Metal-air battery system

Abstract

To provide a metal-air battery system capable of suppressing generation of dendrites.SOLUTION: A metal-air battery system includes an inlet chamber into which an electrolyte flows, an outlet chamber out of which the electrolyte flows, a hollow outer electrode having an inner space connecting the inlet chamber and the outlet chamber, and an inner electrode provided so as to be inserted into the inner space concentrically with the outer electrode. One of the outer and inner electrodes is a negative electrode including metal. The other is a porous positive electrode capable of making oxygen diffusion possible. A channel through which the electrolyte flows from the inlet chamber to the outlet chamber is formed between the outer and inner electrodes. A cross-sectional area of the channel is configured to decrease from the inlet chamber side to the outlet chamber side.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a metal-air battery system.

Background Art

[0002] A metal-air battery system that uses a metal as a negative electrode active material and oxygen (air) as a positive electrode active material is known. In such a metal-air battery system, during charging, the metal of the negative electrode active material is deposited on the surface of the negative electrode. At this time, on the surface of the negative electrode, there are portions where the current density becomes locally high depending on the surface state, and the metal is selectively deposited on these portions. When this metal grows dendritically (dendrites are generated) as the charge-discharge cycle progresses, the dendrites penetrate the separator and reach the positive electrode, resulting in an internal short circuit.

[0003] Although it is not a metal-air battery system, Patent Document 1 describes an invention in which, in a secondary battery using lithium or zinc or a lithium alloy or a zinc alloy as a negative electrode active material, one or more layers selected from a conductor layer, a semiconductor layer, or an insulator layer are provided between the negative electrode and the separator. According to this invention, even if dendrites grow and short-circuit with the conductor layer, the current density of the negative electrode during charging decreases, and the dendrites cannot grow further, so it is possible to suppress the dendrites from penetrating the separator and reaching the positive electrode.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, even if the invention of Patent Document 1 is applied to a metal-air battery system, the generation of dendrites cannot be suppressed, and therefore it is not possible to completely prevent dendrites from penetrating the separator and reaching the positive electrode.

[0006] In view of the circumstances described above, at least one embodiment of this disclosure aims to provide a metal-air battery system that can suppress the generation of dendrites. [Means for solving the problem]

[0007] To achieve the above objective, the metal-air battery system according to this disclosure comprises an inlet chamber into which an electrolyte flows, an outlet chamber from which the electrolyte flows out, a hollow outer electrode having an internal space connecting the inlet chamber and the outlet chamber, and an inner electrode provided to be inserted concentrically into the internal space with respect to the outer electrode, wherein one of the outer electrode and the inner electrode is a negative electrode containing metal, and the other is a porous positive electrode from which oxygen can diffuse, and a flow path is formed between the outer electrode and the inner electrode through which the electrolyte flows from the inlet chamber toward the outlet chamber, and the cross-sectional area of ​​the flow path is configured to decrease from the inlet chamber side toward the outlet chamber side. The internal space has a frustoconical shape, the inner electrode has a conical portion or frustoconical portion corresponding to the frustoconical shape of the outer electrode, the inner electrode has an inlet portion upstream of the conical portion or frustoconical portion in the direction of electrolyte flow, and the inlet portion has a rotationally symmetric shape with respect to the axis of the inner electrode. . [Effects of the Invention]

[0008] The concentration of active species ions in the electrolyte flowing through the channel decreases towards the downstream side in the direction of electrolyte flow. This variation in concentration leads to non-uniform deposition of metal on the negative electrode, creating an environment conducive to dendrite formation. In contrast, the metal-air battery system of this disclosure is configured such that the cross-sectional area of ​​the channel through which the electrolyte flows decreases from the inlet chamber side to the outlet chamber side. As a result, the flow velocity of the electrolyte flowing through the channel increases towards the downstream side in the direction of electrolyte flow. This makes it less likely for the reaction downstream to be diffusion-limited by the active ion species, and suppresses the formation of regions where metal is deposited locally. Consequently, the formation of dendrites can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram illustrating the configuration of a metal-air battery system according to Embodiment 1 of this disclosure. [Figure 2] A schematic diagram illustrating a part of the configuration of a metal-air battery system according to Embodiment 2 of this disclosure. [Figure 3] This is a schematic diagram illustrating the configuration of an electrode cell in a metal-air battery system according to Embodiment 3 of this disclosure. [Figure 4] This is a schematic diagram illustrating the configuration of an electrode cell in a metal-air battery system according to Embodiment 4 of this disclosure. [Figure 5] This is a schematic partial cross-sectional view illustrating the operation of moving the inner electrode in the electrode cell of a metal-air battery system according to Embodiment 4 of the present disclosure. [Figure 6] This is a schematic diagram showing an example of the configuration of a flow rate control device provided in a metal-air battery system according to Embodiment 4 of the present disclosure. [Figure 7] This is a cross-sectional view illustrating the pattern of the metal electrodeposition morphology on the surface of the inner electrode in a metal-air battery system according to Embodiment 4 of the present disclosure. [Figure 8] A schematic diagram illustrating the configuration of an electrode cell in a metal-air battery system according to Embodiment 5 of this disclosure. [Figure 9] A schematic diagram illustrating the configuration of an electrode cell in a metal-air battery system according to Embodiment 6 of this disclosure. [Figure 10] This is a schematic diagram illustrating a modified configuration of an electrode cell of a metal-air battery system according to Embodiment 6 of this disclosure. [Modes for carrying out the invention]

[0010] Hereinafter, a metal-air battery system according to embodiments of the present disclosure will be described with reference to the drawings. The embodiments described below represent one aspect of the present disclosure and are not limiting, and can be modified at will within the scope of the technical idea of ​​the present disclosure.

[0011] (Embodiment 1) <Configuration of the Metal-Air Battery System According to Embodiment 1 of the Present Disclosure> As shown in FIG. 1, the metal-air battery system 1 according to Embodiment 1 of the present disclosure includes an electrode cell 2. The electrode cell 2 includes an inlet chamber 3, an outlet chamber 4, a hollow outer electrode 5 having an internal space 6 that communicates the inlet chamber 3 and the outlet chamber 4, and an inner electrode 7 that is fixed in a state of being inserted into the internal space 6 concentrically with the outer electrode 5. One end of an electrolyte inflow pipe 8 for allowing an electrolyte, which will be described later, to flow into the inlet chamber 3 is connected to the inlet chamber 3. One end of an electrolyte outflow pipe 9 for allowing the electrolyte to flow out of the outlet chamber 4 is connected to the outlet chamber 4. The other ends of the electrolyte inflow pipe 8 and the electrolyte outflow pipe 9 are connected to an electrolyte tank 10 that stores the electrolyte. A pump 11 is provided in the electrolyte inflow pipe 8.

[0012] As the electrolyte, either an aqueous electrolyte in which an electrolyte is dissolved in water or a non-aqueous electrolyte in which an electrolyte is dissolved in a non-aqueous solution such as an organic solvent can be used. As the aqueous electrolyte, for example, an aqueous solution using hydroxides, chlorides, phosphates, borates, sulfates, etc. of potassium, sodium, lithium, barium, magnesium, etc. as the electrolyte can be used. That is, any indicator salt that imparts electrical conductivity to the aqueous solution can be used as the electrolyte. As the non-aqueous electrolyte, for example, a solution obtained by dissolving an indicator salt composed of an alkali metal, etc. in a liquid such as a cyclic or chain carbonate, cyclic or chain ester, cyclic or chain ether, sulfone compound, ionic liquid, etc. can be used.

[0013] In Embodiment 1, the outer electrode 5 is the positive electrode and the inner electrode 7 is the negative electrode. The outer electrode 5 is configured such that the cross-sectional area of the internal space 6 cut by a plane perpendicular to the axis L5 of the outer electrode 5 decreases from the inlet chamber 3 side toward the outlet chamber 4 side. In Embodiment 1, as a specific example, the internal space 6 is described as having a frustum of a cone shape. The inner electrode 7 is configured to have a portion where the cross-sectional area cut by a plane perpendicular to the axis L7 of the inner electrode 7 decreases from the inlet chamber 3 side toward the outlet chamber 4 side. In Embodiment 1, as a specific example of that portion, the inner electrode 7 is described as including a frustum-shaped portion 12 having a frustum of a cone shape. Note that this portion is not limited to a frustum of a cone shape and may be a conical-shaped portion having a conical shape.

[0014] When the inner electrode 7 is inserted into the internal space 6, a flow path 13 through which the electrolytic solution can flow from the inlet chamber 3 toward the outlet chamber 4 is formed between the outer electrode 5 and the inner electrode 7. Since each of the outer electrode 5 and the inner electrode 7 has the above-described configuration, the flow path 13 is configured such that its flow path cross-sectional area decreases from the inlet chamber 3 side toward the outlet chamber 4 side.

[0015] The inner electrode 7 may have an inlet-side portion 14 upstream of the frustum-shaped portion 12 in the direction of flow of the electrolytic solution. At least a part of the inlet-side portion 14 protrudes from the internal space 6 into the inlet chamber 3. The inlet-side portion 14 preferably has a rotationally symmetric shape with respect to the axis L7 of the inner electrode 7. The rotationally symmetric shape is, for example, a shape symmetric with respect to the circumferential direction centered on the axis L7, such as an inverted frustum of a cone shape or a hemispherical body in the direction of flow of the electrolytic solution, and is a shape that does not disturb the flow of the electrolytic solution along the circumferential direction of the inlet-side portion 14. According to such a configuration, it is possible to suppress the flow of the electrolytic solution from being disturbed by the inlet-side portion 14 before the electrolytic solution flowing into the inlet chamber 3 flows into the flow path 13. If the inlet-side portion 14 is a hemispherical body, the connection portion between the inlet-side portion 14 and the frustum-shaped portion 12 has a smooth configuration, so it is also possible to suppress the flow of the electrolytic solution from being disturbed at the connection portion before the electrolytic solution flowing into the inlet chamber 3 flows into the flow path 13.

[0016] The surface of the inner electrode 7 is provided with an insulating layer 15 in both the upstream region 7a, which is the region upstream in the direction of electrolyte flow, and the downstream region 7b, which is the region downstream in the direction of electrolyte flow. The entire current-carrying region 7c, whose surface is exposed between the upstream region 7a and the downstream region 7b, is located within the internal space 6 and faces the outer electrode 5.

[0017] The negative electrode, the inner electrode 7, is a metal-containing electrode. For example, it may be an electrode made of zinc, or it may be an electrode with a body made of another metal such as stainless steel or aluminum, with zinc plated on the surface. However, the metal contained in the inner electrode 7 is not limited to zinc. Depending on the type of electrolyte (for example, the difference between aqueous electrolyte and non-aqueous electrolyte), iron, aluminum, lithium, sodium, potassium, copper, magnesium, etc., or alloys thereof can be used.

[0018] The positive electrode, the outer electrode 5, is a porous electrode that allows oxygen to diffuse. For example, an electrode with a three-layer structure can be used, comprising a porous outermost layer that allows oxygen to diffuse, a porous intermediate layer made of a metal such as nickel, and an innermost layer on which an oxygen reduction catalyst is supported on a conductive material such as carbon. As the oxygen reduction catalyst, in an acidic liquid environment, a catalyst with platinum as the active component (e.g., platinum-supported carbon) can be used. In an alkaline liquid environment, a catalyst with 3d transition metals such as iron, manganese, nickel, and cobalt, or their oxides, as the active component can be used. In addition, catalysts with ruthenium, silver, gold, and iridium as active components can be used in both acidic and alkaline liquid environments. Furthermore, catalysts with organometallic complexes, carbon fibers (e.g., carbon nanotubes), nitrogen carbides, etc., as active components can also be used.

[0019] The outer electrode 5 and the inner electrode 7 are each electrically connected to the AC / DC converter 16. The AC / DC converter 16 can be electrically connected to the load 17 and the AC power supply 18, respectively. However, if a DC power supply is used instead of the AC power supply 18 and the load 17 operates on DC current, the AC / DC converter 16 is not necessary.

[0020] <Operation of the metal-air battery system according to Embodiment 1 of this disclosure> Next, the operation of the metal-air battery system 1 according to Embodiment 1 of this disclosure will be described. First, the operation in which current flows to the load 17 due to the discharge of the metal-air battery system 1 will be described. By starting the pump 11, the electrolyte in the electrolyte tank 10 is supplied to the inlet chamber 3 via the electrolyte inlet pipe 8. The electrolyte that has flowed into the inlet chamber 3 flows through the flow path 13 and flows into the outlet chamber 4. The electrolyte in the outlet chamber 4 flows out of the outlet chamber 4, flows through the electrolyte outlet pipe 9 and flows into the electrolyte tank 10. In this way, the electrolyte circulates between the electrolyte tank 10 and the electrode cell 2.

[0021] While the electrolyte flows through the channel 13, the following reactions occur at the outer electrode 5 and the inner electrode 7. At the inner electrode 7, in the energized region 7c, a metal contained in the inner electrode 7, such as zinc, reacts with hydroxide ions in the electrolyte to produce zincate ions, and electrons are released to the inner electrode 7. The released electrons pass through the AC / DC converter 16 and flow into the outer electrode 5. At the outer electrode 5, oxygen contained in the air outside the electrode cell 2 diffuses through the outermost and intermediate layers, and hydroxide ions are produced by the reaction of the air, water in the electrolyte, and electrons flowing into the outer electrode 5 through the oxygen reduction catalyst in the innermost layer. The generated hydroxide ions are used in the above reaction at the inner electrode 7.

[0022] In this operation, electrons flow from the inner electrode 7 to the outer electrode 5, causing a direct current to flow from the outer electrode 5 to the inner electrode 7. The AC / DC converter 16 converts this direct current into an alternating current and supplies the alternating current to the load 17.

[0023] Next, the charging operation of the metal-air battery system 1 will be described. With the electrolyte circulating between the electrolyte tank 10 and the electrode cell 2, an alternating current is supplied from the AC power supply 18 to the AC-DC converter 16. The alternating current from the AC power supply 18 is converted to a direct current by the AC-DC converter 16, and the direct current flows to the outer electrode 5. That is, electrons flow to the inner electrode 7. At the inner electrode 7, zinc ions in the electrolyte accept electrons, causing zinc to deposit on the inner electrode 7, and the metal-air battery system 1 is charged.

[0024] If zinc were to deposit uniformly on the surface of the current-carrying region 7c of the inner electrode 7 during charging, there would be no problem. However, in reality, dendrites, which are needle-shaped in some areas, may form. If dendrites form and grow, they may connect the inner electrode 7 and the outer electrode 5. This causes an internal short circuit, reducing the battery voltage to 0V and preventing charging. In particular, the concentration of active species ions in the electrolyte flowing through the channel 13 decreases towards the downstream side in the direction of electrolyte flow. This variation in concentration leads to uneven deposition of metal on the inner electrode 7, creating an environment where dendrites are likely to form.

[0025] In contrast, in the metal-air battery system 1 according to Embodiment 1, the cross-sectional area of ​​the flow path 13 through which the electrolyte flows decreases from the inlet chamber 3 side to the outlet chamber 4 side. As a result, the flow velocity of the electrolyte flowing through the flow path 13 increases towards the downstream side in the direction of electrolyte flow. This makes it less likely for the reaction downstream to be diffusion-limited by the active ion species, and the occurrence of regions where metal is deposited locally can be suppressed. Consequently, the formation of dendrites can be suppressed.

[0026] (Embodiment 2) Next, a metal-air battery system according to Embodiment 2 will be described. The metal-air battery system according to Embodiment 2 has a modified configuration of the outer electrode 5 compared to Embodiment 1. In Embodiment 2, components that are the same as those in Embodiment 1 are given the same reference numerals, and their detailed descriptions are omitted.

[0027] <Configuration of the metal-air battery system according to Embodiment 2 of this disclosure> As shown in Figure 2, the outer electrode 5 has a three-layer structure including a charging positive electrode 21 facing the inner electrode 7, a discharging positive electrode 22 located on the opposite side of the charging positive electrode 21 from the inner electrode 7, and a separator 23 located between the charging positive electrode 21 and the discharging positive electrode 22. The charging positive electrode 21 can be, for example, a cylindrical electrode manufactured in a mesh pattern from a non-oxidizing porous metal material, such as nickel or a nickel alloy or stainless steel. The discharging positive electrode 22 can have the same configuration as in Embodiment 1. The separator 23 can be, for example, an anion exchange membrane or a microporous membrane formed from a polymer or solid oxide.

[0028] The metal-air battery system 1 includes a switching device 25. The switching device 25 is configured to switch so that either the charging positive electrode 21 or the discharging positive electrode 22 energizes the AC / DC converter 16, that is, so that the inner electrode 7 is electrically connected to either the charging positive electrode 21 or the discharging positive electrode 22. The configuration of the switching device 25 is not particularly limited, but for example, it may consist of a first diode 25a that carries current from the discharging positive electrode 22 to the inner electrode 7 and a second diode 25b that carries current from the inner electrode 7 to the charging positive electrode 21. A switching device using a mechanical switch instead of diodes may also be used. The other configurations are the same as in Embodiment 1.

[0029] <Operation of the metal-air battery system according to Embodiment 2 of this disclosure> Next, the operation of the metal-air battery system 1 according to Embodiment 2 of this disclosure will be described. During discharge of the metal-air battery system 1, current flows sequentially from the discharge positive electrode 22 of the outer electrode 5 to the first diode 25a, the AC / DC converter 16, and the inner electrode 7. During charging of the metal-air battery system 1, current flows sequentially from the inner electrode 7 to the AC / DC converter 16, the second diode 25b, and the charging positive electrode 21. Other operations are the same as in Embodiment 1.

[0030] Even if the outer electrode 5, which is the positive electrode, has a configuration that includes a charging positive electrode 21 and a discharging positive electrode 22, as in Embodiment 2, the same effects and advantages as in Embodiment 1 can be obtained if the configuration of the flow path 13 is the same as in Embodiment 1.

[0031] In Embodiment 2, even if dendrites are generated during charging and an internal short circuit occurs, discharge can be performed using the inner electrode 7 and the discharge positive electrode 22. Furthermore, the risk of the reverse reactions occurring at the positive electrode during charging and discharging can be reduced, and improvements in efficiency and lifespan can be expected.

[0032] (Embodiment 3) Next, a metal-air battery system according to Embodiment 3 will be described. The metal-air battery system according to Embodiment 3 is the same as that of Embodiment 1, but with the positive and negative electrodes swapped. In Embodiment 3, components that are the same as those in Embodiment 1 are given the same reference numerals, and their detailed descriptions are omitted.

[0033] <Configuration of the metal-air battery system according to Embodiment 3 of this disclosure> As shown in Figure 3, in Embodiment 3, the outer electrode 5 is the negative electrode and the inner electrode 7 is the positive electrode. Therefore, in Embodiment 3, the outer electrode 5 is an electrode made of metal, and the inner electrode 7 is a porous electrode that allows oxygen to diffuse. The inner electrode 7 is fixed in a state where it is entirely housed within the electrode cell 2. The inner electrode 7 has a hollow portion 37 that penetrates the inner electrode 7 along the axis L7. Since both ends 7d and 7e of the inner electrode 7 along the axis L7 are located inside the inlet chamber 3 and the outlet chamber 4, respectively, the inside of the inlet chamber 3 and the inside of the outlet chamber 4 are in communication not only through the flow path 13 but also through the hollow portion 37.

[0034] Inside the inlet chamber 3 and the outlet chamber 4, an isolation member 30 is provided to separate the electrolyte in the electrode cell 2 into a first flow F1 flowing through the hollow section 37 and a second flow F2 flowing through the flow path 13. The isolation member 30 has a cylindrical shape with end faces 31 and 32 at both ends in the direction of the axis L7 of the inner electrode 7 when installed inside the inlet chamber 3 and the outlet chamber 4, and openings 31a and 32a formed at each of the end faces 31 and 32. When the inner electrode 7 is inserted into one of the openings 32a, with both ends 7d and 7e positioned inside the respective isolation member 30, a sealing member 33 such as an O-ring is provided between the inner periphery of the opening 32a and the outer circumferential surface of the inner electrode 7.

[0035] An oxygen-containing gas supply device 34 is provided inside the isolation member 30 located within the inlet chamber 3 to supply an oxygen-containing gas such as air. As the oxygen-containing gas supply device 34, for example, a bubbling device can be used which has an oxygen-containing gas supply line 35, one end of which is located inside the isolation member 30 and the other end which opens to the outside of the electrode cell 2 or is connected to a cylinder of oxygen-containing gas, and a compressor 36 provided on the oxygen-containing gas supply line 35. The other configurations are the same as in Embodiment 1.

[0036] <Operation of the metal-air battery system according to Embodiment 3 of this disclosure> Next, the operation of the metal-air battery system 1 according to Embodiment 3 of this disclosure will be described, focusing on the parts that differ from the operation of the metal-air battery system 1 according to Embodiment 1. During discharge of the metal-air battery system 1, a portion of the electrolyte that flows into the inlet chamber 3 enters the inside of the isolation member 30 through the opening 31a within the electrode cell 2. Inside the isolation member 30 provided in the inlet chamber 3, oxygen-containing gas pressurized by the compressor 36 is supplied via the oxygen-containing gas supply line 35, causing the oxygen-containing gas to bubble into the electrolyte, resulting in an electrolyte with dissolved oxygen. The electrolyte with dissolved oxygen flows into the hollow section 37 and flows through the hollow section 37 as the first flow F1. The electrolyte that has flowed through the hollow section 37 flows out into the isolation member 30 provided in the outlet chamber 4 and flows out to the outside of the isolation member 30 through the opening 31a.

[0037] Meanwhile, electrolyte that does not enter the isolation member 30 located inside the inlet chamber 3 flows through the channel 13 as a second flow F2 and flows into the outlet chamber 4. Inside the outlet chamber 4, the electrolyte that flowed as the first flow F1 and the electrolyte that flowed as the second flow F2 merge and flow out from the outlet chamber 4.

[0038] In this manner, as the electrolyte flows through the electrode cell 2, the same reactions as those described in Embodiment 1 occur in the outer electrode 5 as the negative electrode and the inner electrode 7 as the positive electrode. However, in Embodiment 3, oxygen contained in the electrolyte flowing through the hollow section 37 diffuses into the inner electrode 7, and hydroxide ions are generated by the reaction of oxygen with water in the electrolyte as the second flow F2 and electrons flowing to the inner electrode 7 by an oxygen reduction catalyst.

[0039] Furthermore, during charging of the metal-air battery system 1, electrons flow to the outer electrode 5, and at the outer electrode 5, metal ions (e.g., zinc ions) in the electrolyte accept the electrons, causing metal (e.g., zinc) to deposit on the outer electrode 5.

[0040] Even in a configuration like that of Embodiment 3, where the outer electrode 5 is the negative electrode and the inner electrode 7 is the positive electrode, the same effects and advantages as in Embodiment 1 can be obtained if the configuration of the flow path 13 is the same as in Embodiment 1.

[0041] <Modified example of the metal-air battery system according to Embodiment 3 of this disclosure> In Embodiment 3, an electrolyte in which oxygen-containing gas is bubbled is circulated through the hollow section 37 as the first flow F1, but the embodiment is not limited to this configuration. Instead of an electrolyte in which oxygen is dissolved, an oxygen-containing gas may be circulated through the hollow section 37 as the first flow F1.

[0042] <Arrangement of positive and negative electrodes in embodiments 1 to 3 of this disclosure> In all three embodiments, by arranging the outer electrode 5 and the inner electrode 7 concentrically, a difference in electrode area between the two electrodes is obtained, allowing the current density of the outer electrode 5 during operation to be reduced compared to that of the inner electrode 7. In embodiments 1 and 2, the inner electrode 7 is the negative electrode, but since the polarization of the positive electrode is greater than that of the negative electrode, and therefore resistance reduction is more necessary, the energy efficiency during charging and discharging can be improved by arranging the inner electrode 7 as the negative electrode and the outer electrode 5 as the positive electrode. In this case, the ratio of the current density at the negative electrode to that at the positive electrode differs depending on the ratio of the diameters at both ends of the frustum in the energized region 7c of the inner electrode 7. For example, if the diameter at the end of the frustum on the inlet chamber 3 side is D in Let D be the diameter at the end of the frustum on the outlet chamber 4 side. out Therefore, the diameter ratio D in / D out The larger the value, the larger the area of ​​the outer electrode 5 facing the current-carrying region 7c, and thus the lower the resistance.

[0043] In Embodiment 3, compared to Embodiment 1 where the inner electrode 7 is the negative electrode, the area of ​​the negative electrode is relatively increased, and the amount of metal deposited on the negative electrode increases, thus increasing the energy storage capacity. At this time, the increase in energy storage capacity differs depending on the ratio of the diameters at both ends of the frustum in the energized region 7c of the inner electrode 7. For example, if the diameter at the end of the frustum on the inlet chamber 3 side is D inLet D be the diameter at the end of the frustum on the outlet chamber 4 side. out Therefore, the diameter ratio D in / D out The larger the value, the larger the area of ​​the outer electrode 5 facing the current-carrying region 7c, and thus the greater the energy storage capacity.

[0044] (Embodiment 4) Next, a metal-air battery system according to Embodiment 4 will be described. The metal-air battery system according to Embodiment 4 is modified in that the inner electrode 7 is movable along its axis L7 compared to each of Embodiments 1 to 3. In the following description, Embodiment 4 will be described as a configuration in which the inner electrode 7 is movable compared to the configuration of Embodiment 1, but Embodiment 4 may also be configured by making the inner electrode 7 movable compared to the configuration of Embodiment 2 or 3. In Embodiment 4, components that are the same as those in Embodiment 1 will be given the same reference numerals, and their detailed descriptions will be omitted.

[0045] <Configuration of the metal-air battery system according to Embodiment 4 of this disclosure> As shown in Figure 4, in the metal-air battery system 1 according to Embodiment 4 of this disclosure, both ends 7d and 7e of the inner electrode 7 penetrate the inlet chamber 3 and the outlet chamber 4, respectively. The inlet chamber 3 and the outlet chamber 4 have openings 3a and 4a formed therein, respectively, through which both ends 7d and 7e of the inner electrode 7 penetrate, and O-rings 48 and 49 are provided on the inner circumferential surfaces of the openings 3a and 4a, respectively. The O-rings 48 and 49 seal the space between the inner circumferential surfaces of the openings 3a and 4a and the inner electrode 7.

[0046] A moving device 40 is provided to move the inner electrode 7 along its axis L7 so as to face the end 7d of the inner electrode 7 that has passed through the inlet chamber 3. The configuration of the moving device 40 is not particularly limited, but for example, the moving device 40 may include a fixed plate 41, a movable plate 42 to which the end 7d is fixed, and a piston part 43 that moves the movable plate 42 relative to the fixed plate 41 so that the distance between the fixed plate 41 and the movable plate 42 changes.

[0047] Furthermore, the metal-air battery system 1 according to Embodiment 4 of this disclosure may include a voltmeter 45 for detecting the voltage between the outer electrode 5 and the inner electrode 7, a differential pressure gauge 46 for detecting the differential pressure between the inlet chamber 3 and the outlet chamber 4, and a control device 44 to which the voltmeter 45 and the differential pressure gauge 46 are electrically connected. The control device 44 is electrically connected to a drive device (not shown) for the piston part 43 of the moving device 40 to drive the piston part 43. Also, by electrically connecting the AC power supply 18 to the control device 44, the control device 44 can detect the number of times the AC power supply 18 has been driven. The number of times the AC power supply 18 has been driven corresponds to the number of charge cycles (or charge / discharge cycles) of the metal-air battery system 1, i.e., the operating time of the metal-air battery system 1. For this reason, the control device 44 has the function of a parameter detection device for detecting a parameter corresponding to the operating time of the metal-air battery system 1. Note that the parameter detection device may be configured as a separate device from the control device 44. The other configurations are the same as in Embodiment 1.

[0048] <Operation of the metal-air battery system according to Embodiment 4 of this disclosure> The operation of Embodiment 4 is the same as that of Embodiment 1, except that the moving device 40 moves the inner electrode 7 along its axis L7. Therefore, the operation of moving the inner electrode 7 will be described below. When the piston portion 43 of the moving device 40 is driven to extend, the moving plate 42 moves away from the fixed plate 41, that is, closer to the inlet chamber 3. As a result, the inner electrode 7, whose end 7d is fixed to the moving plate 42, moves along its axis L7 in the direction from the inlet chamber 3 to the outlet chamber 4. Conversely, when the piston portion 43 of the moving device 40 is driven to retract, the moving plate 42 moves closer to the fixed plate 41, that is, away from the inlet chamber 3. As a result, the inner electrode 7 moves along its axis L7 in the direction from the outlet chamber 4 to the inlet chamber 3. When the inner electrode 7 moves in this way, the O-rings 48 and 49 seal the space between the inner circumferential surfaces of the openings 3a and 4a and the inner electrode 7, respectively, thus preventing electrolyte leakage from the openings 3a and 4a.

[0049] As described above, that is, as shown in Figure 5, when the inner electrode 7 moves in the direction of arrow A, both the internal space 6 of the outer electrode 5 and the frustoconical portion 12 of the inner electrode 7 narrow in the direction of arrow A, so the distance between the outer electrode 5 and the inner electrode 7, i.e., the radial width of the flow path 13, decreases. If the inner electrode 7 continues to move in the direction of arrow A, eventually the inner electrode 7 (or the metal deposited on the surface of the inner electrode 7) will come into contact with the outer electrode 5, and the inner electrode 7 can no longer be moved in the direction of arrow A. This state is referred to as the case where the inner electrode 7 has moved furthest toward the outlet chamber 4. Conversely, when the inner electrode 7 moves in the direction of arrow B, the distance between the outer electrode 5 and the inner electrode 7, i.e., the radial width of the flow path 13, increases. The state in which the inner electrode 7 can no longer move in the direction of arrow B is referred to as the case where the inner electrode 7 has moved furthest toward the inlet chamber 3. The inner electrode 7 can be positioned between these two states, and the radial width of the flow path 13 can be adjusted within a range where the width in each of these states is the minimum and maximum value, respectively.

[0050] It is preferable to set the ranges of the upstream region 7a and the downstream region 7b so that the energized area 7c is located within the internal space in both the case where the inner electrode 7 is moved furthest towards the outlet chamber 4 and the case where the inner electrode 7 is moved furthest towards the inlet chamber 3, and to provide an insulating layer 15 in the upstream region 7a and the downstream region 7b. With this configuration, even if the distance between the outer electrode 5 and the inner electrode 7 is changed, the energized area 7c faces the outer electrode 5, so the effective electrode surface area can be kept constant.

[0051] If the radial width of the flow path 13 is changed, it is necessary to adjust the flow rate of the electrolyte circulating through the flow path 13. The metal-air battery system 1 may be provided with a flow rate adjustment device that adjusts the flow rate of the electrolyte in accordance with the change in the distance between the outer electrode 5 and the inner electrode 7. The configuration of such a flow rate adjustment device is not particularly limited, but for example, the control device 44 may detect the amount of movement of the inner electrode 7 and calculate the distance between the outer electrode 5 and the inner electrode 7 from this amount of movement. Based on this distance, the control device 44 may adjust the discharge amount of the pump 11. In this case, the control device 44 constitutes the flow rate adjustment device.

[0052] Another example of a flow rate control device is described below. As shown in Figure 6, the flow rate control device 60 is provided between the downstream end of the electrolyte inlet pipe 8 and the inlet chamber 3. The flow rate control device 60 includes a first pipe 61 that communicates with the inlet chamber and a second pipe 63 that communicates with the first pipe 61 through a hole 62 formed in the first pipe 61. A chamber portion 8a is formed at the downstream end of the electrolyte inlet pipe 8, extending in a direction along the axis L7 of the inner electrode 7, and the upstream open end 63a of the second pipe 63 is inserted into the chamber portion 8a through a hole 8b formed in the chamber portion 8a. An O-ring 8c is provided on the inner circumferential surface of the hole 8b to seal the space between the inner circumferential surface of the hole 8b and the second pipe 63. The downstream open end 63b of the second pipe 63 is positioned to face the hole 62. The second pipe 63 is provided so as to be movable along the axis L7, and the opening area of ​​the hole 62 relative to the downstream opening end 63b of the second pipe 63 changes as the second pipe 63 moves. When the second pipe 63 and the inner electrode 7 are connected by a connecting member 64, the second pipe 63 moves along the axis L7 as the inner electrode 7 moves along the axis L7.

[0053] To adjust the radial width of the flow path 13 (see Figure 5), moving the inner electrode 7 up and down in Figure 6 also moves the second pipe 63 up and down, so that the opening area of ​​the hole 62 relative to the downstream opening end 63b increases or decreases. By using such a flow rate adjustment device 60, it is possible to adjust the flow rate of the electrolyte in accordance with the change in the distance between the outer electrode 5 and the inner electrode 7 with a simple configuration.

[0054] Based on various operating conditions of the metal-air battery system 1 (voltage between the outer electrode 5 and the inner electrode 7, differential pressure between the inlet chamber 3 and the outlet chamber 4, number of charge cycles of the metal-air battery system 1, etc.), the position of the inner electrode 7 may be manually adjusted by manually driving the mobile device 40, or it may be automatically adjusted according to the operating conditions of the metal-air battery system 1. In the former case, the control device 44 is not necessary, and the electrodeposition morphology of the metal at the negative electrode is estimated based on the detected values ​​of the voltmeter 45, differential pressure gauge 46, and parameter detection device, and the position of the inner electrode 7 is adjusted manually. The operation in the latter case will be described below. In the latter case, the control device 44 estimates the electrodeposition morphology of the metal at the negative electrode based on the detected values ​​of the voltmeter 45, differential pressure gauge 46, and parameter detection device, but the estimation principle is the same in both cases.

[0055] During operation (charging / discharging) of the metal-air battery system 1 and during standby between charging and discharging, the detected values ​​from the voltmeter 45, differential pressure gauge 46, and parameter detection device are transmitted to the control device 44. Based on these detected values, the control device 44 estimates the electrodeposition morphology of the metal deposited on the surface of the inner electrode 7. This estimation method is not particularly limited, but an example of a method for estimating the electrodeposition morphology of the metal is described below.

[0056] The control device 44 has pre-set thresholds for the detected values ​​of the voltmeter 45, differential pressure gauge 46, and parameter detection device, and determines whether the detected value of each of the voltmeter 45, differential pressure gauge 46, and parameter detection device is greater than or less than this threshold. The control device 44 infers the electrodeposition morphology of the metal from the combination of whether each of these three detected values ​​is greater than or less than the threshold. Tables 1 to 3 below summarize the relationship between the combination of whether the detected values ​​are greater than or less than the threshold, the electrodeposition morphology, and the actions to be taken for each of the charging, discharging, and standby phases of the metal-air battery system 1. In the tables below, "Large" indicates that each detected value is greater than the respective threshold, and "Small" indicates that it is less than the respective threshold. Four patterns (1) to (4) of electrodeposition morphology are described. As shown in Figure 7, electrodeposition morphology (1) is a form in which metal 50 is uniformly deposited on the surface of the inner electrode 7, the amount of deposition is small, and the distance between the outer electrode 5 and the inner electrode 7 is large, so the radial width of the channel 13 is sufficiently secured. Electrodeposition morphology (2) is a form in which metal 50 is uniformly deposited on the surface of the inner electrode 7, the amount of deposition is small, but the distance between the outer electrode 5 and the inner electrode 7 is small, so the radial width of the channel 13 is small. Electrodeposition morphology (3) is a form in which metal 50 is uniformly deposited on the surface of the inner electrode 7, the distance between the outer electrode 5 and the inner electrode 7 is large, but the amount of metal 50 deposited is large, so the radial width of the channel 13 is small. Electrodeposition morphology (4) is a form in which the distance between the outer electrode 5 and the inner electrode 7 is large, the amount of metal 50 deposited is small, but the metal is unevenly deposited on the surface of the inner electrode 7, so dendrites 51 are generated, and the radial width of the channel 13 is partially reduced.

[0057] [Table 1]

[0058] [Table 2]

[0059] [Table 3]

[0060] In the "Actions to be taken" in Tables 1-3, the distance between electrodes is reduced or increased by moving the inner electrode 7. Minimizing the distance between electrodes means moving the inner electrode 7 toward the outlet chamber 4 until it can no longer be moved. If there is no internal short circuit, the dendrite 51 is not in contact with the outer electrode 5, so the inner electrode 7 can be moved at least until the dendrite 51 is in contact with the outer electrode 5. In some cases, the dendrite 51 may break and fall off when it comes into contact with the outer electrode 5. In this case, the amount of movement of the inner electrode 7 will be relatively large, but if the dendrite is hard and does not break even when it comes into contact with the outer electrode 5, the amount of movement of the inner electrode 7 will be relatively small. In the latter case, there is a high possibility of an internal short circuit occurring in a short period of time, so electrode replacement is preferable. The detached dendrite can be discharged from the electrode cell 2 by being carried along with the flow of electrolyte. For example, if a filter or the like is provided at the connection point between the electrolyte tank 10 and the electrolyte inlet pipe 8, the dendrites can be retained in the electrolyte tank 10, thereby preventing the dendrites from flowing back into the electrode cell 2.

[0061] Although not shown in Tables 1-3, if the value detected by the voltmeter 45 becomes zero, it indicates that an internal short circuit has occurred, regardless of the values ​​detected by the differential pressure gauge 46 and the parameter detection device. In this case, the inner electrode 7 should be moved to minimize the distance between the electrodes. If the amount of movement of the inner electrode 7 is relatively small, electrode replacement is preferable.

[0062] In this way, the electrodeposition morphology of the metal 50 deposited on the surface of the inner electrode 7 can be predicted, and the generation of dendrites 51 can be predicted early, allowing for a quick response to the risk of internal short circuits.

[0063] (Embodiment 5) Next, a metal-air battery system according to Embodiment 5 will be described. The metal-air battery system according to Embodiment 5 is modified from Embodiment 4 in that the inner electrode 7 is capable of rotating around its axis L7 as the center of rotation. In Embodiment 5, components that are the same as those in Embodiment 4 are given the same reference numerals, and their detailed descriptions are omitted.

[0064] <Configuration of the metal-air battery system according to Embodiment 5 of this disclosure> As shown in Figure 8, the metal-air battery system 1 according to Embodiment 5 of this disclosure is provided with a rotating device 70 that rotates the inner electrode 7 around its axis L7 as the center of rotation. The rotating device 70 is mounted on a movable plate 42 of a movable device 40, so that the inner electrode 7 can be moved along the axis L7 by the movable device 40 and rotate around the axis L7 as the center of rotation. A control device 44 may be provided electrically connected to the rotating device 70, and the control device 44 may drive the rotating device 70. The other configurations are the same as in Embodiment 4. Note that the rotation of the inner electrode 70 is not limited to continuously rotating in one direction, but also includes the operation of rotating by a certain angle in one direction and then rotating by a certain angle in the opposite direction, and repeating this operation.

[0065] <Operation of the metal-air battery system according to Embodiment 5 of this disclosure> In Embodiment 5, the charging and discharging operations of the metal-air battery system 1 are the same as in Embodiment 1, and the operation of moving the inner electrode 7 along the axis L7 is the same as in Embodiment 4. The following description will focus on operations that differ from Embodiments 1 and 4.

[0066] When an internal short circuit occurs, or when it is suspected that a dendrite has formed, the moving device 40 moves the inner electrode 7 toward the outlet chamber 4, or after the inner electrode 7 has moved as far toward the outlet chamber 4, the rotating device 70 rotates the inner electrode 7. When the inner electrode 7 rotates while the dendrite is in contact with the outer electrode 5, the dendrite can be broken off and detached. Furthermore, in Embodiment 5, when the action to be taken in Tables 1 to 3 is to "minimize the distance between electrodes", the inner electrode 7 can be rotated further to make it easier to detach the dendrite.

[0067] When the inner electrode 7 is the negative electrode, metal deposits on the surface of the inner electrode 7, so as the amount of electrodeposition increases, the weight of the inner electrode 7 increases. This increases the load on the rotating device 70 that rotates the inner electrode 7. Therefore, if a load detection device 71 is provided to detect the load on the rotating device 70, the control device 44 can estimate the amount of metal electrodeposited on the surface of the inner electrode 7 using the value detected by the load detection device 71. The configuration of the load detection device 71 is not particularly limited, but for example, the control device 44 can detect the load by measuring the current value of the rotating device 70, so the control device 44 can be configured as the load detection device 71. The load detection device 71 may also be provided as a separate device from the control device 44.

[0068] While the load of the rotating device 70 alone can only estimate the amount of metal electrodeposition on the surface of the inner electrode 7, by combining this with the voltage, differential pressure, and parameters detected in Embodiment 4, the electrodeposition morphology of the metal deposited on the surface of the inner electrode 7 can be estimated with greater accuracy. This allows for early prediction of the formation of dendrites 51, enabling a rapid response to the risk of internal short circuits.

[0069] (Embodiment 6) Next, a metal-air battery system according to Embodiment 6 will be described. The metal-air battery system according to Embodiment 6 is modified from Embodiment 5 by changing the rotating electrode to the outer electrode 5. In Embodiment 6, components that are the same as those in Embodiment 5 are given the same reference numerals, and their detailed descriptions are omitted.

[0070] <Configuration of the metal-air battery system according to Embodiment 6 of this disclosure> As shown in Figure 9, in the metal-air battery system 1 according to Embodiment 5 of the present disclosure, the rotating device 70 includes a rotating body 72 connected to the electrode cell 2 (for example, the bottom of the inlet chamber 3), and the rotating body 72 rotates about the axes L5 and L7 of the outer electrode 5 and the inner electrode 7 as its center of rotation. The other configurations are the same as in Embodiment 6.

[0071] <Operation of the metal-air battery system according to Embodiment 6 of this disclosure> The operation of Embodiment 6 differs from Embodiment 5 in that the outer electrode 5 is rotated by the rotating device 70. In Embodiment 6, the inner electrode 7 does not rotate on its own, so the outer electrode 5 rotates relative to the inner electrode 7. Even in this case, if the outer electrode 5 rotates while the dendrite is in contact with the outer electrode 5, the dendrite can be broken off and detached. Also, in Embodiment 6, if the action to be taken is to "minimize the distance between electrodes" as shown in Tables 1 to 3, the dendrite can be made to detach more easily by further rotating the outer electrode 5. The control of the moving device 40 and the rotating device 70 by the control device 44 is the same as in Embodiment 5, except that the outer electrode 5 is rotated instead of the inner electrode 7.

[0072] <Modified example of the metal-air battery system according to Embodiment 7 of this disclosure> In Embodiment 6, the outer electrode 5 was the positive electrode and the inner electrode 7 was the negative electrode. However, as in the electrode cell configuration shown in Figure 3 of Embodiment 3, the outer electrode 5 may be the negative electrode and the inner electrode 7 may be the positive electrode. In this case, metal is deposited on the outer electrode 5, so as the amount of electrodeposition increases, the weight of the outer electrode 5 increases. This increases the load on the rotating device 70 that rotates the inner electrode 7. Similar to Embodiment 5, the load on the rotating device 70 is detected by the load detection device 71, and the amount of metal electrodeposited on the surface of the outer electrode 5 can be estimated based on the detected load value. By combining this with voltage, differential pressure, and parameters, the electrodeposition morphology of the metal deposited on the surface of the outer electrode 5 can be accurately estimated. This allows for early prediction of the formation of dendrites 51, enabling a quick response to the risk of internal short circuits.

[0073] In Embodiment 6, when the outer electrode 5 rotates, the inlet chamber 3 and outlet chamber 4 also rotate together with the outer electrode 5. One end of the electrolyte inlet pipe 8 and the electrolyte outlet pipe 9 are connected to the inlet chamber 3 and the outlet chamber 4, respectively, and the other ends of these are connected to the electrolyte tank 10. In practice, these may obstruct the rotation of the outer electrode 5.

[0074] In contrast, by employing an electrode cell 2 as shown in Figure 10, the outer electrode 5 can be rotated without being affected by the electrolyte inlet pipe 8, electrolyte outlet pipe 9, electrolyte tank 10, etc. The inner electrode 7 has a first hollow section 81 formed in a part of the interior of the inner electrode 7, and a second hollow section 82 formed in a part of the interior of the inner electrode 7 downstream of the first hollow section 81 in the direction of electrolyte flow. Inside the inner electrode 7, the first hollow section 81 and the second hollow section 82 are not in communication with each other. Both ends 7d and 7e of the inner electrode 7 are provided to protrude to the outside from the inlet chamber 3 and the outlet chamber 4, respectively. The first hollow section 81 is configured to open at end 7d of the inner electrode 7 and is in communication with the outside of the inlet chamber 3. The second hollow section 82 is configured to open at end 7e of the inner electrode 7 and is in communication with the outside of the outlet chamber 4. The inner electrode 7 has through holes 84 and 85 that connect the first hollow portion 81 and the second hollow portion 82, respectively, to the closed space 83 formed by the inside of the inlet chamber 3, the inside of the outlet chamber 3, and the flow path 13.

[0075] In an electrode cell 2 with this configuration, the electrolyte flowing through the electrolyte inlet pipe 8 flows into the first hollow section 81 and flows out from the first hollow section 81 to the closed space 83 through the through hole 84. The electrolyte in the closed space 83, particularly in the outlet chamber 4, flows into the second hollow section 82 through the through hole 85 and flows into the electrolyte outlet pipe 9 outside the outlet chamber 4.

[0076] With this configuration, there is no need to provide piping in the inlet chamber 3 for supplying electrolyte to the inlet chamber 3 and piping for draining electrolyte from the outlet chamber 4, respectively, making it easier to configure the outer electrode 5 to rotate.

[0077] The contents described in each of the above embodiments can be understood, for example, as follows:

[0078] [1] A metal-air battery system according to one embodiment is: The inlet chamber (3) into which the electrolyte flows, The outlet chamber (4) from which the electrolyte flows out, A hollow outer electrode (5) having an internal space (6) that connects the inlet chamber (3) and the outlet chamber (4), An inner electrode (7) is provided so as to be inserted concentrically with the outer electrode (5) into the internal space (6) and Equipped with, One of the outer electrode (5) and the inner electrode (7) is a negative electrode containing metal, and the other is a porous positive electrode that allows oxygen to diffuse. A flow path (13) is formed between the outer electrode (5) and the inner electrode (7) through which the electrolyte flows from the inlet chamber (3) toward the outlet chamber (4), and the cross-sectional area of ​​the flow path (13) is configured to decrease from the inlet chamber (3) side toward the outlet chamber (4) side.

[0079] The concentration of active species ions in the electrolyte flowing through the channel decreases towards the downstream side in the direction of electrolyte flow. This variation in concentration leads to non-uniform deposition of metal on the negative electrode, creating an environment conducive to dendrite formation. In contrast, the metal-air battery system of this disclosure is configured such that the cross-sectional area of ​​the channel through which the electrolyte flows decreases from the inlet chamber side to the outlet chamber side. As a result, the flow velocity of the electrolyte flowing through the channel increases towards the downstream side in the direction of electrolyte flow. This makes it less likely for the reaction downstream to be diffusion-limited by the active ion species, and suppresses the formation of regions where metal is deposited locally. Consequently, the formation of dendrites can be suppressed.

[0080] [2] A metal-air battery system according to another embodiment is the metal-air battery system of [1], The internal space (6) has a frustoconical shape, and the inner electrode (7) has a conical portion or frustoconical portion (12) that corresponds to the frustoconical shape of the outer electrode (5).

[0081] With this configuration, the cross-sectional area of ​​the flow path through which the electrolyte flows can be configured to decrease from the inlet chamber side to the outlet chamber side.

[0082] [3] A metal-air battery system according to yet another embodiment is the metal-air battery system of [2], The inner electrode (5) has an inlet portion (14) located upstream of the conical portion or the frustoconical portion (12) in the direction of the electrolyte flow. The inlet portion (14) has a rotationally symmetrical shape with respect to the axis (L7) of the inner electrode (7).

[0083] With this configuration, it is possible to suppress disturbances in the electrolyte flow at the inlet side before the electrolyte flows into the flow path after entering the inlet chamber.

[0084] [4] A metal-air battery system according to yet another embodiment is the metal-air battery system of [3], The aforementioned inlet portion (14) has a hemispherical shape.

[0085] With this configuration, the connection between the inlet portion and the conical or frustoconical portion is smooth, which suppresses disruption of the electrolyte flow at the connection point between the electrolyte flowing into the inlet chamber and the flow path.

[0086] [5] A metal-air battery system according to yet another embodiment is any of the metal-air battery systems described in [2] to [4], The system includes a moving device (40) for moving the inner electrode (7) along the axis (L7) of the inner electrode (7) relative to the outer electrode (5).

[0087] With this configuration, the distance between the positive and negative electrodes can be easily controlled.

[0088] [6] A metal-air battery system according to yet another embodiment is the metal-air battery system of [5], The surface of the inner electrode (7) is provided with an insulating layer (15) in both the upstream region (7a), which is the region upstream in the direction of electrolyte flow, and the downstream region (7b), which is the region downstream in the direction of electrolyte flow. The energized region (7c) whose surface is exposed between the upstream region (7a) and the downstream region (7b) is located within the internal space (6) in both cases: when the inner electrode (7) is moved furthest toward the outlet chamber (4) and when the inner electrode (7) is moved furthest toward the inlet chamber (3).

[0089] With this configuration, even if the distance between the positive and negative electrodes is changed, the current-carrying region faces the outer electrode, so the effective electrode surface area can be kept constant.

[0090] [7] A metal-air battery system according to yet another embodiment is a metal-air battery system according to either [5] or [6], The system includes a flow rate adjustment device (60) for adjusting the flow rate of the electrolyte that flows into the inlet chamber (3), The flow rate adjustment device (60) is configured to adjust the flow rate of the electrolyte in accordance with the movement of the inner electrode (7).

[0091] With this configuration, the flow rate of the electrolyte through the channel can be appropriately adjusted in response to changes in the distance between the negative electrode and the positive electrode.

[0092] [8] A metal-air battery system according to yet another embodiment is the metal-air battery system of [7], The flow rate control device (60) is A first pipe (61) that communicates with the inlet chamber (3), A second pipe (63) communicates with the first pipe (61) through a hole (62) formed in the first pipe (61) Equipped with, The second pipe (63) moves together with the inner electrode (7), and the opening area of ​​the hole (62) relative to the second pipe (63) changes as the second pipe (63) moves.

[0093] With this configuration, the flow rate of the electrolyte can be adjusted in response to changes in the distance between the negative and positive electrodes using a simple setup.

[0094] [9] A metal-air battery system according to yet another embodiment is any of the metal-air battery systems described in [5] to [8], The system includes a rotating device (70) that causes either the inner electrode (7) or the outer electrode (5) to rotate around the axis (L7 or L5) of the inner electrode (7) or the outer electrode (5) as the center of rotation.

[0095] With this configuration, when a dendrite is generated, the inner electrode is moved to bring the tip of the dendrite into contact with the opposing electrode, and then the dendrite can be mechanically detached by rotating either the inner or outer electrode in that state.

[0096]

[10] A metal-air battery system according to yet another embodiment is the metal-air battery system of [9], The inner electrode (7) or the outer electrode (5) that is rotatable is the negative electrode. The system includes a load detection device (control device 44) for detecting the load on the rotating device (70).

[0097] With this configuration, the amount of metal electrodeposition deposited on the surface of the inner electrode can be estimated, allowing for early prediction of dendrite formation and enabling a rapid response to the risk of internal short circuits.

[0098]

[11] A metal-air battery system according to yet another embodiment is a metal-air battery system according to either [9] or

[10] , A voltmeter (45) for detecting the voltage between the outer electrode (5) and the inner electrode (7), A differential pressure gauge (46) for detecting the differential pressure between the inlet chamber (3) and the outlet chamber (4), A parameter detection device (control device 44) for detecting parameters corresponding to the operating time of the metal-air battery system (1) and It is equipped with.

[0099] With this configuration, the amount and form of electrodeposition of metal deposited on the surface of the inner or outer electrode can be estimated, allowing for early prediction of dendrite formation and enabling a rapid response to the risk of internal short circuits.

[0100]

[12] A metal-air battery system according to yet another embodiment is the metal-air battery system of

[11] , The device includes a control device (44) that controls the aforementioned moving device (40), The control device (44) determines the amount of movement of the inner electrode based on the values ​​detected by the voltmeter (45), the differential pressure meter (46), and the parameter detection device (44), and the moving device (40) moves the inner electrode (7) by the amount of movement.

[0101] With this configuration, the distance between the negative electrode and the positive electrode can be controlled depending on the electrodeposition pattern of the metal deposited on the surface of the inner or outer electrode.

[0102]

[13] A metal-air battery system according to yet another embodiment is the metal-air battery system of

[12] , The control device (44) is also configured to control the rotating device (70), and after the moving device (40) moves the inner electrode (7), it drives the rotating device (70) to rotate the inner electrode (7) or the outer electrode (5).

[0103] With this configuration, when a dendrite is generated, the inner electrode is moved to bring the tip of the dendrite into contact with the opposing electrode, and then the dendrite can be mechanically detached by rotating either the inner or outer electrode in that state.

[0104]

[14] A metal-air battery system according to yet another embodiment is the metal-air battery system of

[10] , A voltmeter (45) for detecting the voltage between the outer electrode (5) and the inner electrode (7), A differential pressure gauge (46) for detecting the differential pressure between the inlet chamber (3) and the outlet chamber (4), A parameter detection device (control device 44) for detecting parameters corresponding to the operating time of the metal-air battery system (1), A control device (44) that controls the moving device (40) and the rotating device (70) and Equipped with, The control device (44) determines the amount of movement of the inner electrode (7) based on the values ​​detected by the load detection device (44), the voltmeter (45), the differential pressure gauge (46), and the parameter detection device (44). The moving device (40) moves the inner electrode (7) by the determined amount, and after the moving device (40) has moved the inner electrode (7), it drives the rotating device (70) to rotate the inner electrode (7) or the outer electrode (5).

[0105] With this configuration, when a dendrite is generated, the inner electrode is moved to bring the tip of the dendrite into contact with the opposing electrode, and then the dendrite can be mechanically detached by rotating either the inner or outer electrode in that state.

[0106]

[15] A metal-air battery system according to yet another embodiment is any of the metal-air battery systems of [1] to

[14] , The inner electrode (7) is the negative electrode, and the outer electrode (5) is the positive electrode.

[0107] Because the polarization of the positive electrode is greater than that of the negative electrode, and therefore resistance reduction is more necessary, an arrangement where the inner electrode is the negative electrode and the outer electrode is the positive electrode can improve energy efficiency during charging and discharging.

[0108]

[16] A metal-air battery system according to yet another embodiment is the metal-air battery system of

[15] , The outer electrode (5) is A charging positive electrode (21) facing the inner electrode (7), A separator (23) is provided on the surface of the charging positive electrode (21) on the side opposite to the side facing the inner electrode (7), A discharge positive electrode (22) is provided so as to be in contact with the separator (23) and It is equipped with.

[0109] With this configuration, charging is performed using the negative electrode and the positive charging electrode, and discharging is performed using the negative electrode and the positive discharging electrode. Therefore, even if an internal short circuit occurs during charging, discharging can be performed, and charging and discharging can be carried out without any problems.

[0110]

[17] A metal-air battery system according to yet another embodiment is the metal-air battery system of

[15] or

[16] , The inner electrode (7) is A first hollow portion (81) formed in a part of the interior of the inner electrode (7), A second hollow portion (82) is formed in a part of the interior of the inner electrode (7) downstream of the first hollow portion (81) in the direction of the flow of the electrolyte, and Includes, The inner electrode (7) is provided so as to extend outwards from each of the inlet chamber (3) and the outlet chamber (4), the first hollow portion (81) communicates with the outside of the inlet chamber (3), and the second hollow portion (82) communicates with the outside of the outlet chamber (4). The inner electrode (7) has through holes (84, 85) that connect the first hollow portion (81) and the second hollow portion (82) to the closed space (83) formed by the inside of the inlet chamber (3), the inside of the outlet chamber (4), and the flow path (13).

[0111] With this configuration, there is no need to provide piping in the inlet chamber for supplying electrolyte to the inlet chamber and piping for draining electrolyte from the outlet chamber in each of the inlet and outlet chambers, making it easier to configure the outer electrode to rotate.

[0112]

[18] A metal-air battery system according to yet another embodiment is any of the metal-air battery systems of [1] to

[14] , The inner electrode (7) is the positive electrode, and the outer electrode (5) is the negative electrode. The inner electrode (7) has a hollow portion (37) formed in it that penetrates the inner electrode (7) along the axis (L7) of the inner electrode (7). The hollow portion (37) is configured to allow an oxygen-containing gas or an electrolyte containing dissolved oxygen to flow through it.

[0113] With this configuration, the area of ​​the negative electrode increases relatively compared to when the inner electrode is the negative electrode, and the amount of metal deposited on the negative electrode increases, thus increasing the energy storage capacity. [Explanation of Symbols]

[0114] 1. Metal-air battery system 3. Entrance Chamber 4. Outlet Chamber 5 outer electrode 6. Interior space 7 Inner electrode 12. The frustum-shaped part 13 Flow channels 14 Entrance side part 15. Insulating layer 21 Positive electrode for charging 22. Positive electrode for discharge 23 Separator 37 Hollow part 40 Mobile device 44 Control devices (load detection devices, parameter detection devices) 45 Voltmeter 46 Differential pressure gauge 60 Flow control device 61. First Piping 62 holes 63. Second Piping 70 Rotation device 81 1st hollow part 82 2nd hollow part 83 Closed space 84 Through holes 85 Through hole L5 (outer electrode) axis L7 (inner electrode) axis

Claims

1. An inlet chamber into which the electrolyte flows, The outlet chamber from which the electrolyte flows out, A hollow outer electrode having an internal space connecting the inlet chamber and the outlet chamber, An inner electrode is provided so as to be inserted into the internal space concentrically with the outer electrode. Equipped with, One of the outer electrode and the inner electrode is a negative electrode containing metal, and the other is a porous positive electrode that allows oxygen to diffuse. A flow path is formed between the outer electrode and the inner electrode through which the electrolyte flows from the inlet chamber toward the outlet chamber, and the cross-sectional area of ​​the flow path is configured to decrease from the inlet chamber side toward the outlet chamber side. The internal space has a frustoconical shape, and the inner electrode has a conical portion or a frustoconical portion corresponding to the frustoconical shape of the outer electrode. The inner electrode has an inlet portion located upstream of the conical portion or the frustoconical portion in the direction of the flow of the electrolyte. A metal-air battery system in which the inlet portion has a shape that is rotationally symmetrical with respect to the axis of the inner electrode.

2. The metal-air battery system according to claim 1, wherein the inlet portion has a hemispherical shape.

3. The metal-air battery system according to claim 1 or 2, further comprising a moving device for moving the inner electrode along the axis of the inner electrode relative to the outer electrode.

4. The surface of the inner electrode is provided with an insulating layer in both an upstream region, which is the region upstream in the direction of electrolyte flow, and a downstream region, which is the region downstream in the direction of electrolyte flow. The metal-air battery system according to claim 3, wherein the energized region whose surface is exposed between the upstream region and the downstream region is located within the internal space in both the case where the inner electrode is moved furthest toward the outlet chamber and the case where the inner electrode is moved furthest toward the inlet chamber.

5. The system includes a flow rate adjustment device for adjusting the flow rate of the electrolyte that flows into the inlet chamber, The metal-air battery system according to claim 3, wherein the flow rate adjustment device is configured to adjust the flow rate of the electrolyte in accordance with the movement of the inner electrode.

6. An inlet chamber into which the electrolyte flows, The outlet chamber from which the electrolyte flows out, A hollow outer electrode having an internal space connecting the inlet chamber and the outlet chamber, An inner electrode is provided so as to be inserted into the internal space concentrically with the outer electrode, A moving device for moving the inner electrode along the axis of the inner electrode relative to the outer electrode. Equipped with, One of the outer electrode and the inner electrode is a negative electrode containing metal, and the other is a porous positive electrode that allows oxygen to diffuse. A flow path is formed between the outer electrode and the inner electrode through which the electrolyte flows from the inlet chamber toward the outlet chamber, and the cross-sectional area of ​​the flow path is configured to decrease from the inlet chamber side toward the outlet chamber side. The internal space has a frustoconical shape, and the inner electrode has a conical portion or a frustoconical portion corresponding to the frustoconical shape of the outer electrode. The surface of the inner electrode is provided with an insulating layer in both an upstream region, which is the region upstream in the direction of electrolyte flow, and a downstream region, which is the region downstream in the direction of electrolyte flow. A metal-air battery system in which the energized region, whose surface is exposed between the upstream region and the downstream region, is located within the internal space, regardless of whether the inner electrode is moved furthest toward the outlet chamber or furthest toward the inlet chamber.

7. An inlet chamber into which the electrolyte flows, The outlet chamber from which the electrolyte flows out, A hollow outer electrode having an internal space connecting the inlet chamber and the outlet chamber, An inner electrode is provided so as to be inserted into the internal space concentrically with the outer electrode, A moving device for moving the inner electrode along the axis of the inner electrode relative to the outer electrode, A flow rate adjustment device for adjusting the flow rate of the electrolyte that flows into the inlet chamber. Equipped with, One of the outer electrode and the inner electrode is a negative electrode containing metal, and the other is a porous positive electrode that allows oxygen to diffuse. A flow path is formed between the outer electrode and the inner electrode through which the electrolyte flows from the inlet chamber toward the outlet chamber, and the cross-sectional area of ​​the flow path is configured to decrease from the inlet chamber side toward the outlet chamber side. The internal space has a frustoconical shape, and the inner electrode has a conical portion or a frustoconical portion corresponding to the frustoconical shape of the outer electrode. A metal-air battery system wherein the flow rate adjustment device is configured to adjust the flow rate of the electrolyte in accordance with the movement of the inner electrode.

8. The flow rate control device is A first pipe communicating with the aforementioned inlet chamber, A second pipe that communicates with the first pipe through a hole formed in the first pipe and Equipped with, The metal-air battery system according to claim 7, wherein the second pipe moves together with the inner electrode, and the opening area of ​​the hole relative to the second pipe changes as a result of the movement of the second pipe.

9. The metal-air battery system according to claim 3, further comprising a rotating device that causes either the inner electrode or the outer electrode to rotate on its axis of rotation with the axis of the inner electrode or the outer electrode as the center of rotation.

10. An inlet chamber into which the electrolyte flows, The outlet chamber from which the electrolyte flows out, A hollow outer electrode having an internal space connecting the inlet chamber and the outlet chamber, An inner electrode is provided so as to be inserted into the internal space concentrically with the outer electrode, A moving device for moving the inner electrode along the axis of the inner electrode relative to the outer electrode, A rotating device that rotates either the inner electrode or the outer electrode around the axis of rotation of the inner electrode or the outer electrode. Equipped with, One of the outer electrode and the inner electrode is a negative electrode containing metal, and the other is a porous positive electrode that allows oxygen to diffuse. A flow path is formed between the outer electrode and the inner electrode through which the electrolyte flows from the inlet chamber toward the outlet chamber, and the cross-sectional area of ​​the flow path is configured to decrease from the inlet chamber side toward the outlet chamber side. A metal-air battery system in which the internal space has a frustoconical shape, and the inner electrode has a conical portion or a frustoconical portion corresponding to the frustoconical shape of the outer electrode.

11. The inner electrode or the outer electrode that is rotatably mounted is the negative electrode. The metal-air battery system according to claim 9, further comprising a load detection device for detecting the load on the rotating device.

12. A voltmeter for detecting the voltage between the outer electrode and the inner electrode, A differential pressure gauge for detecting the differential pressure between the inlet chamber and the outlet chamber, A parameter detection device for detecting parameters corresponding to the operating time of the metal-air battery system, A metal-air battery system according to claim 9, comprising:

13. The device includes a control device for controlling the aforementioned moving device, The metal-air battery system according to claim 12, wherein the control device determines the amount of movement of the inner electrode based on the values ​​detected by the voltmeter, the differential pressure meter, and the parameter detection device, and the moving device moves the inner electrode by the amount of movement.

14. The metal-air battery system according to claim 13, wherein the control device is also configured to control the rotating device, and after the moving device moves the inner electrode, the rotating device is driven to rotate the inner electrode or the outer electrode.

15. A voltmeter for detecting the voltage between the outer electrode and the inner electrode, A differential pressure gauge for detecting the differential pressure between the inlet chamber and the outlet chamber, A parameter detection device for detecting parameters corresponding to the operating time of the metal-air battery system, A control device that controls the moving device and the rotating device. Equipped with, The metal-air battery system according to claim 11, wherein the control device determines the amount of movement of the inner electrode based on the values ​​detected by the load detection device, the voltmeter, the differential pressure meter, and the parameter detection device, the moving device moves the inner electrode by the amount of movement, and after the moving device has moved the inner electrode, the rotating device is driven to rotate the inner electrode or the outer electrode.

16. The metal-air battery system according to claim 1 or 2, wherein the inner electrode is the negative electrode and the outer electrode is the positive electrode.

17. The outer electrode is, A charging positive electrode facing the inner electrode, A separator is provided on the surface of the positive electrode for charging, on the side opposite to the side facing the inner electrode, A discharge positive electrode provided in contact with the separator and A metal-air battery system according to claim 16, comprising:

18. The inner electrode is A first hollow portion formed in a part of the interior of the inner electrode, A second hollow portion is formed in a part of the interior of the inner electrode downstream of the first hollow portion in the direction in which the electrolyte flows. Includes, The inner electrode is provided so as to extend outwards from the inlet chamber and the outlet chamber, respectively, with the first hollow portion communicating with the outside of the inlet chamber and the second hollow portion communicating with the outside of the outlet chamber. The metal-air battery system according to claim 16, wherein the inner electrode has through holes that connect the first hollow portion and the second hollow portion to the closed space formed by the inside of the inlet chamber, the inside of the outlet chamber, and the flow path.

19. An inlet chamber into which the electrolyte flows, The outlet chamber from which the electrolyte flows out, A hollow outer electrode having an internal space connecting the inlet chamber and the outlet chamber, An inner electrode is provided so as to be inserted into the internal space concentrically with the outer electrode. Equipped with, One of the outer electrode and the inner electrode is a negative electrode containing metal, and the other is a porous positive electrode that allows oxygen to diffuse. A flow path is formed between the outer electrode and the inner electrode through which the electrolyte flows from the inlet chamber toward the outlet chamber, and the cross-sectional area of ​​the flow path is configured to decrease from the inlet chamber side toward the outlet chamber side. The inner electrode is the negative electrode, and the outer electrode is the positive electrode. The outer electrode is, A charging positive electrode facing the inner electrode, A separator is provided on the surface of the positive electrode for charging, on the side opposite to the side facing the inner electrode, A discharge positive electrode provided in contact with the separator and A metal-air battery system equipped with the following features.

20. An inlet chamber into which the electrolyte flows, The outlet chamber from which the electrolyte flows out, A hollow outer electrode having an internal space connecting the inlet chamber and the outlet chamber, An inner electrode is provided so as to be inserted into the internal space concentrically with the outer electrode. Equipped with, One of the outer electrode and the inner electrode is a negative electrode containing metal, and the other is a porous positive electrode that allows oxygen to diffuse. A flow path is formed between the outer electrode and the inner electrode through which the electrolyte flows from the inlet chamber toward the outlet chamber, and the cross-sectional area of ​​the flow path is configured to decrease from the inlet chamber side toward the outlet chamber side. The inner electrode is the negative electrode, and the outer electrode is the positive electrode. The inner electrode is A first hollow portion formed in a part of the interior of the inner electrode, A second hollow portion is formed in a part of the interior of the inner electrode downstream of the first hollow portion in the direction in which the electrolyte flows. Includes, The inner electrode is provided so as to extend outwards from the inlet chamber and the outlet chamber, respectively, with the first hollow portion communicating with the outside of the inlet chamber and the second hollow portion communicating with the outside of the outlet chamber. A metal-air battery system in which the inner electrode has through holes that connect the first hollow portion and the second hollow portion to the enclosed space formed by the inside of the inlet chamber, the inside of the outlet chamber, and the flow path.

21. The inner electrode is the positive electrode, and the outer electrode is the negative electrode. The inner electrode has a hollow portion formed in it that penetrates the inner electrode along the axis of the inner electrode. The metal-air battery system according to claim 1 or 2, wherein the hollow portion is configured to allow an oxygen-containing gas or the electrolyte in which oxygen is dissolved to flow through it.

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