Zinc battery electrolyte and zinc battery

Abstract

To provide an electrolyte for a zinc battery capable of obtaining excellent cycle characteristics in the zinc battery and a zinc battery including the electrolyte.SOLUTION: An electrolyte for zinc batteries includes alkali metal hydroxide and non-reducing sugar. A zinc battery includes a positive electrode, a negative electrode, and the electrolyte for zinc batteries.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to an electrolyte for a zinc battery, a zinc battery, and the like. [Background technology]

[0002] Nickel-zinc batteries are aqueous batteries that use an aqueous electrolyte such as a potassium hydroxide solution, and are therefore highly safe. The combination of zinc and nickel electrodes provides a high electromotive force for an aqueous battery. Furthermore, nickel-zinc batteries offer excellent input / output performance and low cost, making them suitable for industrial applications (such as backup power sources) and automotive applications (such as hybrid vehicles).

[0003] The charge and discharge reactions of a nickel-zinc battery proceed, for example, according to the following formula (discharge reaction: rightward, charge reaction: leftward). (Positive electrode)2NiOOH+2H2O+2e - → 2Ni(OH)2+2OH - (Negative electrode) Zn+2OH - → Zn(OH)2+2e -

[0004] As shown in the above formula, in nickel-zinc batteries, zinc hydroxide (Zn(OH)2) is produced by the discharge reaction. Zinc hydroxide is soluble in the electrolyte, and when zinc hydroxide dissolves in the electrolyte, it turns into zinc tetrahydroxide ions ([Zn(OH)4] 2-) diffuses into the electrolyte. As a result, the morphology (deformation) of the negative electrode progresses and the distribution of the charging current becomes uneven, causing zinc to precipitate locally on the negative electrode, resulting in the formation of dendrites (branched crystals). In nickel-zinc batteries, if dendrites grow due to repeated charge and discharge, they can penetrate the separator, causing a short circuit, and the formation of such dendrites leads to a decrease in cycle performance. In response to this, for example, Patent Document 1 discloses a technology for preventing internal short circuits between positive and negative electrodes caused by zinc dendrites by interposing a nickel-plated nonwoven fabric between the positive and negative electrodes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 58-126665 Summary of the Invention [Problem to be solved by the invention]

[0006] Zinc batteries such as nickel-zinc batteries are required to have further improved cycle characteristics.

[0007] An object of one aspect of the present disclosure is to provide a zinc battery electrolyte that can provide excellent cycle characteristics in the zinc battery.An object of another aspect of the present disclosure is to provide a zinc battery including the zinc battery electrolyte. [Means for solving the problem]

[0008] One aspect of the present disclosure provides an electrolyte for a zinc battery, comprising an alkali metal hydroxide and a non-reducing sugar.

[0009] Another aspect of the present disclosure provides a zinc battery including a positive electrode, a negative electrode, and the above-described zinc battery electrolyte.

[0010] The above-described zinc battery electrolyte and zinc battery can provide excellent cycle characteristics. [Effects of the Invention]

[0011] According to one aspect of the present disclosure, it is possible to provide a zinc battery electrolyte that can achieve excellent cycle characteristics in a zinc battery. According to another aspect of the present disclosure, it is possible to provide a zinc battery including the zinc battery electrolyte. DETAILED DESCRIPTION OF THE INVENTION

[0012] A numerical range "A or greater" means a range exceeding A and A. A numerical range "A or less" means a range exceeding A and A. In the numerical ranges described in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. "A or B" may include either A or B, or both. Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more. In this specification, when multiple substances corresponding to each component are present in the composition, the amount of each component in the composition refers to the total amount of the multiple substances present in the composition, unless otherwise specified. In this specification, the terms "film" and "layer" include structures that are formed over the entire surface as well as structures that are formed only partially when observed in a plan view. In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended function of the process is achieved. The unit "C" relatively represents the magnitude of the current when discharging the rated capacity from a fully charged state at a constant current. The unit "C" means "discharge current value (A) / battery capacity (Ah)". For example, a current that can discharge the rated capacity in 1 hour is expressed as "1C", and a current that can discharge the rated capacity in 2 hours is expressed as "0.5C".

[0013] Hereinafter, embodiments of the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments and can be implemented in various modifications within the scope of the present disclosure.

[0014] The zinc battery electrolyte according to this embodiment (hereinafter sometimes simply referred to as "electrolyte") is used as an electrolyte for a zinc battery (e.g., a zinc secondary battery). The zinc battery according to this embodiment includes a positive electrode, a negative electrode, and the electrolyte according to this embodiment. The zinc battery may include a zinc electrode as the negative electrode. Examples of zinc batteries include nickel-zinc batteries (e.g., nickel-zinc secondary batteries) in which the positive electrode is a nickel electrode; air-zinc batteries (e.g., air-zinc secondary batteries) in which the positive electrode is an air electrode; and silver-zinc batteries (e.g., silver-zinc secondary batteries) in which the positive electrode is a silver oxide electrode.

[0015] The electrolyte solution according to this embodiment contains an alkali metal hydroxide and a non-reducing sugar. The electrolyte solution according to this embodiment can provide excellent cycle characteristics. The excellent cycle characteristics can be determined by the charge rate at 120 cycles. Furthermore, the zinc battery electrolyte solution can suppress a decrease in discharge capacity.

[0016] Factors that contribute to achieving this effect include, but are not limited to, the following: When the electrolyte solution contains a non-reducing sugar, the non-reducing sugar coordinates to the surface of the electrode (e.g., zinc in the negative electrode) to form a coating, thereby suppressing the dissolution and diffusion of zinc. This results in uniform zinc electrodeposition and improved cycle characteristics. Furthermore, since the non-reducing sugar does not have a reducing group, oxidative decomposition of the non-reducing sugar due to charge and discharge is suppressed. As a result, the cycle characteristics of the battery are improved and a decrease in discharge capacity can be suppressed.

[0017] Examples of alkali metal hydroxides include potassium hydroxide (KOH), sodium hydroxide (NaOH), and lithium hydroxide (LiOH). The alkali metal hydroxide may be ionized (dissociated) in an aqueous solution or may exist as a salt. From the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity, the alkali metal hydroxide may include at least one selected from the group consisting of potassium hydroxide and lithium hydroxide, and may also include potassium hydroxide.

[0018] The content of alkali metal hydroxide in the electrolyte (total amount of alkali metal hydroxide) may be within the following ranges based on the total amount of the electrolyte, from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The content of alkali metal hydroxide may be 10 mass% or more, 15 mass% or more, 20 mass% or more, 25 mass% or more, or 30 mass% or more. The content of alkali metal hydroxide may be 50 mass% or less, 45 mass% or less, 40 mass% or less, 35 mass% or less, or 30 mass% or less. From these viewpoints, the content of alkali metal hydroxide may be 10 to 50 mass%.

[0019] The content of potassium hydroxide in the electrolyte may be within the following ranges based on the total amount of the electrolyte, from the viewpoints of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The content of potassium hydroxide may be 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, or 28% by mass or more. The content of potassium hydroxide may be 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, or 30% by mass or less. From these viewpoints, the content of potassium hydroxide may be 10 to 50% by mass.

[0020] The content of lithium hydroxide in the electrolyte may be within the following ranges based on the total amount of the electrolyte, from the viewpoints of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The content of lithium hydroxide may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 1.5% by mass or more, 1.8% by mass or more, or 2% by mass or more. The content of lithium hydroxide may be 5% by mass or less, 4% by mass or less, 3% by mass or less, 2.5% by mass or less, or 2% by mass or less. From these viewpoints, the content of lithium hydroxide may be 0.1 to 5% by mass.

[0021] The electrolyte solution according to this embodiment contains a non-reducing sugar. A non-reducing sugar refers to a sugar that does not have a free reducing group, as opposed to a reducing sugar (a sugar that has a free aldehyde or ketone group, or a hemiacetal-bonded aldehyde or ketone group) (Chemical Dictionary, Tokyo Kagaku Dojin Co., Ltd., 1st Edition). That is, a non-reducing sugar refers to a sugar that does not have either a free aldehyde or ketone group or a hemiacetal-bonded aldehyde or ketone group. The non-reducing sugar may be a hydrate.

[0022] Examples of non-reducing sugars include disaccharides such as sucrose, trehalose, and hydrates thereof; trisaccharides such as kestose, melezitose, gentianose, and hydrates thereof; tetrasaccharides such as fungitetraose and hydrates thereof; and polysaccharides such as α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, and hydrates thereof. From the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity, the non-reducing sugar may include a disaccharide, or may include at least one selected from the group consisting of sucrose, trehalose, and hydrates thereof.

[0023] When the non-reducing sugar contains a disaccharide, the disaccharide content in the non-reducing sugar may be 50% by mass or more, 70% by mass or more, 90% by mass or more, 95% by mass or more, 97% by mass or more, or 99% by mass or more based on the non-reducing sugar content (the total amount of non-reducing sugars contained in the electrolyte), from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The non-reducing sugar may be substantially composed of disaccharides (an embodiment in which substantially 100% by mass of the non-reducing sugar is disaccharide). When the non-reducing sugar contains sucrose, the sucrose content in the non-reducing sugar may be within the above-mentioned range, from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. When the non-reducing sugar contains trehalose, the trehalose content in the non-reducing sugar may be within the above-mentioned range, from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity.

[0024] The number of methylol groups (-CHOH) contained in the non-reducing sugar may be within the following ranges, from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The number of methylol groups may be 8 or less, 6 or less, 4 or less, 3 or less, or 2 or less. The number of methylol groups may be 2 or more, or 3 or more. From these viewpoints, the number of methylol groups may be 2 to 8.

[0025] The number of ether groups in the non-reducing sugar may be within the following ranges, from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The number of ether groups may be 16 or less, 12 or less, 8 or less, 6 or less, or 4 or less. The number of ether groups may be 3 or more. From these viewpoints, the number of ether groups may be 3 to 16.

[0026] The number of hydroxy groups (excluding OH structures contained in methylol groups) contained in the non-reducing sugar may be within the following ranges, from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The number of hydroxy groups may be 16 or less, 12 or less, 8 or less, or 6 or less. The number of hydroxy groups may be 5 or more, or 6 or more. From these viewpoints, the number of hydroxy groups may be 5 to 16.

[0027] The number of carbon atoms of the non-reducing sugar may be within the following ranges, from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The number of carbon atoms may be 48 or less, 42 or less, 36 or less, 30 or less, 24 or less, or 18 or less. The number of carbon atoms may be 12 or more. From these viewpoints, the number of carbon atoms may be 12 to 48.

[0028] The number of five-membered ring structures contained in the non-reducing sugar may be within the following ranges, from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The number of five-membered ring structures may be 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, or 0. The number of five-membered ring structures may be 0 or 1 or more. From these viewpoints, the number of five-membered ring structures may be 0 to 5.

[0029] The number of six-membered ring structures contained in the non-reducing sugar may be within the following ranges, from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The number of six-membered ring structures may be 8 or less, 4 or less, 3 or less, 2 or less, or 1. The number of six-membered ring structures may be 1 or more, or 2 or more. From these viewpoints, the number of six-membered ring structures may be 1 to 8.

[0030] The content of non-reducing sugars in the electrolyte solution (the total amount of non-reducing sugars contained in the electrolyte solution) may be within the following ranges based on the total amount of the electrolyte solution, from the viewpoints of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The content of non-reducing sugars may be 0.01% by mass or more, 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 1.5% by mass or more, 2% by mass or more, 3% by mass or more, or 4% by mass or more. The content of non-reducing sugars may be 20% by mass or less, 10% by mass or less, 8% by mass or less, 5% by mass or less, 4% by mass or less, 3% by mass or less, 2% by mass or less, or 1% by mass or less. From these viewpoints, the content of non-reducing sugars may be 0.01 to 20% by mass, 0.1 to 10% by mass, 1 to 8% by mass, 1 to 5% by mass, or 1 to 4% by mass.

[0031] The content of the non-reducing sugar may be in the following ranges per 100 parts by mass of the alkali metal hydroxide, from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The content of the non-reducing sugar may be 1 part by mass or more, 2 parts by mass or more, 3 parts by mass or more, 6 parts by mass or more, 9 parts by mass or more, or 13 parts by mass or more. The content of the non-reducing sugar may be 30 parts by mass or less, 20 parts by mass or less, 16 parts by mass or less, 14 parts by mass or less, 12 parts by mass or less, 10 parts by mass or less, or 7 parts by mass or less. From these viewpoints, the content of the non-reducing sugar may be 1 to 30 parts by mass.

[0032] The electrolyte solution according to this embodiment may further contain a surfactant (excluding non-reducing sugars) from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The reason why the inclusion of a surfactant in the electrolyte solution makes it easier to obtain excellent cycle characteristics is presumed to be, but not limited to, the following: That is, when the electrolyte solution contains a surfactant, a coating is formed on the surface of the zinc in the electrode material, thereby suppressing oxidation of the zinc in the electrode material. It is presumed that suppressing zinc oxidation makes it difficult for a passive state (zinc oxide) to form on the surface of the electrode material, thereby suppressing a decrease in battery performance.

[0033] Examples of the surfactant include a nonionic surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, etc. From the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity, the surfactant may include at least one selected from the group consisting of a nonionic surfactant and an anionic surfactant, or may include a nonionic surfactant and an anionic surfactant.

[0034] The nonionic surfactant has a nonionic hydrophilic group and a hydrophobic group. Examples of the nonionic surfactant include polyoxyethylene-containing ester compounds such as polyoxyethylene fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and polyoxyethylene sorbitol fatty acid esters; and polyoxyethylene-containing ether compounds such as polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers. From the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity, the nonionic surfactant may include at least one selected from the group consisting of polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers, may include polyoxyethylene alkyl phenyl ether, or may include polyoxyethylene octyl phenyl ether.

[0035] Examples of polyoxyethylene alkyl ethers include polyoxyethylene decyl ether, polyoxyethylene undecyl ether, polyoxyethylene dodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene tetradecyl ether, polyoxyethylene pentadecyl ether, polyoxyethylene hexadecyl ether, polyoxyethylene heptadecyl ether, and polyoxyethylene octadecyl ether.

[0036] Examples of polyoxyethylene alkylphenyl ethers include polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether.

[0037] The anionic surfactant has an anionic hydrophilic group and a hydrophobic group. Examples of the anionic surfactant include polyoxyalkylene alkyl ether phosphate esters (e.g., polyoxyethylene alkyl ether phosphate esters), polyoxyethylene alkyl ether sulfates, sodium dodecylbenzenesulfonate, alkali salts of styrene-acrylic acid copolymers, sodium alkylnaphthalenesulfonates, sodium alkyldiphenyletherdisulfonates, monoethanolamine lauryl sulfate, triethanolamine lauryl sulfate, ammonium lauryl sulfate, monoethanolamine stearate, sodium stearate, sodium lauryl sulfate, and monoethanolamine styrene-acrylic acid copolymers. The anionic surfactant may include a polyoxyalkylene alkyl ether phosphate ester or a polyoxyethylene alkyl ether phosphate ester from the viewpoints of easily achieving excellent cycle characteristics and easily suppressing a decrease in discharge capacity.

[0038] The cationic surfactant has a cationic hydrophilic group and a hydrophobic group. Examples of the cationic surfactant include aliphatic amines or their salts, alkylamidoamine salts, monoalkyltrimethylammonium salts, dialkyldimethylammonium salts, alkylbenzyldimethylammonium salts, alkylpyridinium salts, and quaternary ammonium salt-type cationic surfactants such as benzethonium chloride salts. From the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity, the cationic surfactant may include at least one selected from the group consisting of monoalkyltrimethylammonium salts and dialkyldimethylammonium salts, and may include a monoalkyltrimethylammonium salt.

[0039] Examples of monoalkyltrimethylammonium salts include dodecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, tridecyltrimethylammonium bromide, tridecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide, tetradecyltrimethylammonium chloride, pentadecyltrimethylammonium bromide, pentadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, heptadecyltrimethylammonium bromide, heptadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, and octadecyltrimethylammonium chloride.

[0040] Examples of dialkyldimethylammonium salts include didodecyldimethylammonium bromide, didodecyldimethylammonium chloride, ditridecyldimethylammonium bromide, ditridecyldimethylammonium chloride, ditetradecyldimethylammonium bromide, ditetradecyldimethylammonium chloride, dipentadecyldimethylammonium bromide, dipentadecyldimethylammonium chloride, dihexadecyldimethylammonium bromide, dihexadecyldimethylammonium chloride, diheptadecyldimethylammonium bromide, diheptadecyldimethylammonium chloride, dioctadecyldimethylammonium bromide, and dioctadecyldimethylammonium chloride.

[0041] When the surfactant contains a nonionic surfactant or an anionic surfactant, the content of the nonionic surfactant or anionic surfactant in the surfactant may be 50 mass % or more, 70 mass % or more, 90 mass % or more, 95 mass % or more, 97 mass % or more, or 99 mass % or more based on the surfactant content (total amount of surfactants), from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The surfactant may be substantially composed of a nonionic surfactant or an anionic surfactant (an embodiment in which substantially 100 mass % of the surfactant is a nonionic surfactant or an anionic surfactant).

[0042] When the surfactant contains a nonionic surfactant and an anionic surfactant, the mass ratio of the content of the anionic surfactant to the content of the nonionic surfactant (content of anionic surfactant / content of nonionic surfactant) may be within the following ranges, from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The mass ratio may be 0.1 or more, 0.3 or more, 0.5 or more, 0.7 or more, or 1 or more. The mass ratio may be 3 or less, 2.5 or less, 2 or less, 1.5 or less, 1.2 or less, or 1 or less. From these viewpoints, the mass ratio may be 0.1 to 3.

[0043] The content of surfactants in the electrolytic solution (total amount of surfactants) may be within the following ranges based on the total amount of the electrolytic solution, from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The content of surfactants may be 0.001% by mass or more, 0.003% by mass or more, 0.005% by mass or more, or 0.01% by mass or more. The content of surfactants may be 0.1% by mass or less, 0.08% by mass or less, 0.05% by mass or less, or 0.01% by mass or less. From these viewpoints, the content of surfactants may be 0.001 to 0.1% by mass.

[0044] The electrolyte solution according to this embodiment can contain a liquid medium such as water (for example, ion-exchanged water).

[0045] Hereinafter, a nickel-zinc battery will be described as an example of a zinc battery in which the electrolyte solution according to the above embodiment is used.

[0046] The zinc battery according to the present embodiment includes, for example, a battery case, an electrode group (for example, an electrode plate group) and an electrolyte solution housed in the battery case. The zinc battery according to the present embodiment may be either formed or unformed.

[0047] The electrode group includes, for example, a positive electrode (e.g., a positive electrode plate), a negative electrode (e.g., a negative electrode plate), and a separator disposed between the positive electrode and the negative electrode. The positive electrode and the negative electrode are alternately stacked with the separator interposed between them, with the main surface of the positive electrode and the main surface of the negative electrode facing each other. The electrode group may be composed of a plurality of positive electrodes and a plurality of negative electrodes. The plurality of positive electrodes and the plurality of negative electrodes may be connected to each other, for example, by straps.

[0048] The positive electrode has a positive electrode current collector (current collector) and a positive electrode material (electrode material) supported on the positive electrode current collector. The positive electrode material may be disposed on at least one main surface of the positive electrode current collector, or may be disposed on both main surfaces of the positive electrode current collector. The negative electrode has a negative electrode current collector and a negative electrode material supported on the current collector. The negative electrode material may be disposed on at least one main surface of the negative electrode current collector, or may be disposed on both main surfaces of the negative electrode current collector. Each of the positive electrode and the negative electrode may be either before or after chemical formation.

[0049] The current collector (positive electrode current collector or negative electrode current collector) constitutes a conductive path for current from the electrode material (positive electrode material or negative electrode material). The current collector has, for example, a flat plate or sheet shape. The current collector may be a current collector with a three-dimensional mesh structure made of foamed metal, expanded metal, punched metal, metal fiber felt, or the like.

[0050] Specific examples of materials constituting the current collector include platinum; nickel (foamed nickel, etc.); and metal materials (copper, brass, steel, etc.) plated with metal such as tin or nickel.

[0051] The electrode material (positive electrode material or negative electrode material) may be a layered electrode material layer (positive electrode material layer or negative electrode material layer). For example, the electrode material layer may be formed on a current collector, and when the current collector has a three-dimensional mesh structure, the electrode material may be filled between the meshes of the current collector to form the electrode material layer.

[0052] The thickness of the current collector may be 0.01 mm or more, 0.05 mm or more, 0.08 mm or more, or 0.10 mm or more. The thickness of the current collector may be 1.0 mm or less, 0.80 mm or less, 0.50 mm or less, 0.30 mm or less, 0.20 mm or less, or 0.10 mm or less. From these viewpoints, the thickness of the current collector may be 0.01 to 1.0 mm.

[0053] The positive electrode material contains a positive electrode active material (electrode active material) containing nickel. When the zinc battery is a nickel-zinc battery, the positive electrode active material can contain nickel. Examples of the positive electrode active material include nickel oxyhydroxide (NiOOH) and nickel hydroxide. The positive electrode material contains, for example, nickel oxyhydroxide in a fully charged state and nickel hydroxide in an end-of-discharge state. The content of the positive electrode active material may be, for example, 50 to 99 mass% based on the total mass of the positive electrode material.

[0054] The positive electrode material may contain additives other than the positive electrode active material. Examples of additives include a binder, a conductive agent, an expansion inhibitor, and a rare earth metal compound (e.g., yttrium oxide). Examples of binders include hydrophilic or hydrophobic polymers, such as hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), carboxymethyl cellulose (CMC), sodium polyacrylate (SPA), and fluorine-based polymers (e.g., polytetrafluoroethylene (PTFE)). The content of the binder may be, for example, 0.01 to 5 parts by mass per 100 parts by mass of the positive electrode active material. Examples of conductive agents include cobalt compounds (e.g., metallic cobalt, cobalt oxide, cobalt hydroxide). The content of the conductive agent may be, for example, 1 to 20 parts by mass per 100 parts by mass of the positive electrode active material. Examples of expansion inhibitors include zinc oxide. The content of the expansion inhibitor may be, for example, 0.01 to 5 parts by mass per 100 parts by mass of the positive electrode active material.

[0055] The negative electrode material contains a negative electrode active material containing zinc. Examples of the negative electrode active material include metallic zinc, zinc oxide, and zinc hydroxide. The negative electrode active material may contain one of these components alone or a combination of two or more of them. For example, the negative electrode material contains metallic zinc in a fully charged state, and zinc oxide and zinc hydroxide in an end-of-discharge state. The negative electrode active material may be in particulate form, and may contain metallic zinc particles, zinc oxide particles, zinc hydroxide particles, etc. The content of the negative electrode active material is, for example, 50 to 99 mass% based on the total mass of the negative electrode material.

[0056] The negative electrode material may contain additives other than the negative electrode active material. Examples of additives include a binder, a surfactant, and a conductive agent. Examples of binders include polytetrafluoroethylene, hydroxyethyl cellulose (HEC), carboxymethyl cellulose, polyethylene oxide, polyethylene, and polypropylene. The content of the binder may be, for example, 0.5 to 10 parts by mass per 100 parts by mass of the negative electrode active material. Examples of conductive agents include indium compounds (indium oxide, etc.). The content of the conductive agent may be, for example, 1 to 20 parts by mass per 100 parts by mass of the negative electrode active material.

[0057] The separator may be in the form of a bag having an opening so as to accommodate a positive electrode and / or a negative electrode. In a zinc battery, for example, the opening opens vertically upward. The side of the separator in a direction perpendicular to the opening direction of the opening (for example, the side positioned horizontally when the positive electrode and / or the negative electrode are accommodated in the zinc battery) may be shielded or open. The shielding portion can be formed, for example, by heat welding the separator. The separator may be a single-layer porous membrane or a laminate of multiple porous membranes.

[0058] Separator materials include organic materials (such as resin materials) and inorganic materials. Resin materials include polyamide-based polymers (such as polyamides), olefin-based polymers (such as polyolefins such as polyethylene and polypropylene), and nylon-based polymers (such as nylon). Inorganic materials include oxides such as alumina, titania, and silicon dioxide; nitrides such as aluminum nitride and silicon nitride; and sulfates such as barium sulfate and calcium sulfate. The separator may be an ion-exchange resin membrane, a cellophane-based recycled resin membrane, an inorganic-organic separator, a polyolefin-based nonwoven fabric, or the like.

[0059] From the viewpoint of hydrophilization, the separator may contain an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, etc., and may be surface-treated by surfactant treatment, sulfonation treatment, fluorine gas treatment, acrylic acid graft polymerization treatment, corona discharge treatment, plasma treatment, etc. By making the separator hydrophilic, it becomes more compatible with the electrolyte, and a sufficient current density can be easily obtained.

[0060] The manufacturing method of the nickel-zinc battery described above includes, for example, a component manufacturing process for obtaining components of the zinc battery, and an assembly process for assembling the components to obtain the zinc battery. In the component manufacturing process, at least electrodes (positive and negative electrodes) are obtained.

[0061] The electrodes can be obtained, for example, by adding a solvent (e.g., water) to raw materials for the electrode materials (positive electrode material and negative electrode material) and kneading them to obtain an electrode material paste (a paste-like electrode material), and then forming an electrode material layer using the electrode material paste.

[0062] The raw materials for the positive electrode material include raw materials for the positive electrode active material (e.g., nickel hydroxide), additives (e.g., binders), etc. The raw materials for the negative electrode material include raw materials for the negative electrode active material (e.g., metallic zinc, zinc oxide, and zinc hydroxide), additives (e.g., binders), etc.

[0063] As a method for forming the electrode material layer, for example, an electrode material paste may be applied to or filled into a current collector, and then dried to obtain the electrode material layer. The density of the electrode material layer may be increased by pressing or the like, as necessary.

[0064] In the assembly process, for example, the positive and negative electrodes obtained in the component manufacturing process are stacked alternately with separators interposed therebetween, and then the positive electrodes and negative electrodes are connected with straps to form an electrode group. Next, this electrode group is placed in a battery case, and a lid is attached to the top of the battery case to obtain an unformed zinc battery (nickel-zinc battery).

[0065] Next, the electrolyte solution according to this embodiment is poured into the battery case of the unformed zinc battery and left for a certain period of time. Then, the zinc battery (nickel-zinc battery) is formed by charging under predetermined conditions. The formation conditions can be adjusted depending on the properties of the electrode active materials (positive electrode active material and negative electrode active material).

[0066] The above describes an example of a nickel-zinc battery (e.g., a nickel-zinc secondary battery) in which the positive electrode is a nickel electrode, but the zinc battery may also be an air-zinc battery (e.g., an air-zinc secondary battery) in which the positive electrode is an air electrode, or a silver-zinc battery (e.g., a silver-zinc secondary battery) in which the positive electrode is a silver oxide electrode.

[0067] The air electrode of the air-zinc battery can be a known air electrode used in air-zinc batteries. The air electrode includes, for example, an air electrode catalyst, an electron conductive material, etc. The air electrode catalyst can be an air electrode catalyst that also functions as an electron conductive material.

[0068] The air electrode catalyst can function as a positive electrode in an air-zinc battery, and various air electrode catalysts that can utilize oxygen as a positive electrode active material can be used. Examples of the air electrode catalyst include carbon-based materials (such as graphite) that have redox catalytic functions, metal materials (such as platinum and nickel) that have redox catalytic functions, and inorganic oxide materials (such as perovskite-type oxides, manganese dioxide, nickel oxide, cobalt oxide, and spinel oxide) that have redox catalytic functions. The air electrode catalyst may be, for example, in the form of particles. The content of the air electrode catalyst in the air electrode may be 5 to 70 volume %, 5 to 60 volume %, or 5 to 50 volume % relative to the total volume of the air electrode.

[0069] The electron-conductive material may be electrically conductive and capable of conducting electrons between the air electrode catalyst and the separator. Examples of the electron-conductive material include carbon blacks such as ketjen black, acetylene black, channel black, furnace black, lamp black, and thermal black; graphites such as natural graphite (e.g., flake graphite), artificial graphite, and expanded graphite; conductive fibers such as carbon fiber and metal fiber; metal powders such as copper, silver, nickel, and aluminum; organic electron-conductive materials such as polyphenylene derivatives; and mixtures thereof. The electron-conductive material may be in particulate form or other shapes. The electron-conductive material may be used in a form that provides a continuous phase in the thickness direction of the air electrode. For example, the electron-conductive material may be a porous material. The electron-conductive material may also be in the form of a mixture or composite with the air electrode catalyst, or may be an air electrode catalyst that also functions as an electron-conductive material. The content of the electron conductive material in the air electrode may be 10 to 80% by volume, 15 to 80% by volume, or 20 to 80% by volume relative to the total volume of the air electrode.

[0070] The silver oxide electrode of the silver-zinc battery may be a known silver oxide electrode used in silver-zinc batteries, such as silver(I) oxide. [Example]

[0071] The present disclosure will be specifically described below with reference to examples, although the present disclosure is not limited to the following examples.

[0072] <Preparation of electrolyte> (Examples 1 to 4, Comparative Examples 1 and 2) An electrolyte solution (potassium hydroxide concentration: 28% by mass, lithium hydroxide concentration: 2% by mass, additive contents: contents shown in Table 1, nonionic surfactant: 0.005% by mass, anionic surfactant: 0.005% by mass) was prepared by mixing ion-exchanged water, potassium hydroxide (KOH), lithium hydroxide (LiOH), the additives shown in Table 1, a nonionic surfactant (polyoxyethylene octylphenyl ether (Triton X-100, manufactured by Sigma-Aldrich)), and an anionic surfactant (polyoxyethylene alkyl ether phosphate ester (a mixture of monoester and diester, manufactured by Rhodafac, trade name: RA-600). The contents of the above components are based on the total mass of the electrolyte solution.

[0073] <Preparation of positive electrode> A grid made of foamed nickel with a porosity of 95% was prepared and pressure-molded to obtain a positive electrode current collector. Next, a predetermined amount of cobalt-coated nickel hydroxide powder, metallic cobalt, cobalt hydroxide, yttrium oxide, CMC (carboxymethyl cellulose), PTFE (polytetrafluoroethylene), and ion-exchanged water were weighed and mixed to obtain a mixture. The resulting mixture was stirred to prepare a positive electrode material paste. The mass ratio of the solids was adjusted to "nickel hydroxide: metallic cobalt: yttrium oxide: cobalt hydroxide: CMC: PTFE = 88:10.3:1:0.3:0.3:0.1." The moisture content of the positive electrode material paste was adjusted to 27.5 mass% based on the total mass of the positive electrode material paste. Next, the positive electrode material paste was applied to a positive electrode current collector and dried at 80°C for 30 minutes. The resulting mixture was then pressure-molded using a roll press to obtain an unformed positive electrode having a positive electrode material (positive electrode material layer) on both sides.

[0074] <Preparation of negative electrode> A tin-plated copper punched metal (porosity: 50%, thickness: 0.10 mm) was prepared as a negative electrode current collector. Next, zinc oxide, metallic zinc, HEC (hydroxyethyl cellulose, manufactured by Sumitomo Seika Chemicals Co., Ltd., product name: AV-15F), surfactant (manufactured by BASF, product name: Dispex AA 4140), and ion-exchanged water were weighed and mixed to obtain a mixture. The resulting mixture was stirred to prepare a negative electrode material paste. The mass ratio of the solids was adjusted to "zinc oxide: metallic zinc: HEC: surfactant = 84.5:11.5:3.5:0.5." The water content of the negative electrode material paste was adjusted to 32.5 mass% based on the total mass of the negative electrode material paste. Next, the negative electrode material paste was applied to a negative electrode current collector and dried at 80 °C for 30 minutes. The negative electrode material paste was then pressure-molded using a roll press to obtain an unformed negative electrode having negative electrode materials (negative electrode material layers) on both sides.

[0075] <Preparing a Nickel-Zinc Battery> Before battery assembly, a porous membrane (manufactured by Ube Industries, Ltd., product name: UP3355, air permeability: 440 sec / 100 mL) was hydrophilized with a surfactant (manufactured by Sigma-Aldrich Japan, LLC, product name: Triton (registered trademark)-X100). The hydrophilization treatment was performed by immersing the porous membrane in an aqueous solution containing 1% by mass of Triton-X100 for 24 hours, followed by drying at room temperature for 1 hour. The air permeability of the porous membrane indicates the value after hydrophilization treatment. The porous membrane was cut to 3.0 cm x 10.0 cm and then folded in half to obtain porous membrane A (3.0 cm x 5.0 cm). A pair of both side surfaces (long sides) of this porous membrane A were heat-sealed to obtain a bag-shaped porous member, and one unformed positive electrode was placed in this bag-shaped porous member to obtain a positive electrode body. In addition, a pair of both side surfaces (long sides) of the porous membrane A was heat-sealed to obtain a bag-shaped porous member, and then one unformed negative electrode was placed in this bag-shaped porous member to obtain a negative electrode body.

[0076] Nippon Kodoshi Industries' VL100 (material: cellulose, thickness: 100 μm, air permeability: 0.3 sec / 100 mL) was cut to a size of 3.0 cm x 10.0 cm and then folded in half to obtain a nonwoven fabric (3.0 cm x 5.0 cm). Two positive electrodes and three negative electrodes were alternately stacked, and the plates of the same polarity were then connected with straps to produce an electrode assembly (plate assembly). This electrode assembly was placed in a battery case, and a lid was attached to the top of the battery case to obtain an unformed nickel-zinc battery. Next, electrolyte was poured into the unformed nickel-zinc battery case and left for 24 hours. The battery was then charged at 32 mA for 15 hours to produce a formed nickel-zinc battery (nominal capacity: 320 mAh).

[0077] <Characteristics evaluation> The cycle characteristics (life performance) of the nickel-zinc batteries were evaluated using the nickel-zinc batteries of Examples 1 to 4 and Comparative Examples 1 and 2. The specific evaluation method is shown below, and the results are shown in Table 1. In the table, "-" means that the measurement was not performed.

[0078] The nickel-zinc battery was charged at 70°C at a constant voltage of 105.7 mA (0.33 C) and 1.88 V until the current decayed to 16 mA (0.05 C), and then discharged at a constant current of 105.7 mA (0.33 C) until the battery voltage reached 1.1 V. This constituted one cycle. The cycle characteristics were evaluated based on the charge rate, calculated by dividing the charge capacity at 120 cycles by the discharge capacity at 120 cycles. The lower the charge rate, the better the cycle characteristics. The charge rate, calculated by dividing the charge capacity at 10 cycles by the discharge capacity at 10 cycles, and the retention rate of the discharge capacity at 120 cycles relative to the discharge capacity at 1 cycle (discharge capacity retention rate) were also measured.

[0079] [Table 1]

Claims

1. Contains an alkali metal hydroxide and a non-reducing sugar, An electrolyte for a zinc battery, wherein the content of the non-reducing sugar is 3 mass% or less based on the total amount of the electrolyte.

2. A method for producing a food product comprising: An electrolyte solution for a zinc battery, wherein the content of the non-reducing sugar is 12 parts by mass or less per 100 parts by mass of the alkali metal hydroxide.

3. 3. The zinc battery electrolyte according to claim 1, wherein the alkali metal hydroxide comprises potassium hydroxide.

4. The zinc battery electrolyte according to any one of claims 1 to 3, wherein the non-reducing sugar comprises at least one selected from the group consisting of sucrose, trehalose, and hydrates thereof.

5. The zinc battery electrolyte according to any one of claims 1 to 4, further comprising a surfactant.

6. 6. The zinc battery electrolyte according to claim 5, wherein the surfactant comprises at least one selected from the group consisting of a nonionic surfactant and an anionic surfactant.

7. A zinc battery comprising a positive electrode, a negative electrode, and the zinc battery electrolyte solution according to any one of claims 1 to 6.

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