Zinc battery electrolyte and zinc battery

Abstract

To provide an electrolyte for a zinc battery capable of obtaining excellent cycle life performance, and to provide a zinc battery comprising the same.SOLUTION: Provided is an electrolyte for a zinc battery that contains an alkali metal hydroxide and a heterocyclic compound containing a nitrogen atom. Also provided is a zinc battery comprising the same.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrolyte for a zinc battery and a zinc battery. [Background technology]

[0002] Nickel-zinc batteries, air-zinc batteries, and the like are known as zinc batteries that use zinc negative electrodes. Nickel-zinc batteries are aqueous batteries that use an aqueous electrolyte such as an aqueous potassium hydroxide solution, and are therefore highly safe. The combination of zinc and nickel electrodes is known to produce a high electromotive force for an aqueous battery. Furthermore, nickel-zinc batteries have excellent input / output performance and are low cost, so their applicability to industrial applications (e.g., backup power sources) and automotive applications (e.g., hybrid vehicles) is being considered.

[0003] Incidentally, 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 formula above, zinc hydroxide (Zn(OH)2) is produced by the discharge reaction in zinc batteries. Zinc hydroxide (Zn(OH)2) 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 of the negative electrode changes and the distribution of the charging current becomes uneven, causing zinc to precipitate locally on the negative electrode, forming dendrites.

[0005] In conventional zinc batteries, when dendrites grow due to repeated charge and discharge, the dendrites may penetrate the separator, causing a short circuit. Therefore, various attempts have been made to prevent such short circuits caused by dendrites and improve battery life. For example, Patent Document 1 below discloses a technology for preventing short circuits caused by dendrites by interposing a nickel-plated nonwoven fabric between electrodes. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 58-126665 Summary of the Invention [Problem to be solved by the invention]

[0007] Zinc batteries such as nickel-zinc batteries are required to have a further improved lifespan.

[0008] An object of one aspect of the present invention 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 invention is to provide a zinc battery including the zinc battery electrolyte. [Means for solving the problem]

[0009] One aspect of the present invention provides an electrolyte for a zinc battery, which contains an alkali metal hydroxide and a heterocyclic compound containing a nitrogen atom.

[0010] One aspect of the present invention provides an electrolyte solution for a zinc battery containing the above-mentioned salt of a heterocyclic compound containing a nitrogen atom.

[0011] Another aspect of the present invention provides an electrolyte solution for a zinc battery, wherein the cation component of the salt of a heterocyclic compound containing a nitrogen atom contains at least one cation selected from the group consisting of a piperidinium cation, a pyrrolidinium cation, a pyridinium cation, and an imidazolium cation.

[0012] Another aspect of the present invention provides an electrolyte solution for a zinc battery, wherein the anion component of the salt of a heterocyclic compound containing a nitrogen atom contains at least one ion selected from the group consisting of a fluoride ion, a chloride ion, a bromide ion, and a hydroxide ion.

[0013] Another aspect of the present invention provides an electrolyte for a zinc battery, wherein the alkali metal hydroxide contains potassium hydroxide.

[0014] Another aspect of the present invention provides a zinc battery comprising a positive electrode, a negative electrode, and the above-described zinc battery electrolyte.

[0015] According to the above-mentioned zinc battery electrolyte and zinc battery, excellent life performance can be obtained in the zinc battery. [Effects of the Invention]

[0016] The electrolyte solution according to the present embodiment contains an alkali metal hydroxide and a heterocyclic compound containing a nitrogen atom. The electrolyte solution according to the present invention can provide excellent life performance in a zinc battery. DETAILED DESCRIPTION OF THE INVENTION

[0017] In this specification, a numerical range indicated with "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages 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 an experimental example. "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 used 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 effect of the process is achieved.

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the preferred embodiments. However, the present invention is not limited to the following embodiments and can be practiced in various modified forms within the scope of the present invention. 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.

[0019] The electrolyte solution according to the present embodiment contains an alkali metal hydroxide and a heterocyclic compound containing a nitrogen atom. The electrolyte solution according to the present invention can provide excellent life performance in a zinc battery.

[0020] The factors that produce such an effect include, but are not limited to, the following: When the electrolyte solution according to the present invention is used, the heterocyclic compound containing a nitrogen atom is adsorbed to the reactive active sites of the negative electrode, reducing the effective electrode area, thereby increasing the overvoltage required for the electrode reaction and allowing zincate ions eluted from the negative electrode material into the electrolyte solution to be uniformly dispersed in the electrolyte solution near the negative electrode. As a result, the distribution of the charging reaction on the negative electrode is less likely to be uneven, the deposition and growth of zinc dendrites is suppressed, and the occurrence of short circuits due to dendrites is suppressed. For these reasons, it is presumed that excellent life performance can be obtained.

[0021] The electrolyte according to this embodiment is an electrolyte for zinc batteries (for example, zinc secondary batteries) that are incorporated into zinc batteries, such as nickel-zinc batteries and air-zinc batteries. In the zinc battery, a zinc negative electrode can be used. As an example of this embodiment, a nickel-zinc battery will be described below.

[0022] <Nickel-zinc battery> The nickel-zinc battery (e.g., nickel-zinc secondary battery) according to this embodiment comprises an electrolyte solution containing an alkali metal hydroxide and a heterocyclic compound containing a nitrogen atom, and the cationic component of the heterocyclic compound containing a nitrogen atom contains at least one cation selected from the group consisting of piperidinium cation, pyrrolidinium cation, pyridinium cation, and imidazolium cation. The electrolyte solution according to this embodiment is an electrolyte solution for nickel-zinc batteries. The basic configuration of the nickel-zinc battery according to this embodiment can be the same as that of a conventional nickel-zinc battery. For example, the nickel-zinc battery comprises a battery case and an electrode group (such as a plate group) in addition to the electrolyte solution. The electrode group and the electrolyte solution are housed in the battery case.

[0023] (electrolyte) The electrolyte solution according to this embodiment contains an alkali metal hydroxide. 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 the 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.

[0024] The content of alkali metal hydroxide in the electrolyte (total mass 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 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%.

[0025] The content of potassium hydroxide in the electrolyte may be within the following ranges based on the total mass 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 mass% or more, 15 mass% or more, 20 mass% or more, 25 mass% or more, or 28 mass% or more. The content of potassium 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 potassium hydroxide may be 10 to 50 mass%.

[0026] The content of lithium hydroxide in the electrolyte may be within the following ranges based on the total mass 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 mass% or more, 0.5 mass% or more, 1 mass% or more, 1.5 mass% or more, 1.8 mass% or more, or 2 mass% or more. The content of lithium hydroxide may be 5 mass% or less, 4 mass% or less, 3 mass% or less, 2.5 mass% or less, or 2 mass% or less. From these viewpoints, the content of lithium hydroxide may be 0.1 to 5 mass%.

[0027] The electrolyte solution according to this embodiment contains a heterocyclic compound containing a nitrogen atom (excluding compounds that fall under the category of surfactants; hereinafter, sometimes referred to as a "nitrogen-containing compound"). From the viewpoint of solubility, the nitrogen-containing compound is preferably a salt, and preferably contains the following cationic and anionic components. Hereinafter, the term "nitrogen-containing compound" may also refer to salts of nitrogen-containing compounds.

[0028] When the nitrogen-containing compound is a salt, examples of the cationic component include piperidinium cation, pyrrolidinium cation, pyridinium cation, imidazolium cation, etc. From the viewpoint of easily obtaining excellent life performance, it is preferable to have at least one selected from the group consisting of piperidinium cation, pyrrolidinium cation, pyridinium cation, and imidazolium cation.

[0029] The piperidinium cation is, for example, a nitrogen-containing six-membered ring compound represented by the following formula (I).

[0030] [ka] In formula (I), R 1 and R 2 are each independently an alkyl group having 1 to 20 carbon atoms or RO-(CH2) n - (wherein R represents a methyl group or an ethyl group, and n represents an integer of 1 to 4).1 and R 2 The number of carbon atoms in the alkyl group represented by the formula (I) is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 5. do.

[0031] The pyrrolidinium cation is, for example, a five-membered ring compound represented by the following formula (II).

[0032] [ka] In formula (II), R 3 and R 4 are each independently an alkyl group having 1 to 20 carbon atoms or RO-(CH2) n - (wherein R represents a methyl group or an ethyl group, and n represents an integer of 1 to 4). 3 and R 4 The alkyl group represented by the formula (I) preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and even more preferably 1 to 5 carbon atoms.

[0033] The pyridinium cation is, for example, a compound represented by the following formula (III):

[0034] [ka] In formula (III), R 5 ~R 9 are each independently an alkyl group having 1 to 20 carbon atoms, RO-(CH2) n - (wherein R represents a methyl group or an ethyl group, and n represents an integer of 1 to 4), or a hydrogen atom. 5 ~R 9 The alkyl group represented by the formula (I) preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and even more preferably 1 to 5 carbon atoms.

[0035] The imidazolium cation is, for example, a compound represented by the following formula (IV).

[0036] [ka] In formula (IV), R 10 ~R 14 are each independently an alkyl group having 1 to 20 carbon atoms, RO-(CH2) n - (wherein R represents a methyl group or an ethyl group, and n represents an integer of 1 to 4), or a hydrogen atom. 10 ~R 14 The alkyl group represented by the formula (I) preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and even more preferably 1 to 5 carbon atoms.

[0037] When the nitrogen-containing compound is a salt, the anion component is not particularly limited, but may be Cl - , Br - , I - Anions of halogens such as BF4 - , N(SO2F)2 - Inorganic anions such as B(C6H5)4 - , CH3SO2O - , CF3SO2O - , N(SO2C4F9)2 - , N(SO2CF3)2 - , N(SO2C2F5)2 - and the like.

[0038] The content of the nitrogen-containing compound is preferably 0.1 mass% or more, 0.3 mass% or more, 0.5 mass% or more, or 1 mass% or more based on the total mass of the electrolyte, from the viewpoint of easily obtaining excellent life performance. The content of the nitrogen-containing compound is preferably 10 mass% or less, 7 mass% or less, 5 mass% or less, 4 mass% or less, or 3 mass% or less, from the viewpoint of easily obtaining excellent cycle characteristics. From these viewpoints, the content of the nitrogen-containing compound is preferably 0.1 to 10 mass%.

[0039] The electrolyte solution according to this embodiment may further contain an organic compound containing an oxygen atom (excluding compounds corresponding to alkali metal hydroxides or surfactants; hereinafter, sometimes referred to as "oxygen-containing compound"). The oxygen-containing compound may have a functional group containing an oxygen atom. Examples of the functional group containing an oxygen atom include a carboxyl group, a carboxylate group, a hydroxyl group (excluding the OH structure included in a carboxyl group), an epoxy group, an ether group, an alkoxide group, an ester group, a ketone group, and an aldehyde group. From the viewpoint of easily suppressing a decrease in discharge capacity during storage of a zinc battery and easily obtaining excellent high-rate discharge performance, it is preferable that the oxygen-containing compound has at least one selected from the group consisting of a carboxyl group, a carboxylate group, a hydroxyl group, an epoxy group, and an ether group.

[0040] When the oxygen-containing compound has an OH structure, the ratio of the number of OH structures to the number of carbon atoms in the oxygen-containing compound (number of OH structures / number of carbon atoms) is preferably within the following range, from the viewpoints of easily suppressing a decrease in discharge capacity during storage of a zinc battery and easily obtaining excellent high-rate discharge performance. The ratio is preferably 0.01 or more, 0.03 or more, 0.05 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 5 / 6 or more. The ratio is preferably 2 or less, 1.5 or less, 1.2 or less, 1 or less, 0.9 or less, or 5 / 6 or less. The oxygen-containing compound does not necessarily have an OH structure.

[0041] From the viewpoint of easily suppressing the decrease in discharge capacity during storage of a zinc battery and easily obtaining excellent high-rate discharge performance, the oxygen-containing compound preferably contains at least one selected from the group consisting of carbohydrates, carboxylic acids (excluding compounds corresponding to sugars), carboxylates (excluding compounds corresponding to sugars), epoxy compounds (compounds having an epoxy group; excluding compounds corresponding to sugars, carboxylic acids, or carboxylates), and ether compounds (compounds having an ether group; excluding compounds corresponding to carbohydrates, carboxylic acids, carboxylates, or epoxy compounds).

[0042] Carbohydrates that can be used include monosaccharides, disaccharides, trisaccharides, polysaccharides (excluding sugars that fall into the disaccharide or trisaccharide category), etc. Monosaccharides include glucose, fructose, galactose, arabinose, ribose, mannose, xylose, sorbose, rhamnose, fucose, ribonucleotides, and hydrates thereof. Disaccharides include sucrose, maltose, trehalose, cellobiose, gentiobiose, lactose, melibiose, and hydrates thereof. Trisaccharides include kestose, melezitose, gentianose, raffinose, gentianose, melezitose, and hydrates thereof. Polysaccharides include cyclodextrins (e.g., γ-cyclodextrin), stachyose, etc. In addition, the carbohydrate preferably contains a non-reducing sugar, from the viewpoint of easily suppressing a decrease in discharge capacity during storage of the zinc battery and easily achieving excellent high-rate discharge performance.

[0043] Non-reducing sugars refer to sugars that do not have a free reducing group, as opposed to reducing sugars (sugars that have a free aldehyde or ketone group, or a hemiacetal-linked aldehyde or ketone group) (Chemical Dictionary, 1st Edition, published by Tokyo Kagaku Dojin Co., Ltd.). In other words, non-reducing sugars refer to sugars that do not have either a free aldehyde or ketone group or a hemiacetal-linked aldehyde or ketone group. Non-reducing sugars may be hydrated.

[0044] 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.

[0045] When the non-reducing sugar contains a disaccharide, the content of the disaccharide 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 content of the non-reducing sugar (the total mass of the 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 content of sucrose 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 content of trehalose 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] The content of non-reducing sugars in the electrolyte solution (the total mass of non-reducing sugars contained in the electrolyte solution) may be within the following ranges based on the total mass of the electrolyte solution, from the viewpoints of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The mass 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 mass 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.

[0053] The content of non-reducing sugar may be within the following ranges relative to 100% by mass of alkali metal hydroxide, from the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity. The content of non-reducing sugar may be 1% by mass or more, 2% by mass or more, 3% by mass or more, 6% by mass or more, 9% by mass or more, or 13% by mass or more. The content of non-reducing sugar may be 30% by mass or less, 20% by mass or less, 16% by mass or less, 14% by mass or less, 12% by mass or less, 10% by mass or less, or 7% by mass or less. From these viewpoints, the content of non-reducing sugar may be 1 to 30% by mass.

[0054] Examples of carboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, benzoic acid, salicylic acid, 3,4,5-trihydroxybenzoic acid, benzenehexacarboxylic acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, aconitic acid, pyruvic acid, oxaloacetic acid, glycidyl formate, glycidyl acetate, and glycidyl benzoate. Examples of carboxylic acid salts include salts of these carboxylic acids. Examples of carboxylic acid salts include alkali metal salts such as sodium salts (e.g., disodium terephthalate) and potassium salts. From the viewpoints of easily suppressing a decrease in discharge capacity during storage of a zinc battery and easily achieving excellent high-rate discharge performance, the carboxylic acid salt preferably contains an alkali metal salt, and more preferably contains a sodium salt. From the viewpoint of easily suppressing a decrease in discharge capacity during storage of a zinc battery and easily obtaining excellent high-rate discharge performance, the oxygen-containing compound preferably contains at least one selected from the group consisting of carboxylic acids having aromatic rings and carboxylates having aromatic rings, more preferably contains at least one selected from the group consisting of terephthalic acid and terephthalic acid salts, and even more preferably contains at least one selected from the group consisting of terephthalic acid and sodium salts of terephthalic acid.

[0055] The number of carboxyl groups in the carboxylic acid or the number of carboxylate salts in the carboxylic acid salt is 1 or more, and from the viewpoints of easily suppressing a decrease in discharge capacity during storage of the zinc battery and easily obtaining excellent high-rate discharge performance, the following ranges are preferred: The number of carboxyl groups or carboxylate salts is preferably 2 or more. The number of carboxyl groups or carboxylate salts is preferably 4 or less, 3 or less, or 2 or less.

[0056] Examples of the epoxy compound include monofunctional epoxy compounds and polyfunctional epoxy compounds. Examples of the monofunctional epoxy compound include 1,2-epoxyethane, 1,2-epoxypropane, 1,2-epoxybutane, 1,2-epoxy-2-methylpropane, 1-phenyl-1,2-epoxyethane, epichlorohydrin, epibromohydrin, glycidyl methyl ether, allyl glycidyl ether, polyethylene oxide glycidyl ether, glycidyl amide, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, stearyl glycidyl ether, lauryl glycidyl ether, butoxy polyethylene glycol glycidyl ether, phenol polyethylene glycol glycidyl ether, allyl glycidyl ether, phenyl glycidyl ether, p-methylphenyl glycidyl ether, p-ethylphenyl glycidyl ether, p-sec-butylphenyl glycidyl ether, p-tert-butylphenyl glycidyl, glycidyl acrylate, and glycidyl methacrylate. Examples of polyfunctional epoxy compounds include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, phenol novolac type epoxy compounds, cresol novolac type epoxy compounds, polyphenol type epoxy compounds, cycloaliphatic epoxy compounds, aliphatic glycidyl ether type epoxy compounds, glycidyl ester type epoxy compounds, glycidyl diamine type epoxy compounds, heterocyclic epoxy compounds, cycloaliphatic epoxy compounds, etc. From the viewpoints of easily suppressing a decrease in discharge capacity during storage of the zinc battery and easily obtaining excellent high-rate discharge performance, the oxygen-containing compound preferably contains a monofunctional epoxy compound, and more preferably contains 1,2-epoxy-2-methylpropane.

[0057] Examples of the ether compound include crown ether compounds such as 18-crown-6, 15-crown-5, 12-crown-4, dibenzo-18-crown-6, dicyclohexano-18-crown-6, and dibenzo-24-crown-8; polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; and glycerin. Polyether compounds can be used as the ether compound. From the viewpoints of easily suppressing a decrease in discharge capacity during storage of a zinc battery and easily achieving excellent high-rate discharge performance, the oxygen-containing compound preferably includes an ether compound having a heterocycle containing an ether group, and more preferably includes 18-crown-6.

[0058] The number of ether groups in the ether compound is 1 or more, and is preferably in the following ranges from the viewpoint of easily suppressing a decrease in discharge capacity during storage of a zinc battery and easily obtaining excellent high-rate discharge performance: The number of ether groups is preferably 2 or more, 3 or more, 4 or more, 5 or more, or 6 or more. The number of ether groups is preferably 10 or less, 9 or less, 8 or less, 7 or less, or 6 or less.

[0059] The molecular weight of the oxygen-containing compound is preferably 50 or more, 70 or more, 80 or more, 100 or more, 120 or more, 150 or more, 160 or more, 170 or more, or 180 or more, from the viewpoint of easily suppressing a decrease in discharge capacity during storage of a zinc battery and easily obtaining excellent high-rate discharge performance. The molecular weight of the oxygen-containing compound is preferably 2000 or less, 1500 or less, 1300 or less, 1200 or less, 1000 or less, 800 or less, or 600 or less, from the viewpoint of easily suppressing a decrease in discharge capacity during storage of a zinc battery and easily obtaining excellent high-rate discharge performance. From these viewpoints, the molecular weight of the oxygen-containing compound is preferably 50 to 2000. The molecular weight of the oxygen-containing compound may be 190 or more, 200 or more, 210 or more, 220 or more, 240 or more, 260 or more, 300 or more, 340 or more, 350 or more, 400 or more, 450 or more, or 500 or more. The molecular weight of the oxygen-containing compound may be 500 or less, 400 or less, 350 or less, 340 or less, 320 or less, 300 or less, 280 or less, 270 or less, 260 or less, 250 or less, 230 or less, 220 or less, 210 or less, 200 or less, 190 or less, or 185 or less. The molecular weight is a value measured by GPC (Gel Permeation Chromatography).

[0060] As the oxygen-containing compound, it is preferable to use a compound that is highly soluble in the electrolyte. Even if the compound is not highly soluble, it can be used by removing the residue by filtration, etc. The electrolyte according to this embodiment does not need to contain alcohol.

[0061] The content of the oxygen-containing compound in the electrolyte is preferably in the following ranges based on the total mass of the electrolyte. From the viewpoint of easily suppressing a decrease in discharge capacity during storage of the zinc battery and easily obtaining excellent high-rate discharge performance, the content of the oxygen-containing compound is preferably 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. From the viewpoint of easily suppressing a decrease in discharge capacity during storage of the zinc battery and easily obtaining excellent high-rate discharge performance, the content of the oxygen-containing compound is preferably 5 mass% or less, 4.5 mass% or less, 4 mass% or less, 3.5 mass% or less, or 3 mass% or less. From these viewpoints, the content of the oxygen-containing compound is preferably 0.1 to 5 mass%. From the viewpoint of further easily suppressing a decrease in discharge capacity during storage of the zinc battery, the content of the oxygen-containing compound is preferably 1.2 mass% or more, 1.5 mass% or more, 1.8 mass% or more, 2 mass% or more, 2.2 mass% or more, 2.5 mass% or more, 2.7 mass% or more, or 3 mass% or more. The content of the oxygen-containing compound may be 3.5% by mass or more, 4% by mass or more, 4.5% by mass or more, or 5% by mass or more. From the viewpoint of easily obtaining even better high-rate discharge performance, the content of the oxygen-containing compound is preferably 2.7 mass % or less, 2.5 mass % or less, 2.2 mass % or less, 2 mass % or less, 1.7 mass % or less, 1.5 mass % or less, 1.2 mass % or less, or 1 mass % or less, based on the total mass of the electrolyte. The content of the oxygen-containing compound may be less than 0.5 mol / L based on the total amount of the electrolyte.

[0062] The content of the oxygen-containing compound is preferably in the following ranges relative to 1% by mass of the surfactant. From the viewpoint of easily suppressing a decrease in discharge capacity during storage of the zinc battery and easily obtaining excellent high-rate discharge performance, the content of the oxygen-containing compound is preferably 10% by mass or more, 30% by mass or more, 50% by mass or more, 80% by mass or more, or 100% by mass or more. From the viewpoint of easily suppressing a decrease in discharge capacity during storage of the zinc battery and easily obtaining excellent high-rate discharge performance, the content of the oxygen-containing compound is preferably 1000% by mass or less, 800% by mass or less, 600% by mass or less, 500% by mass or less, 450% by mass or less, 400% by mass or less, 350% by mass or less, or 300% by mass or less. From these viewpoints, the content of the oxygen-containing compound is preferably 10 to 1000% by mass. From the viewpoint of further easily suppressing a decrease in discharge capacity during storage of the zinc battery, the content of the oxygen-containing compound is preferably 150% by mass or more, 200% by mass or more, 250% by mass or more, or 300% by mass or more. The content of the oxygen-containing compound may be 350% by mass or more, 400% by mass or more, 450% by mass or more, or 500% by mass or more, and is preferably 250% by mass or less, 200% by mass or less, 150% by mass or less, or 100% by mass or less.

[0063] The content of the oxygen-containing compound is preferably in the following ranges relative to 100% by mass of the alkali metal hydroxide. From the viewpoint of easily suppressing a decrease in discharge capacity during storage of the zinc battery and easily obtaining excellent high-rate discharge performance, the content of the oxygen-containing compound is preferably 1% by mass or more, 1.5% by mass or more, 2% by mass or more, 2.5% by mass or more, or 3% by mass or more. From the viewpoint of easily suppressing a decrease in discharge capacity during storage of the zinc battery and easily obtaining excellent high-rate discharge performance, the content of the oxygen-containing compound is preferably 30% by mass or less, 25% by mass or less, 20% by mass or less, 16% by mass or less, 15% by mass or less, 13% by mass or less, 12% by mass or less, or 10% by mass or less. From these viewpoints, the content of the oxygen-containing compound is preferably 1 to 30% by mass relative to 100% by mass of the alkali metal hydroxide. From the viewpoint of further easily suppressing a decrease in discharge capacity during storage of the zinc battery, the content of the oxygen-containing compound is preferably 4% by mass or more, 5% by mass or more, 6% by mass or more, 7% by mass or more, 8% by mass or more, or 9% by mass or more. The content of the oxygen-containing compound may be 10% by mass or more, 12% by mass or more, 13% by mass or more, 15% by mass or more, or 16% by mass or more. From the viewpoint of easily obtaining even better high-rate discharge performance, the content of the oxygen-containing compound is preferably 9% by mass or less, 8% by mass or less, 7% by mass or less, 6% by mass or less, 5% by mass or less, or 4% by mass or less.

[0064] The electrolyte solution according to this embodiment may further contain a surfactant. Examples of the surfactant include cationic surfactants, nonionic surfactants (nonionic surfactants), anionic surfactants, and amphoteric surfactants. From the viewpoint of easily suppressing a decrease in the low-temperature discharge performance of the zinc battery, the surfactant preferably contains at least one selected from the group consisting of cationic surfactants, nonionic surfactants, and anionic surfactants. The surfactant preferably contains a cationic surfactant, a nonionic surfactant, or an anionic surfactant.

[0065] 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 suppressing a decrease in the low-temperature discharge performance of zinc batteries, the cationic surfactant preferably contains at least one selected from the group consisting of monoalkyltrimethylammonium salts and dialkyldimethylammonium salts, and more preferably contains a monoalkyltrimethylammonium salt.

[0066] The monoalkyltrimethylammonium salt and the dialkyldimethylammonium salt have, for example, a structure represented by the following general formula (2). (R 2a ) n N + (R 2b ) 4-n X - ···(2) [In formula (2), n is 1 or 2, and R 2a and R 2b are each independently a hydrocarbon group having 1 to 20 carbon atoms, and X - is an anion. When n is 2, multiple R 2a may be the same or different. 2b may be the same or different from each other.

[0067] R 2a The hydrocarbon group R may be linear or branched, saturated or unsaturated, and may contain a cyclic structure such as an alicyclic structure. 2a The hydrocarbon group in R is preferably an alkyl group. 2a The hydrocarbon group preferably has 12 to 18 carbon atoms, more preferably 14 to 16 carbon atoms. 2b The hydrocarbon group R may be linear or branched, and may be saturated or unsaturated.2b The hydrocarbon group in R is preferably an alkyl group. 2b The hydrocarbon group preferably has 1 to 4 carbon atoms, more preferably 1, 2 or 3. - is an anion capable of forming a salt with the quaternary ammonium ion of formula (2), for example, F - , Cl - , Br - , I - Halide ions such as CH3COO - Carboxylate ions such as sulfate ions; phosphite ions; The cation may be a phosphate ion or the like.

[0068] Specific 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.

[0069] Specific 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.

[0070] 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 alkylphenyl ethers. From the viewpoint of easily suppressing a decline in the low-temperature discharge performance of zinc batteries, the nonionic surfactant preferably contains at least one selected from the group consisting of polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers, and more preferably contains polyoxyethylene alkyl phenyl ethers.

[0071] The polyoxyethylene alkyl ether has, for example, a structure represented by the following general formula (1a). R 1a O(CH2CH2O) m1 H (1a) [In formula (1a), m1 is an integer of 2 to 60, and R 1a is a hydrocarbon group having 1 to 30 carbon atoms.

[0072] Polyoxyethylene alkylphenyl ether has, for example, a structure represented by the following general formula (1b). R 1b C6H4O(CH2CH2O) m2 H (1b) [In formula (1b), m2 is an integer of 2 to 60, and R 1b is a hydrocarbon group having 1 to 30 carbon atoms.

[0073] R 1a and R 1b The hydrocarbon group R may be linear or branched, and may be saturated or unsaturated. 1a and R 1b The hydrocarbon group is an alkyl group. It is preferable that R 1a The hydrocarbon group preferably has 10 to 18 carbon atoms. 1b The number of carbon atoms in the hydrocarbon group is preferably 4 to 12, more preferably 6 to 10, and even more preferably 8. m1 and m2 are average degrees of polymerization, and are preferably 5 to 12, and more preferably 7 to 10.

[0074] Specific 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.

[0075] Specific examples of polyoxyethylene alkylphenyl ethers include polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether.

[0076] 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. From the viewpoint of easily suppressing a decrease in the low-temperature discharge performance of zinc batteries, the anionic surfactant preferably contains a polyoxyalkylene alkyl ether phosphate ester, and more preferably contains a polyoxyethylene alkyl ether phosphate ester.

[0077] The content of the surfactant in the electrolyte (total mass of the surfactants) is preferably within the following ranges based on the total mass of the electrolyte. From the viewpoint of easily suppressing a decrease in discharge performance of the zinc battery, the content of the surfactant is preferably 0.001 mass% or more, 0.003 mass% or more, 0.005 mass% or more, or 0.01 mass% or more. From the viewpoint of easily obtaining excellent cycle characteristics and easily suppressing a decrease in discharge capacity, the content of the surfactant is preferably 5 mass% or less, 2.5 mass% or less, 1 mass% or less, 0.7 mass% or less, or 0.5 mass% or less. From these viewpoints, the content of the surfactant is preferably 0.001 to 5 mass%. From the viewpoint of easily obtaining even better cycle characteristics and easily suppressing a decrease in discharge capacity, the content of the surfactant is particularly preferably 0.01 to 0.5 mass%.

[0078] The electrolytic solution according to this embodiment contains a solvent, such as water (e.g., ion-exchanged water).

[0079] (electrode group) The electrode group is composed of, for example, a separator, and a positive electrode (such as a positive electrode plate) and a negative electrode (such as a negative electrode plate) that face each other with the separator interposed therebetween. In the electrode group, the positive electrodes and the negative electrodes are connected to each other by, for example, a strap.

[0080] The separator may be, for example, a separator having a shape such as a flat plate or a sheet. Examples of the separator include a polyolefin or nylon microporous membrane, an oxidation-resistant ion-exchange resin membrane, a cellophane-based recycled resin membrane, a microporous membrane containing inorganic particles, and a polyolefin nonwoven fabric.

[0081] The positive electrode includes, for example, a positive electrode current collector and a positive electrode material supported on the positive electrode current collector.

[0082] The positive electrode current collector forms a conductive path for current from the positive electrode material. The positive electrode current collector may have, for example, a flat plate or sheet shape. The positive electrode current collector may be a three-dimensional mesh-structured current collector formed of foamed metal, expanded metal, punched metal, or metal fiber felt. The positive electrode current collector is made of a material that is conductive and alkali-resistant. Examples of such materials include materials that are stable even at the reaction potential of the positive electrode (e.g., materials with a redox potential higher than the reaction potential of the positive electrode, materials that form a protective coating such as an oxide coating on the substrate surface in an alkaline aqueous solution to stabilize the substrate). In addition, at the positive electrode, a side reaction occurs in which the electrolyte decomposes, generating oxygen. Materials with a high oxygen overvoltage are preferred because they can suppress the progression of such side reactions. Specific examples of materials for the positive electrode current collector include platinum, nickel, and metal materials (e.g., copper, brass, steel) plated with nickel, etc.

[0083] The positive electrode material may be in a layered form (positive electrode material layer). For example, the positive electrode material layer may be formed on a positive electrode current collector, and when the positive electrode current collector has a three-dimensional mesh structure, the positive electrode material may be filled between the meshes of the positive electrode current collector to form the positive electrode material layer.

[0084] The positive electrode material contains a positive electrode active material. 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 95 mass % based on the total mass of the positive electrode material.

[0085] The positive electrode material may contain additives. Examples of the additives include binders and other additives. The additives may be used alone or in combination.

[0086] Examples of the binder include hydrophilic or hydrophobic polymers, such as hydroxypropylmethylcellulose (HPMC), carboxymethylcellulose (CMC), sodium polyacrylate (SPA), fluorine-based polymers (polytetrafluoroethylene (PTFE)), etc. The content of the binder may be, for example, 0.01 to 5% by mass relative to 100% by mass of the positive electrode active material.

[0087] Examples of additives other than the binder include metallic cobalt; cobalt compounds such as cobalt oxide and cobalt hydroxide; metallic nickel; metallic zinc; zinc compounds such as zinc oxide and zinc hydroxide; calcium compounds such as calcium hydroxide and calcium carbonate; rare earth metals; and rare earth metal compounds. The content of additives other than the binder may be, for example, 5 to 50 mass% relative to 100 mass% of the positive electrode active material. Note that after charging, at least a portion of the cobalt compounds such as cobalt oxide and cobalt hydroxide may be present in the positive electrode material as cobalt oxyhydroxide.

[0088] The negative electrode includes, for example, a negative electrode current collector and a negative electrode material supported on the negative electrode current collector. The negative electrode current collector forms a conductive path for current from the negative electrode material. The negative electrode current collector has, for example, a flat plate or sheet shape. The negative electrode current collector may be a collector with a three-dimensional mesh structure formed from foam metal, expanded metal, punched metal, metal fiber felt, or the like. The negative electrode current collector is made of a material that is conductive and alkali-resistant. Examples of such materials include materials that are stable even at the reaction potential of the negative electrode (e.g., materials with a redox potential higher than the reaction potential of the negative electrode, materials that form a protective coating such as an oxide coating on the substrate surface in an alkaline aqueous solution for stabilization). Furthermore, at the negative electrode, a decomposition reaction of the electrolyte proceeds as a side reaction, generating hydrogen. Materials with a high hydrogen overvoltage are preferred because they can suppress the progression of such side reactions. Specific examples of materials constituting the negative electrode current collector include zinc, lead, tin, and metal materials (copper, brass, steel, nickel, etc.) plated with a metal such as tin. The negative electrode material may be layered (negative electrode material layer). For example, the negative electrode material layer may be formed on the negative electrode current collector, and when the negative electrode current collector has a three-dimensional mesh structure, the negative electrode material may be filled between the meshes of the negative electrode current collector to form the negative electrode material layer.

[0089] The negative electrode material contains a negative electrode active material. The negative electrode material contains, for example, at least one negative electrode active material selected from the group consisting of metallic zinc, zinc oxide, and zinc hydroxide. The negative electrode material contains, for example, metallic zinc in a fully charged state, and zinc oxide and zinc hydroxide in an end-of-discharge state. The content of the negative electrode active material may be, for example, 50 to 95 mass% based on the total mass of the negative electrode material.

[0090] The negative electrode material may contain additives, such as binders and other additives. The additives may be used alone or in combination.

[0091] Examples of the binder include polytetrafluoroethylene, hydroxyethyl cellulose, polyethylene oxide, polyethylene, polypropylene, etc. The content of the binder may be, for example, 0.5 to 10% by mass relative to 100% by mass of the negative electrode active material.

[0092] Examples of additives other than the binder include metal oxides with a nobler reduction potential than that of zinc, such as indium oxide, bismuth oxide, lead oxide, cadmium oxide, and thallium oxide; metal oxides with high wettability, such as titanium oxide, aluminum oxide, and silicon oxide; calcium compounds, such as calcium oxide and calcium hydroxide; and fluorine compounds, such as potassium fluoride and calcium fluoride. The content of the additives other than the binder may be, for example, 1 to 40% by mass relative to 100% by mass of the negative electrode active material.

[0093] <Nickel-zinc battery manufacturing method> The method for manufacturing a nickel-zinc battery according to this embodiment includes, for example, an electrode manufacturing process for obtaining electrodes (positive and negative electrodes) and an assembly process for assembling components including the electrodes to obtain a nickel-zinc battery.

[0094] In the electrode manufacturing process, positive and negative electrodes are manufactured. For example, a solvent (e.g., water) is added to raw materials for the electrode materials (positive and negative electrode materials) and the mixture is kneaded to obtain a paste-like electrode material (electrode material paste), and then the electrode material paste is used to form an electrode material layer.

[0095] 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 above-mentioned binders and additives other than the above-mentioned binders), etc. Examples of raw materials for the negative electrode material include raw materials for the negative electrode active material (e.g., metal zinc, zinc oxide, and zinc hydroxide), additives (e.g., the above-mentioned binders and additives other than the above-mentioned binders), etc.

[0096] The electrode material layer may be formed, for example, by applying or filling an electrode material paste onto a current collector and then drying the paste to obtain the electrode material layer. If necessary, the density of the electrode material layer may be increased by pressing with a roller or the like.

[0097] In the assembly process, for example, the positive and negative electrodes obtained in the electrode production process are alternately stacked with separators interposed therebetween, and 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 nickel-zinc battery.

[0098] Next, the electrolyte solution according to this embodiment is poured into the battery case of the unformed nickel-zinc battery and left for a certain period of time. Next, charging is performed under predetermined conditions, and a nickel-zinc battery is obtained by forming the battery. The forming conditions can be adjusted depending on the properties of the electrode active materials (positive electrode active material and negative electrode active material). For example, a formed nickel-zinc battery can be produced by charging the battery at an ambient temperature of 25°C, at 32 mA, for 12 hours.

[0099] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the above embodiments, an example of a nickel-zinc battery has been described, but the zinc battery may be an air-zinc battery (e.g., an air-zinc secondary battery) in which the positive electrode is an air electrode.

[0100] The air electrode can be a known air electrode used in air-zinc batteries. The air electrode generally includes 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.

[0101] 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 shape of the air electrode catalyst is not particularly limited, and may be, for example, particulate. 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.

[0102] The electron-conductive material may be electrically conductive and capable of conducting electrons between the air electrode catalyst and the separator. Examples of electron-conductive materials 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 of any of these. The electron-conductive material may be in particulate form or other shapes. It is preferable that the electron-conductive material 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. [Example]

[0103] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0104] <Preparation of electrolyte> (Examples 1 to 3, Comparative Example 1) An electrolyte solution (potassium hydroxide: 28% by mass, lithium hydroxide: 2% by mass, additives: contents shown in Table 1) was prepared by mixing ion-exchanged water, potassium hydroxide (KOH), lithium hydroxide (LiOH), and 1-ethyl-3-methylimidazolium bromide. The contents of the above components are based on the total mass of the electrolyte solution.

[0105] <Preparation of positive electrode> A 95% porosity nickel foam grid was prepared and pressure-molded to obtain a positive electrode current collector. Next, cobalt-coated nickel hydroxide powder (Gold Shine Energy Material Co., Ltd., Y6 (trade name)), metallic cobalt (Nikkoshi Co., Ltd., EXTRA FINE (trade name)), cobalt hydroxide (Ise Chemical Industry Co., Ltd.), yttrium oxide (Fujifilm Wako Pure Chemical Industries Co., Ltd., special grade reagent), carboxymethylcellulose (CMC, Weiyi Chemical (Suzhou) Co., Ltd., BH90-3 (trade name)), polytetrafluoroethylene (PTFE, Daikin Industries, Ltd., D210-C (trade name)), and ion-exchanged water were weighed and mixed in predetermined amounts, and the mixture was stirred to produce a positive electrode material paste. At this time, the mass ratio of the solid contents was adjusted to "nickel hydroxide: metallic cobalt: yttrium oxide: cobalt hydroxide: CMC: PTFE = 88.0: 10.3: 1.0: 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 the positive electrode material support portion of the positive electrode current collector, and then dried for 30 minutes at 80° C. Thereafter, pressure molding was performed using a roll press to obtain an unformed positive electrode having a positive electrode material layer.

[0106] <Preparation of negative electrode> A tin-plated punched steel sheet with a porosity of 50% was prepared as a negative electrode current collector. Next, zinc oxide (Mitsui Mining & Smelting Co., Ltd., general product), metallic zinc (Mitsui Mining & Smelting Co., Ltd., MA-ZB (trade name)), bismuth oxide (Corefront Co., Ltd., 4115CB (trade name)), hydroxyethyl cellulose (HEC, Sumitomo Seika Chemicals Co., Ltd., AV-15F (trade name)), and ion-exchanged water were weighed and mixed in predetermined amounts, and the resulting mixture was stirred to prepare a negative electrode material paste. The mass ratio of the solid contents was adjusted to "zinc oxide: metallic zinc: bismuth oxide: HEC = 73.0: 20.5: 5.0: 1.5." The water content of the negative electrode material paste was adjusted to 22.5% by 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 then dried at 80°C for 30 minutes. Thereafter, pressure molding was performed using a roll press to obtain an unformed negative electrode having a negative electrode material (negative electrode material layer).

[0107] <Preparing the separator> For the separator, a microporous membrane was used, UP3355 (trade name, manufactured by Ube Industries, Ltd., air permeability: 440 sec / 100 mL), and a nonwoven fabric was used (trade name: VL-100, manufactured by Nippon Kodoshi Kogyo Co., Ltd., air permeability: 0.3 sec / 100 mL). Before battery assembly, the microporous membrane was hydrophilized with a surfactant, Triton-X100 (product name, manufactured by Sigma-Aldrich Japan LLC). The hydrophilization was performed by immersing the microporous 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 microporous membrane is the value after the hydrophilization treatment. The microporous membrane was then cut to a specified size, folded in half, and processed into a bag shape by heat welding the sides with the folded part as the bottom. The nonwoven fabric used was cut to a specified size. The air permeability here is a value measured according to JIS P 8117:2009.

[0108] <Making a nickel-zinc battery> A positive electrode (unformed positive electrode) and a negative electrode (unformed negative electrode) were housed in a microporous membrane processed into a bag shape. The positive electrode housed in the bag-shaped microporous membrane, the negative electrode housed in the bag-shaped microporous membrane, and a nonwoven fabric were stacked, and the electrode plates of the same polarity were connected with a strap to prepare an electrode assembly (electrode plate assembly). The electrode assembly consisted of two positive electrodes and three negative electrodes, with one nonwoven fabric placed between each positive electrode and negative electrode (between the microporous membrane on the positive electrode side and the microporous membrane on the negative electrode side). This electrode assembly was placed in a battery container, a lid was attached to the top of the container, and the electrolyte was poured into the container to obtain an unformed nickel-zinc battery. The battery was then charged at an ambient temperature of 25°C, 32 mA, and 12 hours to produce a nickel-zinc battery with a nominal capacity of 320 mAh.

[0109] <Characteristics evaluation> The cycle characteristics (life performance) of the nickel-zinc batteries were evaluated using the nickel-zinc batteries of Examples 1 to 3 and Comparative Example 1. The specific evaluation method is shown below, and the results are shown in Table 1.

[0110] <Evaluation of cycle life performance> The test consisted of charging the nickel-zinc battery at 70°C with a constant voltage of 105.7mA (0.33C) and 1.88V until the current value decayed to 16mA (0.05C), and then discharging the nickel-zinc battery at a constant current of 105.7mA (0.33C) until the battery voltage reached 1.1V, which constituted one cycle. The number of cycles at which the retention rate of the discharge capacity at the first cycle reached 70% was defined as the cycle life performance.

[0111] The "C" above is a relative expression of the magnitude of the current when discharging the rated capacity at a constant current from a fully charged state. The "C" above means "discharge current value (A) / battery capacity (Ah)." For example, the current that can discharge the rated capacity in 1 hour is defined as "1C," and the current that can discharge the rated capacity in 2 hours is defined as "0.5C."

[0112] [Table 1]

[0113] The cycle life performance of the zinc batteries of Examples 1 to 3 was significantly improved compared to the zinc battery of Comparative Example 1. This is thought to be because the inclusion of 1-ethyl-3-methylimidazolium bromide made it difficult for the distribution of the charging reaction on the negative electrode to become uneven, thereby suppressing the deposition and growth of dendritic zinc.

Claims

1. An electrolyte solution for a zinc battery containing an alkali metal hydroxide and a heterocyclic compound containing a nitrogen atom, the heterocyclic compound containing a nitrogen atom is a salt, The zinc battery electrolyte solution, wherein the cationic component of the salt has at least one selected from the group consisting of piperidinium cations, pyrrolidinium cations, pyridinium cations, and imidazolium cations.

2. 2. The zinc battery electrolyte according to claim 1, wherein the anion component of the salt has at least one selected from the group consisting of fluoride ions, chloride ions, bromide ions, and hydroxide ions.

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

4. A zinc battery comprising a positive electrode, a negative electrode, and the zinc battery electrolyte solution according to any one of claims 1 to 3.

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