Charging cell for flow-type metal-air battery

Abstract

To provide a charging cell for a flow-type metal-air battery with high durability since it is possible to detach negative electrode active material particles from a negative electrode without consuming a large amount of power, and since physical contact with a scraper or the like is not required.SOLUTION: A charging cell for a flow-type metal-air battery includes a first layer in which a first flow channel is formed, a positive electrode facing the first flow channel, a second layer in which a second flow channel is formed, a negative electrode facing the second flow channel, a separator separating the first flow channel and the second flow channel from each other, a positive electrode liquid flowing through the first flow channel and having a first viscosity, and a negative electrode liquid flowing through the second flow channel and having a second viscosity higher than the first viscosity.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a charging cell for a flow-type metal-air battery. [Background technology]

[0002] Patent Document 1 discloses a system for producing metal particles. In this system, metal particles are produced on the surface of a cathode by electrolysis of a solution containing dissolved metal. When the formed metal particles reach a sufficient size, they are removed from the surface of the cathode by a scraper or other suitable means (paragraphs 0014 and 0057). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 7,470,351 Summary of the Invention [Problem to be solved by the invention]

[0004] In the system disclosed in Patent Document 1, a scraper or other suitable means must be moved along the surface of the cathode to remove metal particles from the surface of the cathode, which poses problems such as the consumption of power required to move the scraper or other suitable means and reduced durability due to moving the scraper or other suitable means along the surface of the cathode.

[0005] One aspect of the present disclosure has been made in view of this problem, and aims to provide a charging cell for a flow-type metal-air battery that can peel negative electrode active material particles from a negative electrode without consuming a large amount of power and has high durability because physical contact with a scraper or the like is not required. [Means for solving the problem]

[0006] A charging cell for a flow-type metal-air battery according to one embodiment of the present disclosure includes: a first layer having a first flow path formed therein; a positive electrode facing the first flow path; a second layer having a second flow path formed therein; 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 having a first viscosity that flows through the first flow path; and a negative electrode liquid having a second viscosity that is higher than the first viscosity that flows through the second flow path. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram schematically illustrating a flow-type metal-air battery according to a first embodiment. [Figure 2] FIG. 2 is an exploded perspective view schematically illustrating a charging cell provided in the flow-type metal-air battery of the first embodiment. [Figure 3] FIG. 2 is a cross-sectional view schematically illustrating a charging cell provided in the flow-type metal-air battery of the first embodiment. [Figure 4A] 4 is a graph showing a first example of control of the current value of the current flowing between the positive electrode of a charging cell provided in the flow-type metal-air battery of the first embodiment and the negative electrode of the charging cell. [Figure 4B] 4 is a graph showing a first example of control of the flow rate of the negative electrode solution in the second flow path of the charging cell provided in the flow-type metal-air battery of the first embodiment. [Figure 5A] 6 is a graph showing a second example of control of the current value of the current flowing between the positive electrode of a charging cell provided in the flow-type metal-air battery of the first embodiment and the negative electrode of the charging cell. [Figure 5B] 6 is a graph showing a second example of control of the flow rate of the negative electrode solution in the second flow path of the charging cell provided in the flow-type metal-air battery of the first embodiment. [Figure 6A] 10 is a graph showing a third example of control of the current value of the current flowing between the positive electrode of a charging cell provided in the flow-type metal-air battery of the first embodiment and the negative electrode of the charging cell. [Figure 6B] 10 is a graph showing a third example of control of the flow rate of the negative electrode solution in the second flow path of the charging cell provided in the flow-type metal-air battery of the first embodiment. [Figure 7] 10 is a graph showing a fourth example of control of the current value of the current flowing between the positive electrode of a charging cell provided in the flow-type metal-air battery of the first embodiment and the negative electrode of the charging cell. [Figure 8] 10 is a graph showing a fifth example of control of the flow rate of the negative electrode solution in the second flow path of the charging cell provided in the flow-type metal-air battery of the first embodiment. [Figure 9] FIG. 2 is a cross-sectional view schematically illustrating a charging cell provided in a flow-type metal-air battery according to a first modified example of the first embodiment. [Figure 10] FIG. 3 is a cross-sectional view schematically illustrating a charging cell provided in a flow-type metal-air battery according to a second modified example of the first embodiment. [Figure 11] FIG. 10 is a cross-sectional view schematically illustrating a charging cell provided in a flow-type metal-air battery according to a third modified example of the first embodiment. [Figure 12] FIG. 10 is a cross-sectional view schematically illustrating a charging cell provided in a flow-type metal-air battery according to a fourth modified example of the first embodiment. [Figure 13] FIG. 2 is a cross-sectional view schematically illustrating a charging cell stack that can be used in place of the charging cell provided in the flow-type metal-air battery of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0009] 1. First embodiment 1.1 Flow-type metal-air battery FIG. 1 is a diagram schematically illustrating a flow-type metal-air battery according to the first embodiment.

[0010] 1 absorbs oxygen gas 11 from the air surrounding the flow type metal-air battery 1 when discharging. When charging, the flow type metal-air battery 1 releases oxygen gas 12 into the air surrounding the flow type metal-air battery 1.

[0011] The flow type metal-air battery 1 is a flow type zinc-air battery. Therefore, the negative electrode active material in the flow type metal-air battery 1 is a zinc species. However, the flow type metal-air battery 1 may also be a flow type metal-air battery other than a flow type zinc-air battery. Therefore, the negative electrode active material in the flow type metal-air battery 1 may be a metal species other than a zinc species. Examples of metal species other than zinc species include cadmium species, lithium species, sodium species, magnesium species, lead species, tin species, aluminum species, and iron species. The metals constituting the metal species may be composed only of a main component metal, or may be composed of an alloy of a main component metal and a subcomponent metal. The metal species can be either a metal or an oxide. Whether the metal species is a metal or an oxide is determined depending on the degree of progress of the discharge reaction or the charge reaction.

[0012] As shown in FIG. 1, 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, and a charge section 25.

[0013] 1.2 Positive electrolyte As shown in FIG. 1, the positive electrode solution 21 includes a first electrolyte solution 31 .

[0014] The first electrolytic solution 31 is an aqueous potassium hydroxide solution. The first electrolytic solution 31 may be an aqueous solution other than the aqueous potassium hydroxide solution, or may be an electrolytic solution other than an aqueous solution.

[0015] The water contained in first electrolytic solution 31 is a reactant of the charging reaction that occurs in charging section 25.

[0016] 1.3 Negative electrolyte As shown in FIG. 1, the negative electrode liquid 22 contains reduced negative electrode active material particles 41 a, oxidized negative electrode active material particles 41 b, negative electrode active material ions 42 , and a second electrolyte solution 43 .

[0017] As described above, the flow type metal-air battery 1 is a flow type 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 species. The reduced-state negative electrode active material particles 41a are metal zinc (Zn) particles, and the oxidized-state negative electrode active material particles 41b are zinc oxide (ZnO) particles. The reduced-state negative electrode active material particles 41a and the oxidized-state negative electrode active material particles 41b are dispersed in the second electrolyte solution 43. Therefore, the negative electrode liquid 22 has a slurry-like property. The reduced-state negative electrode active material particles 41a have a particle diameter of, for example, several μm, and the oxidized-state negative electrode active material particles 41b have a particle diameter of, for example, several tens to several hundreds of nm. The negative electrode active material ions 42 are zincate ions (Zn(OH)4 2- ) and dissolved in second electrolyte solution 43.

[0018] Second electrolytic solution 43 is an aqueous potassium hydroxide solution. Second electrolytic solution 43 may be an aqueous solution other than the aqueous potassium hydroxide solution, or may be an electrolytic solution other than an aqueous solution.

[0019] The negative electrode active material ions 42 are reactants of 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.

[0020] 1.4 Storage The storage unit 23 stores the negative electrode liquid 22. An outlet 23a, an inlet 23b, an outlet 23c, and an inlet 23d are formed in the storage unit 23. The outlet 23a and the outlet 23c allow the negative electrode liquid 22 to flow out. The inlet 23b and the inlet 23d allow the negative electrode liquid 22 to flow in.

[0021] 1.5 Discharge section The discharge unit 24 absorbs oxygen gas 11 from the air surrounding the discharge unit 24. The anode liquid 22 flows into the discharge unit 24 from the storage unit 23. The discharge unit 24 causes the absorbed oxygen gas 11 and the anode liquid 22 that has flowed in to participate in a discharge reaction that generates discharge power, and causes the anode liquid 22 that has participated in the discharge reaction to flow out to the storage unit 23. The discharge unit 24 causes the oxygen gas 11 and the reduced anode active material particles 41a contained in the anode liquid 22 to participate in the discharge reaction, causing the reduced anode active material particles 41a to disappear and generate anode active material ions 42.

[0022] As shown in FIG. 1, the discharge unit 24 includes a pipe 51 , a pump 52 , a pipe 53 , a discharge cell 54 , and a pipe 55 .

[0023] Pipe 51 guides negative electrode liquid 22 from outlet 23a of storage unit 23 to inlet 52a of pump 52. Thus, pipe 51 causes negative electrode liquid 22 that has flowed out from outlet 23a to flow into inlet 52a.

[0024] Pump 52 causes negative electrode liquid 22, which has flowed into inlet 52a of pump 52, to flow out from outlet 52b of pump 52. At that time, pump 52 generates a flow of negative electrode liquid 22. In this way, pump 52 sends negative electrode liquid 22 from storage unit 23 to discharge cell 54.

[0025] Pipe 53 guides negative electrode liquid 22 from outlet 52b of pump 52 to inlet 54a of discharge cell 54. Thus, pipe 53 causes negative electrode liquid 22 flowing out from outlet 52b to flow into inlet 54a.

[0026] The discharge cell 54 absorbs oxygen gas 11 from the air surrounding the discharge cell 54. The discharge cell 54 causes the anode liquid 22 that has flowed into an inlet 54a of the discharge cell 54 to flow out from an outlet 54b of the discharge cell 54. At that time, the discharge cell 54 causes the absorbed oxygen gas 11 and the anode liquid 22 that has flowed in to participate in a discharge reaction, and causes the anode liquid 22 that has participated in the discharge reaction to flow out from the outlet 54b. The discharge cell 54 outputs discharge power generated by the discharge reaction.

[0027] Pipe 55 guides negative electrode liquid 22 from outlet 54b of discharge cell 54 to inlet 23b of storage unit 23. Thus, pipe 55 causes negative electrode liquid 22 that has flowed out from outlet 54b to flow into inlet 23b.

[0028] 1.6 Discharge Cell As shown in FIG. 1, the discharge cell 54 comprises a layer 61 , an anode liquid 62 , a cathode 63 , a separator 64 and an anode 65 .

[0029] Flow path 61a is formed in layer 61. Flow path 61a extends from inlet 54a of discharge cell 54 to outlet 54b of discharge cell 54. Thus, flow path 61a allows anode liquid 22 that has flowed into inlet 54a to pass through, and causes the passed anode liquid 22 to flow out from outlet 54b.

[0030] The negative electrode liquid 62 flows through the flow paths 61a of the layer 61. The negative electrode liquid 62 is a part of the negative electrode liquid 22 provided in the flow type metal-air battery 1.

[0031] The positive electrode 63 comes into contact with the air around the discharge cell 54. As a result, oxygen gas 11 contained in the air around the discharge cell 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.

[0032] O2+2H2O+4e - →4OH - (1)

[0033] The positive electrode 63 faces the flow path 61a of the layer 61 via the separator 64. As a result, the positive electrode 63 transfers OH, which is the product of the reduction reaction of oxygen represented by formula (1), to the negative electrode liquid 62 flowing through the flow path 61a via the separator 64. ― The delivery will be made.

[0034] The negative electrode 65 faces the flow path 61a of the layer 61. This brings the negative electrode 65 into contact with the negative electrode liquid 62 flowing through the flow path 61a. This causes an oxidation reaction of metallic zinc represented by formulas (2) and (3) to occur in the negative electrode 65.

[0035] Zn+4OH- → Zn(OH)4 2- +2e - (2) Zn(OH)4 2- →ZnO+H2O+2OH - (3)

[0036] Due to the reduction reaction of oxygen at the positive electrode 63 and the oxidation reaction of metallic zinc at the negative electrode 65, the overall reaction represented by formula (4) occurs in the discharge cell 54.

[0037] 2Zn+O2→2ZnO (4)

[0038] Therefore, the discharge cell 54 discharges when the zinc metal changes into zinc oxide.

[0039] 1.7 Live parts Anode liquid 22 flows into charging unit 25 from storage unit 23. Charging unit 25 causes the flowing anode liquid 22 to participate in a charging reaction that regenerates anode liquid 22, and causes the anode liquid 22 involved in the charging reaction to flow out to storage unit 23. Charging unit 25 causes anode active material ions 42 contained in anode liquid 22 to participate in the charging reaction, thereby eliminating anode active material ions 42 and generating reduced anode active material particles 41a.

[0040] As shown in FIG. 1, charging unit 25 includes a pipe 71, a pump 72, a pipe 73, a pipe 74, a pump 75, a pipe 76, a power source 77, a charging cell 78, a pipe 79, a pipe 80, and a control circuit 81.

[0041] Pipe 71 guides positive electrode liquid 21 from a supply source of positive electrode liquid 21 (not shown) to inlet 72a of pump 72. Thus, pipe 71 causes positive electrode liquid 21 flowing out from the supply source of positive electrode liquid 21 to flow into inlet 72a.

[0042] The pump 72 causes the positive electrode solution 21, which has flowed into an inlet 72a of the pump 72, to flow out from an outlet 72b of the pump 72. In doing so, the pump 72 generates a flow of the positive electrode solution 21. In this way, the pump 72 sends the positive electrode solution 21 from a supply source of the positive electrode solution 21 to the charging cell 78.

[0043] Pipe 73 guides positive electrode solution 21 from outlet 72b of pump 72 to inlet 78a of charging cell 78. Thus, pipe 73 causes positive electrode solution 21 that flows out from outlet 72b to flow into inlet 78a.

[0044] Pipe 74 guides negative electrode liquid 22 from outlet 23c of storage unit 23 to inlet 75a of pump 75. Thus, pipe 74 causes negative electrode liquid 22 that has flowed out from outlet 23c to flow into inlet 75a.

[0045] The pump 75 causes the negative electrode solution 22, which has flowed into an inlet 75a of the pump 75, to flow out from an outlet 75b of the pump 75. In doing so, the pump 75 generates a flow of the negative electrode solution 22. In this way, the pump 75 sends the negative electrode solution 22 from the storage unit 23 to the charging cell 78.

[0046] Pipe 76 guides negative electrode liquid 22 from outlet 75b of pump 75 to inlet 78b of charging cell 78. Thus, pipe 76 causes negative electrode liquid 22 that flows out from outlet 75b to flow into inlet 78b.

[0047] The power supply 77 inputs charging power to the charging cell 78 .

[0048] The charging cell 78 causes the positive electrode solution 21 that has flowed into the inlet 78a of the charging cell 78 to flow out from the outlet 78c of the charging cell 78, and causes the negative electrode solution 22 that has flowed into the inlet 78b of the charging cell 78 to flow out from the outlet 78d of the charging cell 78. At this time, the charging cell 78 causes the inflowing positive electrode solution 21 and negative electrode solution 22 to participate in a charging reaction caused by charging power, causes the positive electrode solution 21 that has participated in the charging reaction to flow out from the outlet 78c, causes the negative electrode solution 22 that has participated in the charging reaction to flow out from the outlet 78d, and releases oxygen gas 12 generated by the charging reaction into the air around the charging cell 78.

[0049] The pipe 79 guides the positive electrode liquid 21 from the outlet 78c of the charging cell 78 to the supply source of the positive electrode liquid 21. Thus, the pipe 79 allows the positive electrode liquid 21 that flows out from the outlet 78c to flow into the supply source of the positive electrode liquid 21.

[0050] Pipe 80 guides negative electrode liquid 22 from outlet 78d of charging cell 78 to inlet 23d of storage unit 23. Thus, pipe 80 causes negative electrode liquid 22 that flows out from outlet 78d to flow into inlet 23d.

[0051] Pipe 71 , pump 72 , pipe 73 and pipe 79 constitute a mechanism for generating a flow of positive electrode solution 21 that causes positive electrode solution 21 to flow into inlet 78 a of charging cell 78 and flow out from outlet 78 c of charging cell 78 .

[0052] The piping 74, the pump 75, the piping 76, and the piping 80 constitute a mechanism for generating a flow of the negative electrode liquid 22 that causes the negative electrode liquid 22 to flow into the inlet 78b of the charging cell 78 and out of the outlet 78d of the charging cell 78.

[0053] Control circuit 81 controls pump 72 and pump 75. In this way, control circuit 81 constitutes a control unit that changes the flow rate of positive electrode solution 92 in first flow path 91e of charging cell 78 and / or the flow rate of negative electrode solution 97 in second flow path 96e of charging cell 78.

[0054] Control circuit 81 controls power supply 77. As a result, control circuit 81 constitutes a current control unit that changes the current value of the current flowing between positive electrode 93 of charging cell 78 and negative electrode 98 of charging cell 78.

[0055] The control circuit 81 includes a microcontroller and peripheral circuits. The microcontroller includes a processor and memory. The processor executes a program stored in the memory to cause the microcontroller and peripheral circuits to operate as the control unit and power supply control unit described above. All or part of the processing performed by the microcontroller may be performed by a dedicated electronic circuit.

[0056] 1.8 Charging Cell Fig. 2 is an exploded perspective view schematically illustrating a charging cell provided in the flow-type metal-air battery of the first embodiment. Fig. 3 is a cross-sectional view schematically illustrating a charging cell provided in the flow-type metal-air battery of the first embodiment.

[0057] As shown in FIGS. 2 and 3, the charging cell 78 includes a first layer 91, a positive electrode liquid 92, a positive electrode 93, a current-carrying plate 94, a gasket 95, a second layer 96, a negative electrode liquid 97, a negative electrode 98, a current-carrying plate 99, a gasket 100, a separator 101, a gasket 102, and a gasket 103.

[0058] 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 surface 91p and the opening surface 91q are on opposite sides to each other. The end surface 91a and the end surface 91c are on opposite sides to each other. The first layer 91 may have a frame shape other than a rectangular frame shape.

[0059] In the first layer 91, a first flow path 91e is formed.

[0060] The first flow channel 91e of the first layer 91 is exposed to the opening surface 91p and the opening surface 91q, and has an opening 91pe and an opening 91qe on the opening surface 91p and the opening surface 91q, respectively.

[0061] First flow path 91e is exposed to end face 91a and end face 91c, and has outlet 78a and outlet 78c at end face 91a and end face 91c, respectively. Thus, first flow path 91e extends from inlet 78a to outlet 78c. Thus, first flow path 91e allows positive electrode liquid 92 that has flowed into inlet 78a to pass through, and causes the passed positive electrode liquid 21 to flow out from outlet 78c.

[0062] The inlet 78a and the outlet 78c of the charging cell 78 are disposed on the vertically lower and upper sides, respectively. Therefore, the first flow path 91e of the first layer 91 has a portion that guides the positive electrode solution 92 in the vertical direction. The inlet 78a may be disposed at a position other than the vertically lower side, and the outlet 78c may be disposed at a position other than the vertically upper side.

[0063] The positive electrode liquid 92 flows through the first flow path 91e of the first layer 91. The positive electrode liquid 92 is part of the positive electrode liquid 21. As described above, the inlet 78a and the outlet 78c of the charging cell 78 are disposed on the vertically lower side and the vertically upper side, respectively. Therefore, the flow direction of the positive electrode liquid 92 in the portion where the positive electrode liquid 92 is guided vertically is from the vertically lower side to the vertically upper side.

[0064] When the flow direction of the positive electrode liquid 92 is from upper to lower in the vertical direction, the positive electrode liquid 92 flows down from the first flow path 91e even before the first flow path 91e of the first layer 91 is completely filled with the positive electrode liquid 92. For this reason, it is possible that the first flow path 91e cannot be completely filled with the positive electrode liquid 92. In contrast, when the flow direction of the positive electrode liquid 92 is from lower to upper in the vertical direction, the positive electrode liquid 92 overflows from the first flow path 91e after the first flow path 91e is completely filled with the positive electrode liquid 92. For this reason, it is possible to completely fill the first flow path 91e with the positive electrode liquid 92.

[0065] The oxygen gas 12 generated at the positive electrode 93 not only moves from the lower vertical direction to the upper vertical direction due to buoyancy, but also moves from the lower vertical direction to the upper vertical direction along with the flow of the positive electrode liquid 92. This can promote the discharge of the oxygen gas 12 from the charging cell 78.

[0066] 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. As a result, 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. As a result, the positive electrode 93 comes into contact with the positive electrode solution 92 flowing through the first flow path 91e. As a result, an oxidation reaction of water represented by formula (5) occurs in the positive electrode 93.

[0067] 4OH - →O2+2H2+4e - (5)

[0068] Therefore, the charging cell 78 generates oxygen gas 12 through an oxidation reaction of water at the positive electrode 93. The generated oxygen gas 12 is discharged from the charging cell 78.

[0069] The positive electrode 93 is made of a material with high oxygen generating capacity, which can improve the charging efficiency of the charging cell 78. It can also stabilize the charging operation of the charging cell 78. Examples of materials with high oxygen generating capacity include nickel.

[0070] The current-carrying plate 94 has a rectangular plate shape. The current-carrying plate 94 is placed on the opening surface 91p of the first layer 91, overlapping the positive electrode 93. As a result, the current-carrying plate 94 comes into contact with the positive electrode 93, and forms a current-carrying path to the positive electrode 93.

[0071] The gasket 95 is sandwiched between the opening surface 91p of the first layer 91, the positive electrode 93, and the current-carrying plate 94, and seals the gap between the opening surface 91p of the first layer 91, the positive electrode 93, and the current-carrying plate 94 in a liquid-tight manner.

[0072] 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 surface 96p and the opening surface 96q are located on opposite sides from each other. The end surface 96b and the end surface 96d are located on opposite sides from each other.

[0073] The second layer 96 has a second flow path 96e formed therein.

[0074] The second flow channel 96e of the second layer 96 is exposed to the opening surfaces 96p and 96q, and has openings 96pe and 96qe on the opening surfaces 96p and 96q, respectively.

[0075] The second flow path 96e is exposed to the end face 96b and the end face 96d, and has an inlet 78b and an outlet 78d at the end face 96b and the end face 96d, respectively. Therefore, the second flow path 96e extends from the inlet 78b to the outlet 78d. Therefore, the second flow path 96e allows the anode liquid 97 that has flowed into the inlet 78b to pass through and causes the anode liquid 97 that has passed through to flow out from the outlet 78d.

[0076] The inlet 78b and the outlet 78d of the charging cell 78 are disposed on the vertically lower and upper sides, respectively. Therefore, the second flow path 96e of the second layer 96 has a portion that guides the negative electrode liquid 97 in the vertical direction.

[0077] The negative electrode liquid 97 flows through the second flow path 96e of the second layer 96. The negative electrode liquid 97 is part of the negative electrode liquid 22. As described above, the inlet 78b and the outlet 78d of the charging cell 78 are disposed on the vertically lower side and the vertically upper side, respectively. Therefore, the flow direction of the negative electrode liquid 97 in the portion where the negative electrode liquid 97 is guided vertically is from the vertically lower side to the vertically upper side.

[0078] When the flow direction of the negative electrode liquid 97 is from vertically upward to vertically downward, the negative electrode liquid 97 flows down from the second flow path 96e even before the second flow path 96e of the second layer 96 is completely filled with the negative electrode liquid 97. For this reason, it is possible that the second flow path 96e cannot be completely filled with the negative electrode liquid 97. In contrast, when the flow direction of the negative electrode liquid 97 is from vertically downward to vertically upward, the negative electrode liquid 97 overflows from the second flow path 96e after the second flow path 96e is completely filled with the negative electrode liquid 97. For this reason, the second flow path 96e can be completely filled with the negative electrode liquid 97.

[0079] The specific gravity of the reduced negative electrode active material particles 41a generated in the negative electrode 98 is greater than the specific gravity of the negative electrode liquid 97. Therefore, when the flow direction of the negative electrode liquid 97 is from the upper vertical direction to the lower vertical direction, the reduced negative electrode active material particles 41a move from the upper vertical direction to the lower vertical direction and settle. However, when the flow direction of the negative electrode liquid 97 is from the lower vertical direction to the upper vertical direction, the reduced negative electrode active material particles 41a move from the lower vertical direction to the upper vertical direction along with the flow of the positive electrode liquid 92 against gravity. As a result, the reduced negative electrode active material particles 41a can be discharged from the charging cell 78 after their particle diameters have grown to a size that is sufficient to receive the drag force of the negative electrode liquid 97.

[0080] 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. As a result, the negative electrode 98 closes the opening 96pe of the second layer 96 and faces the second flow path 96e of the second layer 96. As a result, the negative electrode 98 comes into contact with the anode liquid 97 flowing through the second flow path 96e. As a result, in the negative electrode 98, zincate ions Zn(OH)4 produced by the oxidation reaction of metallic zinc represented by formulas (2) and (3) are converted into zincate ions Zn(OH)4 2- An anode liquid containing zinc oxide and / or zinc oxide ZnO is supplied to the anode 98. As a result, a reduction reaction to metallic zinc occurs in the anode 98, as represented by formulas (6) and (7).

[0081] ZnO+H2O+2OH - →Zn(OH)4 2- (6) Zn(OH)4 2- +2e - →Zn+4OH - (7)

[0082] Therefore, the charging cell 78 generates reduced negative electrode active material particles 41a through a reduction reaction to metallic zinc in the negative electrode 98. The generated reduced negative electrode active material particles 41a adhere to the negative electrode 98.

[0083] The anode 98 is made of a material capable of suppressing the hydrogen generation reaction that competes with the reduction reaction to metallic zinc. Examples of materials capable of suppressing the hydrogen generation reaction include at least one selected from the group consisting of carbon, copper, and magnesium. Examples of carbon include graphite. Carbon is resistant to corrosion. Therefore, when the anode 98 is made of carbon, it is possible to prevent the charging efficiency of the charging cell 78 from decreasing due to corrosion of the anode 98. This improves the long-term stability of the charging cell 78. Furthermore, the adhesion of the reduced anode active material particles 41a to magnesium is low. Therefore, when the anode 98 is made of magnesium, it is possible to peel the reduced anode active material particles 41a from the anode 98 and facilitate the removal of the reduced anode active material particles 41a from the charging cell 78.

[0084] The current-carrying plate 99 has a rectangular plate shape. The current-carrying plate 99 is placed on the opening surface 96p of the second layer 96, overlapping the negative electrode 98. As a result, the current-carrying plate 99 comes into contact with the negative electrode 98, and forms a current-carrying path to the negative electrode 98.

[0085] The gasket 100 is sandwiched between the opening surface 96p of the second layer 96, the negative electrode 98, and the current-carrying plate 99, and liquid-tightly seals the gap between the opening surface 96p of the second layer 96, and the negative electrode 98 and the current-carrying plate 99.

[0086] 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. As a result, the separator 101 closes the opening 91qe of the first layer 91 and faces the first flow path 91e of the first layer 91. The separator 101 is also disposed on the opening surface 96q of the second layer 96. As a result, the separator 101 closes the opening 96qe of the second layer 96 and faces the second flow path 96e of the second layer 96.

[0087] The separator 101 is sandwiched between the first layer 91 and the second layer 96. As a result, the separator 101 separates the first flow paths 91e of the first layer 91 from the second flow paths 96e of the second layer 96. The separator 101 does not allow the reduced-state negative electrode active material particles 41a, the oxidized-state negative electrode active material particles 41b, and the thickener 44 to pass through. As a result, the separator 101 prevents the reduced-state negative electrode active material particles 41a, the oxidized-state negative electrode active material particles 41b, and the thickener 44 from migrating from the negative electrode liquid 97 to the positive electrode liquid 92.

[0088] The separator 101 has high ionic conductivity. This allows the separator 101 to convert hydroxide ions OH - This allows hydroxide ions OH - allows the electrolyte to migrate from the negative electrode 97 to the positive electrode 92.

[0089] The separator 101 is preferably a membrane that does not have pores of 50 nm or more, more preferably 100 nm or more, because it is necessary to prevent permeation of the reduced-state negative electrode active material particles 41a, the oxidized-state negative electrode active material particles 41b, and the thickener 44. The separator 101 is, for example, an anion exchange membrane, a hydrous gel membrane, or a membrane that includes a plurality of inorganic ion conductor particles and a resin impregnated into the grain boundaries of the plurality of inorganic ion conductor particles.

[0090] In the reduction reaction to metallic zinc at the negative electrode 98, i.e., the electrodeposition reaction of metallic zinc, non-uniform current distribution may cause tree-like, i.e., dendritic, metallic zinc to grow from the negative electrode 98. The separator 101 has high dendrite resistance. Therefore, the separator 101 inhibits the dendritic metallic zinc from growing beyond the separator 101. This makes it possible to prevent the positive electrode 93 and the negative electrode 98 from shorting out with each other via the dendritic metallic zinc.

[0091] The gasket 102 is sandwiched between the open surface 91q of the first layer 91 and the separator 101, and seals the gap between the open surface 91q of the first layer 91 and the separator 101 in a liquid-tight manner.

[0092] The gasket 103 is sandwiched between the open surface 96q of the second layer 96 and the separator 101, and seals the gap between the open surface 96q of the second layer 96 and the separator 101 in a liquid-tight manner.

[0093] 1.9 Theoretical voltage of flow-type metal-air batteries The oxidation of water at the positive electrode 93 and the reduction to metallic zinc at the negative electrode 98 result in the overall reaction represented by equation (8) in the charging cell 78.

[0094] 2Zn+O2→2ZnO (8)

[0095] Thus, the charging cell 78 converts zinc oxide to zinc metal when charged.

[0096] The potentials of the positive electrode and negative electrode during the discharge and charge reactions are −1.25 V and 0.40 V, respectively, relative to the standard hydrogen electrode. Therefore, the theoretical voltage of the flow-type metal-air battery 1 is 1.65 V.

[0097] 1.10 Viscosity of positive and negative electrolytes The positive electrode liquid 92 has a first viscosity. The negative electrode liquid 97 has a second viscosity higher than the first viscosity. The first viscosity is, for example, 1 mPasec or more and 9 mPasec or less, and preferably 2 mPasec or more and 3 mPasec or less. The second viscosity is, for example, 100 mPasec or more and 2000 mPasec or less, and preferably 200 mPasec or more and 500 mPasec or less. The viscosity of the positive electrode liquid 92 can be measured using an Ubbelohde viscometer or the like, and the viscosity of the negative electrode liquid 97 can be measured using a VT-06 manufactured by Rion Corporation or the like.

[0098] If the positive electrode liquid 92 has a high viscosity, the oxygen gas 12 generated at the positive electrode 93 is easily trapped in the positive electrode liquid 92, causing the positive electrode liquid 92 to become foamy. This makes it difficult to separate the oxygen gas 12 from the positive electrode liquid 92 and to discharge the separated oxygen gas 12 from the charging cell 78. This reduces the charging efficiency of the charging cell 78.

[0099] In contrast, when the positive electrode liquid 92 has a low viscosity, the turbulence of the positive electrode liquid 92 promotes the growth of bubbles of the oxygen gas 12. This makes it easier to separate the oxygen gas 12 from the positive electrode liquid 92 and to discharge the separated oxygen gas 12 from the charging cell 78. This increases the charging efficiency of the charging cell 78.

[0100] If the anode liquid 97 has a low viscosity, the drag force acting on the reduced anode active material particles 41a when the anode liquid 97 acts on the reduced anode active material particles 41a is small. This makes it difficult to peel the reduced anode active material particles 41a from the anode 98 and discharge the peeled reduced anode active material particles 41a from the charging cell 78. It also makes it difficult to prevent the reduced anode active material particles 41a from settling due to gravity.

[0101] In contrast, if the anode liquid 97 has a high viscosity, the drag acting on the reduced anode active material particles 41a when the anode liquid 97 acts on the reduced anode active material particles 41a becomes large. This makes it easier to peel the reduced anode active material particles 41a from the anode 98 and discharge the peeled reduced anode active material particles 41a from the charging cell 78. It also makes it easier to prevent the reduced anode active material particles 41a from settling due to gravity.

[0102] In this way, by making the second viscosity higher than the first viscosity, peeling of the reduced-state negative electrode active material particles 41a from the negative electrode 98 is promoted, eliminating the need for a movable part for peeling the reduced-state negative electrode active material particles 41a from the negative electrode 98. This makes it possible to peel the reduced-state negative electrode active material particles 41a from the negative electrode 98 without consuming a large amount of power, and provides a flow-type metal-air battery 1 having high durability.

[0103] The viscosity of the negative electrode liquid 97 is adjusted by the type and / or concentration of the thickener 44 contained in the negative electrode liquid 97. Examples of the thickener 44 include organic polymer materials and inorganic particles having a particle diameter of less than 1 μm. Examples of the organic polymer materials include polyacrylic acid, carboxymethyl cellulose, sodium alginate, and acrylic acid-alkyl methacrylate copolymers. Examples of the inorganic materials include calcium hydroxide and potassium silicate. The viscosity of the negative electrode liquid 97 may be adjusted by the concentration of the oxidized negative electrode active material particles 41b having a particle diameter of less than 1 μm. When the viscosity of the negative electrode liquid 97 is adjusted by the concentration of the oxidized negative electrode active material particles 41b, the negative electrode liquid 97 does not need to contain the thickener 44. When the negative electrode active material ions 42 are zincate ions (Zn(OH)4 2- ), when calcium hydroxide or potassium silicate is used as the thickener 44, the calcium hydroxide or potassium silicate reacts with zincate ions (Zn(OH)4 2- ) affects the solubility of the negative electrode active material ions 42, so that the concentration of the negative electrode active material ions 42 in the negative electrode solution 97 can be made to be suitable for the charging reaction.

[0104] When the negative electrode liquid 97 contains a thickener 44, the separator 101 does not allow the thickener 44 to pass through. This prevents the thickener 44 from migrating from the negative electrode liquid 97 to the positive electrode liquid 92. This makes it possible to maintain a state in which the viscosity of the negative electrode liquid 97 is higher than that of the positive electrode liquid 92 for a long period of time. This makes it easier than ever to separate oxygen gas 12 from the positive electrode liquid 92 and discharge the separated oxygen gas 12 from the charging cell 78, and it is possible to maintain a state in which the reduced-state negative electrode active material particles 41a can be easily peeled from the negative electrode 98 and the peeled reduced-state negative electrode active material particles 41a can be easily discharged from the charging cell 78 for a long period of time. This makes it possible to maintain a state in which the charging efficiency of the charging cell 78 is high for a long period of time.

[0105] 1.11 Additional components of the negative electrolyte The anode liquid 97 preferably contains at least one ion selected from the group consisting of Group 13 metal elements, Group 14 metal elements, and Group 15 metal elements. More preferably, it contains at least one ion selected from the group consisting of indium and thallium contained in Group 13 metal elements, tin and lead contained in Group 14 metal elements, and antimony and bismuth contained in Group 15 metal elements. It particularly preferably contains indium ions. When the anode liquid 22 contains these ions, the adhesion of the reduced anode active material particles 41a to the anode 98 can be reduced. This makes it easier to peel the reduced anode active material particles 41a from the anode 98 and to eject the peeled reduced anode active material particles 41a from the charging cell 78. When the anode liquid 97 contains these metal ions, the concentration of the metal ions is preferably 20 to 300 ppm, and more preferably 50 to 200 ppm. If the concentration of these metal ions is less than 20 ppm, the adhesion of the reduced negative electrode active material particles 41a to the negative electrode 98 may not be sufficiently reduced. If the concentration of these metal ions exceeds 300 ppm, the metals may not dissolve as ions and may precipitate in the solution. In particular, when the negative electrode liquid 22 contains indium ions, the adhesion of the reduced negative electrode active material particles 41a to the negative electrode 98 may be reduced because the ionization tendency of indium is smaller than that of zinc. Indium is generated from these indium ions before zinc is generated from zinc ions, and a base made of the generated indium is formed. For this reason, it is not appropriate to include gallium, germanium, or arsenic ions, which have an ionization tendency greater than that of zinc, in the negative electrode liquid 22.

[0106] 1.12 First example of current and flow rate control Fig. 4A is a graph showing a first example of control of the current value flowing between the positive electrode of a charging cell provided in the flow-type metal-air battery of Embodiment 1 and the negative electrode of the charging cell. Fig. 4B is a graph showing a first example of control of the flow rate of the negative electrode solution in the second flow path of the second layer of the charging cell provided in the flow-type metal-air battery of Embodiment 1.

[0107] In Figure 4A, the horizontal axis represents time and the vertical axis represents the current value, while in Figure 4B, the horizontal axis represents time and the vertical axis represents the flow velocity.

[0108] In a first control example of the current value of the current flowing between the positive electrode 93 and the negative electrode 98 and the flow rate of the negative electrode liquid 97 in the second flow path 96e of the second layer 96, the control circuit 81 serving as the current flow control unit maintains the current value at a constant current value I1, as shown in Fig. 4A. Therefore, the current flow control unit keeps the current value at the constant current value I1 during the period T0 to T4.

[0109] 4B, the control circuit 81 serving as the control unit periodically changes the flow rate between a first flow rate LV1 and a second flow rate VL2 that is greater than the first flow rate LV1. Therefore, the control unit sets the flow rate to the first flow rate VL1 during the period T0 to T1, sets the flow rate to the second flow rate VL2 during the period T1 to T2, sets the flow rate to the first flow rate VL1 during the period T2 to T3, and sets the flow rate to the second flow rate VL2 during the period T3 to T4.

[0110] When the anode liquid 97 acts on the reduced-state anode active material particles 41a, the drag force acting on the reduced-state anode active material particles 41a increases as the particle diameter of the reduced-state anode active material particles 41a increases and as the flow rate of the anode liquid 97 increases. For this reason, in order to peel the reduced-state anode active material particles 41a from the anode 98 and discharge the peeled reduced-state anode active material particles 41a from the charging cell 78, it is desirable to increase the flow rate of the anode liquid 98 at the timing when the particle diameter of the reduced-state anode active material particles 41a increases, thereby instantaneously exerting a large drag force on the reduced-state anode active material particles 41a.

[0111] 4A and 4B, charging is performed, but during periods T0 to T1 and periods T2 to T3 during charging when the flow rate is reduced to first flow rate VL1, the drag acting on the reduced negative electrode active material particles 41a decreases, causing the reduced negative electrode active material particles 41a to grow, and therefore the particle diameter of the reduced negative electrode active material particles 41a increases.

[0112] During the periods T1 to T2 and T3 to T4 in which the flow rate is increased to the second flow rate VL2, the drag acting on the reduced negative electrode active material particles 41a, whose particle diameter has increased, increases.

[0113] This facilitates peeling of the reduced negative electrode active material particles 41a from the negative electrode 98 and expulsion of the peeled reduced negative electrode active material particles 41a from the charging cell 78. Furthermore, by setting the flow rate to the first flow rate VL1 during the periods T0 to T1 and T2 to T3, the power consumed to flow the negative electrode solution 97 can be reduced.

[0114] When the current value and the flow rate are controlled in this manner to promote the separation of the reduced-state negative electrode active material particles 41a from the negative electrode 98, there is no need for a movable part for separating the reduced-state negative electrode active material particles 41a from the negative electrode 98. This makes it possible to separate the reduced-state negative electrode active material particles 41a from the negative electrode 98 without consuming a large amount of power, and to provide a highly durable flow-type metal-air battery 1.

[0115] 4A illustrates a control method for maintaining the current value at a constant current value I1 during periods T0 to T4, but a control method for varying the current value during periods T0 to T4 under the condition that the current value exceeds a predetermined current value may also be employed. Also, while FIG. 4B illustrates a control method for maintaining the flow rate at VL1 during periods T0 to T1 and periods T2 to T3, and at VL2 during periods T1 to T2 and periods T3 to T4, a control method for setting the flow rate to VL1 or higher during periods T0 to T1 and periods T2 to T3, and to VL2 or lower during periods T1 to T2 and periods T3 to T4 may also be employed.

[0116] Furthermore, FIG. 4B illustrates a control method in which the lengths of the periods T0-T1, T1-T2, T2-T3, and T3-T4 are all the same, but from the perspective of reducing the power consumed to flow the negative electrode liquid 97, it is desirable to make the lengths of the periods T1-T2 and T3-T4 shorter than the lengths of the periods T0-T1 and T2-T3, and it is even more desirable to make the lengths 1 / 5 to 1 / 20 of the lengths of the periods T0-T1 and T2-T3.

[0117] 1.13 Second example of current and flow rate control Fig. 5A is a graph showing a second example of control of the current value flowing between the positive electrode of a charging cell provided in the flow-type metal-air battery of Embodiment 1 and the negative electrode of the charging cell. Fig. 5B is a graph showing a second example of control of the flow rate of the negative electrode solution in the second flow path of the charging cell provided in the flow-type metal-air battery of Embodiment 1.

[0118] In Figure 5A, the horizontal axis represents time and the vertical axis represents the current value, while in Figure 5B, the horizontal axis represents time and the vertical axis represents the flow velocity.

[0119] 5A , in a second control example of the current value of the current flowing between the positive electrode 93 and the negative electrode 98 and the flow rate of the negative electrode liquid 97 in the second flow path 96e of the second layer 96, the control circuit 81 serving as the current flow control unit periodically changes the current value between a first current value I1 and a second current value I2 that is smaller than the first current value I1. Therefore, the current flow control unit sets the current value to the first current value I1 during the period T0 to T1, sets the current value to the second current value I2 during the period T1 to T2, sets the current value to the first current value I1 during the period T2 to T3, and sets the current value to the second current value I2 during the period T3 to T4. The current control unit preferably sets the second current value I2 to be smaller than the first current value I1, and more preferably sets the second current value I2 to 0, and alternately flows current between the positive electrode 93 and the negative electrode 98 and reduces or stops the flow of current between the positive electrode 93 and the negative electrode 98.

[0120] 5B, the control circuit 81 serving as the control unit maintains the flow velocity at a constant flow velocity VL2. Therefore, the control unit maintains the flow velocity at the constant flow velocity VL2 during the period T0 to T4.

[0121] When the anode liquid 98 acts on the reduced-state anode active material particles 41a, the drag acting on the reduced-state anode active material particles 41a increases as the particle diameter of the reduced-state anode active material particles 41a increases. For this reason, it is desirable to increase the particle diameter of the reduced-state anode active material particles 41a in order to peel the reduced-state anode active material particles 41a from the anode 98 and discharge the peeled reduced-state anode active material particles 41a from the charging cell 78. However, it is desirable to stop the growth of the reduced-state anode active material particles 41a while the reduced-state anode active material particles 41a are being peeled from the anode 98.

[0122] 5A and 5B, the reduced negative electrode active material particles 41a grow during the periods T0 to T1 and T2 to T3 when charging is performed at the first current value I1, and therefore the particle diameter of the reduced negative electrode active material particles 41a increases.

[0123] During periods T1 to T2 and T3 to T4 when charging is performed at the second current value I2, a large drag acts on the reduced negative electrode active material particles 41a whose particle diameter has increased, causing the reduced negative electrode active material particles 41a to peel off from the negative electrode 98. During periods T1 to T2 and T3 to T4, the growth of the reduced negative electrode active material particles 41a is suppressed or stopped.

[0124] This can facilitate peeling of the reduced negative electrode active material particles 41 a from the negative electrode 98 and expulsion of the peeled reduced negative electrode active material particles 41 a from the charging cell 78 .

[0125] The first current value I1 may be greater than the current value Ih at which a hydrogen generation reaction, which is a competing reaction with the reduction reaction that produces reduced-state negative electrode active material particles 41a on the negative electrode 98, begins to occur. Therefore, the first current value I1 may be greater than the current value Ih at which hydrogen gas is generated on the negative electrode 98. The generated hydrogen gas increases the internal pressure inside the second flow passage 96e of the second layer 96 and increases the flow rate of the negative electrode liquid 97 in the second flow passage 96e. Therefore, when hydrogen gas is generated on the negative electrode 98, the drag force acting on the reduced-state negative electrode active material particles 41a when the negative electrode liquid 97 acts on the reduced-state negative electrode active material particles 41a increases. This can facilitate peeling of the reduced-state negative electrode active material particles 41a from the negative electrode 98 and expulsion of the peeled reduced-state negative electrode active material particles 41a from the charging cell 78. The generated hydrogen gas adheres to the reduced-state negative electrode active material particles 41a and exerts a buoyant force on the reduced-state negative electrode active material particles 41a. This facilitates the separation of the reduced-state negative electrode active material particles 41a from the negative electrode 98 and the discharge of the separated reduced-state negative electrode active material particles 41a from the charging cell 78. The generated hydrogen gas adheres to the reduced-state negative electrode active material particles 41a and increases the apparent Stokes diameter of the reduced-state negative electrode active material particles 41a. Therefore, when hydrogen gas is generated on the negative electrode 98, the drag force acting on the reduced-state negative electrode active material particles 41a increases when the negative electrode liquid 97 acts on the reduced-state negative electrode active material particles 41a. This facilitates the separation of the reduced-state negative electrode active material particles 41a from the negative electrode 98 and the discharge of the separated reduced-state negative electrode active material particles 41a from the charging cell 78.

[0126] When the current value and the flow rate are controlled in this manner to promote the separation of the reduced-state negative electrode active material particles 41a from the negative electrode 98, there is no need for a movable part for separating the reduced-state negative electrode active material particles 41a from the negative electrode 98. This makes it possible to separate the reduced-state negative electrode active material particles 41a from the negative electrode 98 without consuming a large amount of power, and to provide a highly durable flow-type metal-air battery 1.

[0127] 5A illustrates a control method in which the current value is maintained at I1 during periods T0-T1 and T2-T3, and at I2 during periods T1-T2 and T3-T4. Alternatively, a control method may be employed in which the current value is set to I1 or higher during periods T0-T1 and T2-T3, and to I2 or lower during periods T1-T2 and T3-T4. Also, while FIG. 5B illustrates a control method in which the flow velocity is maintained at a constant VL2 during periods T0-T4, a control method in which the flow velocity is varied under conditions in which the flow velocity exceeds a predetermined flow velocity during periods T0-T4 may be employed.

[0128] Furthermore, FIG. 5A illustrates a control method in which the lengths of periods T0-T1, T1-T2, T2-T3, and T3-T4 are the same, but from the viewpoint of improving the efficiency of the charging reaction, it is desirable to make the lengths of periods T1-T2 and T3-T4 shorter than the lengths of periods T0-T1 and T2-T3, and it is even more desirable to make them 1 / 5 to 1 / 20 of the lengths of periods T0-T1 and T2-T3.

[0129] 1.14 Third example of current and flow rate control Fig. 6A is a graph showing a third example of control of the current value flowing between the positive electrode of a charging cell provided in the flow-type metal-air battery of Embodiment 1 and the negative electrode of the charging cell. Fig. 6B is a graph showing a third example of control of the flow rate of the negative electrode solution in the second flow path of the charging cell provided in the flow-type metal-air battery of Embodiment 1.

[0130] In Figure 6A, the horizontal axis represents time and the vertical axis represents the current value, while in Figure 6B, the horizontal axis represents time and the vertical axis represents the flow velocity.

[0131] 6A , in a third control example of the current value of the current flowing between the positive electrode 93 and the negative electrode 98 and the flow rate of the negative electrode liquid 97 in the second flow path 96e of the second layer 96, a control circuit 81 serving as an energization control unit periodically changes the current value between a first current value I1 and a second current value I2 that is smaller than the first current value I1. Therefore, the energization control unit sets the current value to the first current value I1 during a period T0 to T1, sets the current value to the second current value I2 during a period T1 to T2, sets the current value to the first current value I1 during a period T2 to T3, and sets the current value to the second current value I2 during a period T3 to T4. The current control unit preferably sets the second current value I2 to be smaller than the first current value I1, and more preferably sets the second current value I2 to 0, and alternately flows current between the positive electrode 93 and the negative electrode 98 and reduces or stops the flow of current between the positive electrode 93 and the negative electrode 98.

[0132] 6B, the control circuit 81 serving as the control unit periodically changes the flow rate between a first flow rate LV1 and a second flow rate VL2 that is greater than the first flow rate LV1. Therefore, the control unit sets the flow rate to the first flow rate VL1 during the period T0 to T1, sets the flow rate to the second flow rate VL2 during the period T1 to T2, sets the flow rate to the first flow rate VL1 during the period T2 to T3, and sets the flow rate to the second flow rate VL2 during the period T3 to T4.

[0133] When the anode liquid 98 acts on the reduced-state anode active material particles 41a, the drag force acting on the reduced-state anode active material particles 41a increases as the particle diameter of the reduced-state anode active material particles 41a increases and as the flow rate of the anode liquid 98 increases. For this reason, in order to peel the reduced-state anode active material particles 41a from the anode 98 and discharge the peeled reduced-state anode active material particles 41a from the charging cell 78, it is desirable to increase the flow rate of the anode liquid 98 at the timing when the particle diameter of the reduced-state anode active material particles 41a increases, so that a large drag force is instantaneously exerted on the reduced-state anode active material particles 41a. However, it is desirable to stop the growth of the reduced-state anode active material particles 41a while the reduced-state anode active material particles 41a are being peeled from the anode 98. Therefore, the periods T0-T1 and T2-T3 during which charging is performed at the first current value I1 include the periods T0-T1 and T2-T3 during which the flow rate is set to the first flow rate VL1, and the periods T1-T2 and T3-T4 during which charging is performed at the second current value I2 include the periods T1-T2 and T3-T4 during which the flow rate is set to the second flow rate VL2.

[0134] 6A and 6B, charging is performed at the first current value I1, but during periods T0-T1 and T2-T3 when the flow rate is reduced to the first flow rate VL1, the drag acting on the reduced negative electrode active material particles 41a decreases, causing the reduced negative electrode active material particles 41a to grow, and the particle diameter of the reduced negative electrode active material particles 41a increases.

[0135] During the periods T1-T2 and T3-T4, when the flow rate is increased to the second flow rate VL2, the drag acting on the reduced negative electrode active material particles 41a, whose particle size has increased, increases. During the periods T1-T2 and T3-T4, the growth of the reduced negative electrode active material particles 41a is suppressed or stopped.

[0136] This can promote peeling of the reduced negative electrode active material particles 41a from the negative electrode 98 and discharging of the peeled reduced negative electrode active material particles 41a from the charging cell 78. Furthermore, by setting the flow rate to the first flow rate VL1 during the periods T1 to T2 and T2 to T3, the power consumed to flow the negative electrode solution 97 can be reduced.

[0137] When the current value and the flow rate are controlled in this manner to promote the separation of the reduced-state negative electrode active material particles 41a from the negative electrode 98, there is no need for a movable part for separating the reduced-state negative electrode active material particles 41a from the negative electrode 98. This makes it possible to separate the reduced-state negative electrode active material particles 41a from the negative electrode 98 without consuming a large amount of power, and to provide a highly durable flow-type metal-air battery 1.

[0138] 6A illustrates a control method in which the current value is maintained at I1 during periods T0-T1 and T2-T3 and at I2 during periods T1-T2 and T3-T4, but a control method in which the current value is I1 or more during periods T0-T1 and T2-T3 and at I2 or less during periods T1-T2 and T3-T4 may also be employed. Also, while FIG. 6B illustrates a control method in which the flow rate is maintained at VL1 during periods T0-T1 and T2-T3 and at VL2 during periods T1-T2 and T3-T4, a control method in which the flow rate is VL1 or more during periods T0-T1 and T2-T3 and at VL2 during periods T1-T2 and T3-T4 may also be employed.

[0139] 6A and 6B illustrate a control method in which the lengths of the periods T0 to T1, the periods T1 to T2, the periods T2 to T3, and the periods T3 to T4 are all the same, but from the perspective of reducing the power consumed to flow the negative electrode solution 97 and improving the efficiency of the charging reaction, it is desirable to make the lengths of the periods T1 to T2 and the periods T3 to T4 shorter than the lengths of the periods T0 to T1 and the periods T2 to T3, and it is even more desirable to make them 1 / 5 to 1 / 20 of the lengths of the periods T0 to T1 and the periods T2 to T3.

[0140] 1.15 Fourth example of current and flow rate control FIG. 7 is a graph showing a fourth example of control of the current value of the current flowing between the positive electrode of the charging cell provided in the flow-type metal-air battery of the first embodiment and the negative electrode of the charging cell.

[0141] In FIG. 7, the horizontal axis represents time, and the vertical axis represents the current value.

[0142] Below, the fourth control example of the current value of the current flowing between the positive electrode 93 and the negative electrode 98 and the flow rate of the negative electrode liquid 97 in the second flow path 96e of the second layer 96 will be explained in terms of the differences from the third control example of the current and the flow rate.

[0143] In the fourth control example of the current and the flow rate, similar to the third control example of the current and the flow rate, as shown in FIG. 7, a control circuit 81 serving as a current control unit periodically changes the current value between a first current value I1 and a second current value I2 smaller than the first current value I1.

[0144] However, in the fourth control example of the current and the flow rate, unlike the third control example of the current and the flow rate, the sign of the first current value I1 and the sign of the second current value I2 are opposite, as shown in FIG. 7 . Therefore, the direction of the current flowing between the positive electrode 93 and the negative electrode 98 during periods T0-T1 and T2-T3 is opposite to the direction of the current flowing between the positive electrode 93 and the negative electrode 98 during periods T1-T2 and T3-T4. The sign of the first current value I1 is positive, and the sign of the second current value I2 is negative. Therefore, a reduction reaction to metallic zinc occurs on the negative electrode 98 during periods T0-T1 and T2-T3, and an oxidation reaction to zinc ions occurs on the negative electrode 98 during periods T1-T2 and T3-T4. The oxidation reaction to zinc ions occurs at the interface between the negative electrode 98 and the reduced-state negative electrode active material particles 41a. Therefore, the reduced-state negative electrode active material particles 41a are dissolved at the interface by an oxidation reaction to zinc ions, thereby reducing the adhesion of the reduced-state negative electrode active material particles 41a to the negative electrode 98. This facilitates peeling of the reduced-state negative electrode active material particles 41a from the negative electrode 98 and expulsion of the peeled reduced-state negative electrode active material particles 41a from the charging cell 78.

[0145] When the current value and the flow rate are controlled in this manner to promote the separation of the reduced-state negative electrode active material particles 41a from the negative electrode 98, there is no need for a movable part for separating the reduced-state negative electrode active material particles 41a from the negative electrode 98. This makes it possible to separate the reduced-state negative electrode active material particles 41a from the negative electrode 98 without consuming a large amount of power, and to provide a highly durable flow-type metal-air battery 1.

[0146] 1.16 Fifth example of current and flow rate control FIG. 8 is a graph showing a third example of control of the flow rate of the negative electrode solution in the second flow path of the charging cell provided in the flow-type metal-air battery of the first embodiment.

[0147] In FIG. 8, the horizontal axis represents time, and the vertical axis represents the flow velocity.

[0148] Below, the fifth control example of the current value of the current flowing between the positive electrode 93 and the negative electrode 98 and the flow rate of the negative electrode liquid 97 in the second flow path 96e of the second layer 96 will be explained, with reference to the third control example of the current and the flow rate.

[0149] In the fifth control example, similar to the third control example of the current and the flow rate, as shown in FIG. 8, the control circuit 81, which serves as the control unit, periodically changes the flow rate between a first flow rate LV1 and a second flow rate VL2 that is greater than the first flow rate LV1.

[0150] However, in the fifth control example, unlike the third control example with respect to the current and the flow rate, the first flow rate VL1 is 0 as shown in FIG. 8 . This eliminates the power consumed to flow the anode liquid 97 during the periods T0-T1 and T2-T3. This also limits the supply of anode active material ions 42 onto the anode 98 during the periods T0-T1 and T2-T3. This promotes the growth of bulky, dendritic, reduced anode active material particles 41a on the anode 98. This increases the drag acting on the reduced anode active material particles 41a when the anode liquid 97 acts on the reduced anode active material particles 41a.

[0151] When the current value and the flow rate are controlled in this manner to promote the separation of the reduced-state negative electrode active material particles 41a from the negative electrode 98, there is no need for a movable part for separating the reduced-state negative electrode active material particles 41a from the negative electrode 98. This makes it possible to separate the reduced-state negative electrode active material particles 41a from the negative electrode 98 without consuming a large amount of power, and to provide a highly durable flow-type metal-air battery 1.

[0152] 1.17 Variations FIG. 9 is a cross-sectional view that schematically illustrates a charging cell provided in a flow-type metal-air battery according to a first modified example of the first embodiment.

[0153] In the first embodiment, as shown in FIG. 3 , the positive electrode chamber is formed of three positive electrode chamber components, namely, a first layer 91, a current-carrying plate 94, and a gasket 95, and the negative electrode chamber is formed of three negative electrode chamber components, namely, a second layer 96, a current-carrying plate 99, and a gasket 100.

[0154] In contrast to this, in the first modified example of the first embodiment, as shown in FIG. 9 , the positive electrode chamber is formed by a single positive electrode chamber component 111 that integrates the first layer 91, the current-carrying plate 94, and the gasket 95, and the negative electrode chamber is formed by a single negative electrode chamber component 112 that integrates the second layer 96, the current-carrying plate 99, and the gasket 100.

[0155] FIG. 10 is a cross-sectional view that schematically illustrates a charging cell provided in a flow-type metal-air battery according to a second modified example of the first embodiment.

[0156] In the first embodiment, as shown in FIG. 3, the negative electrode 98 and the current-carrying plate 99 are molded as separate bodies.

[0157] In contrast, in the second modified example of the first embodiment, as shown in FIG. 10 , the current-carrying plate 99 also serves as the negative electrode 98, and the current-carrying plate 99 is configured integrally with the negative electrode 98, with the negative electrode 98 and the current-carrying plate 99 being molded as a single unit. This reduces the number of parts that make up the charging cell 78. It also reduces the number of steps required to assemble the charging cell 78. It also reduces the lead time required to assemble the charging cell 78. As a result, the cost of the charging cell 78 can be reduced.

[0158] FIG. 11 is a cross-sectional view that schematically illustrates a charging cell provided in a flow-type metal-air battery according to a third modified example of the first embodiment.

[0159] In the first embodiment, as shown in FIG. 3, the second layer 96, the negative electrode 98, and the current-carrying plate 99 are molded as separate bodies.

[0160] In contrast, in a third modified example of the first embodiment, as shown in FIG. 11 , a current-carrying plate 99 also serves as the second layer 96 and the negative electrode 98, and is integrally formed with the second layer 96 and the negative electrode 98, such that the second layer 96, the negative electrode 98, and the current-carrying plate 99 are molded as a single unit. This reduces the number of components constituting the charging cell 78. It also reduces the number of steps required to assemble the charging cell 78. It also shortens the lead time required to assemble the charging cell 78. These features reduce the cost of the charging cell 78. It also eliminates the need for a gasket 100 that provides a liquid-tight seal between the second layer 96 and the negative electrode 98 and the current-carrying plate 99. This prevents leakage of the negative electrode solution 97 from the negative electrode chamber. This improves the long-term stability and reliability of the charging cell 78.

[0161] FIG. 12 is a cross-sectional view that schematically illustrates a charging cell provided in a flow-type metal-air battery according to a fourth modified example of the first embodiment.

[0162] In the fourth modified example of the first embodiment, as shown in FIG. 12 , the negative electrode 98 includes a first portion 121 made of a first material and a second portion 122 made of a second material. The hydrogen overvoltage of the second material is lower than the hydrogen overvoltage of the first material. This makes it easier for hydrogen gas to be generated on the second portion 122. As described above, the generated hydrogen gas peels off the reduced negative electrode active material particles 41a from the negative electrode 98, promoting the discharge of the peeled reduced negative electrode active material particles 41a from the charging cell 78. The first material includes, for example, at least one selected from the group consisting of carbon, copper, and magnesium. The second material includes, for example, nickel.

[0163] 1.18 Charging experiment (Charging experiment 1) As Example 1, a charging cell 78 shown in FIG. 3 was fabricated, and a charging experiment was carried out using the fabricated charging cell 78.

[0164] Carbon was used for the negative electrode 98. The size of the portion of the negative electrode 98 that was immersed in the negative electrode liquid 97 was 10 mm x 80 mm.

[0165] A nickel porous body (Celmet (registered trademark) manufactured by Sumitomo Electric Industries, Ltd.) was used for the positive electrode 93. The size of the portion of the positive electrode 93 immersed in the positive electrode solution 92 was 10 mm x 80 mm.

[0166] The configuration other than the negative electrode 98 and the positive electrode 93 was as follows. Separator 101: Nippon Shokubai Co., Ltd. "0.1 mm thick, 20 mm x 110 mm sheet separator" Positive electrolyte 92: Zn saturated KOH aqueous solution "KOH 29.2%, zinc oxide 4%" Anode electrolyte 97: Zn saturated KOH aqueous solution (KOH 29.2%, zinc oxide 4%, thickener 1%) Here, the viscosity of the negative electrode solution was evaluated using VT-06 manufactured by Rion Co., Ltd. and found to be 100 mPasec.

[0167] The charged cell of Comparative Example 1 had the same configuration as the charged cell 78 of Example 1, except for the negative electrode solution 97. The negative electrode solution 97 of Comparative Example 1 was as follows. Anode electrolyte 97: Zn saturated KOH aqueous solution (KOH 29.2%, zinc oxide 4%) Here, the viscosity of the negative electrode liquid was evaluated using an Ubbelohde viscometer and found to be 2 mPasec.

[0168] A charging experiment was carried out by passing the positive electrode solution 92 and the negative electrode solution 97 through the charging cell 78 of Example 1 and the charging cell of the comparative example. In the charging experiment, a current density of 100 mA / cm was applied. 2 A constant current charge of 1000 kJ / cm2 (per projected area of ​​the negative electrode 98) was performed. A battery tester (SPEC20526-PFX2011S, manufactured by Kikusui Electronics Co., Ltd.) was used for the measurement. In the charging experiment, the weight of reduced negative electrode active material (metallic zinc) particles 41a that had been peeled from the negative electrode 98 and discharged from the charged cell 78 of Example 1 and the charged cell of the comparative example was measured, and the zinc recovery rate relative to the amount of electricity input was calculated. The calculation results are shown in Table 1. Zinc recovery rate (%) = weight of discharged zinc (g) x 0.82 (Ah / g: specific capacity of zinc) / input electricity (Ah) x 100

[0169] [Table 1]

[0170] As shown in Table 1, when the negative electrode liquid 97 has a low viscosity (Comparative Example 1), the reduced negative electrode active material (metallic zinc) particles 41a are not discharged from the charged cell. This is because the drag acting on the reduced negative electrode active material (metallic zinc) particles 41a when the negative electrode liquid 97 acts on the reduced negative electrode active material (metallic zinc) particles 41a is small.

[0171] In contrast, when the negative electrode liquid 97 has a high viscosity (Example 1), the reduced negative electrode active material (metallic zinc) particles 41a are easily discharged from the charging cell 78. This is because the drag acting on the reduced negative electrode active material (metallic zinc) particles 41a when the negative electrode liquid 97 acts on the reduced negative electrode active material (metallic zinc) particles 41a becomes large.

[0172] (Charging experiment 2) In Example 2, a charging experiment was carried out using a charging cell 78 that was the same as the charging cell 78 in Example 1 except for the negative electrode solution 97. The negative electrode solution 97 in Example 2 was as follows. Anode electrolyte 97: Zn saturated KOH aqueous solution (KOH 29.2%, zinc oxide 4%, thickener 1%, indium hydroxide 0.01%) Here, the viscosity of the negative electrode solution was evaluated using VT-06 manufactured by Rion Co., Ltd. and found to be 100 mPasec.

[0173] As shown in Table 1, when the anode liquid 97 has a high viscosity and contains an additional component (indium ions), the recovery rate of the reduced-state anode active material (metallic zinc) particles 41a discharged from the charging cell 78 improves. This is because the adhesion of the reduced-state anode active material (metallic zinc) particles 41a to the anode 98 decreases. Therefore, when the anode liquid 97 has a high viscosity and contains an additional component (indium ions), it becomes easier to peel the reduced-state anode active material (zinc) particles 41a from the anode 98 and discharge the peeled reduced-state anode active material (metallic zinc) particles 41a from the charging cell 78.

[0174] (Charging experiment 3) In Example 3, a charging experiment was carried out using the same charging cell 78 as the charging cell 78 in Example 2. The positive electrode solution 92 and the negative electrode solution 97 were also the same as the positive electrode solution 92 and the negative electrode solution 97 in Example 2, respectively. Specifically, the procedure is as follows. Positive electrolyte 92: Zn saturated KOH aqueous solution "KOH 29.2%, zinc oxide 4%" Anode electrolyte 97: Zn saturated KOH aqueous solution (KOH 29.2%, zinc oxide 4%, thickener 1%, indium hydroxide 0.01%) Here, the viscosity of the negative electrode solution was evaluated using VT-06 manufactured by Rion Co., Ltd. and found to be 100 mPasec.

[0175] In charging experiment 3, constant current charging was performed while changing the current density (per projected area of ​​the negative electrode 98). In the charging experiment, the weight of reduced negative electrode active material (metallic zinc) particles 41a that had peeled off from the negative electrode 98 and been discharged from the charging cell 78 was measured, and the zinc recovery rate relative to the amount of electricity input was calculated. The calculation results are shown in Table 2.

[0176] [Table 2]

[0177] As shown in Table 2, there is a preferred range of current density (per projected area of ​​the negative electrode 98) that can increase the recovery rate of reduced negative electrode active material (metallic zinc) particles 41a discharged from the charging cell. When the current density (per projected area of ​​the negative electrode 98) is low (e.g., 30, 50 mA / cm 2 ) makes it difficult to peel off the reduced-state negative electrode active material (metallic zinc) particles 41a from the negative electrode 98. This is because dense reduced-state negative electrode active material (metallic zinc) particles 41a tend to grow on the negative electrode 98, and the drag acting on the reduced-state negative electrode active material (metallic zinc) particles 41a when the negative electrode liquid 97 acts on the reduced-state negative electrode active material (metallic zinc) particles 41a becomes smaller.

[0178] On the other hand, when the current density (per projected area of ​​the negative electrode 98) is high (e.g., 150 mA / cm 2 ) makes it easy to peel off the reduced-state negative electrode active material (metallic zinc) particles 41a from the negative electrode 98, but the zinc recovery rate decreases because a hydrogen generation reaction occurs, which is a competitive reaction with the reduction reaction that generates the reduced-state negative electrode active material (metallic zinc) particles 41a.

[0179] 1.19 Charge Cell Stack FIG. 13 is a cross-sectional view that schematically illustrates a charging cell stack that can be used in place of the charging cell provided in the flow-type metal-air battery of the first embodiment.

[0180] The charge cell stack 131 illustrated in FIG. 13 includes a plurality of charge cells 78.

[0181] A plurality of charging cells 78 are stacked to form a battery pack, which allows the charging cell stack 131 to charge a larger amount of power than a single charging cell 78 can charge.

[0182] The multiple charging cells 78 include two adjacent charging cells 78. The main surface 94p of the current-carrying plate 94 of one of the two adjacent charging cells 78 is in surface contact with the main surface 99p of the current-carrying plate 99 of the other of the two adjacent charging cells 78. This electrically connects the current-carrying plate 94 and the current-carrying plate 99 to each other, forming a bipolar plate 141 that functions as both a positive current-carrying plate and a negative current-carrying plate. This electrically connects the multiple charging cells 78 in series.

[0183] A positive electrode chamber is formed between the bipolar plate 141 and the separator 101 of one of the charging cells 78. A negative electrode chamber is formed between the bipolar plate 141 and the separator 101 of the other charging cell 78. A first flow path 91e is formed in the positive electrode chamber. A second flow path 96e is formed in the negative electrode chamber. Positive electrode solution 92 flows in parallel into the formed multiple first flow paths 91e. Negative electrode solution 97 flows in parallel into the formed multiple second flow paths 96e.

[0184] The present disclosure is not limited to the above-described embodiments, and may be replaced with a configuration that is substantially the same as the configuration shown in the above-described embodiments, a configuration that has the same effect, or a configuration that can achieve the same purpose. [Explanation of symbols]

[0185] 1 flow-type metal-air battery, 11 oxygen gas, 12 oxygen gas, 21 positive electrode liquid, 22 negative electrode liquid, 23 storage section, 23a outlet, 23b inlet, 23c outlet, 23d inlet, 24 discharge section, 25 charging section, 31 first electrolyte, 41a reduced-state negative electrode active material particles, 41b oxidized-state negative electrode active material particles, 42 negative electrode active material ions, 43 second electrolyte, 44 thickener, 51 piping, 52 pump, 52a inlet, 52b outlet, 53 piping, 54 discharge cell, 54a inlet, 54b outlet, 55 piping, 61 layer, 61a flow path, 62 negative electrode liquid, 63 positive electrode, 64 separator, 65 negative electrode, 71 piping, 72 pump, 72a Inlet, 72b outlet, 73 piping, 74 piping, 75 pump, 75a inlet, 75b outlet, 76 piping, 77 power supply, 78 charging cell, 78a inlet, 78b inlet, 78c outlet, 78d outlet, 79 piping, 80 piping, 81 control circuit, 91 first layer, 91p opening surface, 91q opening surface, 91a end surface, 91c end surface, 91e first flow path, 91pe opening, 91qe opening, 92 positive electrode liquid, 93 positive electrode, 94 current-carrying plate, 94p main surface, 95 gasket, 96 second layer, 96p opening surface, 96q opening surface, 96b end surface, 96d end surface, 96e second flow path, 96pe opening, 96qe opening, 97 Anode liquid, 98 anode, 99 current-carrying plate, 99p main surface, 100 gasket, 101 separator, 102 gasket, 103 gasket, 111 cathode chamber component, 112 anode chamber component, 121 first part, 122 second part, 131 charging cell stack, 141 bipolar plate.

Claims

1. a first layer having a first flow path formed therein; a positive electrode facing the first flow path; a second layer having a second flow path formed therein; 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 having a first viscosity; a negative electrode liquid flowing through the second flow path and having a second viscosity higher than the first viscosity; A charging cell for a flow-type metal-air battery.

2. Oxygen gas is generated by a reaction at the positive electrode, and negative electrode active material particles are generated by a reaction at the negative electrode. The rechargeable cell for a flow-type metal-air battery according to claim 1.

3. the positive electrode solution includes a first electrolyte solution, The negative electrode solution includes a second electrolytic solution and negative electrode active material ions dissolved in the second electrolytic solution. The rechargeable cell for a flow-type metal-air battery according to claim 1.

4. The negative electrode liquid contains a thickener The rechargeable cell for a flow-type metal-air battery according to claim 3.

5. The negative electrode liquid contains zinc ions and at least one ion selected from the group consisting of Group 13 metal elements, Group 14 metal elements, and Group 15 metal elements. The charging cell for a flow-type metal-air battery according to any one of claims 1 to 4.

6. The negative electrode liquid contains zinc ions and indium ions. The charging cell for a flow-type metal-air battery according to any one of claims 1 to 4.

7. The separator is an anion exchange membrane, a hydrogel membrane, or a membrane comprising a plurality of inorganic ion conductor particles and a resin impregnated into the grain boundaries of the plurality of inorganic ion conductor particles. The charging cell for a flow-type metal-air battery according to any one of claims 1 to 4.

8. the positive electrode contains nickel, The negative electrode contains at least one selected from the group consisting of carbon, copper, and magnesium. The charging cell for a flow-type metal-air battery according to any one of claims 1 to 4.

9. A current-carrying plate is provided which is integrally formed with the negative electrode. The charging cell for a flow-type metal-air battery according to any one of claims 1 to 4.

10. a current-carrying plate integrally formed with the negative electrode and the second layer; The charging cell for a flow-type metal-air battery according to any one of claims 1 to 4.

11. the first flow path includes a portion that guides the positive electrode liquid in a vertical direction, a mechanism for generating a flow of the positive electrode liquid in the portion such that the flow direction of the positive electrode liquid in the portion is from a vertically downward direction to a vertically upward direction; The charging cell for a flow-type metal-air battery according to any one of claims 1 to 4.

12. the second flow path includes a portion that guides the negative electrode liquid in a vertical direction, a mechanism for generating a flow of the negative electrode liquid in the portion such that the flow direction of the negative electrode liquid in the portion is from a vertically downward direction to a vertically upward direction; The charging cell for a flow-type metal-air battery according to any one of claims 1 to 4.

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