of the current I remaining in the second current I2 ends.

[0215] 6. Sixth Embodiment Hereinafter, the differences between the sixth embodiment and the fourth embodiment will be described. For parts not described, the sixth embodiment also adopts the same configuration as that adopted in the fourth embodiment.

[0216] In the sixth embodiment, the control unit 112 controls the flow rate VL based on the liquid delivery pressure P.

[0217] Figure 9A This is a diagram showing an example of how the current flowing between the positive electrode and the negative electrode of the charging unit in the sixth embodiment of the flow-type metal-air battery changes over time. Figure 9B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the flow-type metal-air battery of the sixth embodiment changes over time.

[0218] In the sixth embodiment, such as Figure 9A As shown, the control unit 112 switches the current I between a first current I1 and a second current I2. The second current I2 is greater than the first current I1.

[0219] In addition, such as Figure 9B As shown, the control unit 112 switches the flow rate VL between a first flow rate VL1 and a second flow rate VL2. The second flow rate VL2 is slower than the first flow rate VL1.

[0220] The first current I1 is the current in which the reduction reaction of the negative electrode active material ions 42 to the reduced state of the negative electrode active material particles 41a occurs at the negative electrode 98, but the hydrogen evolution reaction, which competes with the reduction reaction, does not occur at the negative electrode 98. The second current I2 is the current in which the reduction reaction does not occur at the negative electrode 98, but the hydrogen evolution reaction, which competes with the reduction reaction, occurs at the negative electrode 98.

[0221] The first flow rate VL1 is the flow rate at which the reduction reaction of negative electrode active material ions 42 to reduced negative electrode active material particles 41a occurs in negative electrode 98, but the hydrogen evolution reaction, which competes with the reduction reaction, does not occur in negative electrode 98. The second flow rate VL2 is the flow rate at which the reduction reaction does not occur in negative electrode 98, but the hydrogen evolution reaction, which competes with the reduction reaction, occurs in negative electrode 98.

[0222] Based on the liquid delivery pressure P, the control unit 112 controls the timing T2 and timing T4 for switching the flow rate VL and current I from the second flow rate VL2 and the second current I2 to the first flow rate VL1 and the first current I1. This suppresses the hydrogen evolution reaction to a minimum necessary level, which is the minimum necessary level required to strip the reduced-state negative electrode active material particles 41a from the negative electrode 98 and discharge the stripped reduced-state negative electrode active material particles 41a from the charging unit 78. This improves charging efficiency.

[0223] In response to the rise rate ΔP of the liquid delivery pressure P becoming greater than the set rise rate ΔPs, the control unit 112 switches the flow rate VL and current I from the second flow rate VL2 and the second current I2 to the first flow rate VL1 and the first current I1.

[0224] Figure 17 This is a flowchart of the process performed by the control unit of the flow-type metal-air battery according to the sixth embodiment.

[0225] In the sixth embodiment, the control unit 112 performs... Figure 17 Steps S161 to S164 are shown.

[0226] In steps S161 to S163, the following steps are performed respectively: Figure 10 The processes performed in steps S121 to S123 shown are the same.

[0227] In the next step S164, the control unit 112 determines whether the rate of increase of the liquid delivery pressure P, ΔP, is greater than a set rate of increase, ΔPs. If the control unit 112 determines that the rate of increase of the liquid delivery pressure P, ΔP, is greater than the set rate of increase, ΔPs, then it executes step S161. If the control unit 112 determines that the rate of increase of the liquid delivery pressure P, ΔP, is less than the set rate of increase, ΔPs, then it executes step S163.

[0228] Through steps S163 and S164, the current I remains at the second current I2 and the flow rate VL remains at the second flow rate VL2 until the rate of increase of the liquid delivery pressure P, ΔP, reaches the set rate of increase ΔPs. Furthermore, synchronously with the rate of increase of the liquid delivery pressure P, ΔP, reaching the set rate of increase ΔPs, the state where the current I is the second current I2 and the flow rate VL is the second flow rate VL2 ends.

[0229] Figure 11A This is also a diagram showing an example of how the current flowing between the positive electrode and the negative electrode of the charging unit in the first variation of the sixth embodiment of the flow-type metal-air battery changes over time. Figure 11B This is a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the first modified example of the sixth embodiment of the flow-type metal-air battery changes over time.

[0230] In the first variation of the sixth embodiment, such as Figure 11B As shown, the second flow rate VL2 is 0. When the second flow rate VL2 is 0, compared with the case where the second flow rate VL2 is greater than 0, the lengths of the hydrogen evolution reaction periods T1 to T2 and T3 to T4 can be shortened, and the power consumed by pump 75 and other auxiliary equipment can be reduced.

[0231] Figure 12A This is also a diagram illustrating an example of how the current flowing between the positive and negative terminals of the charging unit in the second variation of the sixth embodiment of the flow-type metal-air battery changes over time. Figure 12B This is also a diagram illustrating an example of how the flow rate of the negative electrode liquid in the second flow path of the second layer of the charging unit of the second modified example of the sixth embodiment of the flow-type metal-air battery changes over time.

[0232] In the second variation of the sixth embodiment, if the rate of increase of voltage V ΔV1 during the current hydrogen evolution reaction T3 to T4 is not lower than the rate of increase of voltage V ΔV2 during the previous hydrogen evolution reaction T1 to T2, then even after the timing T4, the control unit 112 continues to switch the current I and the flow rate VL between the first current I1 and the first flow rate VL1 and the second current I2 and the second flow rate.

[0233] However, if the rate of increase of voltage V ΔV1 during the current hydrogen evolution reaction period T3-T4 is lower than the rate of increase of voltage V ΔV2 during the previous hydrogen evolution reaction period T1-T2, the control unit 112 performs maintenance processing during the following period T4-T5. When maintenance processing begins, if... Figure 12A As shown, the control unit 112 maintains the current I at the second current I2, as... Figure 12B As shown, the flow velocity VL is switched from the second flow velocity VL2 to the third flow velocity VL3. The third flow velocity VL3 has a sign opposite to that of the second flow velocity VL2. The third flow velocity VL3 can have the same absolute value as the second flow velocity VL2, or it can have a different absolute value than the second flow velocity VL2.

[0234] When maintenance is performed, a hydrogen evolution reaction occurs. Therefore, it becomes easy to strip the reduced-state negative electrode active material particles 41a from the negative electrode 98 and discharge the stripped reduced-state negative electrode active material particles 41a from the charging unit 78.

[0235] Based on this, after maintenance treatment, the negative electrode liquid 97 flows countercurrently in the second flow path 96e of the second layer 96. As a result, a force having the opposite direction to the force acting on the reduced negative electrode active material particles 41a before maintenance treatment acts on the reduced negative electrode active material particles 41a. Therefore, it becomes easier to strip the reduced negative electrode active material particles 41a from the negative electrode 98 and discharge the stripped reduced negative electrode active material particles 41a from the charging unit 78.

[0236] Figure 18 This is a flowchart illustrating the process performed by the control unit of the flow-type metal-air battery of the second variation of the sixth embodiment.

[0237] In a second variation of the sixth embodiment, the control unit 112 performs... Figure 18 Steps S171 to S176 are shown.

[0238] In steps S171 to S173, respectively, the following steps are performed: Figure 13 The same process is performed in steps S131 to S133 shown.

[0239] In the next step S174, the control unit 112 determines whether the rate of increase of the liquid delivery pressure P, ΔP, is greater than a set rate of increase, ΔPs. If the control unit 112 determines that the rate of increase of the liquid delivery pressure P, ΔP, is greater than the set rate of increase, ΔPs, then it executes step S175. If the control unit 112 determines that the rate of increase of the liquid delivery pressure P, ΔP, is less than the set rate of increase, ΔPs, then it executes step S173.

[0240] In step S175, the control unit 112 determines whether the rate of increase of the delivery pressure P, ΔP1, during the period when the current I and flow rate VL are the second current I2 and the second flow rate VL2 is lower than the rate of increase of the delivery pressure P, ΔP2, during the previous period when the current I and flow rate VL were the second current I2 and the second flow rate VL2. If the control unit 112 determines that the rate of increase of the delivery pressure P, ΔP1, is lower than the rate of increase of the delivery pressure P, ΔP2, then step S176 is executed, and then step S171 is executed. If the control unit 112 determines that the rate of increase of the delivery pressure P, ΔP1, is not lower than the rate of increase of the delivery pressure P, ΔP2, then step S171 is executed instead of step S176.

[0241] 7. Seventh Implementation Method The differences between the seventh embodiment and the first to sixth embodiments will be explained below. For the parts not explained, the seventh embodiment also adopts the same configuration as that adopted in the first to sixth embodiments.

[0242] Figures 19 to 22 This diagram illustrates the processing performed by the control unit of the flow-type metal-air battery according to the seventh embodiment.

[0243] In the first to sixth embodiments, the control unit 112 controls the lengths of the hydrogen evolution reaction periods T1 to T2 and T3 to T4 by controlling the current I and / or the flow rate VL in response to the voltage V rising rate ΔV becoming higher than the set rising rate ΔVs or the liquid delivery pressure P rising rate ΔP becoming higher than the set rising rate ΔPs.

[0244] In contrast, in the seventh embodiment, as Figure 19As shown, the control unit 112 further controls the current I and / or flow rate VL based on the discharge depth D of the discharge unit 24, thereby controlling the lengths of the hydrogen evolution reaction periods T1 to T2 and T3 to T4 based on the discharge depth D of the discharge unit 24.

[0245] For example, when the control unit 112 switches the flow rate VL between the first flow rate VL1 and the second flow rate VL2 in the same manner as in the first embodiment, the flow rate VL is controlled based on the discharge depth D of the discharge unit 24, and so on. Figure 20 As shown, the shallower the discharge depth D of the discharge section 24, the earlier the timing T2 and timing T4 for switching the flow rate VL from the second flow rate VL2 to the first flow rate VL1 are, thereby shortening the length of the hydrogen evolution reaction period T1~T2 and the period T3~T4.

[0246] Alternatively, similar to the second embodiment, when switching the current I between the first current I1 and the second current I2, the control unit 112 controls the current I based on the discharge depth D of the discharge unit 24, such as... Figure 21 As shown, the shallower the discharge depth D of the discharge section 24, the earlier the timing of switching the current I from the second current I2 to the first current I1 is, thereby shortening the length of the hydrogen evolution reaction period T1~T2 and the period T3~T4.

[0247] Alternatively, similar to the third embodiment, when the control unit 112 switches between the flow rate VL and the current I between the first flow rate VL1 and the first current I1 and the second flow rate VL2 and the second current I2, such as Figure 22 As shown, the flow rate VL and current I are controlled based on the discharge depth D of the discharge section 24. The shallower the discharge depth D of the discharge section 24, the earlier the timing of switching the flow rate VL and current I from the second flow rate VL2 and the second current I2 to the first flow rate VL and the first current I1 is, thereby shortening the length of the hydrogen evolution reaction period T1~T2 and the period T3~T4.

[0248] When the discharge depth D of the discharge section 24 is shallow, the amount of negative electrode active material ions 42 contained in the negative electrode liquid 97 is small, thus the hydrogen evolution reaction is easy to occur. On the other hand, when the discharge depth D of the discharge section 24 is deep, the amount of negative electrode active material ions 42 contained in the negative electrode liquid 97 is large, thus the hydrogen evolution reaction is difficult to occur. Therefore, the shallower the discharge depth D of the discharge section 24 and the shorter the lengths of the hydrogen evolution reaction periods T1~T2 and T3~T, the more appropriate the hydrogen evolution reaction can be achieved.

[0249] The discharging of the discharge unit 24 and the charging of the charging unit 25 are carried out alternately.

[0250] The control unit 112 can calculate the discharge depth D of the discharge section 24 based on the product of the current discharged by the discharge section 24 and the discharge time of the discharge section 24. The calculated discharge depth D of the discharge section 24 is the discharge depth of the discharge section 24 at the end of the most recent discharge performed by the discharge section 24. The current discharged through the discharge section 24 is a constant current.

[0251] The depth of discharge D refers to the value (quotient) obtained by dividing the product of the discharge current and the discharge time (Ah) by the initial (before discharge) capacity Ah of the negative electrode liquid 97 (in the case of zinc Mg, the capacity is M×0.82). A deep discharge depth D is defined as a value greater than 0.1 (depth 10%) obtained by dividing the product of the current discharged from the discharge section 24 and the discharge time of the discharge section 24 by the capacity of the negative electrode liquid 97 before discharge. A shallow discharge depth D is defined as a value less than 0.1 (depth 10%) obtained by dividing the product of the current discharged from the discharge section 24 and the discharge time of the discharge section 24 by the capacity of the negative electrode liquid 97 before discharge.

[0252] This disclosure is not limited to the above-described embodiments, and can be replaced by a configuration that is substantially the same as the configuration shown in the above embodiments, a configuration that can perform the same function or effect, or a configuration that can achieve the same purpose.

Claims

1. A charging system for a flow-type metal-air battery, characterized in that, comprises: a first layer in which a first flow path is formed; a positive electrode facing the first flow path; a second layer in which a second flow path is formed; a negative electrode facing the second flow path; a separator that separates the first flow path and the second flow path from each other; positive electrode solution that flows through the first flow path; and negative electrode solution that flows through the second flow path, and has a period in which hydrogen evolution occurs in the negative electrode.

2. The charging system for a flow-type metal-air battery according to claim 1, further comprising a control device that controls at least one selected from the group consisting of a flow rate of the negative electrode solution and a current flowing between the positive electrode and the negative electrode, on the basis of at least one selected from the group consisting of a voltage applied between the positive electrode and the negative electrode and a solution feeding pressure of the negative electrode solution.

3. The charging system for a flow-type metal-air battery according to claim 2, wherein the control device switches the flow rate between a first flow rate and a second flow rate slower than the first flow rate, and the control of the flow rate on the basis of the voltage includes control of timing at which the flow rate is switched from the second flow rate to the first flow rate on the basis of the voltage.

4. The charging system for a flow-type metal-air battery according to claim 3, wherein the control of the timing on the basis of the voltage includes switching of the flow rate from the second flow rate to the first flow rate in response to an increase rate of the voltage becoming greater than a set increase rate.

5. The charging system for a flow-type metal-air battery according to claim 3 or 4, wherein the first flow rate is a flow rate in which no hydrogen evolution reaction occurs in the negative electrode, and the second flow rate is a flow rate in which the hydrogen evolution reaction occurs in the negative electrode.

6. The charging system for a flow-type metal-air battery according to claim 3 or 4, wherein the second flow rate is 0.

7. The charging system for a flow-type metal-air battery according to claim 2, wherein the control device switches the current between a first current and a second current greater than the first current, and the control of the current on the basis of the voltage includes control of timing at which the current is switched from the second current to the first current on the basis of the voltage.

8. The charging system for a flow-type metal-air battery according to claim 7, wherein the control of the timing on the basis of the voltage includes switching of the current from the second current to the first current in response to an increase rate of the voltage becoming greater than a set increase rate.

9. The charging system for a flow-type metal-air battery according to claim 7 or 8, wherein the first current is a current in which no hydrogen evolution reaction occurs in the negative electrode, and the second current is a current in which the hydrogen evolution reaction occurs in the negative electrode.

10. The charging system for a flow-type metal-air battery according to claim 2, wherein the control device switches the flow rate and the current between a first flow rate and a first current and a second flow rate slower than the first flow rate and a second current greater than the first current. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ controlling the flow rate and the current based on the voltage includes controlling a timing at which the flow rate and the current are switched from the second flow rate and the second current to the first flow rate and the first current based on the voltage.

11. The charging system for a flow-type metal-air battery according to claim 10, wherein controlling the timing based on the voltage includes switching the flow rate and the current from the second flow rate and the second current to the first flow rate and the first current in response to a rate of rise of the voltage becoming greater than a set rate of rise.

12. The charging system for a flow-type metal-air battery according to claim 10 or 11, wherein the first flow rate and the first current are a flow rate and a current at which no hydrogen evolution reaction occurs in the negative electrode, the second flow rate and the second current are a flow rate and a current at which the hydrogen evolution reaction occurs in the negative electrode.

13. The charging system for a flow-type metal-air battery according to claim 10 or 12, wherein the second flow rate is 0.

14. The charging system for a flow-type metal-air battery according to claim 10 or 11, wherein controlling the flow rate and the current based on the voltage includes switching the flow rate from the second flow rate to a third flow rate having a sign opposite to a sign of the second flow rate based on the voltage.

15. The charging system for a flow-type metal-air battery according to claim 14, wherein switching the flow rate from the second flow rate to the third flow rate based on the voltage includes switching the flow rate from the second flow rate to the third flow rate in a case where a rate of rise of the voltage during a period in which the flow rate and the current are set to the second flow rate and the second current is lower than a rate of rise of the voltage during a last period in which the flow rate and the current were set to the second flow rate and the second current.

16. The charging system for a flow-type metal-air battery according to claim 2, wherein the control device controls the flow rate based on the liquid delivery pressure.

17. The charging system for a flow-type metal-air battery according to claim 16, wherein the control device switches the flow rate between a first flow rate and a second flow rate slower than the first flow rate, controlling the flow rate based on the liquid delivery pressure includes controlling a timing at which the flow rate is switched from the second flow rate to the first flow rate based on the liquid delivery pressure.

18. The charging system for a flow-type metal-air battery according to claim 17, wherein controlling the timing based on the liquid delivery pressure includes switching the flow rate from the second flow rate to the first flow rate in response to a rate of rise of the liquid delivery pressure becoming greater than a set rate of rise.

19. The charging system for a flow-type metal-air battery according to claim 17 or 18, wherein the first flow rate is a flow rate at which no hydrogen evolution reaction occurs in the negative electrode, the second flow rate is a flow rate at which the hydrogen evolution reaction occurs in the negative electrode.

20. The charging system for a flow-type metal-air battery according to claim 17 or 18, wherein the second flow rate is 0.

21. The charging system for a flow-type metal-air battery according to claim 2, wherein the control device controls the electric current based on the liquid delivery pressure.

22. The charging system for a flow-type metal-air battery according to claim 21, wherein the control device switches the electric current between a first electric current and a second electric current greater than the first electric current, controlling the electric current based on the liquid delivery pressure includes controlling a timing at which the electric current is switched from the second electric current to the first electric current based on the liquid delivery pressure.

23. The charging system for a flow-type metal-air battery according to claim 22, wherein controlling the timing based on the liquid delivery pressure includes switching the electric current from the second electric current to the first electric current in response to a rate of increase of the liquid delivery pressure becoming greater than a set rate of increase.

24. The charging system for a flow-type metal-air battery according to claim 22 or 23, wherein the first electric current is an electric current in which a hydrogen evolution reaction does not occur in the negative electrode, the second electric current is an electric current in which the hydrogen evolution reaction occurs in the negative electrode.

25. The charging system for a flow-type metal-air battery according to claim 2, wherein the control device controls the flow rate and the electric current based on the liquid delivery pressure.

26. The charging system for a flow-type metal-air battery according to claim 25, wherein the control device switches the flow rate and the electric current between a first flow rate and a first electric current, and a second flow rate slower than the first flow rate and a second electric current greater than the first electric current, controlling the flow rate and the electric current based on the liquid delivery pressure includes controlling a timing at which the flow rate and the electric current are switched from the second flow rate and the second electric current to the first flow rate and the first electric current based on the liquid delivery pressure.

27. The charging system for a flow-type metal-air battery according to claim 26, wherein controlling the timing based on the liquid delivery pressure includes switching the flow rate and the electric current from the second flow rate and the second electric current to the first flow rate and the first electric current in response to a rate of increase of the liquid delivery pressure becoming greater than a set rate of increase.

28. The charging system for a flow-type metal-air battery according to claim 26 or 27, wherein the first flow rate and the first electric current are a flow rate and an electric current in which a hydrogen evolution reaction does not occur in the negative electrode, the second flow rate and the second electric current are a flow rate and an electric current in which the hydrogen evolution reaction occurs in the negative electrode.

29. The charging system for a flow-type metal-air battery according to claim 26 or 27, wherein the second flow rate is 0.

30. The charging system for a flow-type metal-air battery according to claim 26 or 27, wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The controlling the flow rate and the current based on the liquid feeding pressure includes switching the flow rate from the second flow rate to a third flow rate having a sign opposite to a sign of the second flow rate based on the liquid feeding pressure.

31. The charging system for a flow-type metal-air cell according to claim 30, wherein The switching the flow rate from the second flow rate to the third flow rate based on the liquid feeding pressure includes switching the flow rate from the second flow rate to the third flow rate when a rate of increase of the liquid feeding pressure during a period in which the flow rate and the current are set to the second flow rate and the second current is lower than a rate of increase of the liquid feeding pressure during a last period in which the flow rate and the current were set to the second flow rate and the second current.

32. A flow-type metal-air cell comprising: the charging system for a flow-type metal-air cell according to claim 1; a discharging section for a flow-type metal-air cell; and a control device that controls at least one selected from a group consisting of the flow rate and the current based on a depth of discharge of the discharging section for a flow-type metal-air cell.

33. The flow-type metal-air cell according to claim 32, wherein the control device controls the flow rate based on the depth of discharge, the control device switches the flow rate between a first flow rate and a second flow rate slower than the first flow rate, the controlling the flow rate based on the depth of discharge includes switching the flow rate from the second flow rate to the first flow rate earlier as the depth of discharge is shallower.

34. The flow-type metal-air cell according to claim 32, wherein the control device controls the current based on the depth of discharge, the control device switches the current between a first current and a second current greater than the first current, the controlling the current based on the depth of discharge includes switching the current from the second current to the first current earlier as the depth of discharge is shallower.

35. The flow-type metal-air cell according to claim 32, wherein the control device controls the flow rate and the current based on the depth of discharge, the control device switches the flow rate and the current between a first flow rate and a first current, and a second flow rate slower than the first flow rate and a second current greater than the first current, the controlling the flow rate and the current based on the depth of discharge includes switching the flow rate and the current from the second flow rate and the second current to the first flow rate and the first current earlier. ​

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