Charging unit for flow-type metal-air batteries

Abstract

To provide a charging unit 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 unit 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, a negative electrode liquid flowing through the second flow channel, and a control unit that changes the flow rate of the negative electrode liquid in the second flow channel, or a current control unit that changes the current value of a current flowing between the positive electrode and the negative electrode.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This disclosure relates to a charging unit for a flow-type metal-air battery. [Background technology]

[0002] Patent Document 1 discloses a system for generating metal particles. In this system, metal particles are generated on the surface of a cathode by electrolysis of a solution containing molten metal. When the formed metal particles have reached 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. 7470351 [Overview of the project] [Problems that the invention aims to solve]

[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 cathode surface. This raises problems such as the power consumption required to move the scraper or other suitable means, and the reduction in durability caused by 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. One aspect of the present disclosure aims to provide a charging unit for a flow-type metal-air battery that can detach negative electrode active material particles from the negative electrode without consuming a large amount of power, and has high durability because it does not require physical contact with a scraper or the like. [Means for solving the problem]

[0006] A charging unit for a flow-type metal-air battery according to a first aspect of the present disclosure comprises: a first layer having a first flow channel formed therein; a positive electrode facing the first flow channel; a second layer having a second flow channel formed therein; 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; a negative electrode liquid flowing through the second flow channel; and a control unit for changing the flow velocity of the negative electrode liquid in the second flow channel.

[0007] A charging unit for a flow-type metal-air battery according to a second aspect of the present disclosure comprises: a first layer having a first flow channel formed therein; a positive electrode facing the first flow channel; a second layer having a second flow channel formed therein; 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; a negative electrode liquid flowing through the second flow channel; and an energizing control unit that changes the current value of the current flowing between the positive electrode and the negative electrode. [Brief explanation of the drawing]

[0008] [Figure 1] This figure schematically illustrates a flow-type metal-air battery according to the first embodiment. [Figure 2] This is an exploded perspective view schematically illustrating a rechargeable cell provided in the flow-type metal-air battery of the first embodiment. [Figure 3] This is a schematic cross-sectional view illustrating a rechargeable cell provided in the flow-type metal-air battery of the first embodiment. [Figure 4A] This graph shows a first example of controlling the current value of the current flowing between the positive electrode and the negative electrode of a charging cell in a flow-type metal-air battery of the first embodiment. [Figure 4B] This graph shows a first example of controlling the flow velocity of the negative electrode liquid in the second flow path of a charging cell provided in the first embodiment of a flow-type metal-air battery. [Figure 5A] This graph shows a second example of controlling the current value of the current flowing between the positive electrode and the negative electrode of a charging cell in a flow-type metal-air battery of the first embodiment. [Figure 5B]A graph showing a second control example of the flow rate of the negative electrode liquid in the second flow path of the charging cell included in the flow-type metal-air battery of the first embodiment. [Figure 6A] A graph showing a third control example of the current value of the current flowing between the positive electrode of the charging cell included in the flow-type metal-air battery of the first embodiment and the negative electrode of the charging cell. [Figure 6B] A graph showing a third control example of the flow rate of the negative electrode liquid in the second flow path of the charging cell included in the flow-type metal-air battery of the first embodiment. [Figure 7] A graph showing a fourth control example of the current value of the current flowing between the positive electrode of the charging cell included in the flow-type metal-air battery of the first embodiment and the negative electrode of the charging cell. [Figure 8] A graph showing a fifth control example of the flow rate of the negative electrode liquid in the second flow path of the charging cell included in the flow-type metal-air battery of the first embodiment. [Figure 9] A cross-sectional view schematically showing a charging cell included in the flow-type metal-air battery according to the first modification of the first embodiment. [Figure 10] A cross-sectional view schematically showing a charging cell included in the flow-type metal-air battery according to the second modification of the first embodiment. [Figure 11] A cross-sectional view schematically showing a charging cell included in the flow-type metal-air battery according to the third modification of the first embodiment. [Figure 12] A cross-sectional view schematically showing a charging cell included in the flow-type metal-air battery according to the fourth modification of the first embodiment. [Figure 13] A cross-sectional view schematically showing a charging cell stack that can be used in place of the charging cell included in the flow-type metal-air battery of the first embodiment.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Regarding the drawings, the same or equivalent elements are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0010] 1. First Embodiment 1.1 Flow-type metal-air battery Figure 1 is a schematic diagram illustrating a flow-type metal-air battery according to the first embodiment.

[0011] The flow-type metal-air battery 1 of the first embodiment shown in Figure 1 absorbs oxygen gas 11 from the surrounding air when discharging. When the flow-type metal-air battery 1 is charged, it releases oxygen gas 12 into the surrounding air.

[0012] 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 zinc. However, the flow-type metal-air battery 1 may 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 other than zinc. Examples of metals other than zinc include cadmium, lithium, sodium, magnesium, lead, tin, aluminum, or iron. The metal constituting the metal species may consist only of the main component metal, or it may consist of an alloy of the main component metal and minor components. The metal species can be either a metal or an oxide. Whether the metal species is a metal or an oxide is determined according to the progress of the discharge reaction or the charge reaction.

[0013] As shown in Figure 1, the flow-type metal-air battery 1 comprises a positive electrode liquid 21, a negative electrode liquid 22, a storage unit 23, a discharge unit 24, and a charging unit 25.

[0014] 1.2 Positive electrode solution As shown in Figure 1, the positive electrode solution 21 includes the first electrolyte solution 31.

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

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

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

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

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

[0020] 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.

[0021] 1.4 Storage Section The storage section 23 stores the negative electrode liquid 22. The storage section 23 has outlets 23a, inlets 23b, outlets 23c and inlets 23d. Outlets 23a and 23c allow the negative electrode liquid 22 to flow out. Inlets 23b and 23d allow the negative electrode liquid 22 to flow in.

[0022] 1.5 Discharge section The discharge unit 24 absorbs oxygen gas 11 from the surrounding air. Negative electrode liquid 22 flows into the discharge unit 24 from the storage unit 23. The discharge unit 24 uses the absorbed oxygen gas 11 and the incoming negative electrode liquid 22 to participate in a discharge reaction that generates discharge power, and then discharges the negative electrode liquid 22 that has participated in the discharge reaction back into the storage unit 23. The discharge unit 24 uses the reduced negative electrode active material particles 41a contained in the oxygen gas 11 and negative electrode liquid 22 to participate in the discharge reaction, eliminating the reduced negative electrode active material particles 41a and generating negative electrode active material ions 42.

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

[0024] The piping 51 guides the negative electrode liquid 22 from the outlet 23a of the storage unit 23 to the inlet 52a of the pump 52. In this way, the piping 51 allows the negative electrode liquid 22 that has flowed out from the outlet 23a to flow into the inlet 52a.

[0025] Pump 52 discharges the negative electrode fluid 22 that has flowed into its inlet 52a from its outlet 52b. In doing so, pump 52 generates a flow of negative electrode fluid 22. As a result, pump 52 sends the negative electrode fluid 22 from the storage unit 23 to the discharge cell 54.

[0026] The piping 53 guides the negative electrode fluid 22 from the outlet 52b of the pump 52 to the inlet 54a of the discharge cell 54. In this way, the piping 53 allows the negative electrode fluid 22 that has flowed out from the outlet 52b to flow into the inlet 54a.

[0027] The discharge cell 54 absorbs oxygen gas 11 from the surrounding air. The discharge cell 54 discharges the negative electrode liquid 22 that has flowed into the inlet 54a of the discharge cell 54 from the outlet 54b of the discharge cell 54. At the same time, the discharge cell 54 involves the absorbed oxygen gas 11 and the incoming negative electrode liquid 22 in the discharge reaction, and discharges the negative electrode liquid 22 that has been involved in the discharge reaction from the outlet 54b. The discharge cell 54 outputs discharge power generated by the discharge reaction.

[0028] The piping 55 guides the negative electrode fluid 22 from the outlet 54b of the discharge cell 54 to the inlet 23b of the storage unit 23. In this way, the piping 55 allows the negative electrode fluid 22 that has flowed out from the outlet 54b to flow into the inlet 23b.

[0029] 1.6 Discharge Cell As shown in Figure 1, the discharge cell 54 comprises a layer 61, a negative electrode liquid 62, a positive electrode 63, a separator 64, and a negative electrode 65.

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

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

[0032] The positive electrode 63 comes into contact with the air surrounding the discharge cell 54. As a result, the positive electrode 63 is supplied with oxygen gas 11 contained in the air surrounding the discharge cell 54. This causes an oxygen reduction reaction, represented by equation (1), to occur at the positive electrode 63.

[0033] O2 + 2H2O + 4e - →4OH - (1)

[0034] The positive electrode 63 faces the channel 61a of layer 61 via the separator 64. As a result, the positive electrode 63 is exposed to the negative electrode liquid 62 flowing through channel 61a via the separator 64, and the product of the oxygen reduction reaction represented by equation (1), OH ― The handover will take place.

[0035] The negative electrode 65 faces the channel 61a of layer 61. As a result, the negative electrode 65 comes into contact with the negative electrode liquid 62 flowing through the channel 61a. This causes the oxidation reaction of metallic zinc, represented by equations (2) and (3), to occur in the negative electrode 65.

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

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

[0038] 2Zn + O2 → 2ZnO (4)

[0039] Therefore, the discharge cell 54 discharges when metallic zinc changes to zinc oxide.

[0040] 1.7 Live parts The negative electrode liquid 22 flows into the charging section 25 from the storage section 23. The charging section 25 involves the incoming negative electrode liquid 22 in a charging reaction that regenerates the negative electrode liquid 22, and then discharges the negative electrode liquid 22 that has been involved in the charging reaction back into the storage section 23. The charging section 25 involves the negative electrode active material ions 42 contained in the negative electrode liquid 22 in the charging reaction, eliminating the negative electrode active material ions 42 and generating reduced negative electrode active material particles 41a.

[0041] As shown in Figure 1, the charging unit 25 includes piping 71, pump 72, piping 73, piping 74, pump 75, piping 76, power supply 77, charging cell 78, piping 79, piping 80, and control circuit 81.

[0042] The piping 71 guides the positive electrode 21 from a supply source (not shown) to the inlet 72a of the pump 72. In this way, the piping 71 allows the positive electrode 21 that has flowed out of the supply source to flow into the inlet 72a.

[0043] Pump 72 causes the positive electrode liquid 21 that has flowed into the inlet 72a of pump 72 to flow out through the outlet 72b of pump 72. In doing so, pump 72 generates a flow of positive electrode liquid 21. As a result, pump 72 delivers the positive electrode liquid 21 from its supply source to the charging cell 78.

[0044] The piping 73 guides the cathode fluid 21 from the outlet 72b of the pump 72 to the inlet 78a of the charging cell 78. In this way, the piping 73 allows the cathode fluid 21 that has flowed out from the outlet 72b to flow into the inlet 78a.

[0045] The piping 74 guides the negative electrode liquid 22 from the outlet 23c of the storage unit 23 to the inlet 75a of the pump 75. In this way, the piping 74 allows the negative electrode liquid 22 that has flowed out from the outlet 23c to flow into the inlet 75a.

[0046] Pump 75 discharges the negative electrode fluid 22 that has flowed into its inlet 75a from its outlet 75b. In doing so, pump 75 generates a flow of negative electrode fluid 22. As a result, pump 75 sends the negative electrode fluid 22 from the storage unit 23 to the charging cell 78.

[0047] The piping 76 guides the negative electrode fluid 22 from the outlet 75b of the pump 75 to the inlet 78b of the charging cell 78. In this way, the piping 76 allows the negative electrode fluid 22 that has flowed out from the outlet 75b to flow into the inlet 78b.

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

[0049] The charging cell 78 discharges the positive electrode liquid 21 that has flowed into the inlet 78a of the charging cell 78 from the outlet 78c of the charging cell 78, and discharges the negative electrode liquid 22 that has flowed into the inlet 78b of the charging cell 78 from the outlet 78d of the charging cell 78. At the same time, the charging cell 78 involves the incoming positive electrode liquid 21 and negative electrode liquid 22 in a charging reaction caused by the charging power, discharges the positive electrode liquid 21 that has participated in the charging reaction from the outlet 78c, discharges the negative electrode liquid 22 that has participated in the charging reaction from the outlet 78d, and releases the oxygen gas 12 generated by the charging reaction into the air surrounding the charging cell 78.

[0050] The piping 79 guides the cathode electrolyte 21 from the outlet 78c of the charging cell 78 to the source of the cathode electrolyte 21. In this way, the piping 79 allows the cathode electrolyte 21 that has flowed out from the outlet 78c to flow into the source of the cathode electrolyte 21.

[0051] The piping 80 guides the negative electrode fluid 22 from the outlet 78d of the charging cell 78 to the inlet 23d of the storage unit 23. In this way, the piping 80 allows the negative electrode fluid 22 that has flowed out from the outlet 78d to flow into the inlet 23d.

[0052] The piping 71, pump 72, piping 73, and piping 79 constitute a mechanism that generates a flow of positive electrode liquid 21, which flows into the inlet 78a of the charging cell 78 and flows out from the outlet 78c of the charging cell 78.

[0053] The piping 74, pump 75, piping 76, and piping 80 constitute a mechanism that generates a flow of negative electrode fluid 22, which flows into the inlet 78b of the charging cell 78 and out from the outlet 78d of the charging cell 78.

[0054] The control circuit 81 controls pumps 72 and 75. As a result, the control circuit 81 constitutes a control unit that changes the flow rate of the positive electrode liquid 92 in the first flow path 91e of the charging cell 78 and / or the flow rate of the negative electrode liquid 97 in the second flow path 96e of the charging cell 78.

[0055] The control circuit 81 controls the power supply 77. As a result, the control circuit 81 constitutes an energization control unit that changes the current value of the current flowing between the positive electrode 93 and the negative electrode 98 of the charging cell 78.

[0056] The control circuit 81 comprises a microcontroller and peripheral circuits. The microcontroller comprises a processor and memory. The processor executes a program stored in 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 dedicated electronic circuits.

[0057] 1.8 rechargeable cells Figure 2 is an exploded perspective view schematically illustrating a rechargeable cell provided in the flow-type metal-air battery of the first embodiment. Figure 3 is a cross-sectional view schematically illustrating a rechargeable cell provided in the flow-type metal-air battery of the first embodiment.

[0058] As shown in Figures 2 and 3, the charging cell 78 comprises a first layer 91, positive electrode liquid 92, positive electrode 93, current-carrying plate 94, gasket 95, second layer 96, negative electrode liquid 97, negative electrode 98, current-carrying plate 99, gasket 100, separator 101, gasket 102, and gasket 103.

[0059] 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 on opposite sides. The end surfaces 91a and 91c are on opposite sides. The first layer 91 may have a frame shape other than a rectangular frame shape.

[0060] A first channel 91e is formed in the first layer 91.

[0061] The first flow channel 91e of the first layer 91 is exposed to the opening surface 91p and the opening surface 91q, and has openings 91pe and 91qe on the opening surface 91p and the opening surface 91q, respectively.

[0062] The first flow path 91e is exposed to end faces 91a and 91c, and has outlets 78a and 78c at end faces 91a and 91c, 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 that flows into the inlet 78a to pass through, and the positive electrode liquid 21 that has passed through to flow out from the outlet 78c.

[0063] The inlet 78a and outlet 78c of the charging cell 78 are positioned on the vertically downward and vertically upward sides, respectively. Therefore, the first flow path 91e of the first layer 91 includes a portion that guides the positive electrode liquid 92 in the vertical direction. The inlet 78a may be positioned at a location other than the vertically downward side, and the outlet 78c may be positioned at a location other than the vertically upward side.

[0064] The positive electrode fluid 92 flows through the first channel 91e of the first layer 91. The positive electrode fluid 92 is part of the positive electrode fluid 21. As described above, the inlet 78a and outlet 78c of the charging cell 78 are located on the vertically downward side and the vertically upward side, respectively. Therefore, the flow direction of the positive electrode fluid 92 in the portion that guides the positive electrode fluid 92 vertically is from vertically downward to vertically upward.

[0065] If the flow direction of the positive electrode liquid 92 is from vertically upward to vertically downward, the positive electrode liquid 92 will flow out of the first channel 91e of the first layer 91 even before the first channel 91e is completely filled with the positive electrode liquid 92. Therefore, it may not be possible to completely fill the first channel 91e with the positive electrode liquid 92. On the other hand, if the flow direction of the positive electrode liquid 92 is from vertically downward to vertically upward, the positive electrode liquid 92 will overflow from the first channel 91e after the first channel 91e has been completely filled with the positive electrode liquid 92. Therefore, the first channel 91e can be completely filled with the positive electrode liquid 92.

[0066] The oxygen gas 12 generated at the positive electrode 93 moves not only from vertically downward to vertically upward due to buoyancy, but also from vertically downward to vertically upward carried by the flow of the positive electrode liquid 92. This promotes the discharge of oxygen gas 12 from the charging cell 78.

[0067] 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. Thereby, 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. Thereby, the positive electrode 93 contacts the positive electrode liquid 92 flowing through the first flow path 91e. Thereby, in the positive electrode 93, the oxidation reaction of water represented by Equation (5) occurs.

[0068] 4OH - →O2 + 2H2 + 4e - (5)

[0069] Therefore, the charging cell 78 generates oxygen gas 12 by the oxidation reaction of water in the positive electrode 93. The generated oxygen gas 12 is discharged from the charging cell 78.

[0070] The positive electrode 93 is made of a material having a high oxygen generation ability. Thereby, the charging efficiency of the charging cell 78 can be increased. Also, the charging operation of the charging cell 78 can be stabilized. The material having a high oxygen generation ability includes, for example, nickel.

[0071] The current conducting plate 94 has a rectangular plate shape. The current conducting plate 94 is disposed on the opening surface 91p of the first layer 91 so as to overlap the positive electrode 93. Thereby, the current conducting plate 94 contacts the positive electrode 93 and constitutes a current conduction path to the positive electrode 93.

[0072] The gasket 95 is sandwiched between the opening surface 91p of the first layer 91, the positive electrode 93, and the current conducting plate 94, and liquid-tightly closes the space between the opening surface 91p of the first layer 91, the positive electrode 93, and the current conducting plate 94.

[0073] 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 on opposite sides of each other. The end surface 96b and the end surface 96d are on opposite sides of each other.

[0074] A second flow path 96e is formed in the second layer 96.

[0075] The second flow channel 96e of the second layer 96 is exposed to the opening surface 96p and the opening surface 96q, and has openings 96pe and 96qe on the opening surface 96p and the opening surface 96q, respectively.

[0076] The second flow path 96e is exposed to end faces 96b and 96d, and has an inlet 78b and an outlet 78d at end faces 96b and 96d, 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 that has flowed into the inlet 78b to pass through, and the negative electrode liquid 97 that has passed through to flow out from the outlet 78d.

[0077] The inlet 78b and outlet 78d of the charging cell 78 are located on the vertically downward and vertically upward sides, respectively. Therefore, the second flow path 96e of the second layer 96 includes a portion that guides the negative electrode liquid 97 in the vertical direction.

[0078] The negative electrode fluid 97 flows through the second channel 96e of the second layer 96. The negative electrode fluid 97 is part of the negative electrode fluid 22. As described above, the inlet 78b and outlet 78d of the charging cell 78 are located on the vertically downward and vertically upward sides, respectively. Therefore, the flow direction of the negative electrode fluid 97 in the portion that guides the negative electrode fluid 97 vertically is from vertically downward to vertically upward.

[0079] If the flow direction of the negative electrode liquid 97 is from vertically upward to vertically downward, the negative electrode liquid 97 will flow out of the second channel 96e of the second layer 96 even before the second channel 96e is completely filled with the negative electrode liquid 97. Therefore, it may not be possible to completely fill the second channel 96e with the negative electrode liquid 97. On the other hand, if the flow direction of the negative electrode liquid 97 is from vertically downward to vertically upward, the negative electrode liquid 97 will overflow from the second channel 96e after the second channel 96e has been completely filled with the negative electrode liquid 97. Therefore, the second channel 96e can be completely filled with the negative electrode liquid 97.

[0080] The specific gravity of the reduced negative electrode active material particles 41a generated at the negative electrode 98 is greater than the specific gravity of the negative electrode liquid 97. Therefore, if the flow direction of the negative electrode liquid 97 is from vertically upward to vertically downward, the reduced negative electrode active material particles 41a will move vertically downward from vertically upward and settle. However, if the flow direction of the negative electrode liquid 97 is from vertically downward to vertically upward, the reduced negative electrode active material particles 41a will move vertically upward from vertically downward, riding on 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 size has grown to a size where they can sufficiently withstand the drag force of the negative electrode liquid 97.

[0081] The negative electrode 98 has a rectangular plate shape. The negative electrode 98 is placed 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 channel 96e of the second layer 96. As a result, the negative electrode 98 comes into contact with the negative electrode liquid 97 flowing through the second flow channel 96e. As a result, zincate ions Zn(OH)4, which are produced by the oxidation reaction of metallic zinc represented by formulas (2) and (3), are formed at the negative electrode 98. 2- A negative electrode solution containing and / or zinc oxide (ZnO) is supplied to the negative electrode 98. This causes a reduction reaction to metallic zinc, represented by equations (6) and (7), to occur at the negative electrode 98.

[0082] ZnO + H2O + 2OH - →Zn(OH)4 2- (6) Zn(OH)4 2- +2e - →Zn+4OH - (7)

[0083] Therefore, the charging cell 78 generates reduced negative electrode active material particles 41a through a reduction reaction with metallic zinc at the negative electrode 98. The generated reduced negative electrode active material particles 41a adhere to the negative electrode 98.

[0084] The negative electrode 98 is made of a material that can suppress a hydrogen generation reaction that competes with the reduction reaction to metallic zinc. The material that can suppress the hydrogen generation reaction includes, for example, at least one selected from the group consisting of carbon, copper, and magnesium. Carbon includes, for example, graphite. Carbon is resistant to corrosion. Therefore, when the negative electrode 98 is made of carbon, it is possible to suppress the decrease in the charging efficiency of the charging cell 78 due to corrosion of the negative electrode 98. This makes it possible to increase the long-term stability of the charging cell 78. In addition, the adhesion of the reduced negative electrode active material particles 41a to magnesium is low. Therefore, when the negative electrode 98 is made of magnesium, it is possible to detach the reduced negative electrode active material particles 41a from the negative electrode 98 and facilitate the removal of the reduced negative electrode active material particles 41a from the charging cell 78.

[0085] The conductive plate 99 has a rectangular plate shape. The conductive plate 99 is placed on the opening surface 96p of the second layer 96, superimposed on the negative electrode 98. As a result, the conductive plate 99 contacts the negative electrode 98 and forms a current supply path to the negative electrode 98.

[0086] The gasket 100 is sandwiched between the opening surface 96p of the second layer 96 and the negative electrode 98 and the conductive plate 99, and liquid-tightly seals the space between the opening surface 96p of the second layer 96 and the negative electrode 98 and the conductive plate 99.

[0087] The separator 101 has a sheet-like shape. The separator 101 is flexible. The separator 101 is placed on the opening surface 91q of the first layer 91. In this way, 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 placed on the opening surface 96q of the second layer 96. In this way, the separator 101 closes the opening 96qe of the second layer 96 and faces the second flow path 96e of the second layer 96.

[0088] The separator 101 is sandwiched between the first layer 91 and the second layer 96. This separates the first channel 91e of the first layer 91 and the second channel 96e of the second layer 96 from each other. The separator 101 prevents the reduced negative electrode active material particles 41a, the oxidized negative electrode active material particles 41b, and the thickener 44 from passing through. As a result, the separator 101 suppresses the movement of the reduced negative electrode active material particles 41a, the oxidized negative electrode active material particles 41b, and the thickener 44 from the negative electrode liquid 97 to the positive electrode liquid 92.

[0089] Separator 101 has high ionic conductivity. As a result, separator 101 has high ionic conductivity. - It allows the hydroxide ions OH to pass through. - This allows the liquid to move from the negative electrode liquid 97 to the positive electrode liquid 92.

[0090] Since the separator 101 needs to prevent the permeation of reduced negative electrode active material particles 41a, oxidized negative electrode active material particles 41b, and thickener 44, it is preferably a film without pores of 50 nm or more, and more preferably 100 nm or more. The separator 101 is, for example, an anion exchange film, a water-containing gel film, or a film comprising a plurality of inorganic ion conductor particles and a resin impregnated at the grain boundaries of the plurality of inorganic ion conductor particles.

[0091] In the reduction reaction to metallic zinc at the negative electrode 98, i.e., the electrodeposition reaction of metallic zinc, the non-uniformity of the current distribution may cause dendritic metallic zinc to grow from the negative electrode 98. The separator 101 has high dendritic resistance. Therefore, the separator 101 prevents the growth of dendritic metallic zinc beyond the separator 101. This prevents the positive electrode 93 and the negative electrode 98 from short-circuiting each other via dendritic metallic zinc.

[0092] The gasket 102 is sandwiched between the opening surface 91q of the first layer 91 and the separator 101, and seals the space between the opening surface 91q of the first layer 91 and the separator 101 in a liquid-tight manner.

[0093] The gasket 103 is sandwiched between the opening surface 96q of the second layer 96 and the separator 101, and liquid-tightly seals the space between the opening surface 96q of the second layer 96 and the separator 101.

[0094] 1.9 Theoretical Voltage of Flow-Type Metal-Air Battery In the charging cell 78, the oxidation reaction of water at the positive electrode 93 and the reduction reaction to metallic zinc at the negative electrode 98 cause all the reactions represented by equation (8) to occur.

[0095] 2Zn + O2 → 2ZnO (8)

[0096] Therefore, the charging cell 78 changes zinc oxide to metallic zinc when it is charged.

[0097] During the discharge and charge reactions, the potentials of the positive and negative electrodes are -1.25V and 0.40V, respectively, relative to a standard hydrogen electrode. Therefore, the theoretical voltage of the flow-type metal-air battery 1 is 1.65V.

[0098] 1.10 Viscosity of positive and negative electrode fluids The positive electrode fluid 92 has a first viscosity. The negative electrode fluid 97 has a second viscosity that is higher than the first viscosity. The first viscosity is, for example, 1 mPasec to 9 mPasec, preferably 2 mPasec to 3 mPasec. The second viscosity is, for example, 100 mPasec to 2000 mPasec, preferably 200 mPasec to 500 mPasec. The viscosity of the positive electrode fluid 92 can be measured with an Ubbelohde viscometer or the like, and the viscosity of the negative electrode fluid 97 can be measured with a VT-06 manufactured by Rion Co., Ltd. or the like.

[0099] If the positive electrode liquid 92 has high viscosity, the oxygen gas 12 generated at the positive electrode 93 is easily incorporated into the positive electrode liquid 92, causing the positive electrode liquid 92 to become foamy. As a result, it becomes 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. Consequently, the charging efficiency of the charging cell 78 decreases.

[0100] In contrast, if the positive electrode liquid 92 has low viscosity, the turbulence of the positive electrode liquid 92 promotes the growth of oxygen gas 12 bubbles. This makes it easier to separate the oxygen gas 12 from the positive electrode liquid 92 and discharge the separated oxygen gas 12 from the charging cell 78. As a result, the charging efficiency of the charging cell 78 is increased.

[0101] If the negative electrode fluid 97 has a low viscosity, the resistance force acting on the reduced negative electrode active material particles 41a when the negative electrode fluid 97 acts on them becomes small. As a result, it becomes difficult to detach the reduced negative electrode active material particles 41a from the negative electrode 98 and discharge the detached reduced negative electrode active material particles 41a from the charging cell 78. Furthermore, it becomes difficult to prevent the reduced negative electrode active material particles 41a from settling due to gravity.

[0102] In contrast, if the negative electrode liquid 97 has a high viscosity, the resistance force acting on the reduced negative electrode active material particles 41a when the negative electrode liquid 97 acts on them becomes larger. Therefore, it becomes easier to detach the reduced negative electrode active material particles 41a from the negative electrode 98 and discharge the detached reduced negative electrode active material particles 41a from the charging cell 78. Furthermore, it becomes easier to prevent the reduced negative electrode active material particles 41a from settling due to gravity.

[0103] In this way, by making the second viscosity higher than the first viscosity, if the detachment of the reduced negative electrode active material particles 41a from the negative electrode 98 is promoted, then a movable part for detaching the reduced negative electrode active material particles 41a from the negative electrode 98 becomes unnecessary. As a result, it is possible to provide a flow-type metal-air battery 1 that has high durability and can detach the reduced negative electrode active material particles 41a from the negative electrode 98 without consuming a large amount of power.

[0104] The viscosity of the negative electrode solution 97 is adjusted by the type and / or concentration of the thickener 44 included in the negative electrode solution 97. Examples of the thickener 44 include organic polymer materials and inorganic particles with a particle size of less than 1 μm. Examples of organic polymer materials include polyacrylic acid, carboxymethylcellulose, sodium alginate, and acrylic acid / alkyl methacrylate copolymers. Examples of inorganic materials include calcium hydroxide and potassium silicate. The viscosity of the negative electrode solution 97 may also be adjusted by the concentration of oxidized negative electrode active material particles 41b with a particle size of less than 1 μm. If the viscosity of the negative electrode solution 97 is adjusted by the concentration of oxidized negative electrode active material particles 41b, the thickener 44 may not be included in the negative electrode solution 97. The negative electrode active material ions 42 are zincate ions (Zn(OH)4). 2- ) If calcium hydroxide or potassium silicate is used as the thickener 44, then calcium hydroxide or potassium silicate will contain zincate ions (Zn(OH)4 2- Since this affects the solubility of the negative electrode active material ions 42 in the negative electrode solution 97, the concentration of the negative electrode active material ions 42 in the negative electrode solution 97 can be set to a concentration suitable for the charging reaction.

[0105] If the negative electrode liquid 97 contains a thickening agent 44, the separator 101 prevents the thickening agent 44 from passing through. This prevents the separator 101 from moving the thickening agent 44 from the negative electrode liquid 97 to the positive electrode liquid 92. As a result, the viscosity of the negative electrode liquid 97 is higher than that of the positive electrode liquid 92, which can be maintained for a long period of time. This makes it easier than before to separate the oxygen gas 12 from the positive electrode liquid 92 and discharge the separated oxygen gas 12 from the charging cell 78, and makes it easier to detach the reduced negative electrode active material particles 41a from the negative electrode 98 and discharge the detached reduced negative electrode active material particles 41a from the charging cell 78, which can be maintained for a long period of time. As a result, the charging efficiency of the charging cell 78 can be maintained for a long period of time.

[0106] 1.11 Additional components of the negative electrode solution The negative electrode liquid 97 preferably contains at least one ion selected from the group consisting of Group 13, Group 14, and Group 15 metal elements, more preferably contains at least one ion selected from the group consisting of indium and thallium (included in Group 13 metal elements), tin and lead (included in Group 14 metal elements), and antimony and bismuth (included in Group 15 metal elements), and particularly preferably contains indium ions. When the negative electrode liquid 22 contains these ions, the adhesion of the reduced negative electrode active material particles 41a to the negative electrode 98 can be reduced. This makes it easier to detach the reduced negative electrode active material particles 41a from the negative electrode 98 and discharge the detached reduced negative electrode active material particles 41a from the charging cell 78. When the negative electrode liquid 97 contains these metal ions, it is preferable that it contains them at a concentration of 20 to 300 ppm, and more preferably at a concentration of 50 to 200 ppm. If the concentration of these metal ions is less than 20 ppm, there is a risk that the adhesion of the reduced negative electrode active material particles 41a to the negative electrode 98 cannot be sufficiently reduced. If the concentration of these metal ions exceeds 300 ppm, there is a risk that these metals will not be able to dissolve as ions and will precipitate in the solution. In particular, when the negative electrode solution 22 contains indium ions, the adhesion of the reduced negative electrode active material particles 41a to the negative electrode 98 is low because the ionization tendency of indium is lower than that of zinc, and indium is generated from these indium ions before zinc is generated from zinc ions, forming a base made of the generated indium. For this reason, it is not appropriate to include gallium, germanium, or arsenic ions, which have a higher ionization tendency than zinc, in the negative electrode solution 22.

[0107] 1.12 First control example of current value and flow rate Figure 4A is a graph showing a first example of controlling the current value of the current flowing between the positive electrode and the negative electrode of a charging cell provided in the first embodiment of a flow-type metal-air battery. Figure 4B is a graph showing a first example of controlling the flow velocity of the negative electrode liquid in the second flow path of the second layer of the charging cell provided in the first embodiment of a flow-type metal-air battery.

[0108] In Figure 4A, time is plotted on the horizontal axis and the current value on the vertical axis. In Figure 4B, time is plotted on the horizontal axis and the flow velocity on the vertical axis.

[0109] In the first control example of the current value of the current flowing between the positive electrode 93 and the negative electrode 98, and the flow velocity of the negative electrode liquid 97 in the second flow path 96e of the second layer 96, as shown in Figure 4A, the control circuit 81, which acts as the current supply control unit, maintains the current value at a constant current value I1. Therefore, the current supply control unit maintains the current value at a constant current value I1 during the period T0 to T4.

[0110] Furthermore, as shown in Figure 4B, the control circuit 81, which acts as the control unit, periodically changes the flow velocity between a first flow velocity LV1 and a second flow velocity VL2 that is greater than the first flow velocity LV1. Therefore, the control unit sets the flow velocity to the first flow velocity VL1 during the period T0 to T1, to the second flow velocity VL2 during the period T1 to T2, to the first flow velocity VL1 during the period T2 to T3, and to the second flow velocity VL2 during the period T3 to T4.

[0111] When the negative electrode liquid 97 acts on the reduced negative electrode active material particles 41a, the drag force acting on the reduced negative electrode active material particles 41a increases as the particle size of the reduced negative electrode active material particles 41a increases, and also increases as the flow velocity of the negative electrode liquid 97 increases. Therefore, in order to detach the reduced negative electrode active material particles 41a from the negative electrode 98 and discharge the detached reduced negative electrode active material particles 41a from the charging cell 78, it is desirable to increase the flow velocity of the negative electrode liquid 98 at the moment when the particle size of the reduced negative electrode active material particles 41a increases, thereby instantaneously applying a large drag force to the reduced negative electrode active material particles 41a.

[0112] When the current value and flow velocity are set as shown in Figures 4A and 4B, respectively, charging occurs, but during the charging period T0-T1 and T2-T3, when the flow velocity is reduced to the first flow velocity VL1, the drag force acting on the reduced negative electrode active material particles 41a decreases, causing the reduced negative electrode active material particles 41a to grow. As a result, the particle size of the reduced negative electrode active material particles 41a increases.

[0113] Then, during periods T1-T2 and T3-T4, when the flow velocity is increased to the second flow velocity VL2, the drag force acting on the reduced negative electrode active material particles 41a, whose particle size has increased, becomes larger.

[0114] These measures facilitate the detachment of reduced negative electrode active material particles 41a from the negative electrode 98 and the discharge of the detached 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 periods T0-T1 and T2-T3, the power consumed to flow the negative electrode liquid 97 can be reduced.

[0115] By controlling the current value and flow rate in this manner, if the removal of reduced negative electrode active material particles 41a from the negative electrode 98 is promoted, a movable part for removing the reduced negative electrode active material particles 41a from the negative electrode 98 becomes unnecessary. As a result, it is possible to provide a flow-type metal-air battery 1 with high durability that can remove reduced negative electrode active material particles 41a from the negative electrode 98 without consuming a large amount of power.

[0116] Here, Figure 4A illustrates a control method in which the current value is maintained at a constant current value I1 during the period T0 to T4. However, a control method may be adopted in which the current value is varied under conditions that exceed a predetermined current value during the period T0 to T4. Also, Figure 4B illustrates a control method in which the flow velocity is maintained at VL1 during the periods T0 to T1 and T2 to T3, and at VL2 during the periods T1 to T2 and T3 to T4. However, a control method may be adopted in which the flow velocity is set to VL1 or higher during the periods T0 to T1 and T2 to T3, and to VL2 or lower during the periods T1 to T2 and T3 to T4.

[0117] Furthermore, while Figure 4B illustrates a control method in which the lengths of periods T0-T1, T1-T2, T2-T3, and T3-T4 are the same, from the viewpoint of reducing the power consumed to flow the negative electrode liquid 97, 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 even more desirable to make them 1 / 5 to 1 / 20 the length of periods T0-T1 and T2-T3.

[0118] 1.13 Second control example of current value and flow rate Figure 5A is a graph showing a second example of controlling the current value of the current flowing between the positive electrode and the negative electrode of a charging cell in the flow-type metal-air battery of the first embodiment. Figure 5B is a graph showing a second example of controlling the flow velocity of the negative electrode liquid in the second flow path of the charging cell in the flow-type metal-air battery of the first embodiment.

[0119] In Figure 5A, time is plotted on the horizontal axis and the current value on the vertical axis. In Figure 5B, time is plotted on the horizontal axis and the flow velocity on the vertical axis.

[0120] In a second example of controlling the current value of the current flowing between the positive electrode 93 and the negative electrode 98, and the flow velocity of the negative electrode liquid 97 in the second flow path 96e of the second layer 96, as shown in Figure 5A, the control circuit 81, which acts as the energizing 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 energizing control unit sets the current value to the first current value I1 during the period T0 to T1, to the second current value I2 during the period T1 to T2, to the first current value I1 during the period T2 to T3, and to the second current value I2 during the period T3 to T4. The current control unit preferably makes the second current value I2 less than the first current value I1, and more preferably makes the second current value I2 zero, and alternately reduces or stops the flow of current between the positive electrode 93 and the negative electrode 98.

[0121] Furthermore, as shown in Figure 5B, the control circuit 81, which acts as the control unit, maintains the flow velocity at a constant flow velocity VL2. Therefore, the control unit maintains the flow velocity at a constant flow velocity VL2 during the period T0 to T4.

[0122] When the negative electrode liquid 98 acts on the reduced negative electrode active material particles 41a, the resistance force acting on the reduced negative electrode active material particles 41a increases as the particle size of the reduced negative electrode active material particles 41a increases. Therefore, in order to detach the reduced negative electrode active material particles 41a from the negative electrode 98 and discharge the detached reduced negative electrode active material particles 41a from the charging cell 78, it is desirable to increase the particle size of the reduced negative electrode active material particles 41a. However, it is desirable to stop the growth of the reduced negative electrode active material particles 41a while they are being detached from the negative electrode 98.

[0123] When the current value and flow rate are set as shown in Figures 5A and 5B, respectively, the reduced negative electrode active material particles 41a grow during the periods T0-T1 and T2-T3 when charging is performed at the first current value I1. As a result, the particle size of the reduced negative electrode active material particles 41a increases.

[0124] Then, during periods T1-T2 and T3-T4, when charging is performed with the second current value I2, the reduced negative electrode active material particles 41a, whose particle size has increased, are detached from the negative electrode 98 due to the large resistance force acting on them. During periods T1-T2 and T3-T4, the growth of the reduced negative electrode active material particles 41a is suppressed or stopped.

[0125] These measures facilitate the removal of reduced negative electrode active material particles 41a from the negative electrode 98 and the discharge of the removed reduced negative electrode active material particles 41a from the charging cell 78.

[0126] The first current value I1 may be greater than the current value Ih at which the hydrogen generation reaction, a competitive reduction reaction that generates reduced negative electrode active material particles 41a at the negative electrode 98, begins. For this reason, 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 channel 96e of the second layer 96, and increases the flow velocity of the negative electrode liquid 97 in the second channel 96e. Therefore, when hydrogen gas is generated on the negative electrode 98, the resistance force acting on the reduced negative electrode active material particles 41a when the negative electrode liquid 97 acts on them becomes greater. This promotes the detachment of the reduced negative electrode active material particles 41a from the negative electrode 98 and the discharge of the detached reduced negative electrode active material particles 41a from the charging cell 78. Furthermore, the generated hydrogen gas adheres to the reduced negative electrode active material particles 41a, creating buoyancy on them. This facilitates the detachment of the reduced negative electrode active material particles 41a from the negative electrode 98 and the discharge of the detached reduced negative electrode active material particles 41a from the charging cell 78. Additionally, the generated hydrogen gas adheres to the reduced negative electrode active material particles 41a, increasing their apparent Stokes diameter. Therefore, when hydrogen gas is generated on the negative electrode 98, the resistance force acting on the reduced negative electrode active material particles 41a when the negative electrode liquid 97 acts on them increases. This facilitates the detachment of the reduced negative electrode active material particles 41a from the negative electrode 98 and the discharge of the detached reduced negative electrode active material particles 41a from the charging cell 78.

[0127] By controlling the current value and flow rate in this manner, if the removal of reduced negative electrode active material particles 41a from the negative electrode 98 is promoted, a movable part for removing the reduced negative electrode active material particles 41a from the negative electrode 98 becomes unnecessary. As a result, it is possible to provide a flow-type metal-air battery 1 with high durability that can remove reduced negative electrode active material particles 41a from the negative electrode 98 without consuming a large amount of power.

[0128] Here, Figure 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. However, a control method may also be adopted in which the current value is I1 or greater during periods T0-T1 and T2-T3, and I2 or less during periods T1-T2 and T3-T4. Furthermore, Figure 5B illustrates a control method in which the flow velocity is maintained at a constant VL2 during periods T0-T4. However, a control method may also be adopted in which the flow velocity is varied under conditions that exceed a predetermined flow velocity during periods T0-T4.

[0129] Furthermore, while Figure 5A illustrates a control method in which the lengths of periods T0-T1, T1-T2, T2-T3, and T3-T4 are the same, 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 even more desirable to make them 1 / 5 to 1 / 20 of the lengths of periods T0-T1 and T2-T3.

[0130] 1.14 Third Control Example of Current Value and Flow Rate Figure 6A is a graph showing a third example of controlling the current value of the current flowing between the positive electrode and the negative electrode of a charging cell in the flow-type metal-air battery of the first embodiment. Figure 6B is a graph showing a third example of controlling the flow velocity of the negative electrode liquid in the second flow path of the charging cell in the flow-type metal-air battery of the first embodiment.

[0131] In Figure 6A, time is plotted on the horizontal axis and the current value on the vertical axis. In Figure 6B, time is plotted on the horizontal axis and the flow velocity on the vertical axis.

[0132] 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 velocity of the negative electrode liquid 97 in the second flow path 96e of the second layer 96, as shown in Figure 6A, the control circuit 81, which acts as the 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 the period T0 to T1, to the second current value I2 during the period T1 to T2, to the first current value I1 during the period T2 to T3, and to the second current value I2 during the period T3 to T4. The current control unit preferably makes the second current value I2 smaller than the first current value I1, and more preferably makes the second current value I2 zero, and alternately reduces or stops the flow of current between the positive electrode 93 and the negative electrode 98.

[0133] Furthermore, as shown in Figure 6B, the control circuit 81, which acts as the control unit, periodically changes the flow velocity between a first flow velocity LV1 and a second flow velocity VL2 that is greater than the first flow velocity LV1. Therefore, the control unit sets the flow velocity to the first flow velocity VL1 during the period T0 to T1, to the second flow velocity VL2 during the period T1 to T2, to the first flow velocity VL1 during the period T2 to T3, and to the second flow velocity VL2 during the period T3 to T4.

[0134] When the negative electrode liquid 98 acts on the reduced negative electrode active material particles 41a, the drag force acting on the reduced negative electrode active material particles 41a increases as the particle size of the reduced negative electrode active material particles 41a increases, and also increases as the flow velocity of the negative electrode liquid 98 increases. Therefore, in order to detach the reduced negative electrode active material particles 41a from the negative electrode 98 and discharge the detached reduced negative electrode active material particles 41a from the charging cell 78, it is desirable to increase the flow velocity of the negative electrode liquid 98 at the moment when the particle size of the reduced negative electrode active material particles 41a increases, thereby instantaneously applying a large drag force to the reduced negative electrode active material particles 41a. However, it is desirable to stop the growth of the reduced negative electrode active material particles 41a while detaching the reduced negative electrode active material particles 41a from the negative electrode 98. Therefore, the periods T0-T1 and T2-T3 in which charging is performed with the first current value I1 include the periods T0-T1 and T2-T3 in which the flow rate is set to the first flow rate VL1. Also, the periods T1-T2 and T3-T4 in which charging is performed with the second current value I2 include the periods T1-T2 and T3-T4 in which the flow rate is set to the second flow rate VL2.

[0135] When the current value and flow velocity are set as shown in Figures 6A and 6B, respectively, charging is performed at the first current value I1, but during periods T0-T1 and T2-T3 when the flow velocity is reduced to the first flow velocity VL1, the drag force acting on the reduced negative electrode active material particles 41a decreases, causing the reduced negative electrode active material particles 41a to grow. As a result, the particle size of the reduced negative electrode active material particles 41a increases.

[0136] Then, during periods T1-T2 and T3-T4, when the flow velocity is increased to the second flow velocity VL2, the drag force acting on the reduced negative electrode active material particles 41a, whose particle size has increased, becomes larger. During periods T1-T2 and T3-T4, the growth of the reduced negative electrode active material particles 41a is suppressed or stopped.

[0137] These measures facilitate the detachment of reduced negative electrode active material particles 41a from the negative electrode 98 and the discharge of the detached 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 periods T1-T2 and T2-T3, the power consumed to flow the negative electrode liquid 97 can be reduced.

[0138] By controlling the current value and flow rate in this manner, if the removal of reduced negative electrode active material particles 41a from the negative electrode 98 is promoted, a movable part for removing the reduced negative electrode active material particles 41a from the negative electrode 98 becomes unnecessary. As a result, it is possible to provide a flow-type metal-air battery 1 with high durability that can remove reduced negative electrode active material particles 41a from the negative electrode 98 without consuming a large amount of power.

[0139] Here, Figure 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. However, a control method may be adopted in which the current value is I1 or greater during periods T0-T1 and T2-T3, and at I2 or less during periods T1-T2 and T3-T4. Also, Figure 6B illustrates a control method in which the flow velocity is maintained at VL1 during periods T0-T1 and T2-T3, and at VL2 during periods T1-T2 and T3-T4. However, a control method may be adopted in which the flow velocity is VL1 or greater during periods T0-T1 and T2-T3, and at VL2 or less during periods T1-T2 and T3-T4.

[0140] Furthermore, while Figures 6A and 6B illustrate control methods in which the lengths of periods T0-T1, T1-T2, T2-T3, and T3-T4 are the same, from the viewpoint of reducing the power consumed to flow the negative electrode liquid 97 and 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 even more desirable to make them 1 / 5 to 1 / 20 of the lengths of periods T0-T1 and T2-T3.

[0141] 1.15 Fourth control example of current value and flow rate Figure 7 is a graph showing a fourth example of controlling the current value of the current flowing between the positive electrode and the negative electrode of a charging cell in the flow-type metal-air battery of the first embodiment.

[0142] In Figure 7, the horizontal axis represents time, and the vertical axis represents the current value.

[0143] The following describes the differences between the fourth control example of the current value flowing between the positive electrode 93 and the negative electrode 98, and the flow velocity of the negative electrode liquid 97 in the second flow path 96e of the second layer 96, compared to the third control example of the said current and flow velocity.

[0144] In the fourth control example of the current and flow velocity, as in the third control example of the current and flow velocity, the control circuit 81, which is the 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, as shown in Figure 7.

[0145] However, in the fourth control example of the current and flow rate, unlike the third control example of the current and flow rate, as shown in Figure 7, the sign of the first current value I1 and the sign of the second current value I2 are opposite. 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, during periods T0-T1 and T2-T3, a reduction reaction to metallic zinc occurs on the negative electrode 98, and during periods T1-T2 and T3-T4, an oxidation reaction to zinc ions occurs on the negative electrode 98. The oxidation reaction to zinc ions occurs at the interface between the negative electrode 98 and the reduced negative electrode active material particles 41a. Therefore, the oxidation reaction with zinc ions causes the reduced negative electrode active material particles 41a to dissolve at the interface. This reduces the adhesion of the reduced negative electrode active material particles 41a to the negative electrode 98. This facilitates the detachment of the reduced negative electrode active material particles 41a from the negative electrode 98 and the discharge of the detached reduced negative electrode active material particles 41a from the charging cell 78.

[0146] By controlling the current value and flow rate in this manner, if the removal of reduced negative electrode active material particles 41a from the negative electrode 98 is promoted, a movable part for removing the reduced negative electrode active material particles 41a from the negative electrode 98 becomes unnecessary. As a result, it is possible to provide a flow-type metal-air battery 1 with high durability that can remove reduced negative electrode active material particles 41a from the negative electrode 98 without consuming a large amount of power.

[0147] 1.16 Fifth control example of current value and flow rate Figure 8 is a graph showing a third example of controlling the flow velocity of the negative electrode liquid in the second flow path of a charging cell provided in the flow-type metal-air battery of the first embodiment.

[0148] In Figure 8, time is plotted on the horizontal axis, and the flow velocity is plotted on the vertical axis.

[0149] The following describes the differences between a fifth control example of the current value flowing between the positive electrode 93 and the negative electrode 98, and the flow velocity of the negative electrode liquid 97 in the second flow path 96e of the second layer 96, compared to a third control example of the said current and flow velocity.

[0150] In the fifth control example, as in the third control example for the current and the flow velocity, the control circuit 81, which acts as the control unit, periodically changes the flow velocity between a first flow velocity LV1 and a second flow velocity VL2 that is greater than the first flow velocity LV1, as shown in Figure 8.

[0151] However, in this fifth control example, unlike the third control example of the current and flow rate, the first flow rate VL1 is 0, as shown in Figure 8. This eliminates the power consumed to flow the negative electrode liquid 97 during periods T0-T1 and T2-T3. It also limits the supply of negative electrode active material ions 42 onto the negative electrode 98 during periods T0-T1 and T2-T3. This promotes the growth of bulky, dendrite-like reduced negative electrode active material particles 41a on the negative electrode 98. This increases the resistance force acting on the reduced negative electrode active material particles 41a when the negative electrode liquid 97 acts on them.

[0152] By controlling the current value and flow rate in this manner, if the removal of reduced negative electrode active material particles 41a from the negative electrode 98 is promoted, a movable part for removing the reduced negative electrode active material particles 41a from the negative electrode 98 becomes unnecessary. As a result, it is possible to provide a flow-type metal-air battery 1 with high durability that can remove reduced negative electrode active material particles 41a from the negative electrode 98 without consuming a large amount of power.

[0153] 1.17 Variations Figure 9 is a schematic cross-sectional view illustrating a rechargeable cell provided in a flow-type metal-air battery of a first modification of the first embodiment.

[0154] In the first embodiment, as shown in Figure 3, the positive electrode chamber is composed of three positive electrode chamber components consisting of a first layer 91, a conductive plate 94, and a gasket 95, and the negative electrode chamber is composed of three negative electrode chamber components consisting of a second layer 96, a conductive plate 99, and a gasket 100.

[0155] In contrast, in the first modified example of the first embodiment, as shown in Figure 9, the positive electrode chamber is formed by a single positive electrode chamber component 111 which integrates the first layer 91, the conductive plate 94, and the gasket 95, and the negative electrode chamber is formed by a single negative electrode chamber component 112 which integrates the second layer 96, the conductive plate 99, and the gasket 100.

[0156] Figure 10 is a schematic cross-sectional view illustrating a rechargeable cell provided in a flow-type metal-air battery of a second modification of the first embodiment.

[0157] In the first embodiment, as shown in Figure 3, the negative electrode 98 and the conductive plate 99 are molded as separate components.

[0158] In contrast, in the second modified example of the first embodiment, as shown in Figure 10, the conductive plate 99 also serves as the negative electrode 98, the conductive plate 99 is integrally formed with the negative electrode 98, and the negative electrode 98 and the conductive plate 99 are molded as a single unit. This reduces the number of components that make up the charging cell 78. It also reduces the man-hours required to assemble the charging cell 78. Furthermore, it shortens the lead time required to assemble the charging cell 78. As a result, the cost of the charging cell 78 can be reduced.

[0159] Figure 11 is a schematic cross-sectional view illustrating a rechargeable cell provided in a flow-type metal-air battery of a third modification of the first embodiment.

[0160] In the first embodiment, as shown in Figure 3, the second layer 96, the negative electrode 98, and the conductive plate 99 are molded as separate components.

[0161] In contrast, in the third modified example of the first embodiment, as shown in Figure 11, the conductive plate 99 also serves as the second layer 96 and the negative electrode 98, and the conductive plate 99 is integrally formed with the second layer 96 and the negative electrode 98, and the second layer 96, the negative electrode 98 and the conductive plate 99 are molded as a single unit. This reduces the number of parts that make up the charging cell 78. It also reduces the man-hours required to assemble the charging cell 78. Furthermore, it shortens the lead time required to assemble the charging cell 78. As a result, the cost of the charging cell 78 can be reduced. In addition, a gasket 100 that liquid-tightly seals the space between the second layer 96 and the negative electrode 98 and the conductive plate 99 becomes unnecessary. This prevents leakage of negative electrode fluid 97 from the negative electrode chamber. As a result, the long-term stability and reliability of the charging cell 78 can be increased.

[0162] Figure 12 is a schematic cross-sectional view illustrating a rechargeable cell provided in a flow-type metal-air battery of a fourth modification of the first embodiment.

[0163] In the fourth modified example of the first embodiment, as shown in Figure 12, the negative electrode 98 comprises a first portion 121 made of a first material and a second portion 122 made of a second material. The hydrogen overpotential of the second material is smaller than that 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 detaches the reduced negative electrode active material particles 41a from the negative electrode 98 and facilitates the discharge of the detached 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.

[0164] 1.18 Charging Experiment (Charging experiment 1) As Example 1, a charging cell 78 as shown in Figure 3 was fabricated, and a charging experiment was conducted using the fabricated charging cell 78.

[0165] Carbon was used for the negative electrode 98. The size of the portion of the negative electrode 98 that is immersed in the negative electrode solution 97 was set to 10 mm x 80 mm.

[0166] A nickel porous material (Selmet®, 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.

[0167] The configuration other than the negative electrode 98 and positive electrode 93 was as follows: Separator 101: Manufactured by Nippon Shokubai Co., Ltd. "Sheet-type separator with a thickness of 0.1 mm and dimensions of 20 mm x 110 mm" Cathode solution 92: Zn saturated KOH aqueous solution ("KOH 29.2%, zinc oxide 4%") Negative electrode solution 97: Zn saturated KOH aqueous solution ("KOH 29.2%, zinc oxide 4%, thickener 1%") The viscosity of the negative electrode fluid was evaluated using VT-06 manufactured by Rion Co., Ltd., and was found to be 100 mPasec.

[0168] In the charging cell of Comparative Example 1, the configuration was the same as that of the charging cell 78 of Example 1, except for the negative electrode fluid 97. The negative electrode fluid 97 of Comparative Example 1 is as follows. Negative electrode solution 97: Zn saturated KOH aqueous solution ("KOH 29.2%, zinc oxide 4%") The viscosity of the negative electrode fluid was evaluated using an Ubbelohde viscometer and found to be 2 mPasec.

[0169] The positive electrode solution 92 and the negative electrode solution 97 were circulated through the charging cell 78 of Example 1 and the charging cell of the comparative example, and a charging experiment was conducted. In the charging experiment, the current density was 100 mA / cm². 2 Constant current charging was performed (per projected area of ​​the negative electrode 98). A battery tester (Kikusui Electronics Co., Ltd.: SPEC20526-PFX2011S) was used for measurement. In the charging experiment, the weight of reduced negative electrode active material (metallic zinc) particles 41a, which were detached from the negative electrode 98 and discharged from the charging cell 78 of Example 1 and the charging 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 zinc discharged (g) × 0.82 (Ah / g: specific capacity of zinc) / Amount of electricity input (Ah) × 100

[0170] [Table 1]

[0171] As shown in Table 1, when the negative electrode fluid 97 has a low viscosity (Comparative Example 1), reduced negative electrode active material (metallic zinc) particles 41a are not discharged from the charging cell. This is because when the negative electrode fluid 97 acts on the reduced negative electrode active material (metallic zinc) particles 41a, the resistance force acting on the reduced negative electrode active material (metallic zinc) particles 41a becomes smaller.

[0172] In contrast, when the negative electrode liquid 97 has 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 when the negative electrode liquid 97 acts on the reduced negative electrode active material (metallic zinc) particles 41a, the resistance force acting on the reduced negative electrode active material (metallic zinc) particles 41a becomes large.

[0173] (Charging experiment 2) As Example 2, a charging experiment was conducted using the same charging cell 78 as in Example 1, except for the negative electrode fluid 97. The negative electrode fluid 97 in Example 2 is as follows. Negative electrode solution 97: Zn saturated KOH aqueous solution ("KOH 29.2%, zinc oxide 4%, thickener 1%, indium hydroxide 0.01%)" The viscosity of the negative electrode fluid was evaluated using VT-06 manufactured by Rion Co., Ltd., and was found to be 100 mPasec.

[0174] As shown in Table 1, when the negative electrode fluid 97 has high viscosity and contains additional components (indium ions), the recovery rate of reduced negative electrode active material (metallic zinc) particles 41a discharged from the charging cell 78 is improved. This is because the adhesion of reduced negative electrode active material (metallic zinc) particles 41a to the negative electrode 98 is reduced. Therefore, when the negative electrode fluid 97 has high viscosity and contains additional components (indium ions), it becomes even easier to detach the reduced negative electrode active material (zinc) particles 41a from the negative electrode 98 and discharge the detached reduced negative electrode active material (metallic zinc) particles 41a from the charging cell 78.

[0175] (Charging experiment 3) As Example 3, a charging experiment was conducted using the same charging cell 78 as in Example 2. The positive electrode solution 92 and negative electrode solution 97 were also the same as those used in Example 2. Specifically, the details are as follows. Cathode solution 92: Zn saturated KOH aqueous solution ("KOH 29.2%, zinc oxide 4%") Negative electrode solution 97: Zn saturated KOH aqueous solution ("KOH 29.2%, zinc oxide 4%, thickener 1%, indium hydroxide 0.01%)" The viscosity of the negative electrode fluid was evaluated using VT-06 manufactured by Rion Co., Ltd., and was found to be 100 mPasec.

[0176] In charging experiment 3, constant current charging was performed by varying the current density (per projected area of ​​the negative electrode 98). The weight of the reduced negative electrode active material (metallic zinc) particles 41a that were detached from the negative electrode 98 and discharged from the charging cell 78 during the charging experiment was measured, and the zinc recovery rate relative to the amount of electricity input was calculated. The calculation results are shown in Table 2.

[0177] [Table 2]

[0178] As shown in Table 2, there is a preferred current density (per projected area of ​​the negative electrode 98) range that allows for a high 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 / cm²), the recovery rate is low. 2 ) makes it difficult to detach the reduced negative electrode active material (metallic zinc) particles 41a from the negative electrode 98. This is because dense reduced negative electrode active material (metallic zinc) particles 41a tend to grow on the negative electrode 98, and the resistance force acting on the reduced negative electrode active material (metallic zinc) particles 41a when the negative electrode liquid 97 acts on them becomes smaller.

[0179] On the other hand, when the current density (per projected area of ​​the negative electrode 98) is high (e.g., 150 mA / cm²), 2 Although it is easy to detach the reduced negative electrode active material (metallic zinc) particles 41a from the negative electrode 98, the zinc recovery rate is low because a hydrogen generation reaction occurs, which is a competitive reaction in the reduction reaction that produces the reduced negative electrode active material (metallic zinc) particles 41a.

[0180] 1.19 Charging Cell Stack Figure 13 is a schematic cross-sectional view 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.

[0181] The charging cell stack 131 shown in Figure 13 comprises a plurality of charging cells 78.

[0182] Multiple charging cells 78 are stacked to form a battery pack. This allows the charging cell stack 131 to charge more power than a single charging cell 78 can charge.

[0183] The multiple charging cells 78 include two charging cells 78 adjacent to each other. The main surface 94p of the conductive plate 94 of one of the two adjacent charging cells 78 is in surface contact with the main surface 99p of the conductive plate 99 of the other charging cell 78. As a result, the conductive plate 94 and the conductive plate 99 are electrically connected to each other, forming a bipolar plate 141 that combines the functions of a positive electrode conductive plate and a negative electrode conductive plate. This connects the multiple charging cells 78 electrically in series.

[0184] A positive electrode chamber is formed between the bipolar plate 141 and the separator 101 of one charging cell 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. The positive electrode liquid 92 flows in parallel into the multiple first flow paths 91e. The negative electrode liquid 97 flows in parallel into the multiple second flow paths 96e.

[0185] This disclosure is not limited to the embodiments described above, and may be replaced with configurations that are substantially the same as those shown in the embodiments, configurations that produce the same effects, or configurations that can achieve the same purpose. [Explanation of Symbols]

[0186] 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 Negative electrode active material particles in reduced state, 41b Negative electrode active material particles in oxidized state, 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 Cathode liquid, 93 Cathode, 94 Conductive 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 98 Negative electrode, 99 Conductive plate, 99p Main surface, 100 Gasket, 101 Separator, 102 Gasket, 103 Gasket, 111 Positive electrode chamber component, 112 Negative electrode chamber component, 121 First part, 122 Second part, 131 Charging cell stack, 141 Bipolar plate.

Claims

1. A first layer in which the first channel is formed, The positive electrode facing the first flow path, A second layer in which a second channel is formed, The negative electrode facing the second flow path, A separator that separates the first flow path and the second flow path from each other, The positive electrode liquid flowing through the first channel, The negative electrode liquid flowing through the second channel, A control unit that changes the flow velocity of the negative electrode liquid in the second flow path, Equipped with, The control unit periodically changes the flow velocity between a first flow velocity and a second flow velocity greater than the first flow velocity. The control unit is a charging unit for a flow-type metal-air battery that changes the flow rate so that the charging period includes a period in which the flow rate is the first flow rate.

2. A first layer in which a first flow channel is formed, The positive electrode facing the first flow path, A second layer in which a second channel is formed, The negative electrode facing the second flow path, A separator that separates the first flow path and the second flow path from each other, The positive electrode liquid flowing through the first channel, The negative electrode liquid flowing through the second channel, A control unit that changes the flow velocity of the negative electrode liquid in the second flow path, Equipped with, The control unit periodically changes the flow velocity between a first flow velocity and a second flow velocity greater than the first flow velocity. The control unit changes the flow velocity such that the period during which charging is stopped includes a period during which the flow velocity is the second flow velocity. Charging unit for flow-type metal-air batteries.

3. A first layer in which the first channel is formed, The positive electrode facing the first flow path, A second layer in which a second channel is formed, The negative electrode facing the second flow path, A separator that separates the first flow path and the second flow path from each other, The positive electrode liquid flowing through the first channel, The negative electrode liquid flowing through the second channel, A current control unit that changes the current value of the current flowing between the positive electrode and the negative electrode, Equipped with, The current control unit is a charging unit for a flow-type metal-air battery that periodically changes the current value between a first current value and a second current value smaller than the first current value.

4. A first layer in which a first flow channel is formed, The positive electrode facing the first flow path, A second layer in which a second channel is formed, The negative electrode facing the second flow path, A separator that separates the first flow path and the second flow path from each other, The positive electrode liquid flowing through the first channel, The negative electrode liquid flowing through the second channel, A current control unit that changes the current value of the current flowing between the positive electrode and the negative electrode, Equipped with, The current control unit periodically changes the current value between a first current value and a second current value smaller than the first current value. The signs of the first current value and the second current value are opposite. Charging unit for flow-type metal-air batteries.

5. A first layer in which a first flow channel is formed, The positive electrode facing the first flow path, A second layer in which a second channel is formed, The negative electrode facing the second flow path, A separator that separates the first flow path and the second flow path from each other, The positive electrode liquid flowing through the first channel, The negative electrode liquid flowing through the second channel, A current control unit that changes the current value of the current flowing between the positive electrode and the negative electrode, Equipped with, The current control unit periodically changes the current value between a first current value and a second current value smaller than the first current value. The first current value is the current value at which hydrogen gas is generated on the negative electrode. Charging unit for flow-type metal-air batteries.

6. A first layer in which a first flow channel is formed, The positive electrode facing the first flow path, A second layer in which a second channel is formed, The negative electrode facing the second flow path, A separator that separates the first flow path and the second flow path from each other, The positive electrode liquid flowing through the first channel, The negative electrode liquid flowing through the second channel, A current control unit that changes the current value of the current flowing between the positive electrode and the negative electrode, Equipped with, The negative electrode comprises a first portion made of a first material and a second portion made of a second material having a lower hydrogen overpotential compared to the first material. Charging unit for flow-type metal-air batteries.

7. The reaction at the positive electrode generates oxygen gas, and the reaction at the negative electrode generates negative electrode active material particles. A charging unit for a flow-type metal-air battery according to claim 1.

8. The positive electrode solution includes a first electrolyte solution, The negative electrode solution comprises a second electrolyte and negative electrode active material ions dissolved in the second electrolyte. A charging unit for a flow-type metal-air battery according to claim 1.

9. The negative electrode solution contains a thickening agent. The charging unit for a flow-type metal-air battery according to claim 8.

10. The negative electrode solution comprises zinc ions and at least one ion selected from the group consisting of Group 13, Group 14, and Group 15 metal elements. A charging unit for a flow-type metal-air battery according to claim 1.

11. The negative electrode solution contains zinc ions and indium ions. A charging unit for a flow-type metal-air battery according to claim 1.

12. The separator is a membrane comprising an anion exchange membrane, a water-containing gel membrane, or a plurality of inorganic ion conductor particles and a resin impregnated at the grain boundaries of the plurality of inorganic ion conductor particles. A charging unit for a flow-type metal-air battery according to claim 1.

13. The positive electrode contains nickel, The negative electrode includes at least one selected from the group consisting of carbon, copper, and magnesium. A charging unit for a flow-type metal-air battery according to claim 1.

14. It includes a current-carrying plate that is integrally formed with the negative electrode. A charging unit for a flow-type metal-air battery according to claim 1.

15. The negative electrode and the current-carrying plate are integrally formed with the second layer. A charging unit for a flow-type metal-air battery according to claim 1.

16. The first flow path includes a portion that guides the positive electrode liquid in a vertical direction, The system includes a mechanism for generating the flow of the positive electrode liquid in the aforementioned portion, such that the flow direction of the positive electrode liquid is from vertically downward to vertically upward. A charging unit for a flow-type metal-air battery according to claim 1.

17. The second flow path includes a portion that guides the negative electrode liquid in a vertical direction, The system includes a mechanism for generating the flow of the negative electrode fluid in the aforementioned portion, such that the flow direction of the negative electrode fluid is from vertically downward to vertically upward. A charging unit for a flow-type metal-air battery according to claim 1.

18. A first layer in which a first flow channel is formed, The positive electrode facing the first flow path, A second layer in which a second channel is formed, The negative electrode facing the second flow path, A separator that separates the first flow path and the second flow path from each other, The positive electrode liquid flowing through the first channel, The negative electrode liquid flowing through the second channel, A control unit that changes the flow velocity of the negative electrode liquid in the second flow path, Equipped with, The control unit periodically changes the flow velocity between a first flow velocity and a second flow velocity greater than the first flow velocity. The control unit changes the flow velocity so that the charging period includes a period in which the flow velocity is the first flow velocity. The control unit changes the flow velocity such that the period during which charging is stopped includes a period during which the flow velocity is the second flow velocity. Charging unit for flow-type metal-air batteries.

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