JP2019102179A - Flow battery - Google Patents

Abstract

To provide a flow battery by which a satisfactory amount of a negative electrode active material can be dissolved in an electrolyte solution even if an amount of powder to be mixed in the electrolyte solution is reduced.SOLUTION: A flow battery comprises: positive and negative electrodes; an electrolyte solution; a flow device; and a zinc plate. The electrolyte solution is in contact with the positive and negative electrodes. The flow device causes the electrolyte solution to flow. The zinc plate is immersed in the electrolyte solution.SELECTED DRAWING: Figure 1

Description

  Embodiments of the disclosure relate to flow batteries.

Conventionally, a flow battery is known in which an electrolytic solution containing tetrahydroxyzincate ion ([Zn (OH) ₄ ] ²⁻ ) is circulated between a positive electrode and a negative electrode (see, for example, Non-Patent Document 1) .

  There is also proposed a technology for suppressing the growth of dendrite by covering a negative electrode containing an active material such as a zinc species with an ion conductive layer having selective ion conductivity (see, for example, Patent Document 1).

JP, 2015-185259, A

Y. Ito. Et al .: Zinc morphology in zinc-nickel flow assisted batteries and impact on performance, Journal of Power Sources, Vol. 196, pp. 2340-2345, 2011

  However, in the battery described above, when a large amount of powder in which an anode active material such as zinc is dissolved in an electrolyte is mixed in the electrolyte, such powder causes clogging or the like in a fluidizer that circulates the electrolyte. There is a fear. On the other hand, when such powder is mixed less in the electrolyte, there is a risk that the negative electrode active material in the electrolyte will run short.

  One aspect of the embodiment is made in view of the above, and a sufficient amount of the negative electrode active material can be dissolved in the electrolyte even if the amount of powder mixed in the electrolyte is reduced. The purpose is to provide a flow battery.

  The flow battery according to one aspect of the embodiment includes a positive electrode and a negative electrode, an electrolytic solution, a flow device, and a zinc plate. The electrolyte contacts the positive electrode and the negative electrode. The flow device flows the electrolyte. The zinc plate is immersed in the electrolyte.

  According to one aspect of the embodiment, a sufficient amount of the negative electrode active material can be dissolved in the electrolyte even if the amount of powder mixed in the electrolyte is reduced.

FIG. 1 is a schematic view of a flow battery according to an embodiment. FIG. 2: is a figure explaining an example of the connection between the positive electrode of the flow battery which concerns on embodiment, a negative electrode, and a zinc plate. FIG. 3 is a block diagram showing a functional configuration of the flow battery according to the embodiment. FIG. 4 is a diagram for explaining a connection state between the positive electrode, the negative electrode, and the zinc plate in the charge mode according to the embodiment. FIG. 5 is a diagram for explaining the connection between the positive electrode, the negative electrode, and the zinc plate in the discharge mode according to the embodiment. FIG. 6 is a diagram for explaining the connection between the positive electrode, the negative electrode, and the zinc plate in the special charge mode according to the embodiment. FIG. 7 is a diagram for explaining the connection between the positive electrode, the negative electrode, and the zinc plate in the special discharge mode according to the embodiment. FIG. 8 is a diagram showing an example of the logic circuit on the plus terminal side according to the embodiment. FIG. 9 is a diagram showing an example of the logic circuit on the negative terminal side according to the embodiment. FIG. 10 is a diagram showing the relationship between various operation modes and ON / OFF of a plurality of switches according to the embodiment. FIG. 11 is a flowchart showing a processing procedure of processing executed by the flow battery according to the embodiment at the time of charging. FIG. 12 is a flowchart showing a processing procedure of processing executed by the flow battery according to the embodiment at the time of discharge.

  Hereinafter, embodiments of the disclosed flow battery will be described in detail with reference to the attached drawings. Note that the present invention is not limited by the embodiments described below.

Embodiment
FIG. 1 is a schematic view of a flow battery 1 according to an embodiment. The flow battery 1 shown in FIG. 1 includes the positive electrode 2, the negative electrode 3, the diaphragms 4 and 5, the electrolytic solution 6, the powder 7, the generating unit 9, the zinc plate 10, the supply unit 14, and the housing 17. And an upper plate 18. The flow battery 1 is a device that causes the electrolytic solution 6 to flow by causing the bubbles 8 generated in the generation unit 9 to float. The generation unit 9 is an example of a flow device.

  In order to make the description easy to understand, FIG. 1 illustrates a three-dimensional orthogonal coordinate system including a Z axis in which the vertically upward direction is a positive direction and the vertically downward direction is a negative direction.

  The positive electrode 2 is a conductive member containing, for example, a nickel compound, a manganese compound or a cobalt compound as a positive electrode active material. As the nickel compound, for example, nickel oxyhydroxide, nickel hydroxide, nickel compound-containing nickel hydroxide and the like can be used. As the manganese compound, for example, manganese dioxide can be used. As the cobalt compound, for example, cobalt hydroxide, cobalt oxyhydroxide and the like can be used. In addition, the positive electrode 2 may contain graphite, carbon black, a conductive resin, and the like. From the viewpoint of the redox potential at which the electrolytic solution 6 is decomposed, the positive electrode 2 may contain a nickel compound.

  The negative electrode 3 contains a negative electrode active material as a metal. The negative electrode 3 may be, for example, a metal plate of stainless steel, copper or the like, or a stainless steel plate or copper plate whose surface is plated with nickel, tin or zinc. In addition, the negative electrode 3 may be used in which the plated surface is partially oxidized.

  Positive electrode 2 includes a positive electrode 2A and a positive electrode 2B. Negative electrode 3 includes negative electrode 3A, negative electrode 3B and negative electrode 3C. The positive electrode 2 and the negative electrode 3 are arranged such that the negative electrode 3A, the positive electrode 2A, the negative electrode 3B, the positive electrode 2B, and the negative electrode 3C are arranged in order along the Y-axis direction at predetermined intervals. Thus, by providing the space | interval of the positive electrode 2 and the negative electrode 3 which adjoin each other, the flow path of the electrolyte solution 6 and the bubble 8 between the positive electrode 2 and the negative electrode 3 is ensured.

  The diaphragms 4 and 5 are disposed so as to sandwich both sides in the thickness direction of the positive electrode 2, that is, the Y-axis direction. The diaphragms 4 and 5 are made of a material that allows the movement of ions contained in the electrolytic solution 6. Examples of the material of the membranes 4 and 5 include anion conductive materials having hydroxide ion conductivity. Examples of the anion-conductive material include gel-like anion-conductive materials having a three-dimensional structure such as organic hydrogels, solid polymer-type anion-conductive materials, and the like. The solid polymer type anion conductive material is, for example, an oxide, hydroxide, layered double hydroxide, containing a polymer and at least one element selected from Groups 1 to 17 of the periodic table. And at least one compound selected from the group consisting of sulfuric acid compounds and phosphoric acid compounds.

The diaphragms 4 and 5 are preferably made of a compact material so as to suppress the permeation of metal ion complexes such as [Zn (OH) ₄ ] ^2- or the like having a larger ion radius than hydroxide ions. It has a predetermined thickness. Examples of the dense material include materials having a relative density of 90% or more, more preferably 92% or more, and even more preferably 95% or more, as calculated by the Archimedes method. The predetermined thickness is, for example, 10 μm to 1000 μm, more preferably 50 μm to 500 μm.

  In this case, zinc deposited in the negative electrodes 3A to 3C grows as dendrites (needle-like crystals) during charging, and penetration of the diaphragms 4 and 5 can be reduced. As a result, the conduction between the negative electrode 3 and the positive electrode 2 facing each other can be reduced.

The electrolytic solution 6 is an alkaline aqueous solution containing a zinc species. Zinc species in the electrolyte 6 are dissolved in the electrolyte 6 as [Zn (OH) ₄ ] ²⁻ . As the electrolytic solution 6, for example, one in which an alkaline aqueous solution containing K ⁺ or OH ⁻ is saturated with zinc species can be used. In addition, if the electrolyte solution 6 is prepared with the powder 7 mentioned later, charge capacity can be enlarged. Here, as an aqueous alkali solution, for example, an aqueous solution of 6.7 moldm ⁻³ potassium hydroxide can be used. Moreover, the electrolyte solution 6 can be prepared by adding ZnO in the ratio of 0.5 mol with respect to the potassium hydroxide aqueous solution of 1 dm < ^-3 >, and adding the powder 7 mentioned later as needed. Further, hydroxides of alkali metals such as lithium hydroxide and sodium hydroxide may be added for the purpose of suppressing the generation of oxygen.

Powder 7 contains zinc. Specifically, the powder 7 is, for example, zinc oxide, zinc hydroxide or the like processed or produced into powder. The powder 7 is easily dissolved in the alkaline aqueous solution, but dispersed or suspended in the electrolytic solution 6 saturated with zinc species without being dissolved or suspended, and mixed in the electrolytic solution 6 in a partially precipitated state. When the electrolyte solution 6 is left standing for a long time, most of the powder 7 may be in a state of settling in the electrolyte solution 6, but if convection is caused in the electrolyte solution 6, sedimentation occurs. A portion of the powder 7 is dispersed or suspended in the electrolyte solution 6. That is, the powder 7 is movably present in the electrolytic solution 6. Here, movable means that the powder 7 can move only in the local space formed between other surrounding powders 7 but the powder 7 can be moved to another position in the electrolytic solution 6 The movement indicates that the powder 7 is exposed to the electrolyte solution 6 other than the initial position. Furthermore, in the movable category, the powder 7 can be moved to the vicinity of both of the positive electrode 2 and the negative electrode 3, or the powder 7 can be almost anywhere in the electrolytic solution 6 present in the housing 17. Includes being able to move. When the zinc species [Zn (OH) ₄ ] ^2- dissolved in the electrolyte solution 6 is consumed, the powder 7 mixed with the electrolyte solution 6 maintains the powder 7 and the electrolyte solution 6 in equilibrium with each other. Thus, the zinc species dissolved in the electrolyte solution 6 are dissolved until saturation.

  The bubble 8 is made of, for example, a gas inert to the positive electrodes 2A, 2B, the negative electrodes 3A, 3B, 3C and the electrolytic solution 6. Examples of such a gas include nitrogen gas, helium gas, neon gas, or argon gas. Degeneration of the electrolyte solution 6 can be reduced by generating an inert gas bubble 8 in the electrolyte solution 6. Further, for example, deterioration of the electrolyte solution 6 which is an alkaline aqueous solution containing a zinc species can be reduced, and the ion conductivity of the electrolyte solution 6 can be maintained high. The gas may be air.

  The bubbles 8 generated by the gas supplied from the generating portion 9 into the electrolytic solution 6 are between the electrodes arranged at predetermined intervals, that is, between the negative electrode 3A and the positive electrode 2A, between the positive electrode 2A and the negative electrode 3B, The electrolytic solution 6 floats up between the negative electrode 3B and the positive electrode 2B and between the positive electrode 2B and the negative electrode 3C. The gas that floats up as bubbles 8 in the electrolyte solution 6 disappears at the liquid surface of the electrolyte solution 6, and forms a gas layer 13 between the upper plate 18 and the liquid surface of the electrolyte solution 6.

  Here, the electrode reaction in the flow battery 1 will be described by taking a nickel zinc battery to which nickel hydroxide is applied as a positive electrode active material as an example. The reaction formulas at the positive electrode 2 and the negative electrode 3 at the time of charge are as follows.

Positive electrode: Ni (OH) ₂ + OH ⁻ → NiOOH + H ₂ O + e ⁻
The negative ^{_{electrode: [Zn (OH) 4]}} 2- + 2e - → Zn + 4OH -

In general, there is a concern that the dendrite generated at the negative electrode 3 grows toward the positive electrode 2 along with this reaction, and the positive electrode 2 and the negative electrode 3 become conductive. As apparent from the reaction formula, in the negative electrode 3, the concentration of [Zn (OH) ₄ ] ²⁻ in the vicinity of the negative electrode 3 decreases as zinc is deposited by charging. And the phenomenon in which the concentration of [Zn (OH) ₄ ] ^2- is lowered in the vicinity of the deposited zinc is one of the causes for the growth as dendrite. That is, by replenishing [Zn (OH) ₄ ] ^2- in the electrolyte solution 6 consumed at the time of charge, the concentration of the zinc species [Zn (OH) ₄ ] ^2-in the electrolyte solution 6 is saturated. Will be held by Thereby, the growth of dendrite is reduced and the conduction between the positive electrode 2 and the negative electrode 3 is reduced.

  In the flow battery 1 according to the embodiment, the powder 7 containing zinc is mixed in the electrolytic solution 6, and a gas is supplied from the discharge port 9 a of the generation unit 9 into the electrolytic solution 6 to generate the bubbles 8. The bubbles 8 are from the lower side to the upper side of the housing 17 in between the negative electrode 3A and the positive electrode 2A, between the positive electrode 2A and the negative electrode 3B, between the negative electrode 3B and the positive electrode 2B, and between the positive electrode 2B and the negative electrode 3C. The surface of the electrolytic solution 6 is floated upward.

  Further, with the floating of the air bubbles 8 between the electrodes, a rising liquid flow is generated in the electrolytic solution 6, and the negative electrode 3B and the positive electrode 2B are generated between the negative electrode 3A and the positive electrode 2A, between the positive electrode 2A and the negative electrode 3B. During the period, the electrolytic solution 6 flows upward from the inner bottom side of the housing 17 between the positive electrode 2B and the negative electrode 3C. Then, with the rising liquid flow of the electrolyte 6, a descending liquid flow is mainly generated between the inner wall 17a of the housing 17 and the negative electrode 3A and between the inner wall 17b and the negative electrode 3C, and the electrolyte 6 is It flows from the top of 17 to the bottom.

Thereby, when [Zn (OH) ₄ ] ^2- in the electrolytic solution 6 is consumed by charging, zinc in the powder 7 is dissolved to follow this [Zn (OH) ₄ ] ^2-2 Is replenished into the electrolyte solution 6. Therefore, the concentration of [Zn (OH) ₄ ] ^2-in the electrolytic solution 6 can be maintained in a saturated state, and the conduction between the positive electrode 2 and the negative electrode 3 can be reduced along with the growth of dendrite.

  In addition to zinc oxide and zinc hydroxide, examples of the powder 7 include metal zinc, calcium zincate, zinc carbonate, zinc sulfate, zinc chloride and the like, with zinc oxide and zinc hydroxide being preferable.

In addition, in the negative electrode 3, Zn is consumed by discharge to generate [Zn (OH) ₄ ] ²⁻ , but since the electrolytic solution 6 is already in a saturated state, it becomes excessive in the electrolytic solution 6 [Zn ZnO is precipitated from (OH) ₄ ] ²⁻ . The zinc consumed by the negative electrode 3 at this time is zinc deposited on the surface of the negative electrode 3 at the time of charge. Therefore, unlike the case where charge and discharge are repeated using the negative electrode originally containing zinc species, so-called shape change in which the surface shape of the negative electrode 3 changes is not generated. Thereby, according to the flow battery 1 which concerns on embodiment, the time-dependent deterioration of the negative electrode 3 can be reduced. In addition, depending on the state of the electrolyte solution 6, what precipitates out from [Zn (OH) ₄ ] ^{2 −} which is excessive is a mixture of Zn (OH) ₂ or ZnO and Zn (OH) ₂ .

  The generating unit 9 is disposed below the housing 17, more specifically below the positive electrode 2 and the negative electrode 3. The generation unit 9 has a plurality of discharge ports 9 a aligned along the X-axis direction and the Y-axis direction. The discharge port 9 a generates bubbles 8 in the electrolytic solution 6 by discharging a gas supplied from a supply unit 14 described later. The discharge port 9a has a diameter of, for example, 0.05 mm or more and 0.1 mm or less. By defining the diameter of the discharge port 9 a in this manner, it is possible to reduce the problem that the electrolytic solution 6 and the powder 7 enter from the discharge port 9 a into the inside of the generating portion 9. Further, a pressure loss suitable for generating the bubbles 8 can be given to the gas discharged from the discharge port 9a.

  Moreover, the space | interval (pitch) along the X-axis direction of the discharge port 9a is 2.5 mm or more and 10 mm or less, for example. However, the size and the interval of the discharge ports 9a are not limited as long as the generated bubbles 8 can be appropriately flowed between the positive electrode 2 and the negative electrode 3 facing each other.

  The generator 9, the housing 17 and the upper plate 18 are made of, for example, a resin material having alkali resistance and insulation, such as polystyrene, polypropylene, polyethylene terephthalate, polytetrafluoroethylene, polyvinyl chloride and the like. The housing 17 and the upper plate 18 are preferably made of the same material as each other, but may be made of different materials. In addition, the housing 17 and the upper plate 18 may be made of the same material as the generator 9 or may be made of a different material.

  The supply unit 14 supplies the gas recovered from the inside of the housing 17 via the pipe 16 to the generator 9 via the pipe 15. The supply unit 14 is, for example, a pump (gas pump) capable of transferring gas, a compressor, or a blower. If the air tightness of the supply unit 14 is increased, the power generation performance of the flow battery 1 is unlikely to be lowered due to the gas or the water vapor derived from the electrolytic solution 6 leaking to the outside.

  As described above, in the flow battery 1 according to the embodiment, the powder 7 is mixed in the electrolytic solution 6 and zinc contained in the powder 7 is dissolved to make the negative electrode active material in the electrolytic solution 6. Some zinc can be supplied. However, when a large amount of powder 7 is mixed in the electrolyte solution 6, there may be a problem such as clogging of the discharge port 9 a of the generation unit 9. On the other hand, when the powder 7 is mixed in a small amount in the electrolyte solution 6, there is a possibility that zinc as a negative electrode active material can not be sufficiently supplied into the electrolyte solution 6.

  Therefore, in the flow battery 1 according to the embodiment, the zinc plate 10 is immersed in the electrolytic solution 6. For example, as shown in FIG. 1, the zinc plate 10 includes a zinc plate 10A and a zinc plate 10B. Then, the zinc plate 10A is fixed between the inner wall 17a of the housing 17 and the negative electrode 3A, and the zinc plate 10B is fixed between the inner wall 17b and the negative electrode 3C. Then, by dissolving zinc contained in the zinc plate 10 in the electrolytic solution 6, zinc which is a negative electrode active material can be supplied to the electrolytic solution 6. Therefore, according to the embodiment, even if the amount of the powder 7 mixed in the electrolytic solution 6 is reduced, a sufficient amount of the negative electrode active material can be dissolved in the electrolytic solution 6. Furthermore, since the zinc plate 10 is fixed in the flow battery 1, clogging at the discharge port 9 a of the generation unit 9 does not occur.

For example, since the density of zinc is 7.1 g / cm ³ , when the zinc plate 10 has a size of 10 cm long × 20 cm wide × 0.1 cm thick, the weight of the zinc plate 10 is 10 × 20 × It will be 0.1 × 7.1 = 142 g. And since the atomic weight of zinc is 65.39, the amount of substance of the zinc plate 10 will be 142 / 65.39 = 2.17 mol. Therefore, in the flow battery 1 according to the embodiment, 2.17 × 2 = 4.34 mol of zinc can be used as a negative electrode active material by immersing the pair of zinc plates 10A and 10B in the electrolytic solution 6. . The size, shape, and number of the zinc plates 10 are not limited to the above-described embodiment.

  The zinc plate 10 is disposed apart from the positive electrode 2 and the negative electrode 3 and contains zinc as a main component. In addition, the zinc plate 10 may be made of zinc and unavoidable impurities. As a result, mixing of impurities from the zinc plate 10 into the electrolytic solution 6 can be suppressed, and the flow battery 1 can be operated stably.

  In addition, the flow battery 1 according to the embodiment includes the gas detection unit 22 that detects a gas such as oxygen or hydrogen generated inside the housing 17 at the time of charging. The gas detection unit 22 is provided, for example, in the pipe 16 and can detect a gas such as oxygen or hydrogen contained in the gas flowing in the pipe 16. Note that the gas detection unit 22 is not limited to being provided in the pipe 16, and may be provided in any place as long as it can detect the gas generated inside the housing 17 at the time of charging. The application of the gas detection unit 22 will be described later.

  Furthermore, the flow battery 1 according to the embodiment includes the control device 30. The control device 30 includes a control unit 31 that controls charging and discharging of the flow battery 1, and a storage unit 32.

  The control unit 31 includes, for example, a computer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a hard desk drive (HDD), an input / output port, and various circuits. The CPU of the computer functions as the control unit 31 by, for example, reading and executing a program stored in the ROM.

  The control unit 31 can also be configured by hardware such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).

  The storage unit 32 corresponds to, for example, a ROM and an HDD. The ROM and the HDD can store various setting information in the control device 30. The control unit 31 may acquire various information via another computer connected via a wired or wireless network or a portable recording medium.

  Here, in the flow battery 1 according to the embodiment, the zinc plate 10 and the positive terminal 20 (see FIG. 2) are connected via the switch S3 (see FIG. 2). Then, the control unit 31 can connect the zinc plate 10 to the plus terminal 20 by controlling the switch S3, and can apply a positive voltage to the zinc plate 10. As a result, zinc contained in the zinc plate 10 can be efficiently dissolved in the electrolytic solution 6, so that zinc which is a negative electrode active material can be efficiently supplied to the electrolytic solution 6.

  Next, the connection between the positive electrode 2, the negative electrode 3 and the zinc plate 10 in the flow battery 1 will be described. FIG. 2 is a view for explaining an example of connection between the positive electrode 2, the negative electrode 3 and the zinc plate 10 of the flow battery 1 according to the embodiment.

  As shown in FIG. 2, the positive electrodes 2A and 2B are connected in parallel via the tabs 2A1 and 2B1 which the positive electrodes 2A and 2B respectively have. The positive electrodes 2A and 2B are connected to the positive terminal 20 via the switch S1 and to the negative terminal 21 via the switch S4. The negative electrodes 3A, 3B and 3C are connected in parallel via the tabs 3A1, 3B1 and 3C1 which the negative electrodes 3A, 3B and 3C respectively have. The negative electrodes 3A, 3B and 3C are connected to the positive terminal 20 via the switch S2 and to the negative terminal 21 via the switch S5. By thus respectively connecting the positive electrode 2 and the negative electrode 3 in parallel, the electrodes of the flow battery 1 can be appropriately connected and used even if the total number of the positive electrode 2 and the negative electrode 3 is different.

  Further, the zinc plates 10A and 10B are connected in parallel via the tabs 10A1 and 10B1 which the zinc plates 10A and 10B respectively have. The zinc plates 10A and 10B are connected to the plus terminal 20 via the switch S3. By connecting the zinc plates 10A and 10B in parallel in this manner, a positive voltage can be appropriately applied to the zinc plate 10 even if a plurality of zinc plates 10 are provided.

  In the flow battery 1 shown in FIGS. 1 and 2, a total of five electrodes are configured such that the negative electrode 3 and the positive electrode 2 are alternately disposed. However, the present invention is not limited to this. Alternatively, the positive and negative electrodes 2 and 3 may be disposed one by one. Further, in the flow battery 1 shown in FIGS. 1 and 2, both ends are configured to be negative electrodes (3A, 3C). However, the present invention is not limited thereto, and both ends may be configured to be positive electrodes. .

  Furthermore, the same number of negative electrodes 3 and positive electrodes 2 may be alternately arranged so that one end is the positive electrode 2 and the other end is the negative electrode 3. In such a case, the connection between the electrodes may be in parallel or in series.

  FIG. 3 is a block diagram showing a functional configuration of the flow battery 1 according to the embodiment. The flow battery 1 has a voltage detection unit 23 and a coulomb efficiency calculation unit 24 in addition to the gas detection unit 22 described above, the control device 30, and the switches S1 to S5.

  The gas detection unit 22 detects a gas such as oxygen or hydrogen generated inside the housing 17 at the time of charging, and transmits information on the gas detection to the control unit 31. The voltage detection unit 23 detects a voltage between the plus terminal 20 and the minus terminal 21 of the flow battery 1 (hereinafter, also referred to as “inter-terminal voltage”), and controls the information on the inter-terminal voltage. Send to The coulomb efficiency calculation unit 24 monitors the charge amount and the discharge capacity of the flow battery 1 respectively, calculates the coulomb efficiency which is the ratio of the discharge capacity to the charge amount, and controls the information of the calculated coulomb efficiency Send to section 31.

  The control unit 31 controls the switches S1 to S5 based on various information sent from the gas detection unit 22, the voltage detection unit 23, and the coulomb efficiency calculation unit 24 and various setting information stored in the storage unit 32. Control ON / OFF. Also, the control unit 31 can control ON / OFF of the switches S1 to S5 based on an instruction from the terminal 100.

  Then, the detail of the various processes in the flow battery 1 which concerns on embodiment is demonstrated, referring FIGS. 4-7. FIG. 4 is a diagram for explaining a connection state between the positive electrode 2, the negative electrode 3 and the zinc plate 10 in the charge mode according to the embodiment. When instructed to charge the flow battery 1 through the terminal 100, the control unit 31 turns on the switches S1 and S5 and turns off the switches S2 to S4 as shown in FIG. As a result, the positive electrode 2 is connected to the positive terminal 20 and the negative electrode 3 is connected to the negative terminal 21 to charge the flow battery 1. In this charge mode, for example, when the charge amount of the flow battery 1 is used up, when charging the flow battery 1 with surplus power from the solar panel in the daytime, charging the flow battery 1 with night electricity charge in the nighttime, etc. To be implemented.

  FIG. 5 is a view for explaining a connection state between the positive electrode 2, the negative electrode 3 and the zinc plate 10 in the discharge mode according to the embodiment. When instructed to discharge the flow battery 1 through the terminal 100, the controller 31 turns on the switches S2 and S4 and turns off the switches S1, S3 and S5 as shown in FIG. Do. As a result, the positive electrode 2 is connected to the negative terminal 21 and the negative electrode 3 is connected to the positive terminal 20, and the flow battery 1 is discharged.

  FIG. 6 is a view for explaining a connection state between the positive electrode 2, the negative electrode 3 and the zinc plate 10 in the special charge mode according to the embodiment. The “special charge mode” is an operation mode which is switched from the charge mode and implemented when the predetermined condition is satisfied while the flow battery 1 is being charged. Specifically, when the voltage between terminals detected by the voltage detection unit 23 exceeds a predetermined charging upper limit voltage (for example, 2.1 V), or the gas detection unit 22 generates gas inside the housing 17 When charging is detected, the charging mode is switched to the special charging mode.

  The control unit 31 turns on the switches S3 and S5 as shown in FIG. 6 when the voltage between terminals exceeds the charge upper limit voltage in the charge mode or when gas is generated inside the housing 17. Switches S1, S2 and S4 are turned off. Thereby, the zinc plate 10 is connected to the plus terminal 20, and the negative electrode 3 is connected to the minus terminal 21.

  As described above, in the special charging mode, the positive electrode 2 is damaged during charging, for example, when the voltage between terminals exceeds the charging upper limit voltage or when gas is generated inside the housing 17. The positive electrode 2 can be protected by stopping the application of the positive voltage. Furthermore, in the special charging mode, since a positive voltage is applied to the zinc plate 10, zinc contained in the zinc plate 10 can be efficiently dissolved in the electrolyte solution 6.

  In addition, when the voltage between terminals exceeds the charge upper limit voltage and it switches to the special charge mode, the power conditioner (it calls "PCS" hereafter) connected to the flow battery 1 exceeds the charge upper limit voltage. And the special charge mode is implemented until the PCS stops charging the flow battery 1. Further, when gas is generated inside the housing 17 and switched to the special charge mode, the special charge mode is implemented until the remaining charge amount of the negative electrode 3 becomes zero (that is, the charge amount of the negative electrode 3 becomes 100%). Ru. The remaining charge amount is a value obtained by subtracting the capacity of the negative electrode 3 at the start of the special charge mode from the total capacity of the negative electrode 3.

  FIG. 7 is a view for explaining a connection state between the positive electrode 2, the negative electrode 3 and the zinc plate 10 in the special discharge mode according to the embodiment. The “special discharge mode” is an operation mode which is switched from the discharge mode and executed when the flow battery 1 is discharged and the predetermined condition is satisfied. Specifically, when the voltage between terminals detected by the voltage detection unit 23 becomes equal to or lower than a predetermined discharge lower limit voltage (for example, 1.2 V) or the coulombic efficiency of the flow battery 1 is a predetermined threshold (for example, , 80%) or less, the discharge mode is switched to the special discharge mode.

  In the discharge mode, as shown in FIG. 7, the control unit 31 performs the switch S3 and the switch S3 as shown in FIG. 7 when the inter-terminal voltage becomes lower than the discharge lower limit voltage or when the coulomb efficiency becomes lower than a predetermined threshold S4 is turned ON, and switches S1, S2 and S5 are turned OFF. Thereby, the zinc plate 10 is connected to the plus terminal 20, and the positive electrode 2 is connected to the minus terminal 21.

  Thus, in the special discharge mode, when the voltage across the terminals becomes equal to or lower than the discharge lower limit voltage and the flow battery 1 is in the overdischarge state, the negative electrode 3 is protected by stopping the application of the positive voltage to the negative electrode 3 can do. Further, in the special discharge mode, when the coulomb efficiency becomes equal to or less than a predetermined threshold value and the refresh operation of the positive electrode 2 is required, the positive electrode 2 can be refreshed by applying a negative voltage to the positive electrode 2 it can. Furthermore, in the special discharge mode, since a positive voltage is applied to the zinc plate 10, zinc contained in the zinc plate 10 can be efficiently dissolved in the electrolytic solution 6.

When the inter-terminal voltage becomes lower than the discharge lower limit voltage and switched to the special discharge mode, the PCS attached to the flow battery 1 detects that the discharge lower limit voltage becomes lower than the discharge lower limit voltage, and the PCS from the flow battery 1 The special discharge mode is implemented until the discharge is stopped. In addition, when the coulombic efficiency becomes lower than a predetermined threshold and the special discharge mode is switched, the special discharge mode is implemented until the refresh operation of the positive electrode 2 is completed. The refresh operation of the positive electrode 2 is performed, for example, during the discharge time calculated by the following equation (1).
Discharge time (h) = total capacity of positive electrode 2 (Ah) × 1.6 / discharge current (A) ··· (1)

  FIG. 8 is a diagram showing an example of the logic circuit on the plus terminal 20 side according to the embodiment, and FIG. 9 is a diagram showing an example of the logic circuit on the minus terminal 21 side according to the embodiment. In the embodiment, for example, as shown in FIG. 10, ON / OFF of the switches S1 to S5 in the various operation modes described above can be controlled by the logic circuits shown in FIGS. 8 and 9. FIG. 10 is a diagram showing the relationship between various operation modes and the ON / OFF of the plurality of switches S1 to S5 according to the embodiment, where "0" represents non-operation (switch OFF) and "1" represents operation. (Switch ON) is shown.

  In the embodiment, the surface of the zinc plate 10 may be rough or not. For example, when the surface of the zinc plate 10 is roughened, the zinc contained in the zinc plate 10 can be more efficiently dissolved in the electrolytic solution 6. When the surface of the zinc plate 10 is not roughened, excessive dissolution of zinc contained in the zinc plate 10 in the electrolyte 6 can be suppressed in the special charge mode or the special discharge mode.

<Details of processing to be performed during charge and discharge>
Subsequently, the details of the process executed by the flow battery 1 according to the embodiment at the time of charge and discharge will be described with reference to FIGS. 11 and 12. FIG. 11 is a flowchart showing a processing procedure of processing executed by the flow battery 1 at the time of charging according to the embodiment.

  When instructed to charge the flow battery 1 through the terminal 100, the control unit 31 sets the operation mode to the charge mode to start charging the flow battery 1 (step S101). In this charge mode, for example, as shown in FIG. 4, the switches S1 and S5 are turned on and the switches S2 to S4 are turned off to connect the positive electrode 2 to the positive terminal 20 and the negative electrode 3 to the negative terminal 21. Connect to

  Next, based on the information sent from the voltage detection unit 23, the control unit 31 determines whether or not the inter-terminal voltage exceeds a predetermined charging upper limit voltage (step S102). Then, if the inter-terminal voltage does not exceed the predetermined charging upper limit voltage (step S102, No), the control unit 31 determines whether gas is generated in the housing 17 based on the information sent from the gas detection unit 22 It is determined whether or not it is (step S103). When no gas is generated in the housing 17 (step S103, No), the control unit 31 determines whether the charging is completed (step S104). When the charging is completed by an instruction to finish charging from terminal 100 or when the remaining charge amount of positive electrode 2 and negative electrode 3 becomes zero (step S104, Yes), the charging mode is ended (step S105). , End the processing at the time of charging. On the other hand, if the charging is not completed (No at Step S104), the process returns to Step S102.

  When the inter-terminal voltage exceeds the predetermined charging upper limit voltage (Yes in step S102), the control unit 31 changes the operation mode to the special charging mode (step S106). In this special charging mode, as shown in FIG. 6, the switches S3 and S5 are turned on and the switches S1, S2 and S4 are turned off to connect the zinc plate 10 to the positive terminal 20 and to set the negative electrode 3 negative. Connect to terminal 21. Next, the control unit 31 determines whether the power supply from the PCS is stopped (step S107), and when the power supply from the PCS is stopped (step S107, Yes), the special charging mode is ended. Then (step S108), the processing at the time of charging ends. If the power supply from the PCS is not stopped (No at Step S107), the process at Step S107 is repeated.

  Furthermore, when gas is generated in the housing 17 (step S103, Yes), the control unit 31 changes the operation mode to the special charging mode (step S109). Next, the control unit 31 determines whether or not the remaining charge amount of the negative electrode 3 has become zero (step S110). If the remaining charge amount of the negative electrode 3 has become zero (step S110, Yes), the special charging is performed. The mode is ended (step S108), and the processing at the time of charging is ended. Moreover, when the remaining charge amount of the negative electrode 3 is not zero (step S110, No), the process of step S110 is repeated.

  FIG. 12 is a flowchart showing a processing procedure of processing executed by the flow battery 1 at the time of discharge according to the embodiment.

  When instructed to discharge the flow battery 1 through the terminal 100, the control unit 31 sets the operation mode to the discharge mode to start discharging the flow battery 1 (step S201). In the discharge mode, for example, as shown in FIG. 5, the switches S2 and S4 are turned on and the switches S1, S3 and S5 are turned off to connect the negative electrode 3 to the positive terminal 20 and also to negative electrode 2 Connect to terminal 21.

  Next, based on the information sent from the voltage detection unit 23, the control unit 31 determines whether the inter-terminal voltage is less than or equal to a predetermined discharge lower limit voltage (step S202). When the inter-terminal voltage is not lower than the predetermined discharge lower limit voltage (No in step S202), the control unit 31 determines that the coulombic efficiency of the flow battery 1 is a predetermined threshold based on the information sent from the coulombic efficiency calculator 24. It is determined whether it is less than or equal to the value (step S203). Then, when the coulombic efficiency of the flow battery 1 is not equal to or less than the predetermined threshold (No in step S203), the control unit 31 determines whether the discharge is completed (step S204). Then, when the discharge is completed due to an instruction to end the discharge from the terminal 100 or the capacity of the positive electrode 2 or the negative electrode 3 becomes zero (step S204, Yes), the discharge mode is ended (step S205), End the processing at the time of discharge. On the other hand, when the discharge is not completed (step S204, No), the process returns to the process of step S202.

  If the inter-terminal voltage is less than or equal to the predetermined discharge lower limit voltage (Yes at step S202), the control unit 31 changes the operation mode to the special discharge mode (step S206). In the special discharge mode, as shown in FIG. 7, the switches S3 and S4 are turned on and the switches S1, S2 and S5 are turned off to connect the zinc plate 10 to the positive terminal 20 and to cut the positive electrode 2 negative. Connect to terminal 21. Next, the control unit 31 determines whether discharge to the outside through the PCS is stopped (step S207), and discharge to the outside through the PCS is stopped (step S207, Yes), The special discharge mode is ended (step S208), and the processing at the time of discharge is ended. When the discharge to the outside through the PCS is not stopped (No at step S207), the process at step S207 is repeated.

  Furthermore, when the coulomb efficiency is equal to or less than the predetermined threshold (Yes at step S203), the control unit 31 changes the operation mode to the special charging mode (step S209). Next, control unit 31 determines whether or not the refresh operation of positive electrode 2 is completed (step S210). When the refresh operation of positive electrode 2 is completed (step S210, Yes), the special discharge mode is ended. (Step S208), the processing at the time of discharge ends. When the refresh operation of the positive electrode 2 is not completed (No at step S210), the process at step S210 is repeated.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible unless it deviates from the meaning. For example, in the embodiment described above, the powder 7 is described as being mixed in the electrolytic solution 6, but the present invention is not limited to this, and the powder 7 may not be included. In such a case, the amount of the negative electrode active material contained in the zinc plate 10 may be increased.

  In the above-described embodiment, the diaphragms 4 and 5 are described as being disposed so as to sandwich the both sides in the thickness direction of the positive electrode 2. However, the present invention is not limited thereto, and may be disposed between the positive electrode 2 and the negative electrode 3 In addition, the positive electrode 2 may be coated.

  Although the supply unit 14 may be operated at all times, from the viewpoint of reducing power consumption, the supply rate of gas may be reduced during discharge rather than during charge.

  Further, in the above-described embodiment, the electrolytic solution 6 is made to flow inside the housing 17 by generating the bubbles 8 at the generating portion 9, but the method of making the electrolytic solution 6 flow inside the housing 17 is this It is not limited to the method.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the invention are not limited to the specific details and representative embodiments represented and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 flow battery 2, 2A, 2B positive electrode 3, 3A, 3B, 3C negative electrode 4, 5 diaphragm 6 electrolyte solution 7 powder 8 bubbles 9 generation | occurrence | production part 9a discharge port 10, 10A, 10B zinc plate 14 supply part 17 housing 18 upper plate Reference Signs List 20 plus terminal 21 minus terminal 22 gas detection unit 23 voltage detection unit 24 coulomb efficiency calculation unit 30 control device 31 control unit 32 storage unit S1 to S5 switch

Claims (7)

Positive electrode and negative electrode,
An electrolytic solution contacting the positive electrode and the negative electrode;
A flow device for flowing the electrolyte;
And a zinc plate to be immersed in the electrolytic solution. Plus and minus terminals,
And a controller for controlling charging and discharging,
The flow battery according to claim 1, wherein the control unit connects the zinc plate to the positive terminal.   The control unit connects the zinc plate to the positive terminal when the voltage between the positive terminal and the negative terminal exceeds the charging upper limit voltage during charging, or when the gas is generated inside, and the negative electrode is the negative electrode. The flow battery according to claim 2, wherein the flow cell is connected to the negative terminal.   The control unit is configured to set the zinc plate to a positive value when the voltage between the positive terminal and the negative terminal becomes equal to or lower than a discharge lower limit voltage during discharge, or when the coulomb efficiency becomes equal to or lower than a predetermined threshold. The flow battery according to claim 2, wherein the flow battery is connected to a terminal and the positive electrode is connected to the negative terminal.   The flow battery according to any one of claims 1 to 4, wherein the flow device includes a generation unit that generates a bubble in the electrolytic solution. The negative electrode includes a first negative electrode and a second negative electrode facing each other with the positive electrode interposed therebetween,
The air bubbles float between the first negative electrode and the positive electrode, and between the positive electrode and the second negative electrode.
The electrolytic solution descends between a first inner wall and a first negative electrode of a case containing the electrolytic solution, and between a second inner wall of the case facing the first inner wall and the second negative electrode. The flow battery according to claim 5, characterized in that: The flow battery according to any one of claims 1 to 6, further comprising: a powder containing zinc and movably mixed in the electrolyte.

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