Electrolyte for zinc battery and zinc battery

Abstract

To provide an electrolyte for a zinc battery capable of obtaining excellent life performance in the zinc battery.SOLUTION: An electrolyte for a zinc battery includes an alkali metal hydroxide, and an organic compound having at least one selected from the group consisting of a carboxyl group, a carboxylic acid group, an ether group, and a hydroxy group (excluding polyoxyethylene octylphenyl ether and polyoxyethylene alkyl ether phosphate).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 charging and discharging, they can penetrate the separator and cause a short circuit, leading to a decrease in lifespan. 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 a further improved lifespan.

[0007] An object of one aspect of the present disclosure is to provide a zinc battery electrolyte that can provide excellent life performance in a 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 solution for a zinc battery, comprising an alkali metal hydroxide and an organic compound having at least one selected from the group consisting of a carboxyl group, a carboxylate salt group, an ether group, and a hydroxy group (excluding polyoxyethylene octylphenyl ether and polyoxyethylene alkyl ether phosphate ester).

[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 life performance. [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 life performance 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 an organic compound having at least one selected from the group consisting of a carboxyl group, a carboxylate group, an ether group, and a hydroxy group (excluding polyoxyethylene octylphenyl ether and polyoxyethylene alkyl ether phosphate ester; hereinafter, this organic compound may be referred to as "organic compound A").

[0016] The electrolyte solution according to this embodiment can provide excellent battery life. The reasons for this effect include, but are not limited to, the following: The electrolyte solution contains an alkali metal hydroxide and an organic compound A, which coordinates with zinc. This inhibits zinc elution and diffusion, thereby inhibiting deterioration of battery performance.

[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 achieving excellent life performance, 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 mass of the electrolyte, from the viewpoint of easily achieving excellent life performance. 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, or 35 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 in the following ranges based on the total mass of the electrolyte, from the viewpoint of easily obtaining excellent life performance. The content of potassium 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 potassium hydroxide may be 50 mass% or less, 45 mass% or less, 40 mass% or less, or 35 mass% or less. From these viewpoints, the content of potassium hydroxide may be 10 to 50 mass%.

[0020] The content of lithium hydroxide in the electrolyte may be in the following ranges based on the total mass of the electrolyte, from the viewpoint of easily obtaining excellent life performance. The content of lithium hydroxide may be 0.1 mass% or more, 0.3 mass% or more, 0.5 mass% or more, 0.8 mass% or more, or 1 mass% or more. The content of lithium hydroxide may be 3 mass% or less, 2 mass% or less, 1.5 mass% or less, or 1.2 mass% or less. From these viewpoints, the content of lithium hydroxide may be 0.1 to 3 mass%.

[0021] The electrolyte solution according to this embodiment contains an organic compound A having at least one selected from the group consisting of a carboxyl group, a carboxylate group, an ether group, and a hydroxy group. Examples of the salt of the carboxylate group include sodium salts and potassium salts.

[0022] The organic compound A may include, as an organic compound other than polyoxyethylene octylphenyl ether and polyoxyethylene alkyl ether phosphate ester, an organic compound having at least one selected from the group consisting of a carboxyl group and a carboxylate salt group (hereinafter also referred to as a "carboxyl group-containing compound"), an organic compound having an ether group (excluding carboxyl group-containing compounds; hereinafter also referred to as an "ether group-containing compound"), or an organic compound having a hydroxy group (excluding carboxyl group-containing compounds and ether group-containing compounds; hereinafter also referred to as a "hydroxy group-containing compound").

[0023] The organic compound A may be an aliphatic compound or a saturated aliphatic compound. The electrolytic solution according to this embodiment may contain an organic compound other than the organic compound A, or may contain the organic compound A and polyoxyethylene octylphenyl ether and / or polyoxyethylene alkyl ether phosphate ester. The electrolytic solution according to this embodiment may contain a compound having a polyoxyethylene structure (general formula R 1 (CH2CH2O) n R 2 The structure is represented by n, where n is a natural number and R 1 and R 2 each independently represents a hydrogen atom, a metal atom, or an organic group).

[0024] The carboxyl group-containing compound may have a functional group other than a carboxyl group. Examples of such functional groups include an ether group, a hydroxy group (excluding the OH structure included in a carboxyl group), an alkyl group, an aryl group, a vinyl group, an ester group, a ketone group, an aldehyde group, and an amino group. The carboxyl group-containing compound may include a compound that does not have an ether group, a compound that does not have a hydroxy group, or a compound that does not have an ether group or a hydroxy group.

[0025] The total number of carboxyl groups and carboxylate salt groups in the carboxyl group-containing compound may be within the following ranges, from the viewpoint of easily achieving excellent life performance. The total number of carboxyl groups and carboxylate salt groups may be 10 or less, 7 or less, 5 or less, 3 or less, 2 or less, or 1 or less. The total number of carboxyl groups and carboxylate salt groups may be 1 or more, or 2 or more. From these viewpoints, the total number of carboxyl groups and carboxylate salt groups may be 1 to 10.

[0026] The number of ether groups in the carboxyl group-containing compound may be within the following ranges, from the viewpoint of easily obtaining excellent life performance. The number of ether groups may be 10 or less, 5 or less, 3 or less, 2 or less, or 1 or less. The number of ether groups may be 0 or more, or 1 or more. From these viewpoints, the number of ether groups may be 0 to 10.

[0027] The number of hydroxy groups in the carboxyl group-containing compound may be within the following ranges, from the viewpoint of easily obtaining excellent life performance. The number of hydroxy groups may be 10 or less, 5 or less, 3 or less, 2 or less, or 1 or less. The number of hydroxy groups may be 0 or more, 1 or more, or 2 or more. From these viewpoints, the number of hydroxy groups may be 0 to 10.

[0028] Examples of carboxyl group-containing compounds include carboxylic acid compounds that do not have an ether group or a hydroxy group, such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, and benzoic acid, and salts thereof; ether group-containing carboxylic acid compounds (carboxylic acid compounds having an ether group), such as methoxyacetic acid, ethoxyacetic acid, and 4-(β-D-glucopyranosyloxy)-2-methylenebutanoic acid, and salts thereof; and hydroxy group-containing carboxylic acid compounds (carboxylic acid compounds having a hydroxy group, excluding ether group-containing carboxylic acid compounds), such as glycolic acid, lactic acid, tartronic acid, glyceric acid, malic acid, tartaric acid, and citric acid, and salts thereof. From the viewpoint of easily obtaining excellent life performance, the organic compound A may contain at least one selected from the group consisting of a carboxylic acid compound having no ether group or hydroxy group, an ether group-containing carboxylic acid compound, a hydroxy group-containing carboxylic acid compound, and salts thereof, may contain at least one selected from the group consisting of oxalic acid, lactic acid, methoxyacetic acid, glyceric acid, and salts thereof, or may contain at least one selected from the group consisting of lactic acid and salts thereof.

[0029] From the viewpoint of easily obtaining excellent life performance, the content of the carboxyl group-containing compound may be 50 mass % or more, 70 mass % or more, 90 mass % or more, 95 mass % or more, 98 mass % or more, 99 mass % or more, or substantially 100 mass % (an embodiment in which the organic compound A in the electrolyte solution consists of the carboxyl group-containing compound) based on the total mass of the organic compound A in the electrolyte solution.

[0030] The ether group-containing compound may have a functional group other than a carboxyl group, a carboxylate salt group, and an ether group. Examples of such functional groups include a hydroxyl group (excluding the OH structure included in a carboxyl group), an alkyl group, an aryl group, a vinyl group, an ester group, a ketone group, an aldehyde group, and an amino group. The ether group-containing compound may include a compound that does not have a hydroxyl group.

[0031] The number of ether groups in the ether group-containing compound may be within the following ranges, from the viewpoint of easily obtaining excellent life performance. The number of ether groups may be 10 or less, 7 or less, 5 or less, 3 or less, 2 or less, or 1. The number of ether groups may be 1 or more. From these viewpoints, the number of ether groups may be 1 to 10.

[0032] The number of hydroxy groups in the ether group-containing compound may be within the following ranges, from the viewpoint of easily obtaining excellent life performance. The number of hydroxy groups may be 10 or less, 5 or less, 3 or less, or 2 or less. The number of hydroxy groups may be 0 or more, 1 or more, or 2 or more. From these viewpoints, the number of hydroxy groups may be 0 to 10.

[0033] Examples of the ether group-containing compound include compounds containing a polyoxyethylene structure (polyoxyethylene structure (general formula R 1 (CH2CH2O) n R 2 The structure is represented by n, where n is a natural number and R 1 and R 2 each independently represent a hydrogen atom, a metal atom, or an organic group); ether compounds without a hydroxy group, such as dimethyl ether, ethyl methyl ether, and diethyl ether (excluding compounds containing a polyoxyethylene structure); and hydroxy group-containing ether compounds (ether compounds with a hydroxy group, excluding compounds containing a polyoxyethylene structure), such as 2-methoxyethanol, 2-ethoxyethanol, 3-methoxy-1,2-propanediol, glucose, and glucosylglycerol. From the viewpoint of easily achieving excellent life performance, the organic compound A may contain a hydroxy group-containing ether compound or 3-methoxy-1,2-propanediol. The ether group-containing compound may contain a compound without a polyoxyethylene structure.

[0034] From the viewpoint of easily obtaining excellent life performance, the content of the ether group-containing compound may be 50 mass % or more, 70 mass % or more, 90 mass % or more, 95 mass % or more, 98 mass % or more, 99 mass % or more, or substantially 100 mass % (an embodiment in which the organic compound A in the electrolyte solution consists of the ether group-containing compound) based on the total mass of the organic compound A in the electrolyte solution.

[0035] The hydroxyl group-containing compound may have a functional group other than a carboxyl group, a carboxylate salt group, an ether group, and a hydroxyl group, such as an alkyl group, an aryl group, a vinyl group, an ester group, a ketone group, an aldehyde group, or an amino group.

[0036] The number of hydroxy groups in the hydroxy group-containing compound may be within the following ranges, from the viewpoint of easily obtaining excellent life performance. The number of hydroxy groups may be 10 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1. The number of hydroxy groups may be 1 or more, 2 or more, or 3 or more. From these viewpoints, the number of hydroxy groups may be 1 to 10.

[0037] The number of ester groups in the hydroxy group-containing compound may be within the following ranges, from the viewpoint of easily achieving excellent life performance. The number of ester groups may be 10 or less, 5 or less, 3 or less, 2 or less, or 1 or less. The number of ester groups may be 0 or more, or 1 or more. From these viewpoints, the number of ester groups may be 0 to 10.

[0038] Examples of the hydroxyl group-containing compound include monohydric alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, methyl glycolate, and ethyl glycolate; dihydric alcohols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, and dihydroxyacetone; trihydric alcohols such as 1,2,3-propanetriol, 1,2,3-butanetriol, 1,2,4-butanetriol, and 1,2,5-pentanetriol; and polyhydric alcohols such as polyvinyl alcohol. From the viewpoint of easily achieving excellent life performance, the organic compound A may contain at least one selected from the group consisting of monohydric alcohols and trihydric alcohols, and may contain at least one selected from the group consisting of methyl glycolate, 1,2,3-butanetriol, and 1,2,4-butanetriol. The hydroxy group-containing compound may include a compound different from ethylene glycol, 1,2-propanediol, 1,3-propanediol, and 1,2,3-propanetriol. The electrolyte solution according to this embodiment may not contain ethylene glycol, 1,2-propanediol, 1,3-propanediol, or 1,2,3-propanetriol.

[0039] From the viewpoint of easily obtaining excellent life performance, the content of the hydroxy group-containing compound may be 50 mass % or more, 70 mass % or more, 90 mass % or more, 95 mass % or more, 98 mass % or more, 99 mass % or more, or substantially 100 mass % (an embodiment in which the organic compound A in the electrolyte solution consists of the hydroxy group-containing compound) based on the total mass of the organic compound A in the electrolyte solution.

[0040] The total number of carboxyl groups, carboxylate salt groups, ether groups, and hydroxy groups in organic compound A may be within the following ranges, from the viewpoint of easily achieving excellent life performance. The total number of carboxyl groups, carboxylate salt groups, ether groups, and hydroxy groups may be 15 or less, 10 or less, 8 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1. The total number of carboxyl groups, carboxylate salt groups, ether groups, and hydroxy groups may be 1 or more, 2 or more, or 3 or more. From these viewpoints, the total number of carboxyl groups, carboxylate salt groups, ether groups, and hydroxy groups may be 1 to 15.

[0041] The number of carbon atoms in the organic compound A may be within the following ranges from the viewpoint of easily obtaining excellent life performance. The number of carbon atoms may be 20 or less, 15 or less, 10 or less, 8 or less, 6 or less, 4 or less, 3 or less, or 2 or less. The number of carbon atoms may be 1 or more, 2 or more, or 3 or more. From these viewpoints, the number of carbon atoms may be 1 to 20.

[0042] The molecular weight of organic compound A may be in the following ranges from the viewpoint of easily obtaining excellent life performance. The molecular weight may be 300 or less, 260 or less, 220 or less, 180 or less, 150 or less, 130 or less, 110 or less, or 100 or less. The molecular weight may be 30 or more, 50 or more, 70 or more, 80 or more, 90 or more, or 100 or more. From these viewpoints, the molecular weight may be 30 to 300.

[0043] The content of organic compound A in the electrolyte solution (total amount of organic compound A contained in the electrolyte solution) may be within the following ranges based on the total mass of the electrolyte solution. From the viewpoint of easily obtaining excellent life performance, the content of organic compound A may be 0.01 mass% or more, 0.1 mass% or more, 0.5 mass% or more, 1 mass% or more, 2 mass% or more, 3 mass% or more, 4 mass% or more, or 5 mass% or more. From the viewpoint of easily obtaining excellent discharge performance, the content of organic compound A may be 20 mass% or less, 10 mass% or less, 8 mass% or less, 6 mass% or less, 5 mass% or less, 4 mass% or less, 3 mass% or less, 2 mass% or less, or 1 mass% or less. From these viewpoints, the content of organic compound A may be 0.01 to 20 mass%, 0.1 to 10 mass%, 0.5 to 8 mass%, or 1 to 5 mass%.

[0044] The content of organic compound A in the electrolyte (total amount of organic compound A contained in the electrolyte) may be in the following ranges relative to 100 parts by mass of alkali metal hydroxide. From the viewpoint of easily obtaining excellent life performance, the content of organic compound A may be 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 7 parts by mass or more, 9 parts by mass or more, 12 parts by mass or more, or 15 parts by mass or more. From the viewpoint of easily obtaining excellent discharge performance, the content of organic compound A may be 30 parts by mass or less, 20 parts by mass or less, 15 parts by mass or less, 12 parts by mass or less, 10 parts by mass or less, 7 parts by mass or less, 5 parts by mass or less, or 4 parts by mass or less. From these viewpoints, the content of organic compound A may be 1 to 30 parts by mass.

[0045] The content of organic compound A in the electrolyte solution (total amount of organic compound A contained in the electrolyte solution) may be in the following ranges relative to 1 mole of alkali metal hydroxide. From the viewpoint of easily obtaining excellent life performance, the content of organic compound A may be 0.0010 moles or more, 0.0050 moles or more, 0.010 moles or more, 0.015 moles or more, 0.018 moles or more, 0.030 moles or more, 0.055 moles or more, 0.075 moles or more, or 0.090 moles or more. From the viewpoint of easily obtaining excellent discharge performance, the content of organic compound A may be 1.0 mole or less, 0.50 moles or less, 0.25 moles or less, 0.12 moles or less, 0.10 moles or less, less than 0.10 moles, 0.080 moles or less, 0.060 moles or less, 0.040 moles or less, or 0.020 moles or less. From these viewpoints, the content of organic compound A may be 0.0010 to 1.0 mole.

[0046] The electrolyte solution according to this embodiment may further contain a surfactant (excluding organic compound A) from the viewpoint of easily achieving excellent life performance. The reason why the inclusion of a surfactant in the electrolyte solution makes it easier to achieve excellent life performance 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 zinc in the electrode material, thereby preventing oxidation of the zinc in the electrode material. It is presumed that the prevention of zinc oxidation makes it difficult for a passive state (zinc oxide) to form on the surface of the electrode material, thereby preventing a decrease in battery performance.

[0047] 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 life performance, 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.

[0048] The nonionic surfactant has a nonionic hydrophilic group and a hydrophobic group. Examples of the nonionic surfactant include polyoxyethylene octylphenyl ether and polyacrylamide. The nonionic surfactant may contain polyoxyethylene octylphenyl ether from the viewpoint of easily achieving excellent life performance.

[0049] The anionic surfactant has an anionic hydrophilic group and a hydrophobic group. Examples of the anionic surfactant include polyoxyethylene alkyl ether phosphate ester, sodium alkylbenzenesulfonate, sodium alkylnaphthalenesulfonate, ammonium lauryl sulfate, and sodium lauryl sulfate. The anionic surfactant may contain polyoxyethylene alkyl ether phosphate ester in order to easily obtain excellent life performance.

[0050] 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 achieving excellent life performance, 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.

[0051] 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.

[0052] 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.

[0053] 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 life performance. 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).

[0054] 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 (anionic surfactant content / nonionic surfactant content) may be within the following ranges, from the viewpoint of easily obtaining excellent life performance. 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.

[0055] The content of surfactants in the electrolyte solution (total amount of surfactants) may be in the following ranges based on the total mass of the electrolyte solution, from the viewpoint of easily achieving excellent life performance. The content of surfactants may be 0.001 mass% or more, 0.003 mass% or more, 0.005 mass% or more, or 0.01 mass% or more. The content of surfactants may be 0.1 mass% or less, 0.08 mass% or less, 0.05 mass% or less, or 0.01 mass% or less. From these viewpoints, the content of surfactants may be 0.001 to 0.1 mass%.

[0056] The electrolyte solution according to this embodiment can contain a liquid medium such as water (for example, ion-exchanged water).

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] To provide hydrophilicity to the separator, the separator may contain an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, or the like, and may be surface-treated by surfactant treatment, sulfonation treatment, fluorine gas treatment, acrylic acid graft polymerization treatment, corona discharge treatment, plasma treatment, or the like. By providing hydrophilicity to the separator, it becomes more compatible with the electrolyte, making it easier to obtain a sufficient current density.

[0072] 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.

[0073] 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.

[0074] Examples of raw materials for the positive electrode material include raw materials for the positive electrode active material (e.g., nickel hydroxide), additives (e.g., the binder), etc. Examples of raw materials for the negative electrode material include raw materials for the negative electrode active material (e.g., metallic zinc, zinc oxide, zinc hydroxide), additives (e.g., the binder), etc.

[0075] As a method for forming the electrode material layer, for example, a method of applying or filling an electrode material paste onto a current collector and then drying the paste to obtain an electrode material layer can be mentioned. The density of the electrode material layer may be increased by pressing or the like, if necessary.

[0076] 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).

[0077] 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).

[0078] 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.

[0079] 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.

[0080] The air electrode catalyst can be one that functions 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.

[0081] 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, as described above, 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.

[0082] 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]

[0083] The present disclosure will be specifically described below with reference to examples, although the present disclosure is not limited to the following examples.

[0084] <Preparation of electrolyte> (Examples 1 to 14) An electrolyte solution (potassium hydroxide concentration: 30% by mass, lithium hydroxide concentration: 1% by mass, organic compound content: 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 organic compounds 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, 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.

[0085] (Comparative Example 1) An electrolyte solution (potassium hydroxide concentration: 30 mass %, lithium hydroxide concentration: 1 mass %, nonionic surfactant: 0.005 mass %, anionic surfactant: 0.005 mass %) was prepared in the same manner as in Examples 1 to 14, except that no organic compound was used.

[0086] <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.

[0087] <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 in predetermined amounts. 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 moisture 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 the 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.

[0088] <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.

[0089] 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).

[0090] <Characteristics evaluation> The life performance (cycle life performance) and high-rate discharge performance of the nickel-zinc batteries were evaluated using the nickel-zinc batteries of Examples 1 to 14 and Comparative Example 1. The specific evaluation methods are shown below, and the results are shown in Table 1.

[0091] (Evaluation of life performance) The test consisted of charging the nickel-zinc battery at 40°C with a constant voltage of 1.88 V at 105.7 mA (0.33 C) until the current value decayed to 16 mA (0.05 C), and then discharging the nickel-zinc battery at a constant current of 105.7 mA (0.33 C) until the battery voltage reached 1.1 V. The test was terminated when the discharge capacity fell below 60% of the discharge capacity of the first cycle, and the life performance was evaluated based on the number of cycles performed until the end of the test.

[0092] (Evaluation of high rate discharge performance) At 25°C, the nickel-zinc battery was charged at a constant voltage of 1.88 V at 320 mA (1 C) until the current value decayed to 16 mA (0.05 C), and then discharged at a constant current of 3200 mA (10.0 C) until the battery voltage reached 1.1 V, and the discharge capacity was measured. The high-rate discharge performance was evaluated based on the measured discharge capacity.

[0093]

Table 1

Claims

1. an alkali metal hydroxide; An electrolyte for a zinc battery, comprising an organic compound (excluding polyoxyethylene octylphenyl ether and polyoxyethylene alkyl ether phosphate ester) having at least one selected from the group consisting of a carboxyl group, a carboxylate salt group, an ether group, and a hydroxyl group.

2. 2. The zinc battery electrolyte of claim 1, wherein the alkali metal hydroxide comprises potassium hydroxide.

3. 3. The zinc battery electrolyte solution according to claim 1, wherein the organic compound comprises an organic compound having at least one selected from the group consisting of a carboxyl group and a carboxylate salt group.

4. The zinc battery electrolyte according to any one of claims 1 to 3, wherein the organic compound comprises at least one selected from the group consisting of lactic acid and salts thereof.

5. The zinc battery electrolyte according to any one of claims 1 to 4, wherein the organic compound has a molecular weight of 300 or less.

6. The zinc battery electrolyte according to any one of claims 1 to 5, wherein the content of the organic compound is less than 0.10 mol per 1 mol of the alkali metal hydroxide.

7. The zinc battery electrolyte solution according to any one of claims 1 to 6, further comprising a surfactant.

8. 8. The zinc battery electrolyte solution according to claim 7, wherein the surfactant comprises at least one selected from the group consisting of a nonionic surfactant and an anionic surfactant.

9. A zinc battery comprising a positive electrode, a negative electrode, and the zinc battery electrolyte solution according to any one of claims 1 to 8.

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