Zinc negative electrode and method for producing the same, and secondary battery including the zinc negative electrode and method for producing the same

Abstract

Provided are: a zinc negative electrode having exceptional repeating resistance, and excellent charge / discharge cycling characteristics even at a high charge / discharge rate; a manufacturing method therefor; a secondary cell using the zinc negative electrode; and a manufacturing method therefor.　A zinc negative electrode used in a secondary cell, wherein the zinc negative electrode comprises: an active material part in which zinc is generated during charging, and oxidized zinc is generated during discharging, the zinc being used as a negative electrode active material; a collector that is electrically connected to the active material part; and a non-electron-conductive reaction space restriction part that is integrally formed with or connected to the collector and / or the active material part. The reaction space restriction part has a plurality of electrolyte-holding parts comprising a space that can hold a liquid electrolyte.

Description

[Technical Field]

[0001] The present invention relates to a zinc negative electrode, which is a negative electrode for a secondary battery, that produces zinc upon charging and zinc oxide upon discharging, a method for producing the same, a secondary battery including the zinc negative electrode, and a method for producing the secondary battery. [Background technology]

[0002] A secondary battery requires three components: a positive electrode, a negative electrode, and an electrolyte that connects them via ionic conduction. These components vary depending on the type of battery. For example, comparing the electrolytes of typical secondary batteries, the electrolyte of a lead-acid battery is an acidic aqueous solution of sulfuric acid, the electrolyte of a nickel-metal hydride battery is an alkaline aqueous solution such as a potassium hydroxide solution, and the electrolyte of a lithium-ion battery is an organic solvent or ionic liquid. The materials that react at the positive and negative electrodes of a secondary battery are called active materials (also called reactive active materials or electrode active materials). Comparing the negative electrode active materials of the three types of secondary batteries mentioned above, the negative electrode active material of a lead-acid battery is lead, the negative electrode active material of a nickel-metal hydride battery is hydrogen, and the negative electrode active material of a lithium-ion battery is lithium. Note that the negative electrode active materials mentioned here are examples of materials produced during charging of the negative electrode. When each battery is discharged, lead turns into lead sulfate, hydrogen turns into water, and lithium turns into lithium ions, respectively, resulting in the oxidation products. The term active material can refer to materials produced during charging, discharging, or both. In the following, the substance produced upon charging, i.e., the metal in the case of a metal negative electrode, is often exemplified as the active material. However, as mentioned above, the active material may also refer to the oxidation product of the metal produced upon discharge, or both the metal and the oxidation product of that metal, and these are not excluded in this specification.

[0003] The negative electrode of the aforementioned lithium-ion battery uses a matrix of graphite or other carbon materials, or a metal or metal oxide other than lithium, such as tin. During charging, lithium ions present in the electrolyte become lithium atoms on the negative electrode, and the lithium atoms are then absorbed into the matrix. In contrast, there are negative electrodes generally referred to as metal negative electrodes. However, charging of a metal negative electrode involves a reaction in which metal oxidation products are converted into metal, and metal atoms are actually precipitated and accumulated at the negative electrode. Because metal negative electrodes do not utilize the absorption of metal atoms into a matrix like lithium-ion batteries, their composition, structure, and reaction mechanism are significantly different from those of lithium-ion batteries.

[0004] Specific examples of secondary batteries that use metal anodes include zinc-air secondary batteries, zinc-nickel secondary batteries, and zinc-silver secondary batteries that use zinc anodes, and lithium-air secondary batteries and lithium-sulfur secondary batteries that use lithium anodes. All of these secondary batteries are still under development, and have not yet been put into practical use or commercialized, except for mechanical zinc-air secondary batteries. Mechanical zinc-air secondary batteries are charged by replacing the anode with a new zinc anode after discharging the zinc in the anode to zinc oxide, which is significantly different from the mechanism of secondary batteries, which are usually thought of as being charged by passing electricity through them.

[0005] More specifically, a metal anode is generally a combination of a current collector and an active material such as zinc or lithium. During charging, electrons flow from the current collector to the active material such as zinc or lithium, and during discharging, electrons flow from the active material to the current collector. The metal anode is electrically connected to an external circuit via the current collector.

[0006] As mentioned above, the metal atoms in a metal anode are not only reactants but also responsible for electronic conductivity between metal atoms and between the metal atoms and the current collector. Therefore, it is difficult to use all of the metal atoms as active material in a metal anode, and only a portion of them is usually used in the battery reaction. In the case of a zinc anode, which is a typical metal anode, when the electrolyte is an alkaline aqueous solution, the following two-step reaction occurs during discharge: Zn+4OH - →Zn(OH)4 2- +2e - ···(1) Zn(OH)4 2- →ZnO+H2O+2OH - ···(2) On the other hand, during charging, the opposite reaction occurs, that is, the following two-step reaction occurs: ZnO+H2O+2OH - →Zn(OH)4 2- ···(3) Zn(OH)4 2- +2e - →Zn+4OH - ···(4)

[0007] In the above formulas (1) and (2), Zn (solid) provides two electrons to the negative electrode, and Zn(OH)4 2- (ions), which dissolve in the alkaline aqueous solution that serves as the electrolyte, and then precipitate as ZnO (solid) on the negative electrode from the alkaline aqueous solution. On the other hand, the above formulas (3) and (4) show that Zn(OH)4 dissolved in the alkaline aqueous solution from ZnO 2- However, this shows that the cathode receives two electrons from the anode and precipitates as Zn (solid) on the anode.

[0008] Zinc anodes are widely known as metal anodes that are difficult to put into practical use due to their poor charge-discharge cycle characteristics. The cause of this is thought to be the influence of the ions in the reaction mechanism described above. Specifically, when a zinc anode is repeatedly charged and discharged, zinc precipitates locally during charging, and the precipitated zinc becomes dendrites (crystals that grow in a dendritic shape), which continue to grow toward the positive electrode. If they grow to reach the positive electrode, an internal short circuit occurs. This problem is well known as "internal short circuit due to dendrites (hereinafter referred to as dendrite short circuit)" in zinc anodes. In addition, whether charging or discharging, the reaction mechanism involves the deposition of Zn(OH)4 in an alkaline aqueous solution. 2-The exact effect of these ions is unclear, but in the case of commonly used plate-shaped zinc anodes, the distribution of zinc or zinc oxide in the two-dimensional direction on the anode surface becomes uneven with repeated charging and discharging, which reduces the proportion of zinc atoms available for charging and discharging, resulting in the problem of the amount of electricity that can be discharged decreasing with the number of cycles.

[0009] More specifically, it is widely known that repeated charge and discharge of a plate-shaped zinc negative electrode results in a heterogeneity of the active material (hereinafter referred to as "active material heterogeneity"), in which more active material accumulates in the center and less active material at the edges compared to the initial state. This heterogeneity of the active material results in the active material being thicker in the center of the negative electrode and thinner at the edges, promoting dendrite formation in the center. Furthermore, it is speculated that the increased thickness of the active material in the center makes it less likely for Zn and ZnO, which are located farther from the alkaline aqueous solution, i.e., present inside the thickened active material, to be used in the reaction. This is because, as shown in the above formulas (1) to (4), the reaction during both charge and discharge requires the Zn(OH)4 2- OH - This is because it is necessary.

[0010] In addition, lithium and magnesium anodes, which are metal anodes similar to zinc anodes, are also known to suffer from dendrite shorting and active material non-uniformity. Therefore, these two types of anodes, like zinc anodes, have a limited number of charge / discharge cycles and are therefore not suitable for practical use in secondary batteries.

[0011] As mentioned above, metal anodes have problems such as "dendrite short circuit" and "non-uniformity of active material," neither of which meet the requirements for anodes in secondary batteries. Therefore, various studies have been conducted to solve these problems, and information on the technologies that have been invented has been disclosed.

[0012] For example, Patent Document 1 discloses a negative electrode used in a zinc secondary battery, which contains titanium oxide and a zinc material that is at least one selected from the group consisting of zinc, zinc oxide, zinc alloys, and zinc compounds.

[0013] Furthermore, Patent Document 2 discloses an electrochemical cell useful for improving cycle life and performance such as energy and power, which includes a positive electrode, a negative electrode, and an ionically conductive and electronically insulating separator positioned between the positive and negative electrodes. In this electrochemical cell, the separator is described as managing and controlling dendrite formation in metal-based batteries such as lithium-based batteries, alkaline-based batteries, zinc-based batteries, and lead-based batteries.

[0014] Patent Document 3 also discloses a separator for a zinc negative electrode secondary battery, which has a central portion and a peripheral portion surrounding the outer periphery of the central portion, and at least a portion of the peripheral portion has a larger contact angle (based on the θ / 2 method) than the central portion.

[0015] Patent Document 4 discloses a method for producing a separator for a zinc negative electrode secondary battery, which includes an impregnation step of impregnating a nonwoven fabric with a dispersion containing a layered double hydroxide, and a drying step of drying the nonwoven fabric impregnated with the dispersion.

[0016] Furthermore, Patent Document 5 discloses a secondary battery that is expected to have increased capacity, has high stability during charging and discharging, and is free from the problem of short circuits due to zinc dendrites. The secondary battery comprises a positive electrode containing, as a positive electrode active material, a layered double hydroxide (LDH) containing, as a constituent element, at least one element selected from the group consisting of Ni, Fe, and Mn; a negative electrode containing, as a negative electrode active material, a layered double hydroxide (LDH) containing, as a constituent element, at least one element selected from the group consisting of Cu, Al, and Zn; and an alkaline electrolyte (liquid electrolyte) and / or a hydroxide ion-conductive solid electrolyte.

[0017] Furthermore, Patent Document 6 discloses a negative electrode structure for a zinc secondary battery that can ensure an efficient conduction path for hydroxide ions between positive and negative electrodes, improve space efficiency within the battery, and effectively prevent short circuits between the positive and negative electrodes due to zinc dendrites, and that includes a porous current collector plate made of porous metal, a negative electrode active material layer containing zinc and / or zinc oxide and provided on one side of the porous current collector plate, and a hydroxide ion conductive ceramic separator that is provided on the side of the porous current collector plate opposite the negative electrode active material layer and has high density defined by having no through holes or air permeability, and a zinc secondary battery using the same.

[0018] Furthermore, Patent Document 7 discloses a battery including a separator containing inorganic particles for preventing short circuits, from which the inorganic particles are unlikely to be detached.

[0019] Furthermore, Patent Document 8 discloses a zinc secondary battery having a separator structure including a hydroxide ion conductive separator, which can improve overcharge resistance while maintaining excellent separator characteristics that are effective in preventing short circuits caused by zinc dendrites.

[0020] Furthermore, Patent Document 9 discloses a secondary battery that efficiently includes multiple unit cells while reliably isolating positive and negative electrodes with a hydroxide ion conductive ceramic separator. The secondary battery includes a columnar porous substrate having multiple cell holes arranged parallel to each other from a first end face toward a second end face and / or from the second end face toward the first end face, positive electrodes and negative electrodes alternately arranged in the multiple cell holes, one for each hole or in each row of holes, a positive electrode internal current collector inserted in the positive electrode and extending to the first end face or the outer peripheral surface, a negative electrode internal current collector inserted in the negative electrode and extending to the second end face, the outer peripheral surface, or the first end face, hydroxide ion conductive ceramic separators formed on the inner wall surfaces of the cell holes and isolating the positive electrode and / or the negative electrode from the porous substrate, and a liquid electrolyte.

[0021] In addition, Patent Document 10 discloses a separator for a zinc secondary battery that can effectively suppress short circuits caused by zinc dendrites, which is a separator for a zinc secondary battery that selectively passes hydroxide ions between the positive and negative electrodes of the zinc secondary battery, and converts hydroxide ions into zinc complex ions Zn(OH)4 by the molecular sieve effect. 2- A separator for a zinc secondary battery is disclosed, which comprises a porous membrane having pores that allow separation of a zinc secondary battery from a zinc oxide.

[0022] Furthermore, Patent Document 11 discloses a separator structure that can reliably separate the positive electrode side and the negative electrode side of a zinc secondary battery, which includes a ceramic separator made of an inorganic solid electrolyte body, which has hydroxide ion conductivity but no gas permeability, and an outer peripheral member that is provided along the periphery of the ceramic separator and is made of at least one of a resin outer frame and a resin film, and which is no longer gas permeable as a whole.

[0023] Furthermore, Patent Document 12 discloses a multilayer porous separator for isolating the positive and negative electrodes of a secondary battery as a porous separator that can more effectively suppress or delay the extension of dendrites and the resulting short circuit between the positive and negative electrodes in a secondary battery, the multilayer porous separator comprising first and third layers that are spaced apart and opposite each other and made of porous ceramics, and a second layer that is provided between the first and third layers and made of porous ceramics with more pores than the first and third layers and / or space.

[0024] Furthermore, Patent Document 13 discloses a separator and battery that can suppress shape changes in active materials that occur with long-term use of the battery, and the separator is used in the battery and has a multilayer structure including an insulating layer and a conductive layer, and a battery that includes the separator, electrodes, and an electrolyte.

[0025] Furthermore, Patent Document 14 discloses a secondary battery that can more reliably achieve a longer life than conventional secondary batteries. The secondary battery has a separator and an aqueous electrolyte disposed in a region sandwiched between the surfaces of the positive and negative electrodes, the separator has particulate active material (noble potential active material particles Am) that has a potential nobler than the potential of the negative electrode so that the active material particles Am of the separator are present along the surface of the separator, and the noble potential active material particles Am of the separator decompose dendrites.

[0026] Furthermore, Patent Document 15 discloses a negative electrode material for metal secondary batteries in which dendrite formation is suppressed, which is characterized in that the negative electrode material for metal secondary batteries is formed by supporting metal oxide nanosheets on a carbon-based conductive support, and the metal of the metal oxide is titanium, ruthenium, or niobium.

[0027] Furthermore, Patent Document 16 discloses a zinc negative electrode mixture for forming a battery negative electrode that is economical, safe, and has excellent battery performance, the zinc negative electrode mixture containing a zinc-containing compound and a conductive additive, wherein the zinc-containing compound and / or the conductive additive contain particles having an average particle diameter of 1000 μm or less and / or particles having an aspect ratio (length / width) of 1.1 or more.

[0028] Furthermore, Patent Document 17 discloses a separator system for electrochemical systems that provides electronic, mechanical, and chemical properties useful for various applications including electrochemical energy storage and conversion. For example, it is described as providing structural, physical, and electrostatic properties useful for managing and controlling dendrite formation in lithium and zinc-based batteries, and for improving the cycle life and rate capability of electrochemical cells such as silicon anode-based batteries, air cathode-based batteries, and redox flow batteries.

[0029] Furthermore, Patent Document 18 and Non-Patent Document 1 disclose that a zinc electrode for a secondary battery, which is composed of a network of zinc sponge having voids and has a zinc oxide shell formed on the surface of the zinc, has improved cycle characteristics.

[0030] Furthermore, Patent Document 19 discloses a method of coating the surfaces of zinc particles with a metal oxide (Ti oxide, Zr oxide, etc.).

[0031] Furthermore, Patent Document 20 discloses a metal-air secondary battery that uses conductive oxide ceramics as a diaphragm to suppress metal dendrite short-circuiting.

[0032] Furthermore, Patent Document 21 discloses an ion-conductive film and a secondary battery in which the film is integrated with a zinc negative electrode.

[0033] Patent Document 22 discloses a metal electrode cartridge comprising a metal electrode, a separator covering at least a portion of the metal electrode, and a support covering at least a portion of the separator, the separator being ion-permeable, the support having an opening at a position where it overlaps the separator, and the Young's modulus of the support being greater than that of the separator. Patent Document 22 shows results from one charge / discharge cycle showing that a structure with a support suppresses deflection of the metal electrode compared to a structure without a support, but this result is a comparison of the amount of deflection before and after only one charge / discharge cycle, and does not show results on charge / discharge cycle characteristics. Furthermore, the effect of suppressing dendrite formation or uneven reaction distribution in the zinc electrode is neither explicitly nor implicitly mentioned.

[0034] Furthermore, Non-Patent Document 2 discloses an electrolyte solution in which the solubility of zinc is reduced by using various additives in order to suppress zinc dendrites.

[0035] Furthermore, Non-Patent Document 3 discloses zinc dissolution by surface treatment with an anion exchange membrane or the like, with the aim of suppressing zinc dendrites.

[0036] Furthermore, Non-Patent Document 4 discloses a concentrated aqueous carbonate solution as an electrolyte solution in which the solubility of zinc is reduced.

[0037] Furthermore, Non-Patent Document 5 discloses the suppression of dendrite precipitation by controlling zinc diffusion using a nanoporous electrode. [Prior art documents] [Patent documents]

[0038] [Patent Document 1] Japanese Patent Application Publication No. 2019-21518 [Patent Document 2] Japanese Patent Application Publication No. 2019-16602 [Patent Document 3] Japanese Patent Application Publication No. 2018-147739 [Patent Document 4] Japanese Patent Application Publication No. 2018-147738 [Patent Document 5] Japanese Patent Application Publication No. 2018-133324 [Patent Document 6] Japanese Patent Application Publication No. 2018-26205 [Patent Document 7] International Publication No. 2017 / 183633 [Patent Document 8] Japanese Patent Application Publication No. 2017-091949 [Patent Document 9] Japanese Patent Application Laid-Open No. 2016-201199 [Patent Document 10] Japanese Patent Application Laid-Open No. 2016-194990 [Patent Document 11] Japanese Patent Application Laid-Open No. 2016-189356 [Patent Document 12] Japanese Patent Application Laid-Open No. 2016-170944 [Patent Document 13] Japanese Patent Application Laid-Open No. 2016-146263 [Patent Document 14] Japanese Patent Application Laid-Open No. 2014-222570 [Patent Document 15] International Publication No. 2014 / 069541 [Patent Document 16] Japanese Patent Application Laid-Open No. 2014-026951 [Patent Document 17] Special Publication No. 2015-519686

Patent Document 18

Patent Document 19

Patent Document 20

Patent Document 21

Patent Document 22

Non - Patent Document

[0039]

Non - Patent Document 1

Non - Patent Document 2

Non - Patent Document 3

Non - Patent Document 4

Non - Patent Document 5

Summary of the Invention

[0040] While Patent Document 22 relates to a technology aimed at suppressing deformation of metal electrodes, the other documents, Patent Documents 1 to 21 and Non-Patent Documents 1 to 5, have attempted to address the problems of "dendrite shorting" and "non-uniform active material" in zinc or other metal negative electrodes. However, the technologies developed to date for zinc negative electrodes and secondary batteries using zinc negative electrodes have not been able to fully resolve these problems. That is, no zinc negative electrode has been obtained that has sufficient durability against charge-discharge cycles for use in secondary batteries. Furthermore, even improving the electrolyte has not been able to fully suppress dendrite shorting in zinc negative electrodes. Furthermore, even when results have been obtained regarding changes in voltage and capacity with respect to charge-discharge cycles of zinc negative electrodes, even for hundreds of cycles or more, the results were obtained under charge-discharge test conditions that involved very low charge-discharge rates or very low current densities (current divided by the area of ​​the negative electrode). That is, the zinc anode is charged at a current of 1 C or more (1 C is also called the 1-hour rate, and corresponds to the current at which the battery capacity or anode capacity is charged or discharged in 1 hour. For example, if the battery capacity is 1 Ah, 1 C means that the battery is charged or discharged at a current of 1 A.) or 10 mA / cm 2Even under the conditions of operation at such high charge / discharge rates or current densities, results showed that battery capacity did not decrease or charge / discharge voltage did not change significantly even after several thousand cycles. Furthermore, separators developed to suppress dendrite shorting did not effectively suppress dendrite formation, and thus the suppression effect of dendrite formation deteriorated over time. Furthermore, because dendrite shorting and active material homogenization are particularly likely to occur at high current densities and high charge / discharge rates, operation at high current densities and high charge / discharge rates, as well as changes in operating current, such as from low current density to high current density (low rate to high rate) or vice versa, must be avoided to avoid these problems, making the battery unusable for applications requiring such operation. While the technology in Patent Document 22 requires a separator, separators (including gelled electrolytes) cannot suppress dendrite formation or non-uniform reaction distribution, and this technology also suffers from similar problems. As described above, zinc negative electrodes are required to have excellent durability against repeated charge and discharge, and such excellent durability is also required to be achieved at a high charge and discharge rate, but there has been a problem that no zinc negative electrode capable of achieving these properties exists. Also, as described above, zinc negative electrodes are required to have excellent durability against repeated charge and discharge, and such excellent durability is also required to be achieved at a high charge and discharge rate, but there has been a problem that no method for producing a zinc negative electrode capable of achieving these properties exists.

[0041] On the other hand, among the various anodes used in secondary batteries, zinc anodes have the potential to achieve higher capacity densities than non-metal anodes. The capacity density of a metal anode is calculated by dividing the theoretical capacity, calculated from the weight of the metal used using Faraday's law, by the weight or volume of the metal, and is expressed in units of Ah / kg or Ah / L. In secondary batteries, high capacity densities are desirable for the reactants in the anode and cathode. This is because the energy density of a battery is calculated as (discharge voltage) × (capacity density). Using active materials with higher capacity densities, not just discharge voltage, increases the energy density. While zinc and lithium are known to have higher theoretical capacity densities than other metals, as mentioned above, their poor charge-discharge cycle characteristics when used in secondary batteries have led to the poor charge-discharge cycle characteristics of secondary batteries using zinc anodes. In secondary batteries using zinc anodes, the cathode and anode are separated by a separator or a ceramic solid electrolyte supporting layered double hydroxides or metal oxides to prevent dendrite shorting and non-uniformity of the active material. This results in an increase in the weight and volume of the battery as a whole, which reduces the energy density. 2-However, reducing the solubility of zinc or coating the zinc anode with ion-conductive materials or metal oxides limits the charge / discharge rate. Furthermore, the formation of dendrites and uneven active material reduces the area of ​​the anode active material that can actually participate in the reaction, resulting in significant changes in battery resistance with charging and discharging or with the SOC (State of Charge, also called the charge rate; for example, 100% SOC refers to a fully charged state, while 0% refers to a fully discharged state. 50% means that half of the battery capacity is charged. When discharging from a fully charged state with a 100% SOC, the SOC reaches 50% when half the battery capacity is discharged, and when half the battery capacity is further discharged, the SOC reaches 0%. When charging from a 0% SOC, the SOC changes depending on the amount of charge, eventually reaching 100%.) Furthermore, in secondary battery applications, in addition to always charging and discharging at a constant current, there are also cases where the charge / discharge rate needs to be changed during operation. For example, applications such as hybrid vehicles, plug-in hybrid vehicles, electric vehicles, power supplies for preventing momentary power outages, emergency power supplies, and power stabilization systems require instantaneous high-power output. However, secondary batteries using zinc negative electrodes face the challenge of switching from low-rate discharge to high-rate discharge because this can promote dendrite shorting and active material heterogeneity. Furthermore, even if high-rate discharge is performed, the battery resistance changes, making it difficult to instantly restore the voltage before high-rate discharge, resulting in poor responsiveness to rate changes during discharge. These same challenges apply to charging, where high-rate charging is difficult because it can promote dendrite shorting and active material heterogeneity. Furthermore, it is difficult to instantly restore the voltage before high-rate charging, resulting in poor responsiveness to rate changes during charging. While the above-mentioned issues are secondary battery issues arising from the zinc negative electrode, zinc-air secondary batteries can also have issues arising from the air electrode (positive electrode) as well as the zinc negative electrode. Below, we will explain examples of issues that can arise from this air electrode. For example, the air electrode is a porous electrode, and oxygen reduction occurs within it during discharge and oxygen generation during charge. However, high resistance to these reactions results in low battery discharge voltage and high battery charge voltage. Another issue is low current efficiency, expressed as discharge voltage / charge voltage. Furthermore, the current density at which discharge and charge are possible at the air electrode is limited, limiting the current density or charge / discharge rate during operation of the zinc-air secondary battery. Even if the charge / discharge cycle characteristics of the zinc negative electrode are good, the charge / discharge cycle characteristics of the air electrode limit the number of charge / discharge cycles that can be used in the zinc-air secondary battery. As mentioned above, the air electrode is a porous electrode, and is generally fabricated by kneading, forming by rolling, or the like, and then firing a conductive material, catalyst, and water-repellent material. The conductive material maintains the electronic conductivity of the entire cathode, and the voids between the conductive material serve as a pathway for oxygen to be supplied from the outside or for oxygen generated within the cathode to be released to the outside. The catalyst, typically 1 / 10 to 1 / 1000 the size of the conductive material, is supported on the conductive material and is expected to function as a reaction site for oxygen reduction and oxygen generation. Furthermore, water-repellent materials, such as PTFE (polytetrafluoroethylene), are smaller than the conductive material. Their presence on or near the surface of the conductive material prevents alkaline aqueous solutions from penetrating into the voids, thereby creating the oxygen pathways necessary for oxygen reduction and oxygen generation. The limitations on the operational current density and cycle performance of the cathode are strongly influenced by the mixing and dispersion of the conductive material, catalyst, and water-repellent material within the cathode, as well as the resulting void state. To overcome the limitations on current density and cycle performance caused by the cathode, it is necessary to optimize the internal structure of the cathode. However, there has been no method for fabricating zinc-air secondary batteries that can address these issues. [Means for solving the problem]

[0042] In order to solve the above problems, the present inventors have conducted extensive research and come up with the idea of ​​restricting the reaction space between the zinc negative electrode and the air electrode, and have completed the zinc negative electrode of the present invention, a method for manufacturing the zinc negative electrode, a secondary battery including the zinc negative electrode, and a method for manufacturing the secondary battery. That is, the gist of the present invention is as follows.

[0043] The zinc negative electrode used in the secondary battery according to the present invention comprises an active material portion in which zinc is used as a negative electrode active material, which generates zinc during charging and generates zinc oxide during discharging, a current collector electrically connected to the active material portion, and a non-electron-conductive reaction space restricting portion integrally formed with or connected to the current collector and / or the active material portion, and the reaction space restricting portion has a plurality of electrolyte retention portions each consisting of a space capable of retaining a liquid electrolyte.

[0044] In the method for producing a zinc negative electrode for use in a secondary battery according to the present invention, the zinc negative electrode comprises an active material portion in which zinc is used as a negative electrode active material, which produces zinc upon charging and zinc oxide upon discharging, a current collector electrically connected to the active material portion, and a non-electron-conductive reaction space restricting portion integrally formed with or connected to the current collector and / or the active material portion, wherein the reaction space restricting portion has a plurality of electrolyte retention portions formed of spaces capable of retaining a liquid electrolyte, and the method includes the steps of integrally forming or connecting the current collector and the non-electron-conductive reaction space restricting portion, and electrically connecting the active material portion and the current collector.

[0045] The secondary battery according to the present invention includes the zinc negative electrode or the zinc negative electrode obtained by the method for producing a zinc negative electrode, and also includes an air electrode and the liquid electrolyte containing an alkaline aqueous solution, The electrolyte retention portion in the zinc negative electrode can retain the liquid electrolyte between the air electrode and the active material portion.

[0046] In a method for producing a secondary battery according to the present invention, the zinc negative electrode comprises an active material part in which zinc is used as a negative electrode active material, which produces zinc upon charging and zinc oxide upon discharging, a current collector electrically connected to the active material part, and a non-electron-conductive reaction space restricting part integrally formed with or connected to the current collector and / or the active material part, and the reaction space restricting part has a plurality of electrolyte retention parts formed of spaces capable of retaining a liquid electrolyte, and the method includes the steps of integrally forming or connecting the current collector and the non-electron-conductive reaction space restricting part, electrically connecting the active material part and the current collector, and forming an air electrode, wherein the air electrode is composed of an air electrode current collector, a conductive material, a catalyst, and a water-repellent material, and the step of forming the air electrode further includes a mixing step of mixing the conductive material, the catalyst, and the water-repellent material, and a molding step of molding the mixture obtained in the mixing step into an air electrode of a predetermined shape. [Effects of the Invention]

[0047] The zinc negative electrode and the method for producing the same of the present invention have the following effects. The zinc anode of the present invention suppresses dendrite short-circuiting, thereby preventing dendrites from reaching the positive electrode at the beginning of the charge-discharge cycle, rendering the secondary battery unusable. Since it is not necessary to reduce the solubility of metal ions or use a solid electrolyte that does not allow dendrites to pass through, the zinc anode of the present invention allows charging and discharging at high charge-discharge rates without increasing the weight or volume of the battery. Furthermore, the zinc anode of the present invention suppresses active material non-uniformity, thereby preventing a decrease in current efficiency and a decrease in battery capacity caused by active material non-uniformity even after repeated charge-discharge. The suppression of active material non-uniformity prevents a local increase in active material thickness from the initial state, which can cause dendrite short-circuiting. The suppression of active material non-uniformity suppresses a decrease in negative electrode capacity and battery capacity with increasing charge-discharge cycles. Therefore, in order to meet the product specifications required for the negative electrode and battery, it is not necessary to manufacture a negative electrode with an excess amount of active material relative to the battery capacity, or the excess amount of negative electrode active material can be minimized. In addition, since dendrite short-circuiting and non-uniformity of the active material are suppressed, it has the effect of enabling operation at high current densities and large charge / discharge rates, and of adapting to usage in which the operating current is changed, such as from low current density to high current density (from low rate to high rate) or vice versa. Furthermore, according to the method for producing a zinc anode of the present invention, a zinc anode having the above-mentioned excellent effects can be produced with a few steps, at low cost, and by a simple production technique, and continuous production for mass production is also possible. Furthermore, the method for producing a zinc anode of the present invention can include an oxidation step of converting zinc, which is an active material, into its oxidation product, and has the effect of providing a zinc anode having the above-mentioned excellent effects as a zinc anode suitable for producing a battery from a discharged state.

[0048] Furthermore, the secondary battery of the present invention, which achieves the above-described effects on zinc negative electrodes, has the effect of producing secondary batteries with excellent charge-discharge cycle characteristics, even in secondary batteries using zinc negative electrodes that have not yet been put to practical use. Furthermore, the improved charge-discharge cycle characteristics of secondary batteries using zinc negative electrodes result in secondary batteries that can exhibit high energy density and high power density. Furthermore, the present invention has the effect of suppressing changes in battery resistance relative to SOC during charge and discharge. Furthermore, the present invention enables operation at different charge-discharge rates, such as from low-rate discharge or charge to high-rate discharge or charge, and vice versa, and enables instantaneous recovery to the voltage before high-rate discharge or charge, thereby improving responsiveness to rate changes during charge and discharge. These effects can be obtained not only in zinc-nickel secondary batteries, but also in various other secondary batteries, such as zinc-air secondary batteries and zinc-silver secondary batteries. Furthermore, the method for producing a secondary battery of the present invention has the advantage that a secondary battery having the above-described excellent effects can be produced with a few steps, at low cost, and by a simple production technique, and that continuous production for mass production is also possible.Furthermore, the method for producing a secondary battery having the above-described excellent effects can be produced not only from a charged state but also from a discharged state. [Brief explanation of the drawings]

[0049] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a zinc negative electrode according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of a secondary battery including the zinc negative electrode shown in FIG. [Figure 3] FIG. 2 is a first example of a shape diagram of a reaction space restricting portion in a zinc negative electrode according to one embodiment of the present invention. [Figure 4] FIG. 2 is a second example of a shape diagram of a reaction space restricting portion in a zinc negative electrode according to one embodiment of the present invention. [Figure 5] FIG. 10 is a third example of a shape diagram of a reaction space restricting portion in a zinc negative electrode according to one embodiment of the present invention. [Figure 6]FIG. 10 is a fourth example of a shape diagram of a reaction space restricting portion in a zinc negative electrode according to one embodiment of the present invention. [Figure 7] FIG. 5 is a fifth example of a shape diagram of a reaction space restricting portion in a zinc negative electrode according to one embodiment of the present invention. [Figure 8] FIG. 6 is a sixth example of a shape diagram of a reaction space restricting portion in a zinc negative electrode according to one embodiment of the present invention. [Figure 9] FIG. 7 is a seventh example of a shape diagram of a reaction space restricting portion in a zinc negative electrode according to one embodiment of the present invention. [Figure 10] FIG. 10 is an eighth example of a shape diagram of a reaction space restricting portion in a zinc negative electrode according to one embodiment of the present invention. [Figure 11] FIG. 1 is a flow diagram illustrating a first example of a method for producing a zinc negative electrode according to one embodiment of the present invention. [Figure 12] FIG. 2 is a flow diagram illustrating a second example of a method for making a zinc negative electrode in accordance with one embodiment of the present invention. [Figure 13] FIG. 1 is a flow diagram illustrating a third example of a method for producing a zinc negative electrode in accordance with one embodiment of the present invention. [Figure 14] FIG. 10 is a flow diagram illustrating a fourth example of a method for producing a zinc negative electrode according to one embodiment of the present invention. [Figure 15] FIG. 2 is a diagram showing the shape of a copper plate used as a current collector for a zinc negative electrode in the examples. [Figure 16] This is a diagram showing the shape of the copper plate current collector shown in FIG. 15 after it has been zinc-plated and then masked except for one circular zinc-plated area with a diameter of 20 mm. [Figure 17] Continuing from Figure 16, this figure shows the shape after masking was performed except for the four circular zinc-plated areas with a diameter of 5 mm. [Figure 18] FIG. 1 is a diagram showing the configuration of a cell of a zinc-nickel secondary battery used in Example 1. [Figure 19] FIG. 1 is a graph showing the relationship between the discharge voltage and charge voltage and the number of cycles of the zinc-nickel secondary battery of Example 1. [Figure 20] FIG. 1 is a graph showing the relationship between the current efficiency and the number of cycles of the zinc-nickel secondary battery of Example 1. [Figure 21] FIG. 2 is a diagram showing the shape of a separator used in the zinc-nickel secondary battery of Comparative Example 1. [Figure 22] FIG. 1 is a graph showing the relationship between the discharge voltage and charge voltage and the number of cycles of the zinc-nickel secondary battery of Comparative Example 1. [Figure 23] FIG. 1 is a graph showing the relationship between the current efficiency and the number of cycles of the zinc-nickel secondary battery of Comparative Example 1. [Figure 24] 10 is a graph showing the relationship between the discharge curve and the number of cycles of the zinc-nickel secondary battery of Comparative Example 2. FIG. [Figure 25] 10 is a diagram showing the relationship between the charge curve and the number of cycles of the zinc-nickel secondary battery of Comparative Example 2. FIG. [Figure 26] 1 is a photograph of the negative electrode side of the nonwoven fabric taken out after the charge-discharge test of the zinc-nickel secondary battery of Comparative Example 2 was completed. [Figure 27] 1 is a photograph of the positive electrode side of the nonwoven fabric taken out after completing the charge-discharge curve of the zinc-nickel secondary battery of Comparative Example 2. [Figure 28] 1 is a photograph of the surface of the negative electrode after 30 cycles of charge and discharge under the same conditions as in Example 1. [Figure 29] 1 is a photograph of the surface of the negative electrode after 30 cycles of charge and discharge under the same conditions as in Comparative Example 1. [Figure 30] 1 is a photograph of the lower part of the negative electrode surface after 30 cycles of charge and discharge under the same conditions as in Comparative Example 1. [Figure 31] 10 is a photograph of the surface of the negative electrode after the charge-discharge test in Comparative Example 2. [Figure 32] FIG. 10 is a diagram showing the shape of the reaction space restricting portion used in the zinc negative electrode of Example 2. [Figure 33] FIG. 10 is a graph showing the relationship between the discharge voltage and charge voltage and the number of cycles of the zinc-nickel secondary battery of Example 2. [Figure 34] FIG. 10 is a graph showing the relationship between the current efficiency and the number of cycles of the zinc-nickel secondary battery of Example 2. [Figure 35] FIG. 10 is a graph showing the relationship between the discharge voltage and charge voltage and the number of cycles of the zinc-nickel secondary battery of Example 3. [Figure 36]FIG. 10 is a graph showing the relationship between the current efficiency and the number of cycles of the zinc-nickel secondary battery of Example 3. [Figure 37] FIG. 10 is a graph showing the relationship between the discharge voltage and charge voltage and the number of cycles for the zinc-nickel secondary battery of Example 4. [Figure 38] FIG. 10 is a graph showing the relationship between the current efficiency and the number of cycles of the zinc-nickel secondary battery of Example 4. [Figure 39] FIG. 10 is a diagram showing the configuration of a cell of a zinc-nickel secondary battery used in Example 5. [Figure 40] FIG. 10 is a graph showing the relationship between the discharge voltage and charge voltage and the number of cycles for the zinc-nickel secondary battery of Example 5. [Figure 41] FIG. 10 is a graph showing the relationship between the current efficiency and the number of cycles of the zinc-nickel secondary battery of Example 5. [Figure 42] FIG. 10 is a graph showing the relationship between the discharge voltage and charge voltage and the number of cycles for the zinc-nickel secondary battery of Example 6. [Figure 43] FIG. 10 is a graph showing the relationship between the current efficiency and the number of cycles of the zinc-nickel secondary battery of Example 6. [Figure 44] FIG. 1 is a structural diagram showing an example of a zinc negative electrode applicable to the present invention. [Figure 45] FIG. 10 is a diagram showing the shape of the reaction space restricting portion used in the zinc negative electrode of Example 7. [Figure 46] FIG. 10 is a graph showing the relationship between the battery voltage and the discharge rate of the zinc-nickel secondary battery of Example 7. [Figure 47] FIG. 10 is a graph showing the relationship between the battery voltage and the charge rate of the zinc-nickel secondary battery of Example 7. [Figure 48] FIG. 10 is a diagram showing the shape of a partially masked copper plate used in Example 8. [Figure 49] FIG. 10 is a diagram showing the shape of the reaction space restricting portion used in the zinc negative electrode of Example 8. [Figure 50] FIG. 10 is a diagram showing the configuration of a cell of a zinc-air secondary battery used in Example 8. [Figure 51] FIG. 10 is a graph showing the relationship between the battery voltage and the discharge rate of the zinc-air secondary battery of Example 8. [Figure 52]FIG. 10 is a graph showing the relationship between the battery voltage and the charge rate of the zinc-air secondary battery of Example 8. [Figure 53] FIG. 10 is a diagram showing the configuration of a cell of a zinc-air secondary battery used in Example 9. [Figure 54] FIG. 10 is a graph showing the relationship between the battery voltage and the discharge rate of the zinc-air secondary battery of Example 9. [Figure 55] FIG. 10 is a graph showing the relationship between the battery voltage and the charge rate of the zinc-air secondary battery of Example 9. [Figure 56] FIG. 10 is a graph showing the relationship between the discharge voltage and charge voltage and the number of cycles for the zinc-nickel secondary battery of Example 10. [Figure 57] FIG. 10 is a graph showing the relationship between the current efficiency and the number of cycles of the zinc-nickel secondary battery of Example 10. DETAILED DESCRIPTION OF THE INVENTION

[0050] (zinc anode) A zinc negative electrode according to one embodiment of the present invention is a zinc negative electrode for use in a secondary battery, and comprises an active material portion in which zinc is used as a negative electrode active material, which produces zinc upon charging and zinc oxide upon discharging, a current collector electrically connected to the active material portion, and a non-electron-conductive reaction space restricting portion integrally formed with or connected to the current collector and / or the active material portion, and the reaction space restricting portion has a plurality of electrolyte retention portions consisting of spaces capable of retaining a liquid electrolyte.

[0051] Such a zinc negative electrode can have, for example, multiple recesses, with the negative electrode active material exposed at at least a portion of the bottom surface of each recess, and the sidewalls of each recess can be made of a non-electron-conductive material. In battery fabrication, an electrolyte is injected into the multiple recesses of the zinc negative electrode and a positive electrode is placed to cover the recesses, enabling charge / discharge reactions in each recess. In this case, the space in which the charge / discharge reactions occur is divided into multiple sections by non-electron-conductive sidewalls, thereby restricting the reaction space. The following descriptions of the reaction space restricting section and the method for fabricating a zinc negative electrode can be applied to the formation of the sidewalls and bottom surface of the recesses. The negative electrode active material exposed at the bottom surface can be part of an active material section electrically connected to a current collector. In this case, the following descriptions of the active material section and the current collector can be applied.

[0052] A specific example of the structure of a zinc negative electrode 10 will be described with reference to the schematic cross-sectional views of FIGS. 1 and 2. The zinc negative electrode 10 illustrated in FIG. 1 includes an active material portion 110, a current collector 120 electrically connected to the active material portion 110, and a non-electron-conductive reaction space restricting portion 130 integrally formed with the current collector 120 and the active material portion 110. The reaction space restricting portion 130 includes a plurality of electrolyte retention portions 132a, 132b each of which is a space capable of retaining a liquid electrolyte 50 (see FIG. 2). In other words, the "electrolyte retention portion" in the reaction space restricting portion is a space capable of retaining a liquid electrolyte. Each of the electrolyte retention portions 132a, 132b can be formed by punching out a main body portion 131 of the reaction space restricting portion 130, as will be described in detail below. In the zinc negative electrode 10, one side of each of the electrolyte retention portions 132a, 132b is blocked by the active material portion 110, and the other side is open. FIG. 2 shows an example of a secondary battery 90 including the zinc negative electrode 10 shown in FIG. 2. The secondary battery 90 shown in FIG. 2 includes at least the zinc negative electrode 10, a liquid electrolyte 50, and a positive electrode 60. In the secondary battery 90, the liquid electrolyte 50 is held in the respective spaces of the electrolyte holding portions 132a and 132b. The space between the positive electrode 60 and the zinc negative electrode 10 corresponds to the electrolyte holding portions 132a and 132b. However, the zinc negative electrode 10 described with reference to FIGS. 1 and 2 is merely one example. In the secondary battery 90, it is also preferable that the contact surface of the reaction space-restricting portion 130 with the positive electrode 60 be smooth so that the zinc negative electrode 10 can contact the positive electrode 60 in the reaction space-restricting portion 130. Furthermore, the reaction space-restricting portion 130 can hold the liquid electrolyte 50 in the electrolyte holding portions 132a and 132b, while being made of an impermeable material that prevents the liquid electrolyte 50 from permeating into the main body portion 131.

[0053] An embodiment of the present invention including the above specific example will be described, including its effects. Note that the following example does not exclude an active material part including a negative electrode active material made of zinc oxide, which is an oxidation product of zinc, nor does it exclude an active material part including a negative electrode active material made of both zinc and zinc oxide. The active material part of the zinc negative electrode of the present invention can thus include a negative electrode active material made of zinc or zinc oxide, or both.

[0054] First, in the active material section, zinc is produced during charging, and zinc oxide, an oxidation product of zinc, is produced during discharging. The reaction between zinc and zinc oxide requires the addition of zincate ions, Zn(OH)4 2- The active material portion in the zinc negative electrode is electrically connected to a current collector, such as a copper plate or copper mesh, by deposition, accumulation, or the like on the current collector using a chemical, electrochemical, mechanical, or other method. The zinc negative electrode has a non-electron-conductive reaction space restricting portion integrally formed with or connected to the current collector and / or the active material portion. The reason why the reaction space restricting portion is non-electron-conductive is to prevent internal short-circuiting even if the reaction space restricting portion comes into contact with the positive electrode. Furthermore, in the case of a zinc-air secondary battery using a zinc negative electrode and a potassium hydroxide aqueous solution, the reaction space restricting portion has a plurality of electrolyte retention portions each consisting of a space capable of retaining the potassium hydroxide aqueous solution.

[0055] <Reaction space control part> Specific examples of thin plate-like members applicable to a reaction space-restricting part having such an electrolyte retention part will be described in more detail with reference to Figures 3 to 10, which are schematic diagrams of the reaction space-restricting part extracted from the zinc negative electrode. In the following reaction space-restricting parts, the last two digits of the three-digit number refer to the same type of configuration, and duplicated explanations will be omitted.

[0056] <<First Example of Reaction Space Restricting Portion>> The reaction space-restricting portion 230 in FIG. 3 has a thin plate-like outer shape and four circular through-holes (cylindrical structures) punched out of the main body portion 231. In this example, these through-holes constitute electrolyte retention portions 232a, 232b, 232c, and 232d. Note that the term "through-hole" here refers to the fact that the reaction space-restricting portion 230 penetrates from front to back when viewed as a single component. As explained with reference to FIGS. 1 and 2, one side of the reaction space-restricting portion is blocked in the zinc negative electrode as a whole. In this example, each electrolyte retention portion has a circular cross-sectional shape in a plane parallel to the blocked surface. One flat portion of the reaction space-restricting portion 230 in FIG. 3 is integrally formed with or connected to the current collector and / or zinc active material portion. When used as a secondary battery, a positive electrode can be placed on the flat portion opposite the flat portion, and the electrolyte retention portion is filled with liquid electrolyte.

[0057] <<Second Example of Reaction Space Restricting Portion>> As in Figure 3, the reaction space-restricting unit 330 in Figure 4 has electrolyte retention units 332a, 332b, 332c, and 332d formed by four through-holes with circular cross sections. Furthermore, the left and right upper and lower electrolyte retention units 332a, 332c and 332b, 332d, each have communication holes 333a and 333b that connect them. Furthermore, in the reaction space-restricting unit 330 in Figure 4, each electrolyte retention unit is connected to the end of the reaction space-restricting unit 330 (the side surface of the main body 331 in the vertical direction in the drawing) by opening holes 334a, 334b, 334c, and 334d, respectively, on the side opposite communication holes 333a and 333b. The communication holes allow liquid electrolyte to be transferred from one electrolyte retention unit to another, facilitating the same amount of liquid electrolyte being retained in multiple electrolyte retention units. For example, in a horizontally oriented secondary battery as shown in Figure 2, the presence of communicating holes facilitates leveling of the liquid electrolyte held in multiple electrolyte holding sections, making it easier to add the required amount of liquid electrolyte. Furthermore, the presence of openings allows the liquid electrolyte to be introduced into the electrolyte holding sections through the openings without having to be directly introduced into the electrolyte holding sections. For example, in a vertically oriented secondary battery as shown in Figure 2, the presence of openings allows the liquid electrolyte to be introduced through the openings at the top, making it easier to add the required amount of liquid electrolyte to multiple electrolyte holding sections. Furthermore, providing both communicating holes and openings simultaneously achieves the above-described effects, making it easier to retain the liquid electrolyte in the electrolyte holding sections. For example, there is an advantage in that the liquid electrolyte can be filled into the electrolyte holding sections after the zinc negative electrode and positive electrode are brought into contact via the reaction space-restricting section. In Figure 4, the communicating holes 333a and 333b may be grooves (communicating grooves) that are open at the top or bottom. These grooves form spaces between the positive electrode and the metal negative electrode, forming communicating holes. Furthermore, the openings 334a, 334b, 334c, and 334d may be grooves (open grooves) that are open at the top or bottom. These grooves form spaces between the positive electrode or the metal negative electrode, thereby forming openings.However, when a space is formed between the zinc negative electrode and the zinc negative electrode, the part of the zinc negative electrode that coincides with the groove (communicating groove or open groove) may be designed so that the negative electrode active material is not exposed, and for example, this part may be sealed.

[0058] <<Third Example of Reaction Space Restricting Portion>> 5 has five electrolyte retention portions 432a, 432b, 432c, 432d, and 432e. The electrolyte retention portions 432a, 432b, 432c, and 432d have the same diameter, and the central electrolyte retention portion 432e is formed by a through-hole with a circular cross section and a smaller diameter than the surrounding four electrolyte retention portions.

[0059] <<Fourth Example of Reaction Space Restricting Portion>> The reaction space restricting portion 530 of FIG. 6 has electrolyte retention portions 532a, 532b, 532c, and 532d, communication holes 533a and 533b, and opening holes 534a, 534b, 534c, and 534d, similar to the reaction space restricting portion 330 of FIG. 4. However, while the electrolyte retention portions 332a, 332b, 332c, and 332d of FIG. 4 are formed as through-holes with circular cross sections, the electrolyte retention portions of FIG. 6 are each formed as through-holes with square cross sections. In FIG. 6, the communication holes 533a and 533b may be grooves (communicating grooves) that are open at the top or bottom. These grooves form spaces between the positive electrode and the zinc negative electrode, forming communication holes. Furthermore, the opening holes 534a, 534b, 534c, and 534d may be grooves (opening grooves) that are open at the top or bottom. These grooves form a space between the positive electrode or the zinc negative electrode and form an open hole. However, when a space is formed between the zinc negative electrode and the groove, the portion of the zinc negative electrode that coincides with the groove (communicating groove or open groove) may be configured so that the negative electrode active material is not exposed, and for example, the portion may be sealed.

[0060] <<Fifth Example of Reaction Space Restricting Portion>> The reaction space-restricting portion 630 in FIG. 7 has a thin plate-like outer shape, similar to the reaction space-restricting portion 230 in FIG. 3, and contains an electrolyte retention portion formed by four through-holes with circular cross sections. However, it is thinner than the reaction space-restricting portion 230 in FIG. 3. The thickness of the reaction space-restricting portion corresponds to the thickness of the electrolyte, so if it is too thick, the ohmic loss of the electrolyte increases, which is undesirable. The thickness of the reaction space-restricting portion is approximately 3 mm or less, but 3 mm is not the upper limit because it is considered that an appropriate amount of electrolyte is required when the area of ​​the active material portion is large or the negative electrode capacity is large. The optimal thickness of the reaction space-restricting portion can be determined based on the relationship between the area of ​​the active material portion, the negative electrode capacity, the ohmic loss of the electrolyte, etc.

[0061] <<Sixth Example of Reaction Space Restricting Portion>> The reaction space-restricting portion 730 in Fig. 8 has a thin plate-like outer shape similar to the reaction space-restricting portion 230 in Fig. 3, and has electrolyte retention portions 732a, 732b, 732c, ... formed by through-holes with circular cross sections, but has more electrolyte retention portions than the reaction space-restricting portion 230 in Fig. 3, and their arrangement is different from the electrolyte retention portions 232a, 232b, 232c, 232d in Fig. 3. While the electrolyte retention portions 232a, 232b, 232c, 232d formed by circular through-holes are arranged in a square lattice pattern in Fig. 3, the electrolyte retention portions 732a, 732b, 732c, ... are arranged alternately in a honeycomb pattern in Fig. 8. Furthermore, in the reaction space restricting portion 730 of FIG. 8, compared to FIG. 3, the proportion of the area occupied by parts other than the electrolyte retention portion is small, and the reaction space restricting portion 730 is designed so that the ratio of the total area of ​​the electrolyte retention portions 732a, 732b, 732c, ... to the area determined by the outer shape (four sides of the flat portion) of the main body portion 731 in the reaction space restricting portion 730 (hereinafter referred to as the "opening ratio") is large.

[0062] <<Seventh Example of Reaction Space Restricting Portion>> Reaction space-restricting portion 830 in Fig. 9 has electrolyte retention portions 832a, 832b, 832c, ... formed by through-holes with a square cross section, like reaction space-restricting portion 530 in Fig. 6, but it has more electrolyte retention portions than reaction space-restricting portion 530 in Fig. 6, and the proportion of the area occupied by main body portion 831 other than the electrolyte retention portions is smaller than reaction space-restricting portion 530 in Fig. 6. Therefore, reaction space-restricting portion 830 in Fig. 9 is designed to have a larger opening ratio.

[0063] <<Eighth Example of Reaction Space Restricting Portion>> 8, the reaction space-restricting portion 930 of FIG. 10 has a thin plate-shaped main body 931 and electrolyte retention portions 932a, 932b, 932c, ... formed by circular cross-sectional through-holes. However, unlike FIG. 8, the ends of the main body 931 are not rectangular. Some of the electrolyte retention portions (932f, 932g, 932h, 932i) are cut off at the ends of the reaction space-restricting portion 930. In this way, the reaction space-restricting portion 930 of FIG. 10 is designed so that the proportion of the area occupied by the main body 931 other than the electrolyte retention portions is even smaller than that of the reaction space-restricting portion 730 of FIG. 8, thereby increasing the opening ratio.

[0064] Although the first to eighth examples have been described above as representative examples of the reaction space-regulating portion, these are merely specific examples, and the shape, number, and size of the electrolyte retention portion, as well as the main body portion, communication holes, and openings, can be set as appropriate. For example, although communication holes and openings are not shown in Figures 3, 5, and 7 to 10, the reaction space-regulating portion may have communication holes, openings, or both. Furthermore, even when communication holes, openings, or both are provided, the reaction space-regulating portion may have one or more of each, or one communication hole and multiple openings, or multiple communication holes and one opening, as needed, and various combinations of numbers can be set. Although not intended to limit the scope of the present invention, when the reaction space-restricting portion including the electrolyte retention portion described above is a plate-shaped member, the thickness range can be 0.5 mm to 5 mm, and when the cross-sectional shape of the electrolyte retention portion is circular, the diameter can be 1 mm to 10 mm, and when the cross-sectional shape of the electrolyte retention portion is square, the diagonal length can be 1 mm to 10 mm. Furthermore, as shown in some of the electrolyte retention portions (932f, 932g, 932h, and 932i) in FIG. 10, the electrolyte retention portion of the reaction space-restricting portion does not need to be surrounded by the main body of the zinc negative electrode alone, as long as it can retain liquid electrolyte. If necessary, the liquid electrolyte may be retained via a member other than the main body (e.g., a container, a positive electrode (air electrode), a spacer, etc.).

[0065] Next, a method for fabricating a zinc negative electrode for use in a secondary battery according to one embodiment of the present invention will be described. As described above, the zinc negative electrode comprises an active material portion using zinc as the negative electrode active material, which produces zinc during charging and zinc oxide during discharging; a current collector electrically connected to the active material portion; and a non-electron-conductive reaction space restricting portion integrally formed with or connected to the current collector and / or the active material portion, the reaction space restricting portion having a plurality of electrolyte retention portions capable of retaining a liquid electrolyte. The fabrication method includes the steps of integrally forming or connecting the current collector and the non-electron-conductive reaction space restricting portion, and electrically connecting the active material portion and the current collector.

[0066] <Method for producing zinc anode> Here, a method for fabricating the zinc negative electrode of the present invention will be described. In the case of a zinc negative electrode using a copper plate or copper mesh as a current collector, for example, a copper plate can be pre-formed with a thin film of zinc in an amount required for charging and discharging, such as by electroplating, or by crimping a thin zinc film onto a copper plate, and then the reaction space-restricting portions 230-930 can be integrated onto the copper plate by crimping, fusing, fixing, heat curing, three-dimensional molding, or by connecting with an adhesive. Alternatively, the copper mesh and the reaction space-restricting portions 230-930 can be crimped together, and then zinc can be deposited on the copper mesh in the electrolyte retention portion by electroplating, or the required amount of zinc powder can be applied to the copper mesh and solidified. The following describes exemplary methods for fabricating zinc negative electrodes.

[0067] <<First example of fabrication method>> See the flowchart in Figure 11. For example, a copper plate is used as a current collector, and the surface of the copper plate is pretreated, if necessary, by degreasing or etching (S11). Then, a zinc active material portion corresponding to the capacity required for the zinc negative electrode is formed using a method capable of forming zinc, such as vapor deposition, sputtering, electroplating, or hot-dip plating (S12). Figure 11 shows zinc plating as a specific example of step S12. Next, a reaction space-restricting portion is connected to the surface and / or end face of the formed zinc active material portion by compression bonding, fusion bonding, fixing, heat curing, or adhesive bonding (S13). In this way, a zinc negative electrode according to one embodiment of the present invention can be obtained. Note that the area where the zinc active material portion is formed may be limited to the area that corresponds to the electrolyte retention portion of the reaction space-restricting portion, or the active material portion may be formed over a wider area than the area that corresponds to the electrolyte retention portion, and the reaction space-restricting portion may be integrated onto the active material portion.

[0068] <<Second example of fabrication method>> See the flowchart in Figure 12. For example, a copper plate is used as a current collector, and a reaction space-restricting portion is connected to the surface of the copper plate by compression bonding, fusion bonding, fixing, heat curing, or adhesive bonding (S21). Thereafter, if necessary, the surface of the copper plate is pretreated by degreasing or etching (S22). Next, a zinc-containing active material portion equivalent to the capacity required for a zinc negative electrode is formed in the electrolyte retention portion of the reaction space-restricting portion using a method capable of forming zinc, such as vapor deposition, sputtering, electroplating, or hot-dip plating (S23). Figure 12 shows zinc plating as a specific example of step S23. This process also allows for the production of a zinc negative electrode according to one embodiment of the present invention. Note that even after the zinc is formed, a space remains in the electrolyte retention portion that can be filled with electrolyte.

[0069] <<Third example of fabrication method>> See the flowchart in Figure 13. For example, a copper mesh is used as a current collector, and a reaction space restricting portion is connected to the copper mesh by compression bonding, fusion bonding, fixing, heat curing, or adhesive bonding to form a reaction space restricting portion (S31). Then, a zinc-containing active material portion is formed by filling the electrolyte retention portion of the reaction space restricting portion with zinc powder of an appropriate particle size, or a mixture of zinc powder and zinc oxide powder, or either of these mixed with an appropriate binder, in an amount corresponding to the zinc content required for the negative electrode (S32). This process also allows for the production of a zinc negative electrode according to one embodiment of the present invention. Note that even after filling the electrolyte retention portion with zinc, a space remains that can be filled with electrolyte.

[0070] <<Fourth example of fabrication method>> See the flowchart in Figure 14. For example, a copper plate is used as a current collector, and a reaction space restricting portion is formed on the copper plate using a 3D printer (S41). Then, zinc powder of an appropriate particle size, a mixture of zinc powder and zinc oxide powder, or a mixture of either of these with an appropriate binder, is filled into the electrolyte retention portion of the reaction space restricting portion in an amount that contains the amount of zinc required for the negative electrode, thereby forming a zinc-containing active material portion (S42). This process also allows for the production of a zinc negative electrode according to one embodiment of the present invention. Note that even after filling the electrolyte retention portion with zinc, a space remains in the electrolyte retention portion that can be filled with electrolyte.

[0071] In the above description of the first to fourth examples of the fabrication method, examples of zinc negative electrodes using a copper plate or copper mesh as the current collector and zinc as the active material are given, but the present invention is not limited to these materials. Furthermore, the fabrication method is also not limited to the above specific examples. For example, when forming a reaction space-restricting portion, a fluid liquid containing the raw materials or base materials of the reaction space-restricting portion may be applied to a metal plate serving as a current collector by printing, dripping, spraying, or the like to form a predetermined shape, and then the reaction space-restricting portion of the desired shape may be formed by drying, heating, pressurizing, cooling, freeze-drying, photocuring, or the like. From an industrial perspective, from the viewpoint of increasing productivity, fabrication by the printing or coating method is appropriate. For example, pattern printing methods such as inkjet printing, screen printing, offset printing, flexography, gravure printing, and microcontact printing, and coating methods such as dip coating, die coating, bar coating, spin coating, offset printing, spray coating, and doctor blade printing can be used. In this case, thermosetting resins, photocurable resins, etc. can be used alone or in combination of two or more. Alternatively, for example, a resin layer of a predetermined thickness may be integrally formed on a metal plate that serves as a current collector, and then a reaction space regulating portion having a desired shape may be formed using various processing techniques such as mechanical processing, laser processing, ultrasonic processing, chemical etching, electrochemical oxidation or reduction, etc.

[0072] -Material for the reaction space control part- Furthermore, it is preferable to select the material for the reaction space-restricting portion based on its specific gravity relative to the liquid electrolyte. For example, when an aqueous solution is used as the electrolyte, the material for the reaction space-restricting portion is preferably one with a specific gravity of 2 or less, such as a resin material or other plastic material that is alkali-resistant. Furthermore, the material for the reaction space-restricting portion may be an inorganic material as long as it is non-electronically conductive. Examples of non-electronically conductive materials include oxides such as alumina and zirconia, as well as nitrides. While not exclusive to these examples, it is preferable to use an inorganic material for the reaction space-restricting portion that is not only non-electronically conductive but also has a low specific gravity, does not increase the weight of the entire battery, and has a wide variety of shapes and good processability.

[0073] For example, in addition to the acrylic resins used in the examples described below, other materials that can be used for the reaction space restricting portion include polyolefin resins such as ultra-high molecular weight polyethylene (UHPE); polyketone resins such as polyether ether ketone (PEEK) and polyether ketone (PEK); polyphenylene resins such as polyphenylene sulfide (PPS) and modified polyphenylene ether (modified PPE); styrene resins such as acrylonitrile-butadiene-styrene (ABS) and acrylonitrile-styrene (AS); and epoxy resins such as bisphenol A epoxy resin and novolac epoxy resin. Fluorine-based resins such as Teflon (registered trademark) and lighter resins can also be used.

[0074] However, the material of the reaction space restricting portion is desirably chemically and electrochemically stable against the electrolyte and the substances produced by the reactions at the zinc negative electrode and positive electrode. Furthermore, as already mentioned, since the reaction space restricting portion comes into contact with the positive electrode, it must not have electronic conductivity. Furthermore, the material should be inexpensive, flexible, and be capable of being integrally formed with or connected to the current collector and / or active material portion by various methods, including crimping, bonding, 3D printing, etc., and it is preferable to use a material that can be easily applied with these various methods.

[0075] <Action and effect> According to the zinc anode according to the embodiment of the present invention described above, zincate ions, Zn(OH)4, in an aqueous potassium hydroxide solution are 2- By restricting the three-dimensional movement range of the active material, it is possible to suppress dendrite short-circuiting and non-uniformity of the active material. Although the detailed mechanism is not clear, the following possibilities are considered as the mechanism of action.

[0076] First, zinc dendrite shorting occurs when zinc precipitates from zincate ions in a localized manner at an angle close to the perpendicular direction to the electrode surface, rather than in a two-dimensional direction parallel to the electrode surface.

[0077] In the deposition of metals by electrochemical reactions, metal ions receive electrons and become metal atoms, which then bond together to form metal crystals that grow two-dimensionally (two-dimensional growth), or some of the metal atoms form crystal nuclei and metal atoms precipitate at the tips of the nuclei (three-dimensional growth), or there are intermediate cases. Dendrite shorting is more likely to occur in the case of three-dimensional growth. Which of these growth patterns occurs not only depends on the type of metal, but also on the deposition rate, even for the same metal. Generally, two-dimensional growth occurs when the metal deposition rate is slow, and three-dimensional growth is more likely to occur when the deposition rate is fast.

[0078] However, the formation of crystal nuclei, which trigger dendrite shorting, is thought to be less likely if the spatial distribution of metal ions in the electrolyte is uniform, but more likely if it is nonuniform. In other words, once the potential is such that metal deposition is possible, the electrode surface in contact with a higher concentration of metal ions is more likely to deposit metal and form crystal nuclei. In fact, in the case of zinc anodes, zincate ions exist three-dimensionally in the potassium hydroxide electrolyte. Therefore, once zinc deposition begins, the zincate ion concentration is low on the negative electrode side and relatively high on the positive electrode side. This also creates a concentration difference in the two-dimensional direction (in-plane direction of the active material surface) of the zinc anode. This concentration difference causes areas where zinc deposition is favorable and areas where it is not, resulting in the formation of dendrites in areas where deposition is favorable.

[0079] For the same reasons as those mentioned above, such non-uniformity in the concentration distribution of metal ions is thought to also cause non-uniformity in the active material. In particular, in the case of secondary batteries, the negative electrode and the positive electrode are separated by a distance of a few millimeters or less, while the size of the electrode surface is larger than a few centimeters, so that the spatial distribution of metal ions in the two-dimensional direction of the electrode surface is likely to be non-uniform. In the zinc negative electrode of the present invention, the non-uniformity in the spatial distribution of zincate ions is suppressed, and therefore, dendrite short-circuiting and non-uniformity in the active material are also thought to be suppressed.

[0080] (Preferred embodiment) Although the zinc anode and its manufacturing method according to one embodiment of the present invention have been described above, the present invention is not limited to these specific examples. As long as the reaction space regulation effect according to the present invention is obtained, the above-described configurations, methods, and known techniques can be appropriately applied. Below, preferred embodiments that are applicable to the present invention will be further described.

[0081] In a zinc negative electrode according to one embodiment of the present invention, the reaction space-restricting portion preferably has a through-hole that connects the electrolyte retention portions to each other. Such a reaction space-restricting portion may have a structure such as that shown in FIG. 4. The electrolyte retention portions are connected by the through-holes, and the electrolyte retention portions are also connected to the ends of the reaction space-restricting portion by openings. As already mentioned, this allows liquid electrolyte to be transferred from one electrolyte retention portion to another for multiple electrolyte retention portions, facilitating liquid electrolyte retention. For example, in a horizontally-oriented secondary battery such as that shown in FIG. 2, the through-holes facilitate leveling of the liquid electrolyte held in multiple electrolyte retention portions, making it easier to transfer the required amount of liquid electrolyte to multiple electrolyte retention portions.

[0082] Furthermore, it is also preferable that the reaction space-restricting portion has an opening that connects the electrolyte retention portion to the end of the reaction space-restricting portion, as in the reaction space-restricting portion 330 shown in FIG. 4. As already mentioned, the presence of an opening allows the liquid electrolyte to be introduced into the electrolyte retention portion through the opening without having to be introduced directly into the electrolyte retention portion. For example, in the case of a secondary battery that is vertically oriented rather than horizontally oriented as shown in FIG. 2, if an opening is provided, the liquid electrolyte can be introduced through the opening at the top, making it possible to easily introduce the required amount of liquid electrolyte into the electrolyte retention portion. Furthermore, as in the reaction space-restricting portion 330 shown in FIG. 4, both a communication hole and an opening hole may be provided. This simultaneously achieves the effects of the communication hole and the opening hole described above, making it even easier to introduce the liquid electrolyte into the electrolyte retention portion and retain the required amount of liquid electrolyte in multiple electrolyte retention portions. For example, if there are communicating holes and openings, it will be particularly easy to introduce the electrolyte when a cylindrical battery structure such as a dry cell is used, in which the zinc negative electrode, positive electrode, and insulating paper of the present invention are stacked inside, rolled up, and placed in a cylindrical battery container, and finally liquid electrolyte is injected into the battery container.

[0083] Furthermore, in the zinc negative electrode according to one embodiment of the present invention, the reaction space restricting portion is preferably made of a plastic material. Plastic materials are inexpensive, highly flexible and shape-variable, have good formability for the electrolyte retention portion, communicating holes, and openings, have good designability and processability for the reaction space restricting portion, are easy to manufacture, have excellent durability even when the electrolyte is highly alkaline, can be integrally molded or connected to the current collector, can accommodate a variety of sizes, have a wide range of material options, and have the effect of allowing the optimal reaction space restricting portion to be produced depending on the type and concentration of the electrolyte used, the required structural durability, etc. Specific plastic material types that are preferably used are as described above, but are not limited thereto.

[0084] Furthermore, the cross-sectional shape of each of the electrolyte retention portions is preferably circular. For example, the through-holes provided in the reaction space-restricting portion in the above-mentioned example can constitute the electrolyte retention portion. As mentioned above, the "through-hole" here refers to the through-hole when viewed from the reaction space-restricting portion alone. In the zinc negative electrode as a whole, one side of the through-hole is blocked by the active material portion. Furthermore, the reaction space-restricting portion in the zinc negative electrode of the present invention is not limited to the electrolyte retention portion having a cylindrical through-hole structure as shown in Figures 3 and 4. However, in the cylindrically cut electrolyte retention portion as shown in these figures, the cross-sectional shape of the electrolyte retention portion is circular. This has better symmetry in all directions in the cross-sectional direction than when the cross-section is elliptical, triangular, rectangular, or the like, and therefore has the effect of most easily suppressing non-uniformity in the spatial distribution of zincate ions. Note that, since increasing the number of corners of a polygonal cross-section ultimately approaches a circle, the shape of the electrolyte retention portion is not limited to a symmetrical shape and may be an asymmetrical or polygonal shape. On the other hand, from the viewpoint of ensuring a reaction area, the cross-sectional shape of each of the electrolyte retention portions is preferably square, or may be polygonal. Furthermore, the cross-sectional shapes may be a mixture of circles and polygons. It is considered most desirable to maintain the same cross-sectional shape and size in the direction perpendicular to the cross section, but this is not limiting.

[0085] Next, according to one embodiment of the present invention, at least one of the electrolyte retention portions preferably has a different maximum diametric length from the other electrolyte retention portions. For example, an example of a reaction space-restricting portion having such an electrolyte retention portion is shown in FIG. 5. In FIG. 5, there are five electrolyte retention portions, and the central electrolyte retention portion sandwiched between four electrolyte retention portions is formed by a through-hole with a circular cross section and a smaller diameter than the surrounding four electrolyte retention portions. By combining large and small cross-sectional shapes of the electrolyte retention portions in this way, the area of ​​the reaction space-restricting portion other than the electrolyte retention portion can be reduced, resulting in an increased aperture ratio and an increased area available for reaction.

[0086] In addition, in a zinc anode according to one embodiment of the present invention, the maximum diameter of the electrolyte retention portion is preferably less than 20 mm, and more preferably 5 mm or less. By setting the maximum diameter to less than 20 mm, the effect of maintaining uniform two-dimensional and three-dimensional spatial distribution of zincate ions in the electrolyte can be more effectively achieved, and by setting the maximum diameter to 5 mm or less, this effect can be more reliably achieved. Here, the maximum diameter of the through-holes refers to the diameter of the circle when the hole is circular, and the length of the diagonal of the square when the hole is square.

[0087] Next, a secondary battery according to one embodiment of the present invention is a secondary battery equipped with the zinc negative electrode described above, for example, a zinc-air secondary battery. As described above, this zinc-air secondary battery can be equipped with a positive electrode and a liquid electrolyte, and the positional relationship between the zinc negative electrode, the positive electrode, and the liquid electrolyte is the same as described above. The zinc-air secondary battery is equipped with a positive electrode, a zinc negative electrode, and a liquid electrolyte containing an alkaline aqueous solution, and the electrolyte retention portion in the zinc negative electrode can retain the liquid electrolyte between the positive electrode and the active material portion. Note that the positive electrode of a zinc-air secondary battery is also called an air electrode, as described above.

[0088] The material for the air electrode is not particularly limited as long as it can be used to form a zinc-air secondary battery. For example, conductive materials for the air electrode include, but are not limited to, doped or undoped carbonaceous materials (including carbon with various crystalline structures and forms, such as graphite, amorphous carbon, glassy carbon, carbon nanotubes, carbon nanofibers, and fullerenes), metal-coated oxide particles (for example, silica, alumina, or resin coated with nickel or a nickel alloy, in which the core material particles are electronically non-conductive and have a specific gravity lower than that of metals, and the surface of this core material is coated by various coating methods, such as electroless plating, electroplating, coating, and mechanical mixing), and metal powders or particles (for example, nickel or nickel alloys that are chemically and electrochemically stable in highly concentrated alkaline aqueous solutions). In addition, there are many types of catalysts for the air electrode, including precious metals such as platinum, silver, and gold, or their alloys; platinum group metals and other transition metal elements and alloys containing them; various oxides and sulfides; doped or undoped carbon-based materials (including carbon with various crystalline structures and forms, such as graphite, amorphous carbon, glassy carbon, carbon nanotubes, carbon nanofibers, and fullerenes. In this case, the carbon material may also serve as a conductive material); various nitrides, carbides, and organic metal compounds. Among these, oxides with crystalline structures known as pyrochlore, perovskite, and spinel can be used as oxygen catalysts. To improve the operation of zinc-air secondary batteries, it is preferable for the air electrode to contain pyrochlore-type bismuth ruthenium oxide, and more preferably, this bismuth ruthenium oxide contains manganese, with the manganese being particularly preferred for being located at the B site of the pyrochlore structure. It is also preferable for the air electrode to contain pyrochlore-type bismuth ruthenium oxide, and for this bismuth ruthenium oxide to contain sodium. In addition, the water-repellent material for the air electrode can be polytetrafluoroethylene (PTFE), which has been used conventionally, as well as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE, density), tetrafluoroethylene-ethylene copolymer (ETFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), as well as polymers and organic-inorganic hybrid materials. For example, linear polymers such as polystyrene, polymethyl methacrylate, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polysulfone, polycarbonate, and polyamide; divinylbenzene, hexatriene, divinyl ether, divinyl sulfone, diallyl carbinol, alkylene diacrylate, oligo- or polyalkylene glycol diacrylate, alkylene triacrylate, alkylene tetraacrylate, alkylene trimethacrylate, alkylene tetramethacrylate, alkylene bisacrylamide, alkylene bismethacrylamide, and polybutadiene polyols modified at both ends with acrylic acid; Examples of suitable polymers include, but are not limited to, network polymers obtained by polymerizing ethylenediamine oligomers alone or with other polymerizable monomers; thermosetting resins such as phenol formaldehyde resins, melamine formaldehyde resins, benzoguanamine formaldehyde resins, and urea formaldehyde resins; resins obtained by polymerizing silane-containing monomers such as γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane alone or with other polymerizable monomers; polymer fine particles in which the hydrolyzable silyl groups of these monomers are crosslinked after hydrolysis; and organopolysiloxane resins such as dimethylpolysiloxane.

[0089] Furthermore, in a method for fabricating a secondary battery according to one embodiment of the present invention, the zinc negative electrode may include an active material portion using zinc as the negative electrode active material, which produces zinc during charging and zinc oxide during discharging, a current collector electrically connected to the active material portion, and a non-conductive reaction space restricting portion integrally formed with or connected to the current collector and / or the active material portion, the reaction space restricting portion having a plurality of electrolyte retention portions each having a space capable of retaining a liquid electrolyte. The fabrication method may include the steps of integrally forming or connecting the current collector and the non-conductive reaction space restricting portion, electrically connecting the active material portion and the current collector, and forming an air electrode. The air electrode may include an air electrode current collector, a conductive material, a catalyst, and a water-repellent material, and the step of forming the air electrode may further include the steps of mixing the conductive material, the catalyst, and the water-repellent material, and forming the mixture obtained in the mixing step into an air electrode having a predetermined shape. The materials for the air electrode in the examples described below are merely examples, and the conductive material, catalyst, and water-repellent material may be the same as those described above. In this way, a zinc-air secondary battery can be fabricated.

[0090] In the method for producing a secondary battery, the mixing step can prepare a suspension of the conductive material, the catalyst, and the water-repellent material by ultrasonic agitation or the like. The molding step can further include a step of spraying the suspension onto the air electrode current collector and drying it. In this case, it is also preferable that the molding step sprays the suspension onto the air electrode current collector while the suspension is maintained at a temperature equal to or higher than a temperature at which the solvent in the suspension can evaporate.

[0091] It is also preferable that in the mixing step in the method for producing a secondary battery, the conductive material, the catalyst, and the water-repellent material are kneaded together, and that in the molding step, the mixture obtained in the mixing step is rolled and heat-treated at a temperature of 400° C. or less. The heat-treatment temperature is more preferably 100° C. or less. [Example]

[0092] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0093] Example 1 A zinc negative electrode according to the present invention was fabricated as follows. First, a copper plate (plated area: 30 mm × 40 mm × 0.2 mm, lead area: 5 mm × 50 mm × 0.2 mm) shown in FIG. 15 was pretreated with abrasive paper and oxalic acid etching. Then, one side and one side of the plated area and both sides and one side of the lead area were masked with a commercially available plating masking material. Next, a zinc plating bath was prepared by dissolving 1.2 mol / L of zinc sulfate heptahydrate, 0.56 mol / L of sodium sulfate, and 0.02 g / L of glue in distilled water and adjusting the pH to 2. This zinc plating bath was placed in a beaker, and the copper plate and a platinum plate (50 mm x 50 mm x 0.1 mm) with platinum wires attached as leads were immersed in the zinc plating bath, facing each other at a distance of about 5 cm. This was then placed on a hot stirrer and heated to 40°C. A constant current was then passed through the copper plate as the cathode and the platinum plate as the anode for a certain period of time to electroplat zinc on the unmasked parts of the copper plate. At this time, a current of 150 mA / cm was applied based on the area of ​​the zinc electroplated part. 2 The current was applied for 281 seconds at 1000 kJ / s. The mixture was stirred with a stirrer while the current was being applied. The weight of the copper plate before the current was subtracted from the weight of the copper plate after the current was applied, and this was taken as the amount of zinc deposited by electroplating. The ratio of this to the theoretical amount of zinc deposited calculated from Faraday's law was calculated to be 89.2%, for example, and the thickness was calculated to be 17.8 μm. The amount of zinc deposited per unit area calculated from the amount of zinc deposited was 12.7 mg / cm. 2 , the capacity per unit area calculated from this is 10.4mAh / cm 2 The capacity is 2mAh / cm, which is the average capacity of the negative electrode of a lithium-ion secondary battery. 2 This value was more than five times larger than that of the conventional method. Note that the capacity here refers to the amount of electricity calculated from the mass of the reactants using Faraday's law, and is sometimes also used to refer to the amount of electricity charged or discharged, such as charge capacity and discharge capacity.

[0094] A commercially available plating masking material was applied to the zinc-plated copper sheet obtained as described above, leaving only a circular area 20 mm in diameter from the center of one of the zinc-plated surfaces, as shown in FIG. 16. Next, as shown in FIG. 17, four 5 mm diameter circles were placed within the 20 mm diameter circular area, with the closest distance between the circular areas vertically or horizontally being 3 mm. A commercially available masking material was then applied to the remaining area. An acrylic resin reaction space-restricting portion having multiple communication holes and openings, as shown in FIG. 4, was then attached to the masking material-coated surface. After allowing the masking material to solidify, a zinc negative electrode according to Example 1 was produced, in which the zinc-plated copper sheet and the reaction space-restricting portion were integrated. The contour of the exposed zinc plating coincided with the cylindrical contour of the reaction space-restricting portion. Referring to the reference numerals in FIG. 4, this reaction space restricting portion 330 is a plate with outer dimensions of 27 mm, 27 mm, and 3 mm as a main body portion 331, and electrolyte holding portions 332a, 332b, 332c, and 332d with a diameter of 5 mm are formed so that the closest distance between them in the vertical or horizontal directions is 3 mm, so as to be positioned corresponding to the exposed zinc portions of the zinc-plated copper plate after the masking. Furthermore, the upper and lower electrolyte holding portions 332a, 332c and the electrolyte holding portions 332b, 332d in the figure are connected by 2 mm×2 mm communication holes. The upper electrolyte retention portions 332a and 332b in Figure 4 have 2 mm x 2 mm openings 334a and 334b ​​formed in the opposite direction from the lower electrolyte retention portions 332c and 332d, and the lower electrolyte retention portions 332c and 332d have 2 mm x 2 mm openings 334c and 334d formed in the opposite direction from the upper electrolyte retention portions 332a and 332b ...

[0095] For ease of explanation of the layout, the schematic diagram in FIG. 18 is referenced. The zinc negative electrode 10 according to Example 1, prepared as described above, and a pre-charged nickel positive electrode 60 (approximately 50 mm square and 5 mm thick) were placed facing each other in an acrylic container. A resin plate (resin spacer) 80 was attached to the back side of the zinc negative electrode 10 so that the reaction space-restricting portion of the zinc negative electrode 10 according to Example 1 and the nickel positive electrode 60 were in close contact with each other, and this was fastened with screws 70. The nickel positive electrode 60 used was a type commonly used in nickel-metal hydride secondary batteries. In a fully discharged state, it is mainly composed of nickel hydroxide, and in a fully charged state, the nickel hydroxide is oxidized to form nickel oxyhydroxide. A liquid electrolyte 50 consisting of a 6 mol / L potassium hydroxide aqueous solution saturated with zinc oxide was then added to the acrylic container to prepare a zinc-nickel secondary battery. The reason why zinc-nickel secondary batteries were fabricated here was because the nickel positive electrode used was known to have sufficiently excellent cycle characteristics, reaching thousands of cycles, and was therefore the most suitable positive electrode for evaluating the cycle characteristics of zinc negative electrodes. That is, since it was known that the battery voltage and cycle characteristics of zinc-nickel secondary batteries fabricated using nickel positive electrodes would vary depending on the zinc negative electrode, charge-discharge tests were first conducted using zinc-nickel secondary batteries to evaluate the excellent cycle characteristics of the zinc negative electrode of the present invention, which differ from conventional technology. The same reason applies when evaluations using zinc-nickel secondary batteries are performed in the following examples from Example 1 onwards.

[0096] <Evaluation> The zinc-nickel secondary battery prepared as described above was charged and discharged at a constant current. The current density was 10 mA / cm, based on the area of ​​four 5 mm diameter circles where the electroplated zinc on the zinc negative electrode was exposed. 2The battery was operated by first discharging at the above current density to an SOC of 50% (a state where the battery is charged to 50% of the fully charged state), and then stopping the current flow for 1 minute (rest). Next, the battery was charged at the same current density as the discharge to an SOC of 80%, and then resting for 1 minute. After this, if the SOC reached 50% during discharge, or if the battery voltage during discharge suddenly dropped below a predetermined voltage before the SOC reached 50%, it was determined that the reaction on the zinc negative electrode was no longer solely a reaction from zinc to zinc oxide, and the discharge was stopped. This voltage was set to 1.6 V in Example 1. The battery was charged until the SOC reached 80% or the battery voltage during charging exceeded 3 V. A rest of 1 minute or more was always taken between discharge and charge, or between charge and discharge. As mentioned above, the capacity of the electroplated zinc was 10.4 mAh / cm 2 However, under the test conditions, the capacity is approximately 3.1mAh / cm, which is 30% of the capacity when the SOC is between 80% and 50%. 2 10mA / cm 2 Since the battery is charged and discharged at this rate, the C rate, which is used to express the charge and discharge speed of a battery, is 3.2C, which is an extremely fast charge and discharge rate for a battery when in use.

[0097] The relationships between the average discharge voltage, average charge voltage, and current efficiency and the number of charge / discharge cycles obtained in Example 1 are shown in Figures 19 and 20, respectively. Note that the current efficiency is the ratio of the amount of electricity discharged in the discharge immediately after charging to the amount of electricity charged into the battery from the second cycle onwards, and if these are the same, the current efficiency is 100%. In other words, it means how much electricity was discharged in the next discharge compared to the amount of electricity charged.

[0098] 19 and 20, in the zinc-nickel secondary battery using the zinc negative electrode of Example 1, the average charge voltage and average discharge voltage were both slightly lower than the initial values ​​after 5,500 charge-discharge cycles for which data was available, but no sudden drop in discharge voltage or increase in charge voltage indicating dendrite shorting was observed, indicating stable charge-discharge operation beyond 5,500 cycles. Furthermore, there was almost no change in current efficiency, and under fast operating conditions of charge-discharge rates of 1 C or higher, no decrease in capacity due to active material non-uniformity or dendrite shorting was observed. It was revealed that the battery capacity could be maintained at a high current efficiency of over 90% for 5,500 cycles or more.

[0099] (Comparative Example 1) A commercially available masking material was applied to a zinc-plated copper plate obtained using the same method and conditions as in Example 1, leaving a 20 mm diameter circle from the center of one of the zinc-plated surfaces shown in Figure 16. Next, a separator as shown in Figure 21 was attached to the masked surface and allowed to solidify. This separator was made of the same acrylic resin as in Example 1 and had a plate shape with external dimensions of 27 mm x 27 mm x 3 mm. It had a 20 mm diameter through-hole in its center and two 2 mm x 2 mm holes extending from this hole to the edge of the resin plate. When the separator and zinc-plated copper plate were attached to each other, the outline of the 20 mm diameter through-hole was aligned with the outline of the exposed zinc plating.

[0100] A zinc-nickel secondary battery was fabricated in the same manner as in Example 1, except that a zinc-plated copper plate with the separator described above was used as the negative electrode instead of the zinc negative electrode used in Example 1. A charge-discharge cycle test was conducted under the same conditions as in Example 1, except that the discharge limit voltage was changed from 1.6 V to 1.5 V. As a result, as shown in Figure 22, large fluctuations in the discharge voltage and charge voltage were observed after approximately 90 cycles. Furthermore, as shown in Figure 23, a large drop in current efficiency was observed after 40 cycles, and after 90 cycles, when charge-discharge voltage oscillations occurred, the current efficiency again dropped significantly. Discharge then became impossible, and the current efficiency became nearly zero, so the charge-discharge test was discontinued.

[0101] (Comparative Example 2) A commercially available masking material was applied to a zinc-plated copper plate obtained by the same method and conditions as in Example 1, leaving a circle 20 mm in diameter from the center of one of the zinc-plated surfaces, as shown in FIG. 16 . In Comparative Example 2, unlike in both Example 1 and Comparative Example 1, a nonwoven fabric made of a polyolefin-based material used in nickel-metal hydride secondary batteries was used as the separator. A zinc-nickel secondary battery according to Comparative Example 2 was fabricated by placing the nonwoven fabric separator between a zinc-plated copper plate electrode masked as described above and a nickel positive electrode similar to that used in Example 1 in an acrylic container similar to that used in Example 1. The zinc-nickel secondary battery of Comparative Example 2 was subjected to a charge-discharge cycle test in the same manner as in Comparative Example 1, except that the rest time was set to 1 to 10 minutes. In charge-discharge cycle tests, if no rest time or a shorter rest time is provided between charge and discharge or between discharge and charge, a rapid change in the state of the electrode surface occurs, making the test conditions severe. However, the cycle characteristics were not affected by the rest time set to 1 to 10 minutes as described above. In Comparative Example 2, charge / discharge was no longer possible after seven cycles. Therefore, the discharge curve up to that point is shown in Figure 24, and the charge curve up to that point is shown in Figure 25. The cycle numbers are shown in Figure 24, and the dashed and dotted lines indicating the cycle numbers are the same in Figure 25. As shown in Figure 24, discharge was possible up to the seventh cycle. However, as shown in Figure 25, the voltage fluctuated significantly during the seventh cycle, even reaching 1.7 V or less, which was lower than the electromotive force, indicating an internal short circuit. Furthermore, in the eighth cycle, the discharge voltage reached its minimum value immediately after the start of current application, and discharge was no longer possible. Therefore, the charge / discharge test was discontinued. After the test was discontinued, the battery was disassembled, the nonwoven fabric was removed and washed, and the negative and positive sides were observed. A photograph of the negative side is shown in Figure 26, and a photograph of the positive side is shown in Figure 27. The nonwoven fabric is the white (light-colored) portion of this figure, and the part of it (encircled by the dashed line) is zinc. These figures reveal that zinc penetrates the nonwoven fabric from the negative side to the positive side. Therefore, it was found that charging and discharging was no longer possible due to an internal short circuit caused by zinc dendrite growth.In addition, in a plurality of zinc-nickel secondary batteries using the same nonwoven fabric as in Comparative Example 2 as a separator, the above-mentioned voltage change was observed within a few cycles, and therefore the charge-discharge test was stopped in all cases.

[0102] Here, a photograph of the negative electrode surface after 30 cycles of charge and discharge under the same conditions as in Example 1 is shown in Figure 28, photographs of the negative electrode surface after 30 cycles of charge and discharge under the same conditions as in Comparative Example 1 are shown in Figures 29 and 30, and a photograph of the negative electrode surface after the charge and discharge test in Comparative Example 2 was completed is shown in Figure 31.

[0103] The surface morphology shown in Figure 28, obtained from an experiment conducted under the same conditions as in Example 1, was almost the same as before the charge-discharge test, and the entire reaction surface was not heterogeneous. The surface morphology shown in Figure 29, obtained from an experiment conducted under the same conditions as in Comparative Example 1, was clearly heterogeneous and distinct from that shown in Figure 28. Furthermore, as shown in Figure 30, zinc that appeared to have fallen off was observed at the bottom of the reaction surface in Figure 29. The surface morphology shown in Figure 31, obtained from the experiment in Comparative Example 2, was even more heterogeneous than that shown in Figure 29, and what appeared to be zinc dendrites penetrating the nonwoven fabric were observed at the bottom, as described above. As described above, it was found that Example 1 significantly improved the charge-discharge cycle characteristics compared to Comparative Examples 1 and 2 by suppressing dendrite short-circuiting and active material heterogeneity.

[0104] Example 2 The zinc negative electrode of the present invention was fabricated as follows. First, the copper plate shown in FIG. 15 was electroplated using the same method and conditions as in Example 1. Furthermore, as shown in FIG. 16, a commercially available masking material was applied to the remaining area of ​​the zinc-plated surface, except for a 20 mm diameter circle from the center. Next, a commercially available masking material was applied to the 20 mm diameter circle, except for the electrolyte retention portion of the reaction space-regulating portion shown in FIG. 32, i.e., four 5 mm diameter circles and one 4 mm diameter circle located in the center of the four 5 mm diameter circles. Furthermore, an acrylic resin reaction space-regulating portion having a plurality of communicating holes and openings, as shown in FIG. 32, was attached to the masking material-coated surface, and the masking material was allowed to solidify, resulting in the fabrication of a zinc negative electrode of the present invention, in which the zinc-plated copper plate and the reaction space-regulating portion are integrated. This reaction space-restricting portion is formed by forming four 5 mm diameter electrolyte retention portions on a plate with outer dimensions of 27 mm, 27 mm, and 3 mm, with the closest vertical or horizontal distance being 3 mm, and a 4 mm diameter electrolyte retention portion being formed in the center of these. The central 4 mm diameter electrolyte retention portion also has communication holes that communicate with the two electrolyte retention portions on the left side of Figure 32. The reaction space-restricting portion in Example 2 can be said to be equivalent to reaction space-restricting portion 430 shown in Figure 5, with additional communication holes and openings.

[0105] The zinc negative electrode of the present invention prepared as described above and a pre-charged nickel positive electrode (approximately 50 mm square and 5 mm thick) were placed facing each other in an acrylic container, as in Example 1. A resin plate was attached to the back side of the zinc negative electrode so that the reaction space-restricting portion of the zinc negative electrode of the present invention was in close contact with the nickel positive electrode, and this was then fastened with screws. The nickel positive electrode used was the one typically used in nickel-metal hydride secondary batteries. In the fully discharged state, it is mainly composed of nickel hydroxide, and in the fully charged state, the nickel hydroxide is oxidized to nickel oxyhydroxide. A 6 mol / L potassium hydroxide solution saturated with zinc oxide was then added to the acrylic container to prepare a zinc-nickel secondary battery, and a charge-discharge cycle test was performed under the same conditions as in Comparative Example 2.

[0106] The relationships between the average discharge voltage, average charge voltage, and current efficiency and the number of charge-discharge cycles obtained in Example 2 are shown in Figures 33 and 34, respectively. The definition and meaning of current efficiency are the same as those described in Example 1. As shown in Figures 33 and 34, for the zinc-nickel secondary battery using the zinc negative electrode of Example 2, at 780 cycles, during data acquisition, the average charge voltage was almost the same as the initial value, and the average discharge voltage was only slightly lower than the initial value. No sudden drop in discharge voltage or increase in charge voltage, which would indicate dendrite shorting, was observed, demonstrating stable charge-discharge operation for 780 cycles or more. Furthermore, there was almost no change in current efficiency. Under fast operating conditions, such as a charge-discharge rate of 1 C or higher, no capacity loss due to active material non-uniformity or dendrite shorting was observed, demonstrating that the battery capacity could be maintained at a high current efficiency. Note that the results of Example 2 only show results during data acquisition, and do not indicate that charge-discharge became impossible at 780 cycles.

[0107] Example 3 A zinc negative electrode according to the present invention was fabricated as follows. First, a copper plate shown in FIG. 15 was electroplated using the same method and conditions as in Example 1. A commercially available masking material was applied to the remaining area of ​​the zinc-plated surface, except for a circular area 20 mm in diameter from the center, as shown in FIG. 15. Next, referring to the reference numerals in FIG. 6, a commercially available masking material was applied to the 20 mm circular area, except for the areas corresponding to the electrolyte retention portions 532a, 532b, 532c, and 532d of the reaction space-restricting portion 530 shown in FIG. 6, i.e., four 4.43 mm square areas. Furthermore, an acrylic resin reaction space-restricting portion 530 having a plurality of communication holes 533a, 533b and openings 534a, 534b, 534c, and 534d shown in FIG. 6 was attached to the surface coated with the masking material. After waiting for the masking material to harden, a zinc negative electrode according to the present invention was fabricated, in which the zinc-plated copper plate and the reaction space-restricting portion 530 were integrated. The reaction space regulating portion 530 is formed by forming four 4.43 mm square electrolyte holding portions 532a, 532b, 532c, and 532d on a plate with outer dimensions of 27 mm, 27 mm, and 3 mm, and the electrolyte holding portions 532a, 532b, 532c, and 532d are formed so that the closest distance between them in the vertical or horizontal directions is 3 mm. 6, the upper and lower electrolyte retention portions 532a, 532c and 532b, 532d are connected by 2 mm x 2 mm communication holes 533a, 533b, respectively. The upper electrolyte retention portions 532a, 532b in the drawing have 2 mm x 2 mm openings 534a, 534b formed in the opposite direction from the lower electrolyte retention portions 532c, 532d, and to the end of the main body portion 531 of the reaction space-restricting portion 530. The lower electrolyte retention portions 532c, 532d have 2 mm x 2 mm openings 534c, 534d formed in the opposite direction from the upper electrolyte retention portions 532a, 532b, and to the end of the main body portion 531 of the reaction space-restricting portion 530. The reaction space-restricting portion 530 of Example 3 was designed so that the total opening area of ​​its electrolyte retention portions was the same as that of Example 1.

[0108] The zinc negative electrode of Example 3 prepared as described above and a pre-charged nickel positive electrode (approximately 50 mm square and 5 mm thick) were placed facing each other in an acrylic container, as in Example 1. A resin plate was attached to the back side of the zinc negative electrode so that the reaction space-restricting portion of the zinc negative electrode of Example 3 and the nickel positive electrode were in close contact, and the two were fastened with screws. The nickel positive electrode used was the one typically used in nickel-metal hydride secondary batteries. In the fully discharged state, it is mainly composed of nickel hydroxide, and in the fully charged state, the nickel hydroxide is oxidized to nickel oxyhydroxide. A 6 mol / L potassium hydroxide aqueous solution saturated with zinc oxide was then added to the acrylic container to prepare a zinc-nickel secondary battery. A charge-discharge cycle test was performed under the same conditions as in Comparative Example 2.

[0109] The relationships between the average discharge voltage, average charge voltage, and current efficiency and the number of charge-discharge cycles obtained in Example 3 are shown in Figures 35 and 36, respectively. The definition and meaning of current efficiency are the same as those described in Example 1. As shown in Figures 35 and 36, for the zinc-nickel secondary battery using the zinc negative electrode of Example 3, at 1,130 cycles, during data acquisition, the average charge voltage remained almost the same as the initial value, and the average discharge voltage only slightly decreased. No sudden drop in discharge voltage or increase in charge voltage, which would indicate dendrite shorting, was observed, demonstrating stable charge-discharge operation for 1,130 cycles or more. Furthermore, there was almost no change in current efficiency. Under fast operating conditions, such as a charge-discharge rate of 1 C or higher, no capacity loss due to active material non-uniformity or dendrite shorting was observed, demonstrating that the battery capacity could be maintained at a high current efficiency. Note that the results of Example 2 only show results during data acquisition, and do not indicate that charge-discharge became impossible at 1,130 cycles.

[0110] Example 4 In Example 4, a zinc negative electrode was fabricated using the same vertically oriented cell and the same design of the reaction space-restricting portion as in Example 1, but the thickness of the reaction space-restricting portion was changed from 3 mm in Example 1 to 2 mm in Example 4. Furthermore, the plating amount was three times that of Example 1. Specifically, a zinc-nickel secondary battery was fabricated as follows.

[0111] The copper plate shown in Figure 15 (plated area: 30 mm × 40 mm × 0.2 mm, lead area: 5 mm × 50 mm × 0.2 mm) was pretreated with abrasive paper and oxalic acid etching. Then, one side and side of the plated area and both sides and sides of the lead area were masked with a commercially available plating masking material. Next, a zinc plating bath was prepared by dissolving 1.2 mol / L zinc sulfate heptahydrate, 0.56 mol / L sodium sulfate, and 0.02 g / L glue in distilled water at a pH of 2. This zinc plating bath was placed in a beaker, and the copper plate and a platinum plate (50 mm × 50 mm × 0.1 mm) with platinum wires attached as leads were immersed in the bath facing each other, approximately 5 cm apart. The bath was then placed on a hot stirrer and heated to 40°C. A constant current was applied for a certain period of time, with the copper plate as the cathode and the platinum plate as the anode, to electroplat the unmasked areas of the copper plate. In this case, the current is 150mA / cm based on the area of ​​the zinc electroplated part. 2 The current was applied for 843 seconds at 1000 kJ / s. The material was stirred with a stirrer during the application of current. The weight of the copper plate before the current was subtracted from the weight of the copper plate after the current was applied, and this was taken as the amount of zinc deposited by electroplating. The ratio of this to the theoretical amount of zinc deposited calculated from Faraday's law was calculated to be 90%, for example, and the thickness was 54 μm. The amount of zinc deposited per unit area calculated from the amount of zinc deposited was 36.9 mg / cm. 2 , the capacity per unit area calculated from this is 30.2mAh / cm 2 The capacity is 2mAh / cm, which is the average capacity of the negative electrode of a lithium-ion secondary battery. 2 This value was more than 15 times larger than that of the conventional method. Note that the capacity here refers to the amount of electricity calculated from the mass of the reactants using Faraday's law, and is sometimes also used to refer to the amount of electricity charged or discharged, such as charge capacity or discharge capacity.

[0112] A commercially available masking material for plating was applied to the zinc-plated copper sheet obtained as described above, leaving only a circular area 20 mm in diameter from the center of one side of the zinc plated surface, as shown in FIG. 16. Next, as shown in FIG. 17, four 5 mm diameter circles were placed within this 20 mm diameter circular area, with the closest distance between the circular areas vertically or horizontally being 3 mm. A commercially available masking material was then applied to the remaining area. An acrylic resin reaction space-restricting portion with multiple communication holes and openings, as shown in FIG. 4, was then attached to the masking material-coated surface. After allowing the masking material to solidify, a zinc negative electrode according to Example 4 was produced, in which the zinc-plated copper sheet and the reaction space-restricting portion were integrated. The contour of the exposed zinc plating coincided with the cylindrical contour of the reaction space-restricting portion. Referring to the reference numerals in FIG. 4, this reaction space restricting portion 330 is a plate having outer dimensions of 27 mm, 27 mm, and 2 mm, which is a main body portion 331. Electrolyte holding portions 332a, 332b, 332c, and 332d, each having a diameter of 5 mm, are formed so that the closest distance between them in the vertical or horizontal directions is 3 mm, and are arranged corresponding to the exposed zinc portions of the zinc-plated copper plate after the masking. Furthermore, the upper and lower electrolyte holding portions 332a, 332c and the electrolyte holding portions 332b, 332d in the figure are connected by communication holes 332a, 332b, 332d having a diameter of 1.4 mm x 1.4 mm. 4 have 1.4 mm x 1.4 mm openings 334a and 334b ​​formed to the ends of the resin plate in the opposite direction from the lower electrolyte retention parts 332c and 332d, respectively, and the lower electrolyte retention parts 332c and 332d have 1.4 mm x 1.4 mm openings 334c and 334d formed to the ends of the resin plate in the opposite direction from the upper electrolyte retention parts 332a and 332b, respectively.

[0113] For ease of explanation of the layout, the schematic diagram in Figure 18 will be referred to again. The zinc negative electrode 10 of Example 4 prepared as described above and a pre-charged nickel positive electrode 60 (approximately 50 mm square and 5 mm thick) were placed facing each other in an acrylic container. A resin plate (resin spacer) 80 was attached to the back side of the zinc negative electrode 10 so that the reaction space-limiting portion of the zinc negative electrode 10 of Example 4 and the nickel positive electrode 60 were in close contact with each other, and this was fastened with screws 70. The nickel positive electrode 60 used was the one typically used in nickel-metal hydride secondary batteries. When fully discharged, it is primarily composed of nickel hydroxide, and when fully charged, the nickel hydroxide is oxidized to nickel oxyhydroxide. A liquid electrolyte 50 consisting of a 6 mol / L potassium hydroxide aqueous solution saturated with zinc oxide was then added to the acrylic container to prepare a zinc-nickel secondary battery. A 1 mm diameter zinc wire was placed near the zinc negative electrode but not in contact with it within the acrylic container of Example 4. The potential of the zinc negative electrode was also measured using this zinc wire as a reference electrode.

[0114] <Evaluation> The zinc-nickel secondary battery fabricated as described above was charged and discharged at a constant current. The charge-discharge cycle test was conducted in the same manner as in Comparative Example 2, except that the conditions for switching between charge and discharge were as follows. As in Example 4, the battery voltage and the potential of the zinc negative electrode were simultaneously measured using a zinc-nickel secondary battery equipped with a zinc reference electrode. It was found that the change in battery voltage corresponded to the change in the potential of the zinc negative electrode. Therefore, the conditions for switching from charge or discharge to rest were set in terms of the potential of the zinc negative electrode so as to match those for the battery voltage. Specifically, when the potential of the zinc negative electrode relative to the zinc reference electrode became higher than 0.2 V during discharge, the battery terminated and the battery switched to rest. When the potential of the zinc negative electrode relative to the zinc reference electrode became lower than -2 V during charge, the battery terminated and the battery switched to rest. Note that the changes in battery voltage and the potential of the zinc negative electrode were opposite; when the battery voltage decreased during discharge, the potential of the zinc negative electrode increased, and when the battery voltage increased during charge, the potential of the zinc negative electrode decreased. In this way, the switching condition was changed from the battery voltage to the zinc negative electrode potential, but the charge and discharge voltages of the battery in the latter case were in the same range as in the former case, as will be shown in the results below. Therefore, the switching condition did not affect the results of the charge-discharge cycle test.

[0115] The relationships between the average discharge voltage, average charge voltage, and current efficiency and the number of charge-discharge cycles obtained in Example 4 are shown in Figures 37 and 38, respectively. The definition and meaning of current efficiency are the same as those described in Example 1. As shown in Figures 37 and 38, for the zinc-nickel secondary battery using the zinc negative electrode of Example 4, at 400 cycles, during data acquisition, the average charge voltage was almost the same as at the initial stage, and the average discharge voltage only slightly decreased. No sudden drop in discharge voltage or increase in charge voltage, which would indicate dendrite shorting, was observed, demonstrating stable charge-discharge capability for 400 cycles or more. Furthermore, the current efficiency was maintained at 100% from the initial stage to 400 cycles, and no capacity loss due to active material non-uniformity or dendrite shorting was observed. It was revealed that the battery capacity could be maintained with high current efficiency. Note that the results of Example 4 only show results obtained during data acquisition, and do not indicate that charge-discharge became impossible at 400 cycles.

[0116] Example 5 The zinc negative electrode produced in Example 5 had the same design and dimensions of the reaction space restricting portion as in Example 3, but the vertical structure in Example 3 was changed to a horizontal structure in Example 5. The pretreatment of the copper plate before zinc plating and the plating amount were the same as in Example 4. Specifically, a zinc-nickel secondary battery was produced as follows.

[0117] The copper plate shown in Figure 15 was electroplated using the same method and conditions as in Example 4. Furthermore, a commercially available masking material was applied to the remaining area of ​​the zinc-plated surface, except for a circular area 20 mm in diameter from the center, as shown in Figure 15. Next, referring to the reference numerals in Figure 6, the commercially available masking material was applied to the 20 mm diameter circular area, except for the areas corresponding to the electrolyte retention portions 532a, 532b, 532c, and 532d of the reaction space-restricting portion 530 shown in Figure 6, i.e., the four 4.43 mm square areas. Furthermore, an acrylic resin reaction space-restricting portion 530 having a plurality of communication holes 533a, 533b and openings 534a, 534b, 534c, and 534d shown in Figure 6 was attached to the surface coated with the masking material, and the zinc negative electrode of the present invention, in which the zinc-plated copper plate and the reaction space-restricting portion 530 were integrated, was fabricated. The reaction space regulating portion 530 is formed by forming four 4.43 mm square electrolyte holding portions 532a, 532b, 532c, and 532d on a plate with outer dimensions of 27 mm, 27 mm, and 3 mm, and the electrolyte holding portions 532a, 532b, 532c, and 532d are formed so that the closest distance between them in the vertical or horizontal directions is 3 mm. 6, the upper and lower electrolyte retention portions 532a, 532c and 532b, 532d are connected by 2 mm x 2 mm communication holes 533a, 533b, respectively. The upper electrolyte retention portions 532a, 532b in the drawing have 2 mm x 2 mm openings 534a, 534b formed in the opposite direction from the lower electrolyte retention portions 532c, 532d, and to the end of the main body portion 531 of the reaction space-restricting portion 530. The lower electrolyte retention portions 532c, 532d have 2 mm x 2 mm openings 534c, 534d formed in the opposite direction from the upper electrolyte retention portions 532a, 532b, and to the end of the main body portion 531 of the reaction space-restricting portion 530. The reaction space-restricting portion 530 of Example 5 was designed so that the total opening area of ​​its electrolyte retention portions was the same as that of Example 1.

[0118] The zinc negative electrode of Example 5 prepared as described above and a pre-charged nickel positive electrode (approximately 50 mm square and 5 mm thick) were placed facing each other in an acrylic container, as in Example 1. A resin plate was attached to the back side of the zinc negative electrode so that the reaction space-restricting portion of the zinc negative electrode of Example 5 and the nickel positive electrode were in close contact, and this was fastened with screws. For ease of explanation of the arrangement, please refer to the schematic diagram of Figure 39. The zinc negative electrode 10 of Example 5 prepared as described above and a pre-charged nickel positive electrode 60 (approximately 50 mm square and 5 mm thick) were placed facing each other in an acrylic container. A resin plate (resin spacer) 80 was attached to the back side of the zinc negative electrode 10 so that the reaction space-restricting portion of the zinc negative electrode 10 of Example 5 and the nickel positive electrode 60 were in close contact, and this was fastened with screws 70. Thus, unlike Examples 1 to 4, in which the zinc negative electrode 10 and the nickel positive electrode 60 were each arranged vertically (see FIG. 18), Example 5 differed from them in that the zinc negative electrode 10 and the nickel positive electrode 60 were each arranged horizontally (horizontally). The nickel positive electrode 60 used was the same as that typically used in nickel-metal hydride secondary batteries, and is primarily composed of nickel hydroxide when fully discharged, and nickel oxyhydroxide when fully charged due to the oxidation of the nickel hydroxide. A liquid electrolyte 50 consisting of a 6 mol / L potassium hydroxide aqueous solution saturated with zinc oxide was then added to an acrylic container to prepare a zinc-nickel secondary battery.

[0119] <Evaluation> The zinc-nickel secondary battery prepared as described above was charged and discharged at a constant current under the same conditions as in Example 4. The relationships between the average discharge voltage, average charge voltage, and current efficiency and the number of charge-discharge cycles obtained in Example 5 are shown in Figures 40 and 41, respectively. The definition and meaning of current efficiency are the same as those described in Example 1. As shown in Figures 40 and 41, for the zinc-nickel secondary battery using the zinc negative electrode of Example 5, at 400 cycles, during data acquisition, the average charge voltage was almost the same as at the initial stage, and the average discharge voltage only slightly decreased. No sudden decrease in discharge voltage or increase in charge voltage, which would indicate dendrite shorting, was observed, demonstrating stable charge-discharge capability for 400 cycles or more. Furthermore, the current efficiency was maintained at 100% from the initial stage to 400 cycles, and no capacity loss due to active material non-uniformity or dendrite shorting was observed. It was revealed that the battery capacity could be maintained with high current efficiency. Note that the results of Example 5 only show results obtained during data acquisition, and do not indicate that charge-discharge became impossible at 400 cycles.

[0120] Example 6 The zinc negative electrode produced in Example 6 had the same design and dimensions of the reaction space restricting portion as in Example 2, but while Example 2 had a vertical structure, Example 6 had a horizontal structure similar to Example 5. The pretreatment of the copper plate before zinc plating and the plating amount were the same as in Example 4. Specifically, a zinc-nickel secondary battery was produced as follows.

[0121] The copper plate shown in FIG. 15 was electroplated using the same method and conditions as in Example 4. Furthermore, a commercially available masking material was applied to the remaining portion of the zinc-plated surface, leaving a circular area 20 mm in diameter from the center as shown in FIG. 15. Next, a zinc negative electrode was fabricated in the same manner as in Example 2, with the reaction space-restricting portion shown in FIG. 32 formed within this 20 mm diameter circular area. For ease of explanation of the layout, the schematic diagram in FIG. 39 will be referred to again. The zinc negative electrode 10 of Example 6 fabricated as described above and a pre-charged nickel positive electrode 60 (approximately 50 mm square and 5 mm thick) were placed facing each other in an acrylic container, as in Example 1. A resin plate (resin spacer) 80 was abutted against the back side of the zinc negative electrode 10 so that the resin reaction space-restricting portion of the zinc negative electrode 10 of Example 6 and the nickel positive electrode were in close contact with each other, and this was fastened with screws 70. As in Example 5, the zinc negative electrode and nickel positive electrode were then arranged horizontally as shown in the schematic diagram in FIG. 39. The nickel positive electrode 60 used is the one typically used in nickel-metal hydride secondary batteries, and when fully discharged, it is mainly composed of nickel hydroxide, and when fully charged, the nickel hydroxide is oxidized to nickel oxyhydroxide. A liquid electrolyte 50 consisting of a 6 mol / L potassium hydroxide aqueous solution saturated with zinc oxide was then added to the acrylic container to prepare a zinc-nickel secondary battery.

[0122] <Evaluation> The zinc-nickel secondary battery prepared as described above was charged and discharged at a constant current under the same conditions as in Example 4. The relationships between the average discharge voltage, average charge voltage, and current efficiency and the number of charge-discharge cycles obtained in Example 6 are shown in Figures 42 and 43, respectively. The definition and meaning of current efficiency are the same as those described in Example 1. As shown in Figures 42 and 43, for the zinc-nickel secondary battery using the zinc negative electrode of Example 6, at 400 cycles, during data acquisition, the average charge voltage was almost the same as at the initial stage, and the average discharge voltage only slightly decreased. No sudden decrease in discharge voltage or increase in charge voltage, which would indicate dendrite shorting, was observed, demonstrating stable charge-discharge capability for over 400 cycles. Furthermore, the current efficiency was maintained at 100% from the initial stage to 400 cycles, and no capacity loss due to active material non-uniformity or dendrite shorting was observed. It was revealed that the battery capacity could be maintained with high current efficiency. Note that the results of Example 6 only show results obtained during data acquisition, and do not indicate that charge-discharge became impossible at 400 cycles.

[0123] The zinc negative electrode according to the present invention is not limited to the one shown in Examples 1 to 6, in which zinc, the active material, is electroplated onto a current collector and then integrated with a reaction space restricting portion by utilizing the adhesion due to the solidification of a masking material. For example, a structure such as that shown in FIG. 44 may also be used. The zinc negative electrode 10 shown in FIG. 44 has a structure in which a negative electrode active material (active material portion 1) is filled into a portion of the electrolyte retention portion of the reaction space restricting portion 3, and the negative electrode active material and current collector 2 are electrically connected by a current collector having protrusions that coincide with the hollow portion formed directly below the active material portion 1 of the reaction space restricting portion 3. A zinc negative electrode having such a structure can be fabricated by fabricating a reaction space restricting portion of resin having a cross-sectional shape and a surface structure such as that shown in FIG. 3, for example, and fabricating a metal current collector having protrusions that coincide with the hollow portion in the reaction space restricting portion as shown in FIG. 44, and then integrally forming the two, and then filling the reaction space restricting portion with the metal, the negative electrode active material, or forming it by electroplating.

[0124] While the examples in this specification show examples using copper as the current collector and zinc as the active material portion, zinc negative electrodes integrally formed with the reaction space-restricting portion of the present invention were also fabricated using zinc plate as the current collector and electroplated zinc as the active material portion, and charge-discharge cycle tests were performed. However, the results of the charge-discharge tests showed significant differences in the charge-discharge cycle characteristics even among zinc negative electrodes with reaction space-restricting portions of the same specifications. Therefore, observation of the zinc negative electrodes after charge-discharge tests revealed that not only the zinc in the active material portion but also the zinc in the current collector may be involved in the charge-discharge reaction. In other words, it is also noted that the effects of the present invention cannot be predicted or demonstrated with such a combination of zinc current collector and zinc active material portion. However, this note does not exclude the use of zinc as the current collector material in the zinc negative electrode of the present invention. In other words, in the implementation of the present invention, both the current collector and the active material portion may be made of zinc or a zinc alloy, or the current collector and the active material portion may be integrated and made of zinc or a zinc alloy. Such a structure may be such that a portion of zinc or zinc alloy in various shapes, such as a plate or foil, formed by various methods such as electroplating or rolling functions as a current collector, and the remainder functions as an active material portion. Furthermore, the secondary battery of the present invention may have the zinc negative electrode and positive electrode of the present invention arranged either vertically or horizontally. For example, Figures 2 and 39 show examples of horizontal arrangement, and Figure 18 shows an example of vertical arrangement.

[0125] Furthermore, although the examples in this specification show examples in which only zinc is used in the active material portion of the zinc negative electrode, zinc oxide may be used instead of zinc as the negative electrode active material, or a mixture of zinc and zinc oxide may also be used. That is, since zinc oxide is a substance generated by discharge, zinc oxide may be used as the negative electrode active material when the battery is fabricated in a discharged state. Thus, the negative electrode active material in the zinc negative electrode and fabrication method thereof of the present invention does not necessarily have to be zinc alone; it may be zinc oxide, or even a mixture of zinc and zinc oxide in an appropriate ratio. In other words, since zinc is a reductant in the electrochemical reaction and zinc oxide is an oxidant in the electrochemical reaction, the active material portion in the zinc negative electrode and fabrication method thereof of the present invention may contain a negative electrode active material in which the reductant or oxidant of the negative electrode reaction, or a mixture of the reductant and oxidant in an appropriate ratio, is present during fabrication. Furthermore, in addition to the reductant and oxidant of the negative electrode reaction, various additives, including those generally referred to as conductive additives and binders, may be mixed into the active material portion. For example, zinc has good conductivity in the active material portion, while zinc oxide generally has low conductivity. Therefore, as discharge progresses, the conductivity of the active material portion decreases. To suppress this, a conductive additive that has conductivity and does not adversely affect the negative electrode reaction itself may be mixed into the active material portion. Furthermore, because zinc and zinc oxide have different densities, the volume of the active material portion expands and contracts during charging and discharging of a zinc negative electrode. To prevent such volume changes from causing a portion of the active material to detach from the active material portion or reducing the conductivity of the active material, a binder for shaping stabilization may be mixed into the active material portion to suppress cracking, shedding, chipping, and shape changes of the active material portion due to expansion and contraction. For example, carbon is a well-known example of a conductive additive, and PTFE, PVA, SBR, PVDF, and other well-known examples of binders are available, and these can be used. However, the conductive additives and binders applicable to the present invention are not limited to these.In addition to the conductive additives and binders described above, a method of preparing a slurry containing a negative electrode active material and using it to fill the negative electrode active material into the active material portion or form it into a specific shape is also available. Auxiliaries added to adjust the viscosity of such slurries may be mixed into the active material portion after preparation. Furthermore, hydrogen generation is a well-known side reaction during charging in zinc negative electrodes using alkaline aqueous solutions as liquid electrolytes. Materials that suppress this hydrogen generation or suppress negative electrode self-discharge may be mixed into the active material portion along with the negative electrode active material. For example, bismuth may be mixed into the active material portion for this purpose, but this is not limited to this. Since side reactions at zinc negative electrodes vary depending on the type and concentration of the electrolyte, a side reaction suppressing material that suppresses not only hydrogen generation but also other side reactions may be mixed into the active material portion.

[0126] Example 7 The copper plate shown in Figure 15 was electroplated using the same method and conditions as in Example 4. Furthermore, as shown in Figure 16, a commercially available masking material was applied to the remaining area of ​​the zinc-plated surface, except for a circular area 20 mm in diameter from the center. Next, a commercially available masking material was applied to the area of ​​this 20 mm circular area where the reaction space-restricting portion shown in Figure 45 would be attached. An acrylic resin reaction space-restricting portion with multiple communicating holes and openings, as shown in Figure 45, was then attached to the masking material-coated surface. After allowing the masking material to harden, a zinc negative electrode according to Example 7 was fabricated, in which the zinc-plated copper plate and the reaction space-restricting portion were integrated. In this zinc negative electrode, the contour of the exposed zinc plating coincided with the cylindrical contour of the reaction space-restricting portion. Referring to the reference numerals in FIG. 45, this reaction space restricting portion 1030 is composed of a main body 1031 having outer dimensions (maximum width) of 12.0 mm in both length and width and a thickness of 3 mm, and electrolyte holding portions 1032a, 1032b, 1032c, and 1032d having a diameter of 5 mm are formed so that the closest distance between them in the vertical or horizontal directions is 1 mm so as to be positioned corresponding to the exposed zinc portions of the zinc-plated copper plate after the masking. Furthermore, the upper and lower electrolyte holding portions 1032a, 1032c and the electrolyte holding portions 1032b, 1032d in FIG. 45 are connected by a 2 mm×2 mm gap. The upper electrolyte retention portions 1032a and 1032b in Figure 45 are connected to each other by holes 1033a and 1033bb, and the upper electrolyte retention portions 1032a and 1032b in Figure 45 have 2 mm x 2 mm opening holes 1034a and 1034b respectively formed to the end of the main body portion 1031 on the opposite side from the lower electrolyte retention portions 1032c and 1032d, and the lower electrolyte retention portions 1032c and 1032d have 2 mm x 2 mm opening holes 1034c and 1034d respectively formed to the end of the main body portion 1031 on the opposite side from the upper electrolyte retention portions 1032a and 1032b. For ease of explanation of the layout, the schematic diagram in Figure 18 will be referred to again. The zinc negative electrode 10 of Example 7, prepared as described above, and a pre-charged nickel positive electrode 60 (approximately 50 mm square and 5 mm thick) were placed facing each other in an acrylic container. A resin plate (resin spacer) 80 was attached to the back side of the zinc negative electrode 10 so that the reaction space-restricting portion of the zinc negative electrode 10 of Example 7 and the nickel positive electrode 60 were in close contact with each other, and this was fastened with screws 70. The nickel positive electrode 60 used was a type commonly used in nickel-metal hydride secondary batteries. In a fully discharged state, it is mainly composed of nickel hydroxide, and in a fully charged state, the nickel hydroxide is oxidized to form nickel oxyhydroxide. A liquid electrolyte 50 consisting of a 6 mol / L potassium hydroxide aqueous solution saturated with zinc oxide was then added to the acrylic container to prepare a zinc-nickel secondary battery.

[0127] <Evaluation> The zinc-nickel secondary battery prepared as described above was charged and discharged as follows. <1> ~ <10> One pattern consisted of 10 steps performed sequentially. <1> 1C (1 minute) <2> 2C (2 seconds) <3> 1C (1 minute) <4> 4C(2 seconds) <5> 1C (1 minute) <6> 6C(2 seconds) <7> 1C (1 minute) <8> 8C(2 seconds) <9> 1C (1 minute) <10> 10C (2 seconds) After fabrication, the battery was first discharged three times in succession from a 100% SOC state, followed by three cycles of charging. This constituted one cycle of high-rate testing. Next, the battery was discharged at 1C until the SOC reached 90%, and another cycle of high-rate testing was performed. After this, the battery was discharged at 1C until the SOC reached 80%, and then another cycle of high-rate testing was performed from 10% SOC reductions of 70%, 60%, 50%, and 40%. A total of seven cycles of high-rate testing were performed, and the discharge voltage, charge voltage, and rest voltage were recorded. The high-rate testing was performed for the specified duration (1 minute or 2 seconds) and was set to switch to the next step when the battery reached 1V for discharge and 3V for charge, but these voltages were never actually reached.

[0128] Figure 46 shows an example of the change over time in discharge voltage obtained for the zinc-nickel secondary battery of Example 7. The horizontal axis of Figure 46 represents time in seconds, and the vertical axis represents the battery voltage during discharge in volts (V). For convenience, the horizontal axis is plotted so that 0 second represents the start of a 2-second period of discharge at rates ranging from 2C to 10C. That is, discharge was at 1C before 0 second, and continued at 1C after 2 seconds. Figure 46 also shows that the zinc-nickel secondary battery of the present invention exhibited a stable discharge voltage of 1.6V or higher even at extremely high discharge rates up to 10C. It was also found that after 2 seconds of high-rate discharge, the battery was able to almost recover to the voltage before high-rate discharge just 1 second later. Such characteristics are required for applications requiring instantaneous high power, such as hybrid vehicles, plug-in hybrid vehicles, electric vehicles, power supplies for preventing momentary power outages, emergency power supplies, and power stabilization supplies. The zinc anode of the present invention exhibited excellent high-rate discharge characteristics that were difficult to achieve with conventional zinc anodes.

[0129] Furthermore, Figure 47 shows an example of the change over time in charge voltage obtained for the zinc-nickel secondary battery of Example 7. As with Figure 46, the horizontal axis in this figure represents time in seconds, and the vertical axis represents the battery voltage during charging in volts (V). For convenience, the horizontal axis is shown with 0 second representing the start of two seconds of charging at rates ranging from 2C to 10C. That is, charging was at 1C before 0 seconds, and charging continued at 1C after 2 seconds. Figure 47 shows that the zinc-nickel secondary battery of the present invention exhibited a stable charge voltage of 2V or less even at extremely high charge rates up to 10C. It was also found that after two seconds of high-rate charging, the voltage returned to almost the level before high-rate charging just one second later. Such characteristics are required when rapid charging is necessary or desirable in various applications such as hybrid vehicles, plug-in hybrid vehicles, electric vehicles, power sources for preventing momentary power outages, emergency power sources, and power stabilization power sources, and it has been found that the zinc negative electrode of the present invention has extremely excellent high-rate charging characteristics that are difficult to achieve with conventional zinc negative electrodes.

[0130] Furthermore, when the C-rates of the results in Figures 46 and 47 were converted to current densities and the relationship between the discharge voltage or charge voltage and the current density was plotted, a linear relationship was obtained, and the battery resistance was calculated from the slope. As a result, the battery resistance during discharge was found to be 1.0 to 1.2 Ωcm over a wide range of SOC. 2 , the resistance during charging is 1.2 to 1.4 Ω cm 2 The results were very low. If zinc dendrites were to form or the active material were to become non-uniform, the amount of active material available for reaction would decrease, or the surface area of ​​the active material would decrease, resulting in increased reaction resistance even at the same current density, leading to increased battery resistance. The zinc anode of the present invention showed little change in battery resistance even when the SOC decreased, i.e., the depth of discharge increased, or when the SOC increased, i.e., the depth of charge increased. It was revealed that the uniformity of the reaction at the anode resulted in small battery resistance and small changes during charging and discharging.

[0131] In the examples shown so far, zinc-nickel secondary batteries were fabricated to evaluate the characteristics of the zinc negative electrode, and were fabricated in a charged state at the time. However, the method for fabricating a zinc negative electrode of the present invention and the method for fabricating a secondary battery using the zinc negative electrode of the present invention are not necessarily limited to fabrication in a charged state. Generally, secondary batteries are often fabricated in a discharged state, but in the case of zinc-air secondary batteries, by using zinc as the negative electrode active material as shown in the examples of this specification, the secondary battery can be fabricated in a charged state, and the charged state can be maintained until use by sealing the atmosphere side of the positive electrode (air electrode) with tape, for example, to prevent contact of oxygen with the positive electrode (air electrode). Zinc-air primary batteries currently on the market for use in hearing aids and the like are also fabricated and sold in this state.

[0132] Example 8 A copper plate (plated area: 20 mm × 20 mm × 0.2 mm, lead area: 5 mm × 90 mm × 0.2 mm) was pretreated with abrasive paper and oxalic acid etching. One side and side of the plated area and both sides and sides of the lead area were then masked with a commercially available plating masking material. Next, one side of the unmasked plated area was further masked with a commercially available plating masking material, leaving four 5 mm × 5 mm squares spaced 1 mm apart. The remaining area was then thoroughly dried. In this way, four 5 mm × 5 mm squares of exposed copper were produced, as shown in Figure 48. Next, a zinc plating bath was prepared by dissolving 1.2 mol / L zinc sulfate heptahydrate, 0.56 mol / L sodium sulfate, and 0.02 g / L glue in distilled water at a pH of 2. This zinc plating bath was placed in a beaker, and the copper plate and a platinum plate (50 mm x 50 mm x 0.1 mm) with platinum wires attached as leads were immersed in the zinc plating bath, facing each other at a distance of about 5 cm. This was then placed on a hot stirrer and heated to 40°C. A constant current was then passed through the copper plate as the cathode and the platinum plate as the anode for a certain period of time to electroplat zinc on the unmasked parts of the copper plate. At this time, a current of 150 mA / cm was applied based on the area of ​​the zinc electroplated part. 2The current was applied for 281 seconds at 1000 kJ / s. The mixture was stirred with a stirrer while the current was being applied. The weight of the copper plate before the current was subtracted from the weight of the copper plate after the current was applied, and this was taken as the amount of zinc deposited by electroplating. The ratio of this to the theoretical amount of zinc deposited calculated from Faraday's law was calculated to be 92%, for example, and the thickness was 18.5 μm. The amount of zinc deposited per unit area calculated from the amount of zinc deposited was 13.2 mg / cm. 2 , the capacity per unit area calculated from this is 10.8mAh / cm 2 The capacity is 2mAh / cm, which is the average capacity of the negative electrode of a lithium-ion secondary battery. 2 This value was more than five times larger than that of the conventional method. Note that the capacity here refers to the amount of electricity calculated from the mass of the reactants using Faraday's law, and is sometimes also used to refer to the amount of electricity charged or discharged, such as charge capacity and discharge capacity.

[0133] A cross-shaped reaction space-restricting portion made of acrylic resin and having two communicating holes, as shown in Figure 49, was prepared. A commercially available plating masking material was thinly applied to one side of the cross. The coated surface of the reaction space-restricting portion was then brought into close contact with the cross defined at the center of the copper plate by the four exposed zinc areas in the center of the copper plate shown in Figure 48. The reaction space-restricting portion was then dried until it was integrated with the copper plate. In this way, a zinc negative electrode according to Example 8 was prepared, in which the zinc-plated copper plate and the reaction space-restricting portion were integrated. In this zinc negative electrode, the outline of the exposed zinc plating areas coincides with the outline of the cross in the reaction space-restricting portion. Referring to the symbols in Figure 49, this reaction space regulating portion 1130 has a main body 1131 which is a cross-shaped plate measuring 11 mm in length, 11 mm in width, and 3 mm in thickness, and has square electrolyte holding portions 1132a, 1132b, 1132c, and 1132d with sides of 5 mm formed so that the closest distance between them in the vertical or horizontal directions is 1 mm so that they correspond to the exposed zinc parts of the zinc-plated copper plate after the masking.Furthermore, the upper and lower electrolyte holding portions 1132a, 1132c and electrolyte holding portions 1132b, 1132d in the figure are connected to each other by 2 mm x 2 mm communicating holes 1133a, 1133b, respectively.

[0134] The layout of a zinc-air secondary battery using the zinc negative electrode of Example 8 fabricated as described above will be described with reference to the schematic diagram in FIG. 50. The zinc negative electrode 10 of Example 8 and an air electrode 65 (approximately 16 mm square and 0.2 mm thick) fabricated by the method described below were placed facing each other in an acrylic container. A resin plate (resin spacer) 80 was attached to the back side of the zinc negative electrode 10 so that the reaction space-restricting portion of the zinc negative electrode 10 of Example 8 and the air electrode 65 were in close contact, and the battery was fastened with screws 70. A liquid electrolyte 50 consisting of a 6 mol / L potassium hydroxide aqueous solution saturated with zinc oxide was then added through an inlet (not shown in FIG. 50) formed in the acrylic container to fabricate a zinc-air secondary battery. In FIG. 50, one side of the air electrode 65 is in contact with the liquid electrolyte 50, and the other side is open to the atmosphere and in contact with air. That is, the air electrode 65 takes in oxygen from the air-open side during discharge and releases oxygen from the air-open side during charge. In addition, in Figure 50, the edges of the four liquid electrolyte retention parts are surrounded by an acrylic container. That is, within the battery in Figure 50, the four liquid electrolyte retention parts are restricted to a shape of 5 mm x 5 mm x 3 mm.

[0135] The air electrode of the zinc-air secondary battery according to Example 8 described above was prepared as follows. First, the catalyst used in the air electrode was prepared as follows. Tetra-n-propylammonium bromide (dispersant), ruthenium (III) chloride hydrate, and bismuth (III) nitrate hydrate were dissolved in distilled water at 75°C to prepare a 500 mL solution. At this time, the concentrations of ruthenium and bismuth were 7.44 × 10 -3 mol / L, and the dispersant concentration is 3.72 × 10 -2The solution was thoroughly stirred, and then 60 mL of a 2 mol / L NaOH aqueous solution was added dropwise. The mixture was stirred for 24 hours at 75°C while aerating oxygen. After stopping the stirring, the mixture was left to stand for 24 hours, then the supernatant was removed. The remaining precipitate was heated at 85°C for approximately 2 hours to form a paste. The paste was dried at 120°C for 3 hours. The dried product was crushed in a mortar and then heated from room temperature to 600°C in an air atmosphere, and then held at 600°C for 1 hour. The fired product was suction filtered using distilled water at approximately 70°C, and then dried at 120°C for 3 hours. The material obtained by the above procedure was analyzed using an X-ray diffractometer. The result was that the Bi 1.87 Ru2O 6.903 The diffraction data obtained matched those of the previous data (registration number 01-073-9239), indicating that the material was an oxygen-deficient pyrochlore oxide. Furthermore, the material was observed under a scanning electron microscope, and the particle size was analyzed using image analysis, revealing that the particle size was approximately 10 to 40 nm. Next, graphite powder with a particle size of approximately 1 μm was placed in a zirconia container along with zirconia balls with a diameter of 5 mm, and dry-milled in a ball mill at 1000 rpm for 10 minutes. After milling was complete, the zirconia container was immersed in ice water, removed from the container, and the milled graphite powder was collected. 25.5 mg of crushed graphite and 34.2 mg of catalyst were placed in a 14 cc sample tube, and 19.9 mg of PTFE suspension and 1 cc of distilled water were added thereto, followed by ultrasonic dispersion for 10 minutes using an ultrasonic stirrer to prepare a suspension. Next, a 200-mesh nickel mesh sheet was cut out so that the lead portion (3 mm × 35 mm) and the electrode portion (16 mm × 16 mm) were integrated, and the cutout was degreased with acetone. A porous PTFE membrane was placed on the nickel mesh sheet, and the sheet was sandwiched between 0.1 mm thick stainless steel plates. Next, the nickel mesh sheet sandwiched between the stainless steel plates was pressed with a uniaxial press at 16.4 kN / cm 2The nickel mesh sheet and the porous PTFE membrane were pressed together for 5 seconds at a pressure of 0.1 MPa, forming a single unit. This is hereafter referred to as the air electrode current collector. The air electrode current collector was placed on a hot plate set at 260°C with the PTFE membrane facing downwards. An airbrush containing the aforementioned suspension was then placed directly above the hot plate, and the suspension was sprayed onto the air electrode current collector for 0.5 seconds, followed by a 2-second pause to fabricate the air electrode. The compressor pressure for the airbrush was 0.1 MPa, and the distance from the tip of the airbrush to the air electrode current collector was 10 cm. Care was taken to prevent the suspension from adhering to the lead portion.

[0136] <Evaluation> The zinc-air secondary battery fabricated as described above was charged and discharged as follows. First, the charge / discharge rate was calculated based on the negative electrode capacity, and the discharge and charge voltages were measured at rates of 0.5C, 0.75C, 1.0C, 1.25C, 1.5C, and 2.0C. At each charge / discharge rate, the battery was cycled at least three times, with a 2-minute rest and a 2-minute current cycle, to confirm the reproducibility of the battery voltage. In addition to the specified current cycle time (2 minutes), the test was set to switch to the next step when the battery reached 1V for discharge and 3V for charge, but these voltages were never actually reached. All tests at each charge / discharge rate were started from an SOC of 80%.

[0137] Figure 51 shows an example of the change over time in discharge voltage obtained for the zinc-air secondary battery of Example 8. The horizontal axis of Figure 51 represents time in seconds, and the vertical axis represents the battery voltage during discharge in volts (V). The horizontal axis is plotted so that the start of the 2-minute discharge at each rate is set to 0 seconds. Figure 51 shows that the zinc-air secondary battery of the present invention stabilized within just 10 seconds of the start of discharge at any discharge rate, and even at a high rate such as 2C, it exhibited a stable discharge voltage of 1.1V or higher. Such characteristics are required for applications requiring large amounts of power instantaneously, such as hybrid vehicles, plug-in hybrid vehicles, electric vehicles, power supplies for preventing power outages, emergency power supplies, and power stabilization supplies. The zinc anode of the present invention and the zinc-air secondary battery using the same exhibited excellent high-rate discharge characteristics that are difficult to achieve with conventional zinc anodes.

[0138] Furthermore, Figure 52 shows an example of the change over time in charge voltage obtained for the zinc-air secondary battery of Example 8. As with Figure 51, the horizontal axis in seconds represents time, and the vertical axis in volts represents the battery voltage during charging. The horizontal axis is plotted so that the start of the 2-second charging period at each rate is set to 0 seconds. Figure 52 shows that the zinc-air secondary battery of the present invention exhibited a stable charge voltage within approximately 50 seconds of the start of charging, regardless of the charge rate. Furthermore, even when charged at a high rate such as 2C, it exhibited a stable voltage of 2V or less. Such characteristics are required when rapid charging is necessary or desirable in various applications, such as hybrid vehicles, plug-in hybrid vehicles, electric vehicles, power supplies for preventing momentary power outages, emergency power supplies, and power stabilization supplies. It was found that the zinc anode and zinc-air secondary battery of the present invention possess extremely excellent high-rate charge characteristics that are difficult to achieve with conventional zinc anodes.

[0139] Example 9 A zinc negative electrode was fabricated in the same manner as in Example 8, in which the zinc-plated copper plate shown in FIG. 48 and the cross-shaped reaction space restricting portion shown in FIG. 49 were integrally formed. The layout of a zinc-air secondary battery using the zinc negative electrode of Example 9 will be described with reference to the schematic diagram of FIG. 53. The zinc negative electrode 10 of Example 9 was placed at the bottom of an acrylic container, and an air electrode 65 (approximately 16 mm square and 0.2 mm thick) fabricated by the method described below was placed on top of the zinc negative electrode 10. An acrylic pressure plate with an opening was placed on top of the air electrode 65 so that the reaction space restricting portion of the zinc negative electrode 10 of Example 9 was in close contact with the air electrode 65. A liquid electrolyte 50 consisting of a 6 mol / L potassium hydroxide aqueous solution saturated with zinc oxide was then added through an inlet channel (not shown in FIG. 53) formed in the acrylic container to fabricate a zinc-air secondary battery. In FIG. 53, the lower side of the air electrode 65 is in contact with the liquid electrolyte 50, and the upper side is open to the atmosphere and in contact with air. That is, the air electrode 65 takes in oxygen from the side open to the atmosphere during discharge, and releases oxygen from the side open to the atmosphere during charge. Also, in FIG. 53, the ends of the four liquid electrolyte retention units are enclosed by an acrylic container. However, an inlet path for introducing the aforementioned liquid electrolyte 50 is provided in part of the wall of the enclosing acrylic container. That is, within the battery of FIG. 53, the four liquid electrolyte retention units, excluding the inlet path, are restricted to a shape of 5 mm x 5 mm x 3 mm.

[0140] The air electrode of the zinc-air secondary battery according to Example 9 shown above was fabricated as follows. First, the catalyst used for the air electrode was prepared as in Example 8. 0.093 g of this catalyst and 0.068 g of carbon powder were mixed for 10 minutes, followed by the addition of 0.04 g of PTFE suspension, 61 mL of liquid paraffin, and 61 mL of distilled water, and the mixture was kneaded until it became a clay-like substance. This mixture was sandwiched between 0.1 mm thick stainless steel plates and placed in a heat roll press. Next, nickel mesh, which would become the air electrode current collector, was cut into a shape that integrated the lead portion (3 mm × 35 mm) and the electrode portion (16 mm × 16 mm). This was degreased with acetone, and the mixture was rolled. This mixture was then layered on top of the nickel mesh and placed in a heat roll press to be integrated. The roll speed was 50 cm / min, the press pressure was 1 MPa, and the roll temperature was 80°C. After the roll press, the sample was immersed in turpentine oil for 1 hour to remove any remaining liquid paraffin, and then in ethanol for 1 hour to remove the turpentine. After removal from the ethanol, the sample was allowed to air dry for approximately half a day. A porous PTFE membrane was placed on the nickel mesh side of the product obtained in this way, and the resultant was sandwiched between stainless steel plates and then roll-pressed again to obtain an air electrode (thickness: 0.18 mm).

[0141] <Evaluation> The zinc-air secondary battery prepared as described above was charged and discharged as follows. First, the prepared zinc-air secondary battery was fully charged with an SOC of 100%, and then discharged at a discharge rate of 1C until the SOC reached 80%. The charge and discharge rate was calculated based on the negative electrode capacity. Next, from an SOC of 80%, the battery was discharged at 1C for 21 seconds in the following order: 1C (21 seconds), 2C (2 seconds), 1C (21 seconds), 4C (2 seconds), 1C (21 seconds), 6C (2 seconds), 1C (21 seconds), 8C (2 seconds), 1C (21 seconds), and 10C (2 seconds). After that, the battery was discharged at 1C for 21 seconds at a high rate between 2C and 10C, and this pattern was repeated three times. After this, the battery was charged using the same pattern.

[0142] Figure 54 shows an example of the change over time in discharge voltage obtained for the zinc-air secondary battery of Example 9. The horizontal axis of Figure 54 represents time in seconds, and the vertical axis represents the battery voltage during discharge in volts (V). For convenience, the horizontal axis is plotted so that 0 second represents the start of a 2-second period of discharge at rates ranging from 2C to 10C. That is, discharge was at 1C before 0 second, and continued at 1C after 2 seconds. Figure 54 shows that the zinc-air secondary battery of the present invention exhibited a high discharge voltage of approximately 1V even at extremely high discharge rates up to 10C. It was also found that after 2 seconds of high-rate discharge, the battery was able to almost recover to the voltage before high-rate discharge just 3 seconds later. Such characteristics are required for applications requiring instantaneous high power, such as hybrid vehicles, plug-in hybrid vehicles, electric vehicles, power supplies for preventing momentary power outages, emergency power supplies, and power stabilization supplies. The zinc anode of the present invention exhibited excellent high-rate discharge characteristics that were difficult to achieve with conventional zinc anodes. Furthermore, such high-rate discharge is possible with the zinc-air secondary battery of the present invention because, as shown in Example 7, the zinc negative electrode of the present invention has excellent high-rate characteristics, and the air electrode used in the zinc-air secondary battery of the present invention also has excellent high-rate characteristics; with zinc-air secondary batteries of conventional technology, it is difficult to maintain a high voltage such as 1 V when discharging at 10 C.

[0143] Furthermore, Figure 55 shows an example of the change over time in charge voltage obtained for the zinc-air secondary battery of Example 9. As with Figure 54, the horizontal axis of Figure 55 represents time in seconds, and the vertical axis represents the battery voltage during charging in volts (V). For convenience, the horizontal axis is plotted so that 0 second represents the start of the 2-second period of charging at rates ranging from 2C to 10C. That is, charging was at 1C before 0 seconds, and charging continued at 1C after 2 seconds. Figure 55 shows that the zinc-air secondary battery of the present invention exhibited a low charge voltage of 2.1V or less, even at extremely high charge rates up to 10C. It was also found that after 2 seconds of high-rate charging, the voltage returned to nearly the level before high-rate charging just 1 second later. Such characteristics are required when rapid charging is necessary or desirable in various applications such as hybrid vehicles, plug-in hybrid vehicles, electric vehicles, power supplies for preventing momentary power outages, emergency power supplies, and power stabilization power supplies, and it has been found that the zinc anode of the present invention has extremely excellent high-rate charging characteristics that are difficult to achieve with conventional zinc anodes.Furthermore, such high-rate charging is possible with the zinc-air secondary battery of the present invention because, as shown in Example 7, the zinc anode of the present invention has excellent high-rate characteristics, and the air electrode used in the zinc-air secondary battery of the present invention also has excellent high-rate characteristics.With conventional zinc-air secondary batteries, it is difficult to reach a low voltage of 2.1 V or less when charging at 10 C.

[0144] Example 10 In Example 10, the same vertically arranged cell as in Example 1 and the same design and dimensions of the reaction space-restricting portion were used, but the plating amount was three times that of Example 1, as in Example 4. A zinc-nickel secondary battery was also fabricated in the same manner as in Example 1. That is, referring again to the schematic diagram in FIG. 18 , the zinc negative electrode 10 according to Example 10 fabricated as described above and a pre-charged nickel positive electrode 60 (approximately 50 mm square and 5 mm thick) were placed facing each other in an acrylic container, and a resin plate (resin spacer) 80 was attached to the back side of the zinc negative electrode 10 according to Example 4 so that the reaction space-restricting portion of the zinc negative electrode 10 and the nickel positive electrode 60 were in close contact with each other, and this was fastened with screws 70. The nickel positive electrode 60 used was a type commonly used in nickel-metal hydride secondary batteries, and in a fully discharged state, it is mainly composed of nickel hydroxide, and in a fully charged state, the nickel hydroxide is oxidized to nickel oxyhydroxide. Thereafter, a liquid electrolyte 50 consisting of a 6 mol / L aqueous potassium hydroxide solution saturated with zinc oxide was added to the acrylic container to prepare a zinc-nickel secondary battery.

[0145] The zinc-nickel secondary battery of Example 10 was first charged at 10 mA / cm 2 at 3.9mAh / cm 2 The zinc negative electrode was discharged for 100 seconds, oxidizing part of the zinc in the zinc negative electrode to form zinc oxide. The zinc negative electrode was then removed from the zinc-nickel secondary battery, washed with distilled water, and thoroughly dried for about a day. In this way, a discharged zinc negative electrode was prepared. While the discharged zinc negative electrode was prepared using a zinc-nickel secondary battery in the above example, it is possible to prepare a discharged zinc negative electrode in a similar manner to the above example, even without a zinc-nickel secondary battery. For example, an alkaline aqueous solution such as a potassium hydroxide aqueous solution was used as the liquid electrolyte, the zinc negative electrode was immersed in the solution, an electrode insoluble in the alkaline aqueous solution was prepared, these were connected to a power source, and a predetermined amount of electricity was applied to the zinc negative electrode as the anode and the other electrode as the cathode. In other words, the oxidation process for converting part or all of the zinc in the zinc negative electrode to zinc oxide can be performed using various combinations of the alkaline aqueous solution and other electrodes described above, and is not limited to the above. Furthermore, the zinc negative electrode can also be heat-treated in an oxidizing atmosphere to convert part or all of the zinc into zinc oxide.

[0146] <Evaluation> The same zinc-nickel secondary battery was fabricated using the zinc negative electrode discharged as described above. Then, a charge-discharge cycle test was conducted under the same conditions as in Example 1. The relationships between the average discharge voltage, average charge-discharge voltage, and current efficiency versus the number of charge-discharge cycles obtained in Example 10 are shown in Figures 56 and 57, respectively. The definition and meaning of current efficiency are the same as those described in Example 1. As shown in Figures 56 and 57, for the zinc-nickel secondary battery using the zinc negative electrode of Example 10, at 377 cycles, during data acquisition, the average charge voltage was nearly the same as the initial value, and the average discharge voltage only slightly decreased. No sudden decrease in discharge voltage or increase in charge voltage, which would indicate dendrite shorting, was observed, demonstrating stable charge and discharge. Furthermore, the current efficiency remained nearly 100% from the initial value to 377 cycles, indicating no capacity loss due to active material nonuniformity or dendrite shorting. This demonstrates that the battery capacity can be maintained with high current efficiency. Note that the results in Example 10 only show results during data acquisition and do not indicate that charging and discharging became impossible at 377 cycles.

[0147] The zinc negative electrode and its manufacturing method, and the secondary battery and its manufacturing method that have been described through the embodiments and examples are illustrative explanations for achieving the effects of the present invention. For example, the electrolyte holding portion of the reaction space restricting portion does not need to be surrounded by only the main body of the zinc negative electrode, as long as it can hold a liquid electrolyte. If necessary, the liquid electrolyte may be held via a member other than the main body (e.g., a container, a positive electrode (air electrode), a spacer, etc.). [Industrial Applicability]

[0148] The zinc negative electrode of the present invention can be used in secondary batteries that use zinc as the negative electrode active material, such as secondary batteries, zinc-nickel secondary batteries, and zinc-silver secondary batteries. The secondary battery of the present invention can be used for a variety of applications, forms, and purposes, from relatively small-capacity batteries for mobile devices, hearing aids, wearable devices, and the like, to large-capacity batteries for hybrid vehicles, plug-in hybrid vehicles, electric vehicles, power supplies for preventing momentary power outages, emergency power supplies, power stabilization power supplies, stationary devices, power storage devices, and storage devices for solar power generation and wind power generation, as well as units consisting of multiple secondary batteries and systems in which control functions are added to the units. [Explanation of symbols]

[0149] 10 Zinc negative electrode 50 liquid electrolyte 60 positive electrode 65 Air electrode 70 screws 80 Resin board 90 Secondary battery 1, 110 Active material part 2, 120 current collector 3, 130 Reaction space control part 131 Main body 132a, 132b Electrolyte holding part 330 Reaction space control section 331 Main body 332a, 332b, 332c, 332d Electrolyte holding section 333a, 333b communication hole 334a, 334b, 334c, 334d open hole

Claims

1. A zinc negative electrode for use in a secondary battery, comprising: an active material portion that generates zinc during charging and generates zinc oxide during discharging, and in which the zinc is used as a negative electrode active material; a current collector electrically connected to the active material portion; a non-electron-conductive reaction space restricting portion integrally formed with or connected to the current collector and / or the active material portion, A zinc negative electrode, wherein the reaction space restricting portion has a plurality of electrolyte retention portions each consisting of a space capable of retaining a liquid electrolyte, and the reaction space restricting portion has either or both of a communication hole connecting the electrolyte retention portions to each other and an opening hole connecting the electrolyte retention portion to the end of the reaction space restricting portion.

2. 2. The zinc negative electrode of claim 1, wherein each of said electrolyte retaining portions has a circular cross-sectional shape.

3. 2. The zinc negative electrode of claim 1, wherein each of said electrolyte retaining portions has a polygonal cross-sectional shape.

4. The zinc negative electrode according to any one of claims 1 to 3, wherein the reaction space restricting portion is made of a plastic material.

5. 5. The zinc negative electrode according to claim 1, wherein at least one of the electrolyte retention portions has a different maximum diametric length from the other electrolyte retention portions.

6. 6. The zinc negative electrode according to claim 1, wherein the electrolyte retention portion has a maximum cross-sectional length of less than 20 mm.

7. The zinc negative electrode according to any one of claims 1 to 5, wherein the maximum diametric length of the electrolyte retention portion is 5 mm or less.

8. A method for producing a zinc negative electrode for use in a secondary battery, comprising: The zinc negative electrode is an active material portion that generates zinc during charging and generates zinc oxide during discharging, and in which the zinc is used as a negative electrode active material; a current collector electrically connected to the active material portion; a non-electron-conductive reaction space restricting portion integrally formed with or connected to the current collector and / or the active material portion, the reaction space restricting portion has a plurality of electrolyte retention portions each formed of a space capable of retaining a liquid electrolyte, and the reaction space restricting portion has either or both of a communication hole that connects the electrolyte retention portions to each other and an opening hole that connects the electrolyte retention portion to an end of the reaction space restricting portion; a step of integrally forming or connecting the current collector and the non-electron-conductive reaction space restricting portion; a step of electrically connecting the active material portion and the current collector; A method for producing a zinc negative electrode, comprising:

9. 9. The method of claim 8, further comprising an oxidation step of converting some or all of the zinc in the zinc negative electrode into an oxidation product of the zinc.

10. 10. The method for producing a zinc negative electrode according to claim 8 or 9, wherein the zinc oxidation product is zinc oxide.

11. A secondary battery comprising the zinc negative electrode according to any one of claims 1 to 7.

12. The secondary battery according to claim 11, an air electrode and the liquid electrolyte containing an alkaline aqueous solution; The electrolyte retention portion in the zinc negative electrode retains the liquid electrolyte between the air electrode and the active material portion.

13. The secondary battery according to claim 12 , wherein the air electrode comprises a pyrochlore-type bismuth ruthenium oxide.

14. 14. The secondary battery according to claim 13, wherein the bismuth ruthenium oxide contains manganese.

15. The secondary battery according to claim 14 , wherein the manganese is located at the B site of the pyrochlore structure.

16. The secondary battery according to any one of claims 13 to 15, wherein the bismuth ruthenium oxide contains sodium.

17. A method for producing a secondary battery, comprising: The zinc anode is an active material portion that generates zinc during charging and generates zinc oxide during discharging, and in which the zinc is used as a negative electrode active material; a current collector electrically connected to the active material portion; a non-electron-conductive reaction space restricting portion integrally formed with or connected to the current collector and / or the active material portion, the reaction space restricting portion has a plurality of electrolyte retention portions each formed of a space capable of retaining a liquid electrolyte, and the reaction space restricting portion has either or both of a communication hole that connects the electrolyte retention portions to each other and an opening hole that connects the electrolyte retention portion to an end of the reaction space restricting portion; a step of integrally forming or connecting the current collector and the non-electron-conductive reaction space restricting portion; a step of electrically connecting the active material portion and the current collector; forming a cathode; the air electrode is composed of an air electrode current collector, a conductive material, a catalyst, and a water-repellent material; the step of forming the air electrode further includes a mixing step of mixing the conductive material, the catalyst, and the water-repellent material, and a molding step of molding the mixture obtained in the mixing step into an air electrode having a predetermined shape.

18. The method for producing a secondary battery according to claim 17 , wherein in the mixing step, a suspension of the conductive material, the catalyst, and the water-repellent material is produced.

19. The method for producing a secondary battery according to claim 18 , wherein the forming step further comprises the step of spraying the suspension onto the air electrode current collector and drying the suspension.

20. 20. The method for producing a secondary battery according to claim 19, wherein in the forming step, the suspension is spray-applied onto the air electrode current collector while being maintained at a temperature equal to or higher than a temperature at which a solvent in the suspension can evaporate.

21. In the mixing step, the conductive material, the catalyst, and the water-repellent material are kneaded together, 18. The method for producing a secondary battery according to claim 17, wherein in the molding step, the mixture obtained in the mixing step is rolled and the mixture is heat-treated at a temperature of 400°C or less.

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