Power generation unit stack and flow type metal-air battery

Abstract

To provide a power generation part stack and a flow type metal-air battery capable of achieving both distribution property of a solid active material to a plurality of battery cells and negative electrode contact property of the solid active material in each battery cell.SOLUTION: The battery stack 200 includes a manifold 220 formed along the stacking direction of the battery cells, a negative electrode flow path 122 provided in each battery cell and formed to be physically connected to the manifold 220, and a negative electrode 121 disposed in each negative electrode flow path 122. The manifold 220 is disposed along the vertical direction. The negative electrode 121 is present vertically below the negative electrode flow path 122.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a power generation stack and a flow-type metal-air battery. [Background technology]

[0002] Conventionally, secondary batteries that use a slurry containing a solid active material (metal active material) and an electrolyte solution are known. In a flow-type metal-air battery, which is one type of such secondary battery, a flow-type metal-air battery stack (hereinafter referred to as a battery stack) consisting of a plurality of stacked flow-type metal-air battery cells (hereinafter referred to as battery cells) is used in the power generation section and the charging section. In such a battery stack, manifolds are connected to the inlet and / or outlet sides of the slurry flow paths of all battery cells, and the slurry can be supplied and discharged via the manifolds. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-062667 Summary of the Invention [Problem to be solved by the invention]

[0004] To improve the power generation efficiency of a flow-type metal-air battery, it is important to not only increase the reaction efficiency in each battery cell (increase the contact efficiency between the solid active material and the negative electrode) but also to improve the distribution (uniformity of distribution) of the solid active material from the manifold to multiple battery cells (eliminate variations in the amount of solid active material distributed among multiple battery cells), particularly in the battery stack used in the power generation section (hereinafter referred to as the power generation section stack). In other words, if the distribution of the negative electrode slurry to the battery cells becomes uneven, variations in the power generation characteristics will occur among the multiple battery cells, and the power generation characteristics of the power generation section stack as a whole will deteriorate.

[0005] Patent Document 1 discloses a technique for improving electrolyte flow distribution in a forced electrolyte flow battery by providing unequal cross sections for the battery's inlet and outlet manifolds. However, the forced electrolyte flow battery of Patent Document 1 does not flow a negative electrode slurry containing solid active material, and its configuration does not improve the distribution of solid active material.

[0006] Furthermore, when a manifold is used to distribute negative electrode slurry to battery cells, if stagnation (accumulation) of solid active material occurs within the manifold, an electronic conduction path is formed by the stagnant (accumulated) solid active material within the manifold, and this electronic conduction path can cause a short circuit between adjacent battery cells.

[0007] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a power generation stack and a flow-type metal-air battery that can achieve both the distribution of solid active material to multiple battery cells and the negative electrode contact of the solid active material within each battery cell. [Means for solving the problem]

[0008] In order to solve the above problems, a power generation stack according to a first aspect of the present disclosure is used in a flow-type metal-air battery, and is formed by stacking a plurality of flow-type metal-air battery cells through which anode slurry is circulated, and is characterized in that it has a manifold formed along the stacking direction of the flow-type metal-air battery cells, anode flow paths provided in the flow-type metal-air battery cells and formed to be physically connected to the manifold, and anodes placed within the anode flow paths, the manifolds being arranged vertically, and the anodes being present vertically below the anode flow paths.

[0009] A flow-type metal-air battery according to a second aspect of the present disclosure is a flow-type metal-air battery having a power generation unit that generates electricity by circulating a negative electrode slurry, a charging unit that charges the battery by circulating the negative electrode slurry, and a storage unit that stores the negative electrode slurry that circulates through the power generation unit and the charging unit, wherein the power generation unit is the power generation unit stack described above. [Effects of the Invention]

[0010] The power generation stack and flow-type metal-air battery of the present disclosure have the advantage of being able to achieve both the distribution of solid active material to multiple battery cells and the contact of the solid active material with the negative electrode within each battery cell. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is an explanatory diagram schematically illustrating the general configuration of a flow-type metal-air battery. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a battery cell in a power generation section. [Figure 3] FIG. 2 is an exploded perspective view illustrating an example of the configuration of a battery stack applied to a power generation unit. [Figure 4] 4 is a perspective view showing the opposite surface of the bipolar plate of FIG. 3. FIG. [Figure 5] 10(a) to 10(c) are diagrams showing examples of the shape of a flow channel. [Figure 6] 1 is a schematic cross-sectional view showing a schematic configuration of a battery stack of a first embodiment. [Figure 7] FIG. 2 is a schematic cross-sectional view showing the general configuration of a battery stack as a comparative example. [Figure 8] FIG. 10 is a schematic diagram showing the positional relationship between a battery stack and a stack connection channel as a comparative example. [Figure 9] FIG. 10 is a schematic diagram showing the positional relationship between a battery stack and a stack connection channel in a third embodiment. [Figure 10] FIG. 10 is a schematic diagram showing the positional relationship between a battery stack and a stack connection channel in a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] A flow-type battery cell and a flow-type metal-air battery according to an embodiment of the present disclosure will be described with reference to the drawings.

[0013] (Flow-type metal-air battery) 1 is an explanatory diagram showing a schematic configuration of a flow-type metal-air battery 1 according to the present disclosure. Note that components common to multiple embodiments described below are designated by common reference numerals, and redundant explanations will be omitted.

[0014] As shown in FIG. 1, the flow-type metal-air battery 1 includes a storage unit 11, a power generation unit 12, and a charging unit 13. The flow-type metal-air battery 1 takes in air and generates (discharges) electricity using the air taken in by the power generation unit 12. The charging unit 13 is responsible for charging and discharges oxygen. Anode slurry, which is a slurry-like fluid containing anode active material and an electrolyte, is supplied from the storage unit 11 to the power generation unit 12. A pipe is connected from the storage unit 11 to the power generation unit 12, and the anode slurry can be pressure-fed via a pump or the like (not shown). The same can be done between the charging unit 13 and the storage unit 11.

[0015] The storage unit 11 stores the negative electrode slurry. The negative electrode active material contained in the negative electrode slurry includes negative electrode active material ions dissolved in the electrolyte and solid active material that has exceeded its saturated solubility in the electrolyte and is suspended in a particle state without dissolving. The solid active material also includes a reduced solid active material (metal active material) and an oxidized solid active material.

[0016] The negative electrode active material is a metal species. Examples of the metal species include zinc species, cadmium species, lithium species, sodium species, magnesium species, lead species, tin species, aluminum species, and iron species. The metal constituting the metal species may be a metal consisting of only the main component metal, or may be an alloy of the main component metal and a subcomponent. The metal species can be either a metal or an oxide. Whether the metal species becomes a metal or an oxide depends on the degree of progress of the discharge reaction or the charge reaction. However, in the discharge reaction described below, the metal species is preferably in a reduced state.

[0017] In this embodiment, the metal species is a zinc species, and the flow-type metal-air battery 1 is a flow-type zinc-air battery. The metal constituting the zinc species may be, for example, a metal consisting only of zinc as the main component, or may be an alloy of zinc as the main component and a subcomponent. When the metal species is zinc, the negative electrode active material ions dissolved in the electrolyte are zincate ions, the reduced solid active material is zinc, and the oxidized solid active material is, for example, zinc oxide.

[0018] The average particle size of the metal species is several μm when it is an oxidized solid active material (e.g., ZnO), and is several tens of μm to 200 μm when it is a reduced solid active material (e.g., Zn). The average particle size can be measured using a particle size distribution analyzer. The particle size distribution analyzer measures the particle size distribution by, for example, laser diffraction or dynamic light scattering, and calculates the median diameter D50 from the measured particle size distribution as the average particle size.

[0019] The electrolyte is selected depending on the metal species. When the metal species is zinc, the electrolyte is an alkaline aqueous solution, such as a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution. When the metal species is lithium, the electrolyte is a non-aqueous electrolyte. When the metal species is magnesium, the electrolyte is a neutral aqueous solution, such as a sodium chloride aqueous solution. The electrolyte may be replaced with a solid electrolyte.

[0020] Power generation unit 12 supplies the negative electrode slurry from storage unit 11 to the negative electrode, and supplies air to the positive electrode. In power generation unit 12, a region where the negative electrode is provided and a region where the positive electrode is provided are separated by separator 130.

[0021] In the case of a flow-type zinc-air battery in which the metal species is zinc, the reaction at the negative electrode of the power generation unit 12 follows formulas (1) and (2). At the negative electrode, the reduced zinc active material reacts with hydroxide ions to generate zincate ions and release electrons. The zincate ions generate zinc oxide, water, and hydroxide ions. The anion involved in the power generation reaction is hydroxide ions.

[0022] Zn+4OH - →Zn(OH)4 2- +2e - …(1) Zn(OH)4 2- →ZnO+H2O+2OH - …(2) The reaction at the positive electrode of the power generation unit 12 follows formula (3): At the positive electrode, electrons are received and hydroxide ions are produced from oxygen and water.

[0023] O2+2H2O+4e - →4OH - …(3) In power generation unit 12, zinc, which is a reduced solid active material, is used for discharge. A negative electrode slurry containing a negative electrode active material is supplied to power generation unit 12 from storage unit 11. The solid active material supplied to power generation unit 12 and stored in storage unit 11 is preferably in a reduced state, or preferably there is more reduced solid active material than oxidized solid active material.

[0024] In charging section 13, negative electrode slurry is supplied to the negative electrode from storage section 11. In charging section 13, a separator 130 separates an area where the negative electrode is provided from an area where the positive electrode is provided.

[0025] When the metal species is zinc, the reaction at the negative electrode of charging unit 13 follows equations (4) and (5). At the negative electrode, zinc oxide, which is a solid active material in an oxidized state, first reacts with water and hydroxide ions to generate zincate ions. The zincate ions then accept electrons to generate zinc and hydroxide ions. The anion involved in the charging reaction is hydroxide ions.

[0026] ZnO+H2O+2OH - →Zn(OH)4 2- …(4) Zn(OH)4 2- +2e - →Zn+4OH - …(5) The reaction at the positive electrode of charging unit 13 follows formula (6): At the positive electrode, oxygen and water are produced from hydroxide ions, and electrons are released.

[0027] 4OH - →O2+2H2O+4e - …(6) In the charging unit 13, charging is performed using zinc oxide, which is a solid active material in an oxidized state (zinc is regenerated). A negative electrode slurry containing a negative electrode active material is supplied to the charging unit 13 from the storage unit 11. The solid active material supplied to the charging unit 13 and stored in the storage unit 11 is preferably in an oxidized state, or preferably there is more oxidized solid active material than reduced solid active material.

[0028] (battery cell) 2 is a cross-sectional view that schematically shows a battery cell (flow-type metal-air battery cell) 100 in the power generation section 12 of the flow-type metal-air battery 1 according to the present disclosure. Although a detailed description will be omitted here, a battery cell with a similar configuration (a configuration having a positive electrode chamber and a negative electrode chamber) can also be used in the charging section 13.

[0029] In the flow-type metal-air battery 1, the power generation section 12 is basically constituted by a battery cell 100 including a positive electrode chamber 110, a negative electrode chamber 120, and a separator 130 that separates them. The battery cell 100 circulates negative electrode slurry B in a negative electrode flow path 122, which will be described later.

[0030] The positive electrode chamber 110 includes a positive electrode 111 where an oxygen reduction reaction occurs, and air A containing oxygen as a reactant flows through it. The positive electrode chamber 110 is provided with a positive electrode flow path 112. The positive electrode flow path 112 is, for example, a groove formed in a striped pattern on a positive electrode current-carrying plate 113, and is a flow path through which oxygen, which is a positive electrode active material, flows. The positive electrode 111 is arranged in contact with the positive electrode current-carrying plate 113.

[0031] The anode chamber 120 includes an anode 121 in which an oxidation reaction of metallic zinc occurs. An anode flow path 122 is provided within the anode chamber 120, through which an anode slurry B containing a solid active material and an electrolyte flows. For example, an anode flow path layer 123 is provided between the anode 121 and the separator 130, and the anode flow path 122 is formed by grooves provided in the anode 121, the separator 130, and the anode flow path layer 123. Note that the anode flow path 122 is not limited to a configuration in which it is formed by the anode flow path layer 123 having grooves, and the flow path may be formed by grooves provided on the surface of the anode 121, or the like.

[0032] 2, an inlet 124 for a negative electrode slurry is provided at one end of the negative electrode flow path 122, and an outlet 125 for a negative electrode slurry is provided at the other end by the negative electrode flow path layer 123. Negative electrode slurry B flows through the negative electrode flow path 122 from the inlet 124 toward the outlet 125.

[0033] The negative electrode 121 forms part of the wall surface of the negative electrode flow path 122. The negative electrode 121 can be made of a conductive material such as a carbon material and a resin material. The separator 130 forms part of the wall surface of the negative electrode flow path 122 facing the negative electrode 121 (it is provided facing the negative electrode 121). The separator 130 separates the positive electrode chamber 110 from the negative electrode chamber 120, and prevents the negative electrode slurry from permeating from the negative electrode chamber 120 side to the positive electrode chamber 110 side. The separator 130 is provided along the positive electrode 111. It is preferable to use a material (e.g., a hydrous gel membrane) suitable for preventing the permeation of the negative electrode slurry for the separator 130. The separator 130 and the positive electrode 111 are held and fixed by a sealing portion 140.

[0034] A negative electrode current-carrying plate 126 may be provided in the negative electrode chamber 120 along the negative electrode 121. A sealing part 140 is disposed and fixed between the negative electrode current-carrying plate 126 and the negative electrode flow path layer 123. The negative electrode chamber 120 is not limited to a configuration including the negative electrode 121, the negative electrode current-carrying plate 126, and the negative electrode flow path layer 123, and these may be configured as a single member.

[0035] The positive electrode 111 can be made by kneading and rolling manganese dioxide as a catalyst, acetylene black acting as a conductor, and PTFE (polytetrafluoroethylene) acting as a water repellent and binder. The separator 130 is made of a material (a hydrogel membrane) suitable for preventing the electrolyte from permeating from the negative electrode chamber 120 to the positive electrode chamber 110 through the separator 130. The negative electrode 121 can be made of a conductive material made of a carbon material and resin.

[0036] (Power generation stack) The power generation section 12 of the flow-type metal-air battery 1 is composed of a battery stack (power generation section stack) 200 formed by stacking a plurality of battery cells 100. Fig. 3 is an exploded perspective view illustrating an example configuration of the battery stack 200. Although detailed description will be omitted here, a battery stack with a similar configuration (a configuration in which a manifold is provided for the battery cells) can also be used in the charging section 13.

[0037] The battery stack 200 is constructed by continuously stacking bipolar plates 210, positive electrodes 111, and separators 130. More specifically, one battery cell 100 is formed by a stacked structure in which one positive electrode 111 and one separator 130 are sandwiched between two bipolar plates 210. In the configuration shown in FIG. 3, the bipolar plate 210 also serves as the negative electrode 121, negative electrode current-carrying plate 126, and positive electrode current-carrying plate 113 of the battery cell 100. While FIG. 3 corresponds to two battery cells 100, a battery stack 200 including more battery cells 100 can be formed by increasing the number of stacked structures. Note that FIG. 3 does not illustrate the sealing portion 140 that secures the positive electrode 111 and separator 130 between the bipolar plates 210. The sealing portion 140 contacts the bipolar plates 210 on both sides in the stacking direction.

[0038] The bipolar plate 210 has a recess 211 formed on one surface in the stacking direction, and a recess 212 (see FIG. 4) formed on the other surface. FIG. 4 is a perspective view showing the surface of the bipolar plate 210 where the recess 212 is formed (the surface opposite to the bipolar plate 210 in FIG. 3). The recess 211 forms the negative electrode flow path 122 in the battery cell 100, and the recess 212 forms the positive electrode flow path 112 in the battery cell 100.

[0039] The bipolar plate 210 has through holes 213 formed in two opposing corners, and through holes 214 formed in the other two opposing corners. The through holes 213 are connected to the recessed portions 211 via grooves 215, and the through holes 214 are connected to the recessed portions 212 via grooves 216. That is, the grooves 215 form the inlet and outlet (inlet 124 and outlet 125) of the negative electrode flow path 122 in the battery cell 100, and the grooves 216 form the inlet and outlet of the positive electrode flow path 112. Note that the positive electrode 111 and the separator 130 do not overlap the through holes 213 and 214 when viewed from the stacking direction. Meanwhile, the sealing portion 140 has through holes formed in its four corners at positions facing the through holes 213 and 214. The through holes 213 and 214 in the bipolar plate 210 communicate with the through holes in the sealing portion 140, thereby forming a manifold in the cell stack 200, which will be described later.

[0040] The manifold formed in the battery stack 200 is not formed to penetrate the battery stack 200 in the stacking direction. That is, one end of the manifold in the stacking direction is open so as to be connected to the storage unit 11, but the other end in the stacking direction is closed. A manifold having such a configuration can be realized by not providing the through-hole 213 or the through-hole 214 in the bipolar plate 210 arranged at one end in the stacking direction in each of the flow paths (flow paths at the four corners) that serve as the manifold.

[0041] Furthermore, there are no particular limitations on the shape of the flow path in the negative electrode flow path 122 (i.e., the recess 211) and the positive electrode flow path 112 (i.e., the recess 212) of the battery cell 100. Examples of the flow path shape include a rectangular parallelepiped flow path formed as a single rectangular parallelepiped space (see FIG. 5(a)), a parallelepiped flow path in which multiple linear flow paths are arranged in parallel (see FIG. 5(b)), and a serpentine flow path formed by a single meandering flow path (see FIG. 5(c)).

[0042] [First embodiment] Fig. 6 is a schematic cross-sectional view showing the general configuration of a battery stack 200 according to the first embodiment. Each of Fig. 6 shows a cross section including a manifold connected to the negative electrode flow path.

[0043] As shown in FIG. 6 , the battery stack 200 includes multiple (but not limited to) battery cells, each of which includes an anode flow path 122. An inlet manifold 220A is connected to the inlet side of the anode flow path 122, and an outlet manifold 220B is connected to the outlet side. However, strictly speaking, the inlet and outlet sides of the battery stack 200 are determined according to the flow direction of the anode slurry (according to the location of the pump that pumps the anode slurry) when the battery stack 200 is used as a flow-type metal-air battery 1 connected to the storage unit 11. The battery stack 200 only needs to have a manifold 220 on at least one side of the anode flow path 122, and it is sufficient for specifications and the like to specify that the manifold 220 is connected to the storage unit 11 so that the manifold 220 is the inlet side. The orientation of the battery stack 200 when in use is also specified in specifications and the like. In the following description, when there is no need to distinguish between the inlet and outlet sides, the manifold 220 will simply be referred to as the manifold 220.

[0044] The inlet manifold 220A can also be considered to include a main path 221A that extends in the stacking direction of the multiple battery cells, and multiple branch paths 222A that branch off from the main path 221A and connect to the anode flow path 122. Similarly, the outlet manifold 220B can also be considered to include a main path 221B and multiple branch paths 222B. However, in the following description, the term "manifold" refers only to the "main path," and the "branch paths" are included in the anode flow path 122.

[0045] Manifold 220 is formed so that one end in the stacking direction is open so as to be connected to storage section 11, and the other end in the stacking direction is closed. In the example of Fig. 6, inlet-side manifold 220A has first connection port 2201 that opens on the upper side of the drawing, and outlet-side manifold 220B has second connection port 2202 that opens on the lower side of the drawing.

[0046] In FIG. 6 , the arrow X direction indicates the horizontal direction, and the arrow Y direction indicates the vertical direction. That is, in the battery stack 200, the manifold 220 is arranged along the vertical direction. The negative electrode flow paths 122 of each battery cell are connected so as to intersect perpendicularly with the manifold 220, and are therefore arranged along the horizontal direction. Furthermore, in each battery cell, the negative electrode 121 is located vertically below the negative electrode flow path 122. Note that, although FIG. 6 illustrates the negative electrode 121 located vertically below the negative electrode flow path 122, the configuration is not limited to the negative electrode 121 being located only vertically below the negative electrode flow path 122. For example, when the bipolar plate 210 in FIG. 3 also serves as the negative electrode 121, the negative electrode 121 is located not only vertically below the negative electrode flow path 122 but also on the sidewall of the negative electrode flow path 122.

[0047] In the battery stack 200, the manifold 220 is arranged in the vertical direction, thereby improving the distribution of the solid active material to the anode flow path 122 of each battery cell. Furthermore, the anode 121 is positioned vertically below the anode flow path 122, thereby improving the anode contact of the solid active material in each battery cell. Here, in describing the effects of the battery stack 200 according to this embodiment, a battery stack 300 as a comparative example will first be described with reference to FIG. 7.

[0048] In the battery stack 300 of the comparative example, the manifold 320 is arranged horizontally, and accordingly, the anode flow path 322 is arranged vertically. In this case, as shown in Fig. 7, if the anode 321 is located upstream of the anode flow path 322 in the direction of slurry flow within the manifold, the solid active material of the anode slurry can be biased toward the anode 321 within the anode flow path 322. In other words, the contact of the solid active material with the anode can be improved.

[0049] However, in order for the solid active material to flow unevenly within the anode flow channel 322, the flow rate of the anode slurry in the manifold 320 needs to be relatively slow. In this case, the solid active material flows unevenly downward within the manifold 320 due to the influence of gravity (the solid active material has a higher specific gravity than the electrolyte within the anode slurry). As a result, the anode slurry distributed from the manifold 320 to the anode flow channel 322 contains more solid active material upstream in the direction of slurry flow within the manifold and less solid active material downstream. In other words, the distribution of the solid active material to the anode flow channel 322 is reduced.

[0050] Furthermore, if the solid active material is biased downward in the manifold 320, the biased solid active material may cause an electronic conduction path in the manifold 320. As a result, particularly on the upstream side in the slurry flow direction where a large amount of solid active material is present, there is a risk of a short circuit between adjacent battery cells (a short circuit between negative electrodes 321) occurring due to the electronic conduction path caused by the solid active material (metal active material having electrical conductivity).

[0051] If the flow rate of the negative electrode slurry in the manifold 320 is increased, the solid active material flows in a dispersed manner within the manifold 320, improving the distribution of the solid active material to the negative electrode flow paths 322. However, in this case, the solid active material also disperses within the negative electrode flow paths 322, reducing the contact of the solid active material with the negative electrode.

[0052] 7, it is also possible to arrange the manifold 320 below the anode flow path 322 and flow the anode slurry through the anode flow path 322 from bottom to top (against the direction of gravity). In this case, when the flow rate of the anode slurry is slowed, less solid active material is distributed to the anode flow path 322 on the upstream side, and more solid active material is distributed to the anode flow path 322 on the downstream side. However, the distribution of the solid active material to the anode flow path 322 is reduced, as in the example of FIG. 7. Furthermore, when the flow rate of the anode slurry is fast, the contact of the solid active material with the anode is reduced, as in the example of FIG. 7.

[0053] In contrast, in the battery stack 200 of this embodiment (the example in FIG. 6 ), the manifold 220 is arranged vertically, so that the solid active material in the negative electrode slurry flowing through the manifold 220 is not biased due to the influence of gravity, and flows in a dispersed state (or a state close to that) within the manifold 220. As a result, the distribution of the solid active material to the negative electrode flow paths 122 of each battery cell can be improved without increasing the flow rate of the negative electrode slurry in the manifold 220 more than necessary.

[0054] Furthermore, eliminating uneven distribution of the solid active material within the manifold 220 not only improves the distribution of the solid active material, but also eliminates the generation of electron conduction paths due to uneven distribution of the solid active material, thereby preventing short circuits between battery cells due to electron conduction paths caused by the solid active material.

[0055] In the battery stack 200 of this embodiment, the anode flow path 122 is arranged horizontally, and therefore, by appropriately suppressing the flow rate of the anode slurry in the anode flow path 122, the solid active material can be biased downward by the action of gravity in the anode flow path 122. Furthermore, in the battery stack 200, the anode 121 is located vertically below the anode flow path 122, and therefore, the contact of the solid active material with the anode can be improved.

[0056] As described above, the battery stack 200 of this embodiment can achieve both the distribution of solid active material among multiple battery cells and the contact of the solid active material with the negative electrode within each battery cell. In addition, it can also prevent short circuits between battery cells due to uneven distribution of solid active material. Note that achieving both the distribution of solid active material and the contact of the solid active material with the negative electrode leads to improved power generation efficiency when the battery stack 200 is applied to the power generation unit 12. Meanwhile, the effect of preventing short circuits can also be obtained when the battery stack 200 is applied to the charging unit 13.

[0057] In the example of the battery stack 200 shown in FIG. 6 , manifolds 220 (i.e., an inlet-side manifold 220A and an outlet-side manifold 220B) are provided on both the inlet and outlet sides of the anode flow path 122. When manifolds 220 are provided on both the inlet and outlet sides in this manner, the piping between the battery stack 200 and the storage unit 11 is simplified, and the size of the battery stack 200 can be reduced. However, to obtain the effect of improving the distribution of the solid active material described above, it is sufficient for the battery stack 200 to have at least the inlet-side manifold 220A, and the outlet-side manifold 220B may be omitted. In other words, a manifold may not be provided on the outlet side, and the outlet sides of the anode flow paths 122 of each battery cell may be connected to the storage unit 11 via piping.

[0058] In the example of the battery stack 200 shown in FIG. 6, the inlet manifold 220A has a first connection port 2201 provided on the upper side, and the outlet manifold 220B has a second connection port 2202 provided on the lower side. In this case, the flow direction of the negative electrode slurry in the manifold 220 is vertically downward. In this case, the negative electrode slurry can be transported within the manifold 220 using the action of gravity, which makes it difficult for the solid active material to stagnate (accumulate) within the manifold 220, and prevents the manifold 220 from being blocked by the stagnant solid active material. Furthermore, by using the action of gravity to transport the negative electrode slurry within the manifold 220, the flow-type metal-air battery 1 can reduce the power consumption of the pump that pumps the negative electrode slurry.

[0059] However, the flow direction of the negative electrode slurry in the manifold 220 is not particularly limited. For example, the first connection port 2201 may be provided on the lower side of the inlet manifold 220A, and the second connection port 2202 may be provided on the upper side of the outlet manifold 220B. In this case, the flow direction of the negative electrode slurry in the manifold 220 is vertically upward. Alternatively, the first connection port 2201 and the second connection port 2202 may both be provided on the upper side or the lower side of the inlet manifold 220A and the outlet manifold 220B.

[0060] Second Embodiment In the first embodiment, it was explained that the contactability of the solid active material with the negative electrode can be improved by appropriately suppressing (relatively slowing down) the flow rate of the negative electrode slurry in the negative electrode flow path 122. It was also explained that the solid active material in the negative electrode slurry can be dispersed (or nearly so) in the manifold 220 without increasing the flow rate of the negative electrode slurry more than necessary, thereby improving the distribution of the solid active material. However, if the flow rate of the negative electrode slurry in the manifold 220 is too low, the solid active material may stagnate at the bottom of the manifold 220 due to the action of gravity, and the stagnant solid active material may clog the manifold 220. For this reason, it is preferable that the flow rate of the negative electrode slurry in the manifold 220 is not too low. More specifically, it is preferable that the flow rate of the negative electrode slurry in the manifold 220 be higher than the flow rate of the negative electrode slurry in the negative electrode flow path 122. The conditions for achieving this are explained below.

[0061] First, in the battery stack 200, the cross-sectional area of ​​the manifold 220 is Sm, the flow rate of the negative electrode slurry in the manifold 220 is Vm, the cross-sectional area of ​​the negative electrode flow path 122 in each battery cell is Sc, the number of battery cells in the battery stack 200 is N, and the flow rate of the negative electrode slurry in the negative electrode flow path 122 is Vc.

[0062] In this case, the flow rate Qm of the manifold 220 is Qm=Sm×Vm The flow rate Qc of the negative electrode flow path 122 in the entire battery stack 200 is expressed as follows: Qc=Sc×Vc×N In the battery stack 200, the negative electrode slurry flowing through the manifold 220 is entirely distributed to the negative electrode flow paths 122 of the battery cells, so the flow rate Qm is equal to the flow rate Qc. Sm×Vm=Sc×Vc×N Therefore, when the flow velocity of the negative electrode slurry in the manifold 220 is greater than the flow velocity of the negative electrode slurry in the negative electrode flow path 122 (i.e., Vm>Vc), Sm <Sc×N The following relation is satisfied.

[0063] The dispersion state of the solid active material in the negative electrode slurry is significantly affected by the flow rate of the negative electrode slurry. It is believed that when the flow rate is equal to or greater than a predetermined rate, the solid active material is less susceptible to the action of gravity and thus becomes dispersed, whereas when the flow rate is less than the predetermined rate, the solid active material becomes more susceptible to the action of gravity. Therefore, under conditions in which the flow rate of the negative electrode slurry in the manifold 220 is greater than the flow rate of the negative electrode slurry in the negative electrode flow path 122, the solid active material in the negative electrode slurry is dispersed during flow through the manifold 220, and the solid active material in the negative electrode slurry is allowed to settle by gravity during flow through the negative electrode flow path 122, allowing it to flow in a sliding state relative to the negative electrode 121.

[0064] In the above description, the cross-sectional area refers to the area of ​​a cross section cut perpendicular to the extension direction of the manifold / negative electrode flow path. Furthermore, if the cross section of the manifold / negative electrode flow path is not circular or rectangular, the maximum cross-sectional area Sm / Sc may be calculated by approximating it to a circle or a rectangle.

[0065] Because the cross-sectional area of ​​the manifold 220 is basically constant along the stretching direction, the cross-sectional area of ​​any point on the manifold 220 can be taken as the cross-sectional area Sm. However, if the cross-sectional area of ​​the manifold 220 varies, it is preferable to use the point with the largest cross-sectional area as the cross-sectional area Sm. For example, the cross-sectional areas of multiple arbitrary points (e.g., three points) on the manifold 220 can be measured, and the largest cross-sectional area among them can be used as the cross-sectional area Sm.

[0066] On the other hand, for the anode flow path 122, the cross-sectional area Sc is determined by an appropriate method according to the flow path shape of the anode flow path 122. In this case, the cross-sectional area Sc of the anode flow path 122 is preferably set to the cross-sectional area at a location where the flow velocity is (expected to be) the highest in the anode flow path 122. This is because the flow velocity in the anode flow path 122 needs to be kept below a desired velocity so as not to cause the solid active material to become dispersed, and if the flow velocity is set below the desired velocity at the location where the flow velocity in the anode flow path 122 is the highest (location where the cross-sectional area is the smallest), the flow velocity throughout the anode flow path 122 will also be below the desired velocity.

[0067] 5(a), the cross-sectional area of ​​the anode flow path 122 is large near the center of the flow path and smallest at the ends of the flow path (near the inlet or outlet). For this reason, in a rectangular flow path, the cross-sectional area of ​​the end of the flow path is preferably set to the cross-sectional area Sc of the anode flow path 122.

[0068] 5(c), the cross-sectional area of ​​the anode flow path 122 is not constant, with the cross-sectional area S1 being small at the straight portions and the cross-sectional area S2 being large at the corner portions. For this reason, in a serpentine flow path, it is preferable to set the cross-sectional area S1 at the straight portions as the cross-sectional area Sc of the anode flow path 122.

[0069] When the flow path shape of the negative electrode flow path 122 is the parallel flow path shown in FIG. 5(b), this parallel flow path includes a confluence path extending in the left-right direction in the figure and a branch path extending in the up-down direction in the figure. That is, in the parallel flow path, a plurality (M) of branch paths are connected to one confluence path. In this case, regarding the branch paths, the cross-sectional area obtained by combining all the branch paths is considered. That is, even if S3 > S4 between the cross-sectional area S3 of the confluence path and the cross-sectional area S4 of one branch path, usually S3 < S4 × M. For this reason, in the parallel flow path, it is preferable to set the cross-sectional area S3 of the confluence path as the cross-sectional area Sc of the negative electrode flow path 122.

[0070] 〔Third Embodiment〕 In this embodiment, a preferred example of the flow-type metal-air battery 1 including the battery stack 200 will be described. As described above, the battery stack 200 is connected to the storage unit 11 via piping in the flow-type metal-air battery 1, and the negative electrode slurry is supplied from the storage unit 11. Here, the flow path formed by the piping connected to the battery stack 200 and formed immediately before the connection point with the battery stack 200 is defined as the stack connection flow path. FIG. 8 is a schematic diagram showing the arrangement relationship between the battery stack 200 as a comparative example and the stack connection flow path 14. FIGS. 9 and 10 are schematic diagrams showing the arrangement relationship between the battery stack 200 and the stack connection flow path 14 in this embodiment.

[0071] In the comparative example of FIG. 8, the stack connection flow path 14 is connected to the upstream side of the manifold 220, and the negative electrode slurry flows from the stack connection flow path 14 to the manifold 220. The stack connection flow path 14 has a horizontal region 14a laid along the horizontal direction. Here, when assuming the connection interface P between the manifold 220 and the negative electrode flow path 122, in a plan view, the horizontal region 14a is connected so as to extend from the manifold 220 to the side opposite to the connection interface P.

[0072] In the comparative example of FIG. 8 , when the flow velocity in the horizontal region 14a is low, the solid active material is biased downward in the horizontal region 14a due to the action of gravity. In this case, in the manifold 220 into which the negative electrode slurry flows from the horizontal region 14a (particularly near the upper portion where the stack connection flow path 14 is connected), the solid active material is biased toward the extension side of the horizontal region 14a (the left side of the flow path in FIG. 8 ). In this example, the bias of the solid active material in the manifold 220 occurs on the side opposite the connection interface P (i.e., the side opposite the negative electrode flow path 122). Therefore, a phenomenon may occur in which the amount of solid active material distributed to the negative electrode flow path 122 decreases near the upper portion of the manifold 220 and the amount of solid active material distributed to the negative electrode flow path 122 increases near the lower portion of the manifold 220 (deteriorating the distribution of the solid active material).

[0073] In contrast, the preferred example of Fig. 9 can solve the above-mentioned problem in the comparative example of Fig. 8. The preferred example of Fig. 9 differs from the comparative example of Fig. 8 in the extending direction of the horizontal region 14a. Specifically, the horizontal region 14a is disposed so as to intersect with the connection interface P in a plan view.

[0074] 9, the solid active material in the manifold 220 is biased on the same side as the connection interface P (i.e., the same side as the negative electrode flow path 122). Therefore, the amount of the solid active material distributed to the negative electrode flow path 122 does not decrease near the upper part of the manifold 220, and a decrease in the distribution of the solid active material to the negative electrode flow path 122 can be suppressed.

[0075] Note that the bias of the solid active material in the manifold 220 here is not as significant as the bias of the solid active material toward the bottom of a horizontal flow channel due to the action of gravity. Therefore, the bias of the solid active material in the manifold 220 in the example of Figure 9 does not excessively increase the amount of solid active material distributed to the anode flow channel 122 near the top of the manifold 220, and acts to an extent that can solve the problem in the comparative example of Figure 8.

[0076] The preferred example of Fig. 10 can also solve the above-mentioned problem in the comparative example of Fig. 8. The preferred example of Fig. 10 also differs from the comparative example of Fig. 8 in the extension direction of the horizontal region 14a. Specifically, the horizontal region 14a is disposed so that the flow path direction (direction perpendicular to the paper surface in Fig. 10) is perpendicular to the flow path direction of the negative electrode flow path 122 (direction parallel to the paper surface in Fig. 10) in a plan view.

[0077] In the example of FIG. 10 , the solid active material in the manifold 220 is unevenly distributed in a direction perpendicular to the plane of the paper. In addition, in a direction parallel to the plane of the paper, the uneven distribution of the solid active material in the manifold 220 occurs near the center of the manifold 220 in the radial direction. In this case, because the uneven distribution of the solid active material in the manifold 220 is not too far from the connection interface P, the amount of the solid active material distributed to the anode flow path 122 near the top of the manifold 220 is not reduced, and a decrease in the distribution of the solid active material to the anode flow path 122 can be suppressed. In addition, because the uneven distribution of the solid active material in the manifold 220 is not too close to the connection interface P, the uneven distribution of the solid active material on the connection interface P side is also suppressed, and short circuits due to the formation of electron conduction paths can also be suppressed.

[0078] The embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be determined based on the claims. [Explanation of symbols]

[0079] 1 Flow-type metal-air battery 11 Storage 12 Power Generation Department 13 Live parts 14 Stack connection channel 14a horizontal area 100 battery cells 110 Positive electrode chamber 120 Anode chamber 121 Negative electrode 122 Anode flow path 200 Battery stack (power generation stack) 220 Manifold P connection interface

Claims

1. A power generation stack used in a flow-type metal-air battery, which is formed by stacking a plurality of flow-type metal-air battery cells through which a negative electrode slurry is circulated, a manifold formed along the stacking direction of the flow-type metal-air battery cells; a negative electrode flow path provided in the flow-type metal-air battery cell and physically connected to the manifold; a negative electrode disposed in the negative electrode flow path, The manifold is arranged along a vertical direction, The power generation stack is characterized in that the negative electrode is located vertically below the negative electrode flow path.

2. The power generation stack according to claim 1 , The power generation stack is characterized in that the manifold is provided on an inlet side of the negative electrode slurry with respect to the negative electrode flow path.

3. The power generation stack according to claim 1 , The power generation stack is characterized in that the manifolds are provided on the inlet and outlet sides of the negative electrode slurry with respect to the negative electrode flow path.

4. The power generation stack according to claim 1 , The manifold allows the negative electrode slurry to flow vertically downward.

5. The power generation stack according to claim 1 , When the cross-sectional area of ​​the manifold is Sm, the cross-sectional area of ​​the negative electrode flow path in each of the flow-type metal-air battery cells is Sc, and the number of the flow-type metal-air battery cells is N, Sm<Sc×N The power generation stack is characterized in that the following relational expression is satisfied.

6. A flow-type metal-air battery having a power generation unit that generates electricity by circulating a negative electrode slurry, a charging unit that charges the battery by circulating the negative electrode slurry, and a storage unit that stores the negative electrode slurry that circulates through the power generation unit and the charging unit, A flow-type metal-air battery, wherein the power generation section is the power generation section stack according to any one of claims 1 to 5.

7. 7. The flow-type metal-air battery according to claim 6, a stack connecting flow path connected to the upstream side of the manifold and supplying the negative electrode slurry to the manifold; a flow-type metal-air battery, characterized in that the stack connection flow path has a horizontal region laid along a horizontal direction, and the horizontal region is arranged so as to intersect with a connection interface between the manifold and the negative electrode flow path in a plan view.

8. 7. The flow-type metal-air battery according to claim 6, a stack connecting flow path connected to the upstream side of the manifold and supplying the negative electrode slurry to the manifold; a flow-type metal-air battery, characterized in that the stack connection flow path has a horizontal region laid along a horizontal direction, and the flow path direction of the horizontal region is arranged so as to be perpendicular to the flow path direction of the negative electrode flow path in a plan view.

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