Flow-type battery cell and flow-type metal-air battery

Abstract

The invention provides a flow-type battery cell and a flow-type metal-air battery, which can improve the reaction efficiency between a metal active material and a negative electrode. This flow-type battery cell is configured so as to have: a positive electrode chamber; a negative electrode chamber facing the positive electrode chamber; and a separator that divides the positive electrode chamber and the negative electrode chamber, the negative electrode chamber being provided with: a negative electrode flow path through which a slurry containing a metal active material and an electrolyte solution flows; and a negative electrode that constitutes a part of a wall surface of the negative electrode flow path, and in a state in which the negative electrode is disposed in a direction intersecting the direction of gravity and is disposed below the direction of gravity with respect to the separator, the metal active material flows in a sliding flow state within the negative electrode flow path.

Description

Technical Field

[0001] The present disclosure relates to a flow-type battery cell and a flow-type metal-air battery. Background Art

[0002] In the past, secondary batteries using slurry containing active materials for electrodes are known. For example, Patent Document 1 shows that in a secondary battery having a positive electrode, a negative electrode and an electrolyte, the electrolyte contains at least one metal selected from the group consisting of Zn, Li, Na, Mg, Al, Ca, Cr and Fe as an active material. Prior art literature Patent Literature

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-53868 Summary of the invention Technical Problems to be Solved by the Invention

[0004] In a flow-type battery, which is a type of secondary battery, a positive electrode active material and a negative electrode active material are respectively supplied to a cell including a positive electrode and a negative electrode, and a separator sandwiched between the positive electrode and the negative electrode for charging and discharging. If the contact efficiency between the metal active material and the negative electrode in the negative electrode slurry including a metal active material and an electrolyte, which is one form of the negative electrode active material, is low, the reaction efficiency is reduced, and the discharge characteristics may be reduced.

[0005] An object of the present disclosure is to provide a flow-type battery cell and a flow-type metal-air battery capable of improving the reaction efficiency between a metal active material and a negative electrode. Solutions for solving problems

[0006] In the flow-type battery cell disclosed in the present invention, there is: a positive electrode chamber; a negative electrode chamber, which is opposite to the positive electrode chamber; and a diaphragm, which divides the positive electrode chamber and the negative electrode chamber, and the negative electrode chamber is provided with: a negative electrode flow path, which is for the slurry containing metal active material and electrolyte to flow; and a negative electrode, which constitutes a part of the wall surface of the negative electrode flow path, and when the negative electrode is arranged in a direction intersecting with the direction of gravity and arranged below the direction of gravity relative to the diaphragm, the metal active material flows in the negative electrode flow path in a sliding flow state.

[0007] In addition, in the flow-type battery cell of the present disclosure, there is a positive electrode chamber; a negative electrode chamber, which is opposite to the positive electrode chamber; and a separator, which divides the positive electrode chamber and the negative electrode chamber, wherein the negative electrode chamber is provided with a negative electrode flow path, through which a slurry containing a metal active material and an electrolyte flows; and a negative electrode, which constitutes a part of the wall surface of the negative electrode flow path, and in a state where the negative electrode is arranged in a direction intersecting the direction of gravity and arranged below the direction of gravity relative to the separator, the viscosity of the slurry is set to η (unit: Pa·s), and the particle size of the metal active material is set to D p (unit m), satisfies: 5×10^-9≤D p ^2 / η<2.5×10^-7.

[0008] In addition, a flow-type metal-air battery including the flow-type battery cell is also within the scope of the technical concept of the present disclosure, and comprises: a power generation section, which includes the flow-type battery cell; a storage section, which accommodates the electrolyte flowing in the power generation section; and a charging section, which is supplied with the electrolyte from the storage section. Effects of the Invention

[0009] According to the present disclosure, the reaction efficiency between the metal active material and the negative electrode can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is an explanatory diagram schematically showing the general configuration of a flow-type metal-air battery according to an embodiment. Figure 2 It is a cross-sectional view schematically showing a flow-type battery cell according to an embodiment. Figure 3A This is a cross-sectional explanatory view schematically showing an example of the flow of negative electrode slurry flowing in the negative electrode flow channel in the flow-type battery cell. Figure 3B This is a cross-sectional explanatory view schematically showing another example of the flow of the negative electrode slurry flowing in the negative electrode flow channel in the flow-type battery cell. Figure 3C This is a cross-sectional explanatory view schematically showing another example of the flow of the negative electrode slurry flowing in the negative electrode flow channel in the flow-type battery cell. Figure 4 This is a table showing the evaluation results of sedimentation separation and flow path clogging of the negative electrode slurry. Figure 5 It is a graph showing the relationship between the metal active material concentration and the viscosity in the negative electrode slurry. Figure 6 It is a graph showing the relationship between the metal active material concentration of the negative electrode slurry and the discharge capacity. Figure 7It is a graph showing the relationship between the metal active material concentration of the negative electrode slurry and the discharge characteristics. Figure 8 It is a graph showing the cross-sectional flow rate of the negative electrode slurry and the discharge characteristics. Fig. 9 It is a cross-sectional view schematically showing a flow-type battery cell according to the embodiment. Fig.10 It is a graph showing the discharge characteristics and cross-sectional flow rate of the negative electrode slurry. Fig.11 It is a graph showing the pressure loss and cross-sectional flow velocity of the negative electrode slurry. Fig.12 It is a plan view showing an example of the channel shape of the negative electrode channel. Fig.13 It is a plan view showing another example of the channel shape of the negative electrode channel. DETAILED DESCRIPTION

[0011] 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.

[0012] (Flow Metal Air Battery) Figure 1 1 is an explanatory diagram schematically showing a schematic configuration of a flowing metal-air battery 1 according to an embodiment. In addition, common components in a plurality of embodiments described below are denoted by common reference numerals, and duplicate descriptions are omitted.

[0013] like Figure 1 As shown, the flow-type metal-air battery 1 includes a storage section 101, a power generation section (discharge section) 102, and a charging section 103. The flow-type metal-air battery 1 takes in air, and generates electricity using the taken-in air in the power generation section 102. The charging section 103 is charged and discharges oxygen. A negative electrode slurry (slurry) as a slurry-like fluid containing a negative electrode active material and an electrolyte is supplied from the storage section 101 to the charging section 103. A pipe is connected from the storage section 101 to the charging section 103, and an electrolyte can be pressure-fed via a pump or the like. The power generation section 102 and the storage section 101 can also be the same.

[0014] The storage unit 101 stores 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 materials that are suspended in the form of particles due to the saturation solubility of the electrolyte being exceeded. In addition, the solid active material includes a reduced solid active material (metal active material) and an oxidized solid active material.

[0015] The negative electrode active material is a metal species. The metal species is, for example, a zinc species, a cadmium species, a lithium species, a sodium species, a magnesium species, a lead species, a tin species, an aluminum species or an iron species. The metal constituting the metal species may be a metal consisting only of a metal as a main component, or an alloy of a metal as a main component and a secondary component. The metal species may be formed of any one of a metal and an oxide. Whether the metal species becomes a metal or an oxide is determined by the degree of progress of the discharge reaction or the charge reaction. However, in the discharge reaction described later, the metal species is preferably in a reduced state.

[0016] In the present embodiment, zinc species can be cited as the metal species, and the mobile metal-air battery 1 is a mobile zinc-air battery. The metal constituting the zinc species may be, for example, a metal consisting only of zinc as a main component, or an alloy of zinc as a main component and a secondary component. When the metal species is zinc, the negative electrode active material ions dissolved in the electrolyte are zincate ions, the solid active material in a reduced state is zinc, and the solid active material in an oxidized state is, for example, zinc oxide.

[0017] The average particle size of the metal species is several μm in the case of a solid active material in an oxidized state (e.g., ZnO), and is about tens of μm to 200 μm in the case of a solid active material in a reduced state (e.g., Zn). The average particle size can be measured by a particle size distribution measuring device. The particle size distribution measuring device measures the particle size distribution by, for example, laser diffraction or dynamic light scattering, and calculates the median diameter D50 as the average particle size based on the measured particle size distribution.

[0018] The electrolyte is selected according to 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. Sometimes the electrolyte is replaced with a solid electrolyte.

[0019] The charging section 103 supplies negative electrode slurry to the negative electrode from the storage section 101. The charging section 103 separates a region where the negative electrode is provided from a region where the positive electrode is provided by a separator 104.

[0020] When the metal species is zinc, the reaction in the negative electrode of the charging unit 103 follows equations (1) and (2). In the negative electrode, first, zinc oxide, which is a solid active material in an oxidized state, reacts with water and hydroxide ions to generate zincate ions. Then, the zincate ions accept electrons to generate zinc and hydroxide ions. The anions involved in the charging reaction and the discharge reaction described later are hydroxide ions. ZnO+H 2 O+2OH - →Zn(OH) 4 2- …(1) Zn(OH) 4 2- +2e - →Zn+4OH - …(2)

[0021] The reaction in the positive electrode of the charging section 103 is in accordance with the formula (3). In the positive electrode, oxygen and water are generated from hydroxide ions, and electrons are released. 4OH - →O 2 +2H 2 O+4e - …(3)

[0022] The charging section 103 is a zinc regeneration section that performs charging using zinc oxide as a solid active material in an oxidized state. The negative electrode slurry containing the negative electrode active material is supplied from the storage section 101 to the charging section 103. The solid active material stored in the storage section 101 and supplied to the charging section 103 is preferably in an oxidized state, or the oxidized solid active material is preferably present in a larger amount than the reduced solid active material.

[0023] The power generation section 102 supplies the negative electrode slurry from the storage section 101 to the negative electrode and supplies air to the positive electrode. In the power generation section 102, a region where the negative electrode is provided is separated from a region where the positive electrode is provided by a separator 104.

[0024] In the case of a flow-type zinc-air battery in which the metal species is zinc, the reaction in the negative electrode of the power generation unit 102 is in accordance with equations (4) and (5). In the negative electrode, zinc, which is a solid active material in a reduced state, reacts with hydroxide ions to generate zincate ions and release electrons. The zincate ions generate zinc oxide, water, and hydroxide ions. The anions involved in the power generation reaction are hydroxide ions. Zn+4OH - →Zn(OH) 4 2- +2e - …(4) Zn(OH) 4 2- →ZnO+H 2 O+2OH - …(5)

[0025] The reaction in the positive electrode of the power generation section 102 is in accordance with the formula (6). In the positive electrode, electrons are accepted and hydroxide ions are generated from oxygen and water. O 2 +2H 2 O+4 e- →4OH - …(6)

[0026] In the power generation section 102, discharge is performed using zinc as a solid active material in a reduced state. In the power generation section 102, a negative electrode slurry containing a negative electrode active material is supplied from the storage section 101. The solid active material supplied to the power generation section 102 and stored in the storage section 101 is preferably in a reduced state, or preferably the solid active material in a reduced state is more present than the solid active material in an oxidized state.

[0027] (Flow cell) Figure 2 It is a cross-sectional view schematically showing a flow-type battery cell 10 in a power generation section 102 of a flow-type metal-air battery 1 according to an embodiment.

[0028] In the flow-type metal-air battery 1, the power generation section 102 includes a flow-type battery cell (power generation section cell) 10 as a basic component unit, which includes a positive electrode chamber 20, a negative electrode chamber 30, and a separator 40 that divides the positive electrode chamber 20 and the negative electrode chamber 30. The flow-type battery cell 10 is a flow-type battery that allows the negative electrode slurry B to flow in the negative electrode flow path 32 described later.

[0029] The positive electrode chamber 20 includes a positive electrode 21 that generates an oxygen reduction reaction, and oxygen-containing air A flows as a reactant. A positive electrode flow path 22 is provided in the positive electrode chamber 20. The positive electrode flow path 22 is a flow path formed of stripe-shaped grooves that flows oxygen as a positive electrode active material.

[0030] The negative electrode chamber 30 includes a negative electrode 31 in which an oxidation reaction of metal zinc occurs. The negative electrode 31 is arranged along the X direction intersecting the gravity direction G. A negative electrode flow path 32 is provided in the negative electrode chamber 30, and the negative electrode flow path 32 is provided for the negative electrode slurry B containing a metal active material and an electrolyte to flow. The negative electrode flow path 32 is a flow path for the negative electrode slurry B to flow. For example, a negative electrode flow path layer 33 is provided between the negative electrode 31 and the separator 40, and the negative electrode flow path 32 is formed by grooves provided in the negative electrode 31, the separator 40, and the negative electrode flow path 32. In addition, the negative electrode flow path 32 is not limited to being provided by the negative electrode flow path layer 33 having grooves, and the flow path can also be formed by grooves provided on the surface of the negative electrode 31.

[0031] The negative electrode flow path 32 is oriented in the X direction (in the direction of the gravitational force G) Figure 2 The negative electrode slurry B flows in the negative electrode flow path 32 from the X1 side to the X2 side.

[0032] The negative electrode 31 constitutes a part of the wall surface below the negative electrode flow path 32. The negative electrode 31 can use a conductive material composed of a carbon material and a resin material, etc. The separator 40 arranged opposite to the negative electrode 31 constitutes a part of the wall surface above the negative electrode flow path 32. The separator 40 divides the positive electrode chamber 20 and the negative electrode chamber 30 to inhibit the negative electrode slurry from penetrating from the negative electrode chamber 30 side to the positive electrode chamber 20 side. The separator 40 is arranged along the positive electrode 21. The separator 40 preferably uses a material suitable for inhibiting the penetration of the negative electrode slurry (such as a hydrogel film, etc.). The separator 40 and the positive electrode 21 are held and fixed by the sealing portion 50.

[0033] In the negative electrode chamber 30, a current-carrying plate 36 may be provided along the negative electrode 31. A sealing portion 50 is disposed and fixed between the current-carrying plate 36 and the negative electrode flow path layer 33. In addition, the negative electrode chamber 30 is not limited to a structure including the negative electrode 31, the current-carrying plate 36, and the negative electrode flow path layer 33, and the negative electrode chamber 30 may be composed of a single component.

[0034] FIG. 3A to FIG. 3C It is a cross-sectional explanatory view schematically showing an example of the flow of the negative electrode slurry flowing in the negative electrode flow channel.

[0035] In the flow-type battery cell 10, it is desirable to ensure that the negative electrode slurry flows well in the negative electrode flow path 32 and is stably delivered, and to improve the discharge characteristics of the power generation unit 102. In order to improve the discharge characteristics, it is desirable to improve the contact efficiency between the solid active material (metal active material) in the reduced state in the circulating negative electrode slurry and the negative electrode 31.

[0036] For example, Figure 3A As shown, when the negative electrode slurry B containing the metal active material 60 and the electrolyte is supplied to the negative electrode flow path 32, the metal active material 60 settles below the gravity direction G in the negative electrode flow path 32, and the metal active material 60 and the electrolyte are separated. As a result, there is a case where the concentration of the metal active material 60 in the upper layer and the lower layer in the negative electrode flow path 32 is different. In this case, as shown in the figure, if the metal active material 60 separated and precipitated from the upper layer composed of the electrolyte is deposited on the negative electrode 31 arranged below the negative electrode flow path 32, and the deposited layer of these metal active materials 60 becomes a flowing sliding fluid that gradually moves toward the X2 side, it becomes a state where the reaction efficiency of the metal active material 60 and the negative electrode 31 is improved, which is preferred.

[0037] In contrast, for example, Figure 3B As shown in FIG. 1 , when the effect of the fluid (slurry) on the metal active material 60 is small, the metal active material 60 becomes a deposited layer where the movement is stagnant, resulting in stagnation on the X2 side, which may block the negative electrode flow path 32. Figure 3CAs shown, when the effect of the fluid (slurry) on the metal active material 60 is large, the metal active material 60 that is about to be deposited below the gravity direction G is rolled up and becomes a suspended fluid, and the contact efficiency between the negative electrode 31 arranged below the gravity direction G and the metal active material 60 is reduced, and the discharge characteristics are likely to be reduced.

[0038] For the purpose of stable liquid delivery in the negative electrode slurry, the sedimentation in the negative electrode flow path 32 was studied, and the terminal velocity (sedimentation velocity) V S ” is calculated by the Stokes equation shown in the following formula (7). In addition, D in formula (7) p is the average particle size of the main constituent particles (m), ρ p is the density of the main constituent particles (g / cm 3 )”,ρ f is the density of the fluid (g / cm 3 )". In addition, g is the acceleration due to gravity (m / s 2 )=980cm / s 2 ", η is the viscosity of the fluid (Pa·s)".

[0039] [Mathematical formula 1]

[0040] Based on the Navier-Stokes equation, it is believed that if the viscosity η of the negative electrode slurry is small, the fluid effect becomes small, and it is possible that the flow stops without becoming a sliding fluid. On the other hand, if the viscosity η is large, the fluid effect is large, and it is easy to generate a suspended fluid without becoming a sliding flow. In addition, if the particle size D of the metal active material is p If the particle size is large, it is easy to settle and the metal active material cannot be transported. If the particle size is small, it is difficult to settle and a suspended fluid is easy to be generated.

[0041] Here, if the concentration of the negative electrode slurry is low, the metal active material in contact with the negative electrode 31 is reduced, and the discharge characteristics are reduced. If it is high, the negative electrode flow path 32 may be blocked. If the density of the metal active material is low, it is difficult to settle, so it is easy to produce a suspended fluid. If the density of the metal active material is high, it is easy to settle, and it becomes impossible to transport the metal active material. If the circulation speed (cross-sectional flow velocity) of the negative electrode slurry is slow, the fluid effect becomes small and it does not become a sliding fluid, and the flow may stop. If the circulation speed (cross-sectional flow velocity) of the negative electrode slurry is fast, the fluid effect becomes large, and it becomes easy to produce a suspended fluid.

[0042] Therefore, in the flow-type battery cell 10 involved in this embodiment, the negative electrode slurry flowing in the negative electrode chamber 30 is constructed by mixing a metal active material (e.g., zinc particles), a thickener (e.g., polyacrylic acid), and an electrolyte (e.g., an aqueous potassium hydroxide solution) and adjusting them to the specified range shown below, thereby improving the contact efficiency between the metal active material and the negative electrode and improving the reaction efficiency.

[0043] That is, if the viscosity of the negative electrode slurry is η (unit: Pa·s), and the particle size of the metal active material is D p (unit: m), the negative electrode slurry is constituted in a manner satisfying formula (8). 5×10^-9≤D p ^2 / η<2.5×10^-7…(8)

[0044] In the present embodiment, “D p ^2 / η" is called the characteristic formula d of the negative electrode slurry, (d = D p ^2 / η).

[0045] Here, during the use of the flow-type metal-air battery 1, the negative electrode active material is oxidized by the solid active material in the reduced state, that is, the zinc particles, to generate the negative electrode active material ions (zincate ions) in the dissolved state and the solid active material (zinc oxide particles) in the oxidized state that exceeds the solubility. Therefore, in the negative electrode slurry, as the negative electrode active material, the negative electrode active material ions (zincate ions) as the dissolved active material, the solid active material in the reduced state (zinc particles) as the undissolved solid component, and the solid active material in the oxidized state (zinc oxide particles), the thickener (polyacrylic acid) and the electrolyte (potassium hydroxide aqueous solution) are included. The dissolution rate of the solid active material in the reduced state of the solid active material in the reduced state is significantly slower than the dissolution rate of the solid active material in the oxidized state, and the solid active material in the oxidized state is preferentially dissolved by the excess potassium hydroxide, and the solid active material in the reduced state is obtained as the residue. Since the solid active material in the reduced state is a metal active material, the density and particle size can be measured. In addition, the solid active material and the solution component can be separated by centrifugation. The density of solution components can be measured using it.

[0046] In the characteristic formula d of the negative electrode slurry, by satisfying formula (8), when the particle size of the metal active material is large and the viscosity of the negative electrode slurry is small, the terminal velocity of the metal active material settling in the negative electrode slurry becomes large, and in the negative electrode chamber 30, the metal active material is deposited below the gravity direction G. The contact efficiency between the deposited metal active material and the conductive flow surface (that is, the negative electrode 31 in this case) arranged below the gravity direction G is improved. As a result, an electron conduction path is formed between the plurality of metal active materials and the negative electrode 31 through the contact between the metal active materials and the contact between the metal active materials and the conductive flow surface, so that the reduction of the discharge voltage can be suppressed.

[0047] On the other hand, in the characteristic formula d of the negative electrode slurry, when the characteristic formula d is too small, that is, when the particle size D of the metal active material is p When the viscosity of the negative electrode slurry is too large or too high, the sedimentation rate of the metal active material slows down. Therefore, it can be said that the metal active material becomes suspended in the negative electrode slurry, and the contact efficiency with the negative electrode 31 decreases. In addition, when the characteristic formula d of the negative electrode slurry is too large, that is, when the particle size D of the metal active material is p If the viscosity of the negative electrode slurry is too low, the sedimentation rate of the metal active material increases, and the force of the fluid acting on the metal active material decreases. Therefore, the transfer of the metal active material stops, and there is a possibility that the negative electrode channel 32 is blocked.

[0048] Therefore, in the flow-type battery cell 10, the negative electrode 31 constituting a part of the wall surface of the negative electrode flow path 32 is arranged along the X direction intersecting the gravity direction G, and the negative electrode 31 is arranged below the gravity direction G, so that the negative electrode slurry is formed in a manner satisfying equation (8), thereby improving the flowability of the negative electrode slurry and improving the reaction efficiency of the metal active material and the negative electrode 31. In addition, in the flow-type battery cell 10, the negative electrode 31 is not limited to being arranged in a direction orthogonal to the gravity direction G, and the negative electrode flow path 32 is not limited to being a flow direction in a direction orthogonal to the gravity direction G, and can also be arranged in other directions such as an inclined direction intersecting the gravity direction as long as they are all directions intersecting the gravity direction.

[0049] (Example 1) Examples of the flow battery cell of the present invention and comparative examples thereof are described.

[0050] As an example of a flow-type zinc-air battery, an electrode produced by kneading and rolling manganese dioxide as a catalyst, acetylene black as a conductor, and PTFE as a water-repellent agent / binder was used as a positive electrode.

[0051] As the negative electrode slurry flowing in the negative electrode flow path of the negative electrode chamber, 50cc of a metal active material (zinc powder) containing 20 wt% of a different viscosity η was adjusted, stirred and then allowed to stand, wherein the metal active material (zinc powder) had three different particle sizes D of 56 μm, 113 μm, and 164 μm. p . The separation after standing was observed, and the metal active material was evaluated while the upper layer of the electrolyte appeared after 20 minutes. In addition, the same negative electrode slurry was allowed to flow in a flow path with a length of 100 mm and a rectangular cross section of 10 mm × 4 mm for 20 minutes to evaluate whether the flow path was blocked. The evaluation results are shown in the following table. Figure 4 .

[0052] As Example 1, in the case of a negative electrode slurry whose characteristic formula d satisfies the condition of being greater than 5×10^-9 and less than 2.5×10^-7, sedimentation separation can be confirmed regardless of the particle size and viscosity (sedimentation separation “yes”), and it is confirmed that no flow path occlusion occurs (flow path occlusion “no”).

[0053] On the other hand, as a comparative example, in the case where the viscosity in the negative electrode slurry with a particle size of 56 μm of the metal active material is 1000 mPa·s, sedimentation separation cannot be confirmed (sedimentation separation "cannot be confirmed"). In addition, the negative electrode slurry with a particle size of 113 μm causes flow path occlusion when the viscosity is 50 mPa·s (flow path occlusion "yes"), and sedimentation separation cannot be confirmed when the viscosity is 3000 mPa·s. In the negative electrode slurry with a particle size of 164 μm, when the viscosity is set to 100 mPa·s, flow path occlusion occurs. These negative electrode slurries do not meet the condition that the characteristic formula d is greater than 5×10^-9 and less than 2.5×10^-7.

[0054] Therefore, in the flow-type battery cell, by satisfying the above-mentioned condition of the characteristic formula d of the negative electrode slurry, sedimentation separation can be performed in the negative electrode slurry, such as Figure 3A As shown, a sliding fluid is generated. This improves the contact efficiency between the metal active material and the negative electrode, and enables stable liquid delivery without causing blockage of the flow path, thereby suppressing the pressure loss of slurry delivery.

[0055] (Example 2) In Example 2, a negative electrode slurry in which a metal active material (zinc powder) having a particle size (D50) of 164 μm was mixed in different weight ratios was adjusted, and the viscosity was measured. The viscosity of the electrolyte at 0% weight was adjusted using a thickener to a viscosity of 90 mPa·s or a viscosity of 4500 mPa·s. The viscosity was evaluated using a slime meter VT-06 manufactured by Leon Corporation. The shear rate dependence of the viscosity was evaluated by changing the rotation speed of the B-type viscometer. The measurement using the viscosity tester VT-06 is roughly equivalent to a rotation speed of 60 rpm in the B-type viscometer.

[0056] Figure 5 It is a graph showing the relationship between the concentration of the metal active material (weight percentage of the metal active material) and the viscosity of the negative electrode slurry. It can be seen that as the concentration of the metal active material increases, the viscosity increases. In addition, under the condition of more thickener, the viscosity exceeds 4800mPa·s, becomes a dispersed state, and the sedimentation separation of the metal active material cannot be confirmed. In contrast, under the condition of less thickener, the viscosity is less than 1000mPa, and the sedimentation separation of the metal active material is confirmed.

[0057] That is, in the negative electrode slurry, if the metal active material is dispersed, the slurry viscosity becomes higher. In particular, when the weight fraction of the metal active material increases, the viscosity can also be said to increase. On the other hand, by reducing the viscosity of the negative electrode slurry, even under the condition of a low weight fraction of the metal active material, as long as the metal active material can be deposited on the negative electrode, the contact efficiency between the metal active material and the negative electrode can be improved.

[0058] Therefore, using Figure 5 The discharge characteristics of the negative electrode slurries shown were evaluated. Figure 6 It is a graph showing the relationship between the concentration of the metal active material in the negative electrode slurry and the discharge capacity.

[0059] like Figure 6 As shown, in the negative electrode slurry of the dispersion system, the discharge capacity tends to be lower than that of the negative electrode slurry of the precipitation system. That is, in the negative electrode slurry of the precipitation system in which sedimentation separation is confirmed, the metal active material can be deposited on the negative electrode, so regardless of the concentration of the metal active material, a discharge capacity of more than 6000mAh is obtained. On the other hand, in the negative electrode slurry of the dispersion system in which sedimentation separation is not confirmed, the effect of depositing the metal active material on the negative electrode does not work, and the contact efficiency between the negative electrode and the metal active material is low. Therefore, under the condition that the concentration of the metal active material is less than 30% by weight, the discharge capacity is significantly low, and under the condition that the concentration of the metal active material exceeds 35% by weight, the discharge capacity tends to increase.

[0060] Therefore, the discharge capacity depends largely on the viscosity of the negative electrode slurry, in other words, the dispersibility of the metal active material. The viscosity of the negative electrode slurry is high, and under the condition that the metal active material is dispersed, sufficient discharge characteristics cannot be obtained under the condition that the concentration of the metal active material is low. In the negative electrode slurry of the dispersion system, the value of the characteristic formula d is 4.4×10^-9. In contrast, in the negative electrode slurry of the precipitation system, even if the concentration of the metal active material is low, a high discharge capacity can be obtained, and the value of the characteristic formula d of the negative electrode slurry is 6.1×10^-8.

[0061] Thus, in the flow-type battery cell, the characteristic formula d of the negative electrode slurry satisfies the conditions of 5×10^-9 or more and 2.5×10^-7 or less, and the contact probability between the negative electrode and the metal active material can be increased even under the condition of a small concentration of the metal active material, and as a result, it is confirmed that a high discharge capacity can be obtained. In addition, by suppressing the viscosity of the negative electrode slurry to a lower level, the accompanying effect of suppressing the pressure loss of the slurry feeding can also be achieved. In addition, the sedimentation of the metal active material of the negative electrode slurry is aggravated, and it is confirmed that the viscosity of the negative electrode slurry that can deposit the metal active material on the negative electrode is less than 1000m·Pa.

[0062] (Example 3) As shown in Example 2, it is generally believed that when the concentration of the metal active material is low, the contact amount between the negative electrode and the metal active material is reduced, so the discharge characteristics are reduced. In Example 3, for a negative electrode slurry having a relatively low concentration of the metal active material and containing 5% by weight or more and 40% by weight or less of the metal active material (zinc powder) relative to the total amount, the negative electrode slurry is adjusted based on an electrolyte containing zinc particles with an average particle size of 50 μm as the metal active material and a viscosity of 210 mPa·s so that it circulates in a negative electrode flow path having a rectangular cross-section of 10 mm×4 mm for a predetermined time. Figure 7 : is a graph showing the relationship between the metal active material concentration and the discharge characteristics in this case.

[0063] like Figure 7 As shown, when the current density is 30mA / cm 2 When the weight fraction is 5 wt%, the voltage is 0.96 V, and when it is 10 wt% or more, the voltage is about 1.0 V. The current density is 50 mA / cm 2 When the weight fraction is 5 wt%, the voltage is 0.73 V, and when it is 10 wt% or more, the voltage is 0.76 V. On the other hand, the current density is 70 mA / cm 2 When the weight fraction was 5 wt %, the voltage was 0.53 V, and even at 10 wt % or more, the voltage showed a low value of 0.54 V.

[0064] It was confirmed that if the weight fraction is 15% by weight or more, all current densities become voltages of 0.70V or more, and sufficient discharge characteristics are obtained. When the weight fraction is too large, there is a concern that the metal active material blocks the negative electrode flow path. For example, if the weight fraction increases to 40% by weight, the viscosity increases, resulting in a greater pressure loss associated with the delivery of the negative electrode slurry.

[0065] Therefore, it can be said that the weight fraction of the negative electrode slurry containing zinc powder as a metal active material is preferably adjusted to 15 wt % or more and 30 wt % or less relative to the total amount.

[0066] (Example 4) In Example 4, the discharge characteristics (current density of 50 mA / cm 2 ). Figure 8 : is a graph showing the discharge characteristics of the flow-type zinc-air battery of each example.

[0067] The zinc particles with an average particle size of 50 μm and a viscosity of 210 mPa·s and a characteristic formula of d=1.2×10 -8 The negative electrode slurry (Example 4-1) contains 20 wt % of zinc particles with an average particle size of 50 μm and a viscosity of 390 mPa·s and a characteristic formula of d=6.4×10 -9 The negative electrode slurry (Example 4-2) contains 20 wt % of zinc particles with an average particle size of 175 μm and a viscosity of 230 mPa·s and a characteristic formula d=1.3×10 -7 The negative electrode slurry (Example 4-3) contains 20 wt % of zinc particles with an average particle size of 175 μm and a viscosity of 330 mPa·s and a characteristic formula of d=9×10 -8 of negative electrode slurry (Example 4-4).

[0068] In any of the examples, the negative electrode slurry satisfied the condition that the characteristic formula d was greater than or equal to 5×10^-9 and less than or equal to 2.5×10^-7, and there was no flow path occlusion, thereby obtaining a good discharge voltage.

[0069] (Example 5) In Example 5, in addition to the configuration of Example 1, a thickener composed of a polymer material was further included in the electrolyte of the negative electrode slurry. The viscosity of the negative electrode slurry was evaluated using a B-type viscometer to evaluate thixotropy.

[0070] In a flow-type metal-air battery, when the negative electrode slurry is stored in a storage unit for a long time, the metal active material is precipitated or precipitated, and as a result, the concentration of the metal active material in the upper layer and the lower layer of the storage unit may become uneven. During storage, if the viscosity of the negative electrode slurry is increased in order to reduce the sedimentation rate of the metal active material in the negative electrode slurry, the sedimentation or precipitation of the metal active material can be suppressed, but when the negative electrode slurry is supplied to the flow-type zinc-air battery, the sedimentation and accumulation of the metal active material on the negative electrode may not progress, and the discharge characteristics may be reduced.

[0071] As a viscosity adjustment of the negative electrode slurry, by using a polymer material such as polyacrylic acid as a thickener, the viscosity of the negative electrode slurry when it is left to stand during storage or other conditions can be given a shear-thinning viscosity that reduces the viscosity under shear force conditions such as during liquid feeding. This is because when a polymer material is used as a thickener, the randomly oriented polymer is oriented along the flow, and the viscosity is reduced.

[0072] In the negative electrode slurry with shear-thinning viscosity that is adjusted by using such a thickener composed of a polymer material, the viscosity of the negative electrode slurry is reduced during liquid feeding compared to when stored (when standing), and the precipitation of the metal active material is carried out. As such a thickener, it is preferred to contain a polymer material containing at least one site selected from acrylic acid, carboxymethyl cellulose pyranose, β-D-mannuronic acid, α-L-guluronic acid and methacrylic acid, such as polyacrylic acid, carboxymethyl cellulose, sodium alginate or acrylic acid · alkyl methacrylate copolymer. Thus, the concentration distribution of the metal active material can be suppressed during storage and other standing conditions, and the precipitation of the metal active material is promoted in the flow-type battery cell, suppressing the reduction of the discharge voltage.

[0073] (Example 6) In Example 6, the characteristic formula d of the negative electrode slurry satisfied the condition of 5×10^-9 or more and 2.5×10^-7 or less, and the flow rate of the negative electrode slurry per unit cross-sectional area in the negative electrode flow path in which the negative electrode of the negative electrode chamber was arranged to intersect the gravity direction was evaluated.

[0074] Fig. 9 FIG. 1 is a cross-sectional view schematically showing a flow-type battery cell of Example 6. Fig. 9 In, through Figure 2The negative electrode flow path 32 shown is represented by a cross section perpendicular to the flow direction of the negative electrode slurry (X direction, X2 direction in the illustrated embodiment). In this case, the negative electrode flow path 32 is presented in a state of being divided into a plurality of parts between the negative electrode 31 and the separator 40 arranged below the gravity direction G. In the divided negative electrode flow path 32, the distance h between the negative electrode 31 and the separator 40, the flow path width W of the negative electrode flow path 32 perpendicular to the distance h, and the flow path cross-sectional area of ​​the cross section perpendicular to the flow direction (X direction) of the negative electrode slurry is represented by W·h.

[0075] As an example, a negative electrode slurry containing zinc particles with an average particle size of 50 μm as a metal active material and a viscosity of 210 mPa·s was flowed through a negative electrode flow path having a rectangular cross-sectional shape of 10 mm×4 mm in flow path cross-sectional area W·h. The metal active material concentration of the zinc particles varied from 5 to 40 wt %.

[0076] Fig.10 The discharge characteristics (current density 50 mA / cm) when five kinds of negative electrode slurries with different metal active material concentrations are passed through the negative electrode flow path are shown. 2 ) and the cross-sectional velocity, Fig.11 It is a graph showing their pressure loss and cross-sectional flow rate. In this case, if the cross-sectional flow rate is less than 75cm / min, the resistance of the flow to the metal active material is small, and the metal active material may be retained in the negative electrode flow path or block the negative electrode flow path. In addition, if the cross-sectional flow layer exceeds 500cm / min, the flow of the fluid will roll up the metal active material (floating fluid) to be accumulated below the gravity, and the contact efficiency between the negative electrode arranged below the gravity direction and the metal active material will be reduced.

[0077] Therefore, in the flow-type battery cell, in the cross section of the negative electrode flow path perpendicular to the flow direction of the negative electrode slurry, the flow rate of the negative electrode slurry passing through the cross section is preferably 75 cm / min or more and 500 cm / min or less per unit flow path cross-sectional area.

[0078] In this way, the characteristic formula d of the negative electrode slurry satisfies the condition of 5×10^-9 or more and 2.5×10^-7 or less, and the cross-sectional flow rate of the negative electrode flow path is set to the above range, so that the metal active material does not block the negative electrode flow path, and the metal active material can be made to flow in a sliding flow state on the negative electrode arranged below the gravity direction G. As a result, an electron conduction path is formed between multiple metal active materials and the negative electrode through contact between the metal active materials and the contact between the metal active materials and the negative electrode, so that the reduction of the discharge voltage can be suppressed.

[0079] (Example 7) like Fig. 9As shown, in the flow-type battery cell 10, one of the walls constituting the negative electrode flow path 32 is the negative electrode 31, and the other is the separator 40. In the region where the negative electrode 31 and the separator 40 are opposed to each other, a plurality of flow paths constituting one negative electrode flow path 32 are preferably arranged. In this case, the distance (interval) h between the negative electrode 31 and the separator 40 and the flow path width W affect the pressure loss during the feeding of the negative electrode slurry.

[0080] If the distance h between the negative electrode 31 and the diaphragm 40 is less than 1 mm, the metal active materials in the negative electrode slurry contact each other, which is easy to cause retention and may block the negative electrode flow path 32. In addition, in this case, the pressure loss during liquid feeding may increase. On the other hand, if the distance h between the negative electrode 31 and the diaphragm 40 is more than 6 mm, the distance "(1 / 2)h" between the central part of the distance h direction of the negative electrode flow path 32 and the wall surface of the negative electrode flow path 32 becomes longer, so the force of the flow action on the metal active materials deposited on the negative electrode 31 becomes smaller. Therefore, it will not become a sliding fluid state in which the metal active materials are transported as they flow, and the metal active materials may be retained in the flow path. In addition, since the negative electrode 31 is separated from the diaphragm 40, the unit resistance increases.

[0081] In addition, when the negative electrode flow path 32 is a single flow path, it is necessary to increase the flow rate of each flow path cross-sectional area, but when the flow path width W is too large, the flow of the negative electrode slurry tends to become uneven, the distribution in the surface of the metal active material is biased, and the contact efficiency with the negative electrode 31 is reduced. Therefore, the distance h between the negative electrode 31 constituting the wall surface of the negative electrode flow path 32 and the separator 40 facing the negative electrode 31 is preferably 1 mm or more and 6 mm or less.

[0082] In addition, considering the realization of sliding fluid in the negative electrode flow path 32, the flow path width W of the negative electrode flow path 32 perpendicular to the distance h is preferably constant. This is because if the flow path width W of the negative electrode flow path 32 is constant from the inlet to the outlet, a large flow rate change will not occur.

[0083] Fig.12 and Fig.13 3 is a plan view showing the shape of the negative electrode channel 32. As described above, the negative electrode channel 32 is composed of grooves formed in the negative electrode channel layer 33, and is provided between the negative electrode 31 and the separator 40 to form a channel with a channel cross-sectional area W·h.

[0084] Here, if Fig.12As shown, the flow path of the negative electrode flow path 32 is branched, and these multiple flow paths are connected in parallel. The negative electrode slurry flows through the negative electrode manifold 37 connected to the inlet 34 and the outlet 35 of the negative electrode flow path 32. If the negative electrode flow path 32 is a flow path shape including such a branched flow path, the flow rate is likely to change greatly before and after the branch. Therefore, it may be difficult to achieve a sliding fluid of the negative electrode slurry in the flow path area before the branch and the flow path area after the branch.

[0085] In contrast, Fig.13 The negative electrode flow path 32 shown has a meandering flow path structure in which a flow path groove repeatedly turns back without including a flow path branching from the inlet 34 to the outlet 35. In this case, a plurality of flow paths constituting a negative electrode flow path 32 can be arranged in the area where the negative electrode 31 and the diaphragm 40 are opposite, and the flow rate of the flow path cross-sectional area W·h can be increased even without increasing the total liquid amount of the negative electrode slurry supplied to the flow-type battery cell, so it is preferred. In addition, there is no branched flow path in the negative electrode flow path 32, so there will be no large flow change in the negative electrode flow path 32, and a sliding fluid can be realized in the entire negative electrode flow path 32.

[0086] As described above, in the flow-type battery cell of the present invention, the contact efficiency between the metal active material and the negative electrode can be improved, the flowability of the negative electrode slurry can be improved, and the reaction efficiency between the metal active material and the negative electrode can be improved.

[0087] The present disclosure is not limited to the above-mentioned embodiments, and various modifications can be made within the scope of the technical gist, and all technical matters contained in the technical ideas recorded in the claims become the objects of the present disclosure. The above-mentioned embodiments show preferred embodiments, but various modifications can be realized according to the disclosed content, and such modifications are also included in the technical scope recorded in the claims. Description of Reference Numerals

[0088] 1 Flow Metal Air Battery 101 Storage Department 102 Power Generation Department 103 Charging Department 10 Flow battery cells 20 positive electrode chamber 21 Positive electrode 22 positive electrode flow path 30 Negative chamber 31 negative electrode 32 Negative electrode flow path 33 Negative electrode flow path layer 34 Inlet 35 Flow outlet 36 Power board 37 Negative busbar 40 Diaphragm 50 Sealing part

Claims

1. A flow-type battery cell, characterized in that: have: positive electrode chamber; a negative electrode chamber, which is opposite to the positive electrode chamber; and a separator that divides the positive electrode chamber and the negative electrode chamber, The negative electrode chamber includes: a negative electrode flow path through which a slurry containing a metal active material and an electrolyte flows; and a negative electrode constituting a part of a wall surface of the negative electrode flow path. The metal active material flows in the negative electrode channel in a sliding flow state in a state where the negative electrode is arranged in a direction intersecting the gravity direction and arranged below the separator in the gravity direction.

2. A flow-type battery cell, characterized in that: have: positive electrode chamber; a negative electrode chamber, which is opposite to the positive electrode chamber; and a separator that divides the positive electrode chamber and the negative electrode chamber, The negative electrode chamber includes: a negative electrode flow path through which a slurry containing a metal active material and an electrolyte flows; and a negative electrode constituting a part of a wall surface of the negative electrode flow path. In a state where the negative electrode is arranged in a direction intersecting the gravity direction and arranged below the separator in the gravity direction, the viscosity of the slurry is denoted by η, where the unit of η is Pa·s, and the particle size of the metal active material is denoted by D p , and D p When the unit is m, it satisfies: 5×10^-9≤D p ^2 / n<2.5×10^-7.

3. The flow type battery cell according to claim 1 or 2, characterized in that: The viscosity of the slurry is less than 1000 m·Pa.

4. The flow type battery cell according to claim 1 or 2, characterized in that: The slurry contains the metal active material in an amount of 15 wt % or more and 30 wt % or less based on the total amount.

5. The flow type battery cell according to claim 1 or 2, characterized in that: The slurry has a shear-thinning viscosity.

6. The flow type battery cell according to claim 1 or 2, characterized in that: The slurry contains a thickener, The thickener is a polymer material containing at least one site selected from acrylic acid, carboxymethylcellulose glucopyranose, β-D-mannuronic acid, α-L-guluronic acid and methacrylic acid.

7. The flow type battery cell according to claim 1 or 2, characterized in that: A flow rate of the slurry passing through a cross section of the negative electrode flow path orthogonal to a flow direction of the slurry is 75 cm / min or more and 500 cm / min or less per flow path cross-sectional area of ​​the cross section.

8. The flow-type battery cell according to claim 1 or 2, characterized in that: The distance h between the negative electrode constituting the wall surface of the negative electrode flow path and the separator facing the negative electrode is 1 mm or more and 6 mm or less, The negative electrode flow path has a constant flow path width W that is perpendicular to the distance h.

9. The flow-type battery cell according to claim 1 or 2, characterized in that: The negative electrode flow path does not include a flow path branching from the slurry inlet to the slurry outlet.

10. A flow-type metal-air battery, characterized in that: have: A power generation unit comprising the flow-type battery cell according to claim 1 or 2; a storage unit that stores the electrolyte solution flowing through the power generation unit; and A charging unit is supplied with the electrolyte solution from the storage unit.

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