Electrolyte for Zinc Battery and Zinc Battery

Abstract

To provide a zinc battery electrolyte capable of realizing an excellent life performance in a zinc battery.SOLUTION: A zinc battery electrolyte contains an alkali metal hydroxide and a chelator. The chelator includes at least one kind selected from a group consisting of aminocarboxylic acid based chelators, hydroxamic acid based chelators and phosphonic acid based chelators.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to an electrolyte for a zinc battery, a zinc battery, etc.

Background Art

[0002] Since a nickel-zinc battery is an aqueous battery using an aqueous electrolyte such as an aqueous potassium hydroxide solution, it has high safety, and it is known to have a high electromotive force as an aqueous battery due to the combination of a zinc electrode and a nickel electrode. Further, since a nickel-zinc battery has excellent input / output performance and is low-cost, its applicability to industrial applications (for example, applications such as backup power sources) and automotive applications (for example, applications such as hybrid vehicles) has been studied.

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

[0004] As shown in the above equations, in a nickel-zinc battery, zinc hydroxide (Zn(OH) 2 ) is generated by the discharge reaction. Zinc hydroxide is soluble in the electrolyte, and when zinc hydroxide dissolves in the electrolyte, zinc tetrahydroxide ion ([Zn(OH) 4 2- ​) diffuses into the electrolyte solution. As a result, the morphological change (deformation) of the negative electrode progresses and the distribution of the charging current becomes non-uniform, etc., causing local zinc deposition on the negative electrode and the generation of dendrites (dendritic crystals). In a nickel-zinc battery, when dendrites grow due to repeated charge and discharge, the dendrites penetrate the separator and a short circuit occurs, so the generation of the above dendrites leads to a decrease in the life performance. On the other hand, for example, Patent Document 1 discloses a technique for preventing an internal short circuit between the positive and negative electrodes due to zinc dendrites by interposing a non-woven fabric coated with nickel between the positive and negative electrode plates.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] There is a further need for improving the life performance of zinc batteries such as nickel-zinc batteries.

[0007] One aspect of the present disclosure aims to provide an electrolyte solution for a zinc battery capable of obtaining excellent life performance in a zinc battery. Another aspect of the present disclosure aims to provide a zinc battery including the electrolyte solution for a zinc battery.

Means for Solving the Problems

[0008] One aspect of the present disclosure provides an electrolyte solution for a zinc battery containing an alkali metal hydroxide and a chelating agent, wherein the chelating agent includes at least one selected from the group consisting of an aminocarboxylic acid-based chelating agent, a hydroxamic acid-based chelating agent, and a phosphonic acid-based chelating agent.

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

[0010] According to the above-described electrolyte for a zinc battery and the zinc battery, excellent life performance can be obtained.

Advantages of the Invention

[0011] According to one aspect of the present disclosure, it is possible to provide an electrolyte for a zinc battery capable of obtaining 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 electrolyte for a zinc battery.

Embodiments for Carrying Out the Invention

[0012] "A or more" in a numerical range means A and a range exceeding A. "A or less" in a numerical range means A and a range less than A. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value of a numerical range at a certain step can be arbitrarily combined with the upper limit value or the lower limit value of a numerical range at another step. In the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. "A or B" means that either A or B may be included, or both may be included. The materials exemplified in this specification can be used alone or in combination of two or more without particular notice. In this specification, the amount of each component in a composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. In this specification, the terms "membrane" or "layer" include not only a structure formed over the entire surface when observed in a plan view, but also a structure formed partially. In this specification, the term "step" includes not only an independent step, but also a step that is included in this term if the intended action of the step is achieved even when it cannot be clearly distinguished from other steps. The unit "C" relatively represents the magnitude of the current when discharging the rated capacity at a constant current from a fully charged state. The unit "C" means "discharge current value (A) / battery capacity (Ah)". For example, the current that can discharge the rated capacity in 1 hour is expressed as "1C", and the 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 with various modifications within the scope of the gist thereof.

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

[0015] The electrolyte according to this embodiment contains an alkali metal hydroxide and a chelating agent, and the chelating agent includes at least one selected from the group consisting of an aminocarboxylic acid-based chelating agent, a hydroxamic acid-based chelating agent, and a phosphonic acid-based chelating agent. According to the electrolyte according to this embodiment, excellent life performance can be obtained.

[0016] Examples of the factors for obtaining such an effect include, but are not limited to, the following factors. That is, since the electrolyte contains a specific chelating agent, this chelating agent coordinates on the surface of zinc at the negative electrode. As a result, the elution and diffusion of zinc are suppressed, so that the deterioration of battery performance is suppressed.

[0017] Examples of the alkali metal hydroxide include potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), and the like. The alkali metal hydroxide may be ionized (dissociated) in an aqueous solution or may exist as a salt. From the viewpoint of easily obtaining excellent life performance, the alkali metal hydroxide may contain at least one selected from the group consisting of potassium hydroxide and lithium hydroxide, and may contain potassium hydroxide.

[0018] The content of the alkali metal hydroxide in the electrolyte (total amount of alkali metal hydroxides) may be in the following range based on the total amount of the electrolyte from the viewpoint of easily obtaining excellent life performance. The content of the alkali metal hydroxide may be 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, or 30% by mass or more. The content of the alkali metal hydroxide may be 50% by mass or less, 45% by mass or less, 40% by mass or less, or 35% by mass or less. From these viewpoints, the content of the alkali metal hydroxide may be 10 to 50% by mass.

[0019] The content of potassium hydroxide in the electrolyte may be in the following range based on the total amount of the electrolyte from the viewpoint of easily obtaining excellent life performance. The content of potassium hydroxide may be 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, or 30% by mass or more. The content of potassium hydroxide may be 50% by mass or less, 45% by mass or less, 40% by mass or less, or 35% by mass or less. From these viewpoints, the content of potassium hydroxide may be 10 to 50% by mass.

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

[0021] The electrolyte according to this embodiment contains a chelating agent, and the chelating agent contains at least one selected from the group consisting of aminocarboxylic acid-based chelating agents, hydroxamic acid-based chelating agents, and phosphonic acid-based chelating agents. The chelating agent may be a salt (such as a sodium salt) or a hydrate of the salt.

[0022] An aminocarboxylic acid-based chelating agent is a chelating agent having an amino group and a carboxyl group. The aminocarboxylic acid-based chelating agent may be a secondary amine compound or a tertiary amine compound, and may be a secondary amine compound, from the viewpoint of easily obtaining excellent life performance.

[0023] The number of amino groups in the aminocarboxylic acid-based chelating agent may be in the following range from the viewpoint of easily obtaining excellent life performance. The number of amino groups may be 4 or less, 3 or less, 2 or less, or 1. The number of amino groups may be 1 or more, or 2 or more. From these viewpoints, the number of amino groups may be 1 to 4.

[0024] The number of carboxyl groups in the aminocarboxylic acid-based chelating agent may be in the following range from the viewpoint of easily obtaining excellent life performance. The number of carboxyl groups may be 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1. The number of carboxyl groups may be 1 or more, 2 or more, 3 or more, or 4 or more. From these viewpoints, the number of carboxyl groups may be 1 to 6, 2 to 5, or 2 to 4.

[0025] The number of carbon atoms in the aminocarboxylic acid-based chelating agent may be in the following range from the viewpoint of easily obtaining excellent life performance. The number of carbon atoms may be 20 or less, 15 or less, 12 or less, 10 or less, 8 or less, 6 or less, 5 or less, or 4 or less. The number of carbon atoms may be 4 or more, 5 or more, 6 or more, 8 or more, or 10 or more. From these viewpoints, the number of carbon atoms may be 4 to 20.

[0026] Examples of aminocarboxylic acid chelating agents include aminoacetic acids and their salts such as iminodiacetic acid (IDA), N-(2-hydroxyethyl)iminodiacetic acid (HIDA), nitrilotriacetic acid (NTA), N-(2-hydroxyethyl)ethylenediamine-N,N’,N’-triacetic acid (HEDTA), ethylenediamine-N,N,N’,N’-tetraacetic acid (EDTA), propylenediaminetetraacetic acid (PDTA), 1,3-diamino-2-hydroxypropane-N,N,N’,N’-tetraacetic acid (DPTA-OH), glycol ether diamine tetraacetic acid (EGTA), trans-1,2-diaminocyclohexane-N,N,N’,N’-tetraacetic acid, diethylenetriamine-N,N,N’,N”,N”-pentaacetic acid (DTPA), triethylenetetramine hexaacetic acid (TTHA), N,N-di(2-hydroxyethyl)glycine (DHEG); ethylenediamine-N,N’-disuccinic acid (EDDS), ethylenediamine-N,N’-diglutamic acid and their salts. From the viewpoint of easily obtaining excellent life performance, the aminocarboxylic acid chelating agent may contain at least one selected from the group consisting of aminoacetic acids and their salts, may contain at least one selected from the group consisting of iminodiacetic acid, nitrilotriacetic acid, ethylenediamine tetraacetic acid and their salts, and may contain at least one selected from the group consisting of iminodiacetic acid and its salts.

[0027] Hydroxamic acid chelating agents are chelating agents having a hydroxamic acid group (-CO-NHOH) (excluding compounds corresponding to aminocarboxylic acid chelating agents). From the viewpoint of easily obtaining excellent life performance, the hydroxamic acid chelating agent may contain at least one selected from the group consisting of aliphatic compounds having a hydroxamic acid group (aliphatic hydroxamic acids), aromatic compounds having a hydroxamic acid group (aromatic hydroxamic acids), and their salts.

[0028] The number of hydroxamic acid groups in the hydroxamic acid-based chelating agent may be in the following range from the viewpoint of easily obtaining excellent life performance. The number of hydroxamic acid groups may be 3 or less, 2 or less, or 1. The number of hydroxamic acid groups may be 1 or more. From these viewpoints, the number of hydroxamic acid groups may be 1 to 3.

[0029] The carbon number of the hydroxamic acid-based chelating agent may be in the following range from the viewpoint of easily obtaining excellent life performance. The carbon number may be 20 or less, 15 or less, 12 or less, 10 or less, 8 or less, 5 or less, 3 or less, or 2 or less. The carbon number may be 2 or more. From these viewpoints, the carbon number may be 2 to 20.

[0030] Examples of the hydroxamic acid-based chelating agent include aliphatic hydroxamic acids such as acetohydroxamic acid and octanohydroxamic acid and their salts; aromatic hydroxamic acids such as benzenesulfohydroxamic acid, salicylhydroxamic acid, and suberoyl anilide hydroxamic acid and their salts. The hydroxamic acid-based chelating agent may contain at least one selected from the group consisting of aliphatic hydroxamic acids and their salts from the viewpoint of easily obtaining excellent life performance, and may contain at least one selected from the group consisting of acetohydroxamic acid and its salts.

[0031] The phosphonic acid-based chelating agent is a chelating agent having a phosphono group (-PO(OH) 2 ), excluding compounds corresponding to aminocarboxylic acid-based chelating agents or hydroxamic acid-based chelating agents. The phosphonic acid-based chelating agent may contain at least one selected from the group consisting of aliphatic compounds having a phosphono group (aliphatic phosphonic acids), aromatic compounds having a phosphono group (aromatic phosphonic acids), and their salts from the viewpoint of easily obtaining excellent life performance.

[0032] The number of phosphono groups in the phosphonic acid chelating agent may be in the following range from the viewpoint of easily obtaining excellent life performance. The number of phosphono groups may be 5 or less, 4 or less, 3 or less, or 2 or less. The number of phosphono groups may be 1 or more, or 2 or more. From these viewpoints, the number of phosphono groups may be 1 to 5, or 2 to 4.

[0033] The phosphonic acid chelating agent may have a functional group other than the phosphono group. Examples of the functional group other than the phosphono group include a hydroxy group (hydroxyl group), a carboxyl group, an amino group, etc. The phosphonic acid chelating agent may have a hydroxy group from the viewpoint of easily obtaining excellent life performance.

[0034] The carbon number of the phosphonic acid chelating agent may be in the following range from the viewpoint of easily obtaining excellent life performance. The carbon number may be 20 or less, 15 or less, 12 or less, 10 or less, 8 or less, 5 or less, 3 or less, or 2 or less. The carbon number may be 2 or more. From these viewpoints, the carbon number may be 2 to 20.

[0035] Examples of the phosphonic acid chelating agent include aliphatic phosphonic acids such as etidronic acid (1-hydroxyethane-1,1-diphosphonic acid (HEDP)), nitrilotris(methylenephosphonic acid) (NTMP), phosphonobutane tricarboxylic acid (PBTC), ethylenediaminetetramethylenephosphonic acid (EDTMP), and salts thereof. The phosphonic acid chelating agent may contain at least one selected from the group consisting of aliphatic phosphonic acids and salts thereof from the viewpoint of easily obtaining excellent life performance, and may contain at least one selected from the group consisting of etidronic acid and salts thereof.

[0036] When the chelating agent contains an aminocarboxylic acid-based chelating agent, a hydroxamic acid-based chelating agent, or a phosphonic acid-based chelating agent, the content of the aminocarboxylic acid-based chelating agent, hydroxamic acid-based chelating agent, or phosphonic acid-based chelating agent in the chelating agent 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, from the viewpoint of easily obtaining excellent life performance, based on the content of the chelating agent (total amount of the chelating agent contained in the electrolyte). The chelating agent may be in a form consisting essentially of an aminocarboxylic acid-based chelating agent, a hydroxamic acid-based chelating agent, or a phosphonic acid-based chelating agent (a form in which substantially 100% by mass of the chelating agent is an aminocarboxylic acid-based chelating agent, a hydroxamic acid-based chelating agent, or a phosphonic acid-based chelating agent).

[0037] The molecular weight of the chelating agent may be in the following range from the viewpoint of easily obtaining excellent life performance. The molecular weight of the chelating agent may be 50 or more, 60 or more, 65 or more, 70 or more, or 75 or more. The molecular weight of the chelating agent may be 2000 or less, 1500 or less, 1000 or less, 800 or less, 600 or less, 500 or less, or 400 or less. From these viewpoints, the molecular weight of the chelating agent may be 50 to 2000. The molecular weight of the chelating agent may be 100 or more, 150 or more, 200 or more, 250 or more, 300 or more, or 350 or more, and may be 350 or less, 300 or less, 250 or less, 200 or less, 150 or less, or 100 or less.

[0038] The content of the chelating agent in the electrolyte (total amount of the chelating agent contained in the electrolyte) may be in the following range based on the total amount of the electrolyte from the viewpoint of easily obtaining excellent life performance. The content of the chelating agent may be 0.01% by mass or more, 0.05% 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, or 2% by mass or more. The content of the chelating agent may be 20% by mass or less, 10% by mass or less, 8% by mass or less, 5% by mass or less, 3% by mass or less, 2.5% by mass or less, or 2% by mass or less. From these viewpoints, the content of the chelating agent may be 0.01 to 20% by mass, 0.05 to 10% by mass, 0.1 to 8% by mass, 0.5 to 5% by mass, or 1 to 3% by mass.

[0039] The content of the chelating agent may be in the following range with respect to 100 parts by mass of the alkali metal hydroxide from the viewpoint of easily obtaining excellent life performance. The content of the chelating agent may be 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 5.5 parts by mass or more, or 6 parts by mass or more. The content of the chelating agent 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, 8 parts by mass or less, 7 parts by mass or less, or 6.5 parts by mass or less. From these viewpoints, the content of the chelating agent may be 1 to 30 parts by mass.

[0040] The chelating agent may contain a chelating agent other than an aminocarboxylic acid-based chelating agent, a hydroxamic acid-based chelating agent, and a phosphonic acid-based chelating agent (hereinafter referred to as "chelating agent X"). Examples of the chelating agent X include hydroxyurea and polyamino acid-based chelating agents.

[0041] The content of the chelating agent X may be 1% by mass or less, 0.1% by mass or less, 0.01% by mass or less, or 0.001% by mass or less based on the total mass of the electrolyte from the viewpoint of easily obtaining excellent life performance. An embodiment may be such that the electrolyte substantially does not contain the chelating agent X (the content of the chelating agent X contained in the electrolyte is substantially 0% by mass).

[0042] From the perspective of easily obtaining excellent life performance, the electrolytic solution according to this embodiment may further contain a surfactant (excluding chelating agents). The reason why it is easy to obtain excellent life performance when the electrolytic solution contains a surfactant is speculated as follows, but is not limited to the following reasons. That is, when the electrolytic solution contains a surfactant, a film is formed on the surface of zinc in the electrode material, so that the oxidation of zinc in the electrode material can be suppressed. By suppressing the oxidation of zinc, it is speculated that the formation of a passive state (zinc oxide) on the surface of the electrode material can be made difficult, and thus the deterioration of battery performance can be suppressed.

[0043] Examples of the surfactant include nonionic surfactants (non-ionic surfactants), anionic surfactants, cationic surfactants, amphoteric surfactants, and the like. From the perspective of easily obtaining excellent life performance, the surfactant may contain at least one selected from the group consisting of nonionic surfactants and anionic surfactants, and may contain nonionic surfactants and anionic surfactants.

[0044] 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; polyoxyethylene-containing ether compounds such as polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers. From the perspective of easily obtaining excellent life performance, the nonionic surfactant may contain at least one selected from the group consisting of polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers, may contain polyoxyethylene alkyl phenyl ethers, and may contain polyoxyethylene octyl phenyl ethers.

[0045] 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, polyoxyethylene octadecyl ether, and the like.

[0046] Examples of polyoxyethylene alkyl phenyl ethers include polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, and the like.

[0047] An anionic surfactant has an anionic hydrophilic group and a hydrophobic group. Examples of anionic surfactants include polyoxyalkylene alkyl ether phosphates (e.g., polyoxyethylene alkyl ether phosphates), polyoxyethylene alkyl ether sulfates, sodium dodecylbenzenesulfonate, alkali salts of styrene-acrylic acid copolymers, sodium alkylnaphthalenesulfonate, sodium alkyldiphenyl ether disulfonate, lauryl sulfate monoethanolamine, lauryl sulfate triethanolamine, ammonium lauryl sulfate, stearic acid monoethanolamine, sodium stearate, sodium lauryl sulfate, monoethanolamine of styrene-acrylic acid copolymers, and the like. From the viewpoint of easily obtaining excellent life performance, the anionic surfactant may contain a polyoxyalkylene alkyl ether phosphate and may contain a polyoxyethylene alkyl ether phosphate.

[0048] A cationic surfactant has a cationic hydrophilic group and a hydrophobic group. Examples of the cationic surfactant include quaternary ammonium salt type cationic surfactants such as aliphatic amines or their salts, alkylamide amine salts, monoalkyltrimethylammonium salts, dialkyldimethylammonium salts, alkylbenzyldimethylammonium salts, alkylpyridinium salts, and benzethonium chloride. From the viewpoint of easily obtaining excellent life performance, the cationic surfactant may contain at least one selected from the group consisting of monoalkyltrimethylammonium salts and dialkyldimethylammonium salts, and may contain a monoalkyltrimethylammonium salt.

[0049] Examples of the monoalkyltrimethylammonium salt 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.

[0050] Examples of the dialkyldimethylammonium salt include dodecyldimethylammonium bromide, dodecyldimethylammonium chloride, tridecyldimethylammonium bromide, tridecyldimethylammonium chloride, tetradecyldimethylammonium bromide, tetradecyldimethylammonium chloride, pentadecyldimethylammonium bromide, pentadecyldimethylammonium chloride, hexadecyldimethylammonium bromide, hexadecyldimethylammonium chloride, heptadecyldimethylammonium bromide, heptadecyldimethylammonium chloride, octadecyldimethylammonium bromide, octadecyldimethylammonium chloride, and the like.

[0051] When the surfactant contains a nonionic surfactant or an anionic surfactant, the content of the nonionic surfactant or the anionic surfactant in the surfactant 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 surfactant (total amount of the surfactant), from the viewpoint of easily obtaining excellent life performance. The surfactant may be in a form consisting essentially of a nonionic surfactant or an anionic surfactant (a form in which substantially 100% by mass of the surfactant is a nonionic surfactant or an anionic surfactant).

[0052] When the surfactant contains a nonionic surfactant and an anionic surfactant, the mass ratio of the content of the anionic surfactant to the content of the nonionic surfactant (content of the anionic surfactant / content of the nonionic surfactant) may be in the following range 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.

[0053] The content of the surfactant in the electrolyte (total amount of surfactants) may be in the following range based on the total amount of the electrolyte from the viewpoint of easily obtaining excellent life performance. The content of the surfactant may be 0.001% by mass or more, 0.003% by mass or more, 0.005% by mass or more, or 0.01% by mass or more. The content of the surfactant may be 0.1% by mass or less, 0.08% by mass or less, 0.05% by mass or less, or 0.01% by mass or less. From these viewpoints, the content of the surfactant may be 0.001 to 0.1% by mass.

[0054] The electrolyte according to this embodiment can contain a liquid medium such as water (e.g., ion-exchanged water).

[0055] Hereinafter, as an example of a zinc battery in which the electrolyte according to the above embodiment is used, a nickel-zinc battery will be described.

[0056] The zinc battery according to this embodiment includes, for example, a battery case, an electrode group (e.g., a plate group) and an electrolyte housed in the battery case. The zinc battery according to this embodiment may be either after formation or before formation.

[0057] 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 laminated via the separator, for example, in a state where the main surface of the positive electrode and the main surface of the negative electrode face 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 by a strap, for example.

[0058] The positive electrode has a positive electrode current collector (current collector) and a positive electrode material (electrode material) supported by 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 by 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 formation or after formation.

[0059] The current collector (positive current collector or negative current collector) constitutes a current conduction path from the electrode material (positive electrode material or negative electrode material). The current collector has a shape such as a flat plate shape or a sheet shape, for example. The current collector may be a current collector having a three-dimensional network structure composed of a foamed metal, an expanded metal, a punched metal, a felt-like material of metal fibers, or the like.

[0060] Specific examples of the material constituting the current collector include platinum; nickel (such as foamed nickel); metal materials (copper, brass, steel, etc.) plated with metals such as tin and nickel.

[0061] 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, an electrode material layer may be formed on the current collector. When the current collector has a three-dimensional network structure, the electrode material may be filled between the meshes of the current collector to form an electrode material layer.

[0062] 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.

[0063] 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), nickel hydroxide, and the like. The positive electrode material contains, for example, nickel oxyhydroxide in a fully charged state and nickel hydroxide in a discharged state. The content of the positive electrode active material may be, for example, 50 to 99% by mass based on the total mass of the positive electrode material.

[0064] The positive electrode material can contain additives other than the positive electrode active material. Examples of the additives include a binder, a conductive agent, an expansion inhibitor, a rare earth metal compound (such as yttrium oxide), and the like. Examples of the binder include hydrophilic or hydrophobic polymers, such as hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), carboxymethyl cellulose (CMC), sodium polyacrylate (SPA), and fluorine-based polymers (such as polytetrafluoroethylene (PTFE)). The content of the binder may be, for example, 0.01 to 5 parts by mass with respect to 100 parts by mass of the positive electrode active material. Examples of the conductive agent include cobalt compounds (such as metallic cobalt, cobalt oxide, and cobalt hydroxide). The content of the conductive agent may be, for example, 1 to 20 parts by mass with respect to 100 parts by mass of the positive electrode active material. Examples of the expansion inhibitor include zinc oxide. The content of the expansion inhibitor may be, for example, 0.01 to 5 parts by mass with respect to 100 parts by mass of the positive electrode active material.

[0065] 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 may contain a plurality of types. For example, the negative electrode material contains metallic zinc in a fully charged state and contains zinc oxide and zinc hydroxide in a discharged state. The negative electrode active material may be, for example, in a particulate form and may include metallic zinc particles, zinc oxide particles, zinc hydroxide particles, and the like. The content of the negative electrode active material is, for example, 50 to 99% by mass based on the total mass of the negative electrode material.

[0066] The negative electrode material can contain additives other than the negative electrode active material. Examples of the additives include binders, surfactants, conductive agents, etc. Examples of the binder include polytetrafluoroethylene, hydroxyethyl cellulose (HEC), carboxymethyl cellulose, polyethylene oxide, polyethylene, polypropylene, etc. The content of the binder may be, for example, 0.5 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material. Examples of the conductive agent include indium compounds (such as indium oxide). The content of the conductive agent may be, for example, 1 to 20 parts by mass with respect to 100 parts by mass of the negative electrode active material.

[0067] The separator may be in the form of a bag having an opening so as to be able to accommodate the positive electrode and / or the negative electrode. In a zinc battery, for example, the opening opens upward in the vertical direction. The side portion in the direction orthogonal to the opening direction of the opening of the separator (for example, the side portion located in the horizontal direction when the positive electrode and / or the negative electrode is accommodated in the zinc battery) may be shielded or may be open. The shielding portion can be formed, for example, by thermally welding the separator. The separator may be a single-layer porous film or a laminate of a plurality of porous films.

[0068] Examples of the material of the separator include organic materials (such as resin materials) and inorganic materials. Examples of the resin materials include polyamide-based polymers (such as polyamide), olefin-based polymers (such as polyolefins such as polyethylene and polypropylene), nylon-based polymers (such as nylon), etc. Examples of the inorganic materials include oxides such as alumina, titania, and silicon dioxide; nitrides such as aluminum nitride and silicon nitride; sulfates such as barium sulfate and calcium sulfate, etc. The separator may be an ion exchange resin membrane, a cellophane-based regenerated resin membrane, an inorganic-organic separator, a polyolefin-based nonwoven fabric, etc.

[0069] From the perspective of hydrophilicity, the separator may contain anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc., and may be surface-treated by surfactant treatment, sulfonation treatment, fluorine gas treatment, acrylic acid graft polymerization treatment, corona discharge treatment, plasma treatment, etc. By making it hydrophilic, it is easy to mix with the electrolyte and easy to obtain a sufficient current density.

[0070] The manufacturing method of the nickel-zinc battery described above includes, for example, a component manufacturing process for obtaining the constituent members of the zinc battery and an assembly process for assembling the constituent members to obtain a zinc battery. In the component manufacturing process, at least electrodes (positive electrode and negative electrode) are obtained.

[0071] For example, the electrode can be obtained by adding a solvent (such as water) to the raw materials of the electrode material (positive electrode material and negative electrode material) and kneading them to obtain an electrode material paste (paste-like electrode material), and then forming an electrode material layer using the electrode material paste.

[0072] Examples of the raw materials for the positive electrode material include raw materials for the positive electrode active material (such as nickel hydroxide), additives (such as the binder), etc. Examples of the raw materials for the negative electrode material include raw materials for the negative electrode active material (such as metallic zinc, zinc oxide, and zinc hydroxide), additives (such as the binder), etc.

[0073] Examples of the method for forming the electrode material layer include a method of obtaining the electrode material layer by applying or filling the electrode material paste onto a current collector and then drying it. The electrode material layer may be densified by pressing or the like as necessary.

[0074] In the assembly process, for example, the positive electrode and negative electrode obtained in the component manufacturing process are alternately laminated via a separator, and then the positive electrodes and negative electrodes are connected with straps to produce an electrode group. Next, after placing this electrode group in the battery case, a lid is adhered to the upper surface of the battery case to obtain an unformed zinc battery (nickel-zinc battery).

[0075] Subsequently, after injecting the electrolytic solution according to the present embodiment into the cell of an unformed zinc battery, it is left for a certain period of time. Then, it is formed by performing charging under predetermined conditions to obtain a zinc battery (nickel-zinc battery). The forming conditions can be adjusted according to the properties of the electrode active materials (positive electrode active material and negative electrode active material).

[0076] As described above, an example of a nickel-zinc battery (for example, a nickel-zinc secondary battery) in which the positive electrode is a nickel electrode has been described. However, the zinc battery may be an air-zinc battery (for example, an air-zinc secondary battery) in which the positive electrode is an air electrode, or a silver-zinc battery (for example, a silver-zinc secondary battery) in which the positive electrode is a silver oxide electrode.

[0077] As the air electrode of the air-zinc battery, a known air electrode used in an air-zinc battery can be used. The air electrode includes, for example, an air electrode catalyst, an electron conductive material, and the like. As the air electrode catalyst, an air electrode catalyst that also functions as an electron conductive material can be used.

[0078] As the air electrode catalyst, those that function as the positive electrode in an air-zinc battery can be used, and various air electrode catalysts capable of using oxygen as the positive electrode active material can be used. Examples of the air electrode catalyst include carbon-based materials (such as graphite) having a redox catalyst function, metal materials (such as platinum and nickel) having a redox catalyst function, and inorganic oxide materials (such as perovskite-type oxides, manganese dioxide, nickel oxide, cobalt oxide, and spinel oxides) having a redox catalyst function. The shape of the air electrode catalyst may be, for example, particulate. The content of the air electrode catalyst in the air electrode may be 5 to 70% by volume, 5 to 60% by volume, or 5 to 50% by volume based on the total amount of the air electrode.

[0079] As the electron conductive material, those having conductivity and enabling electron conduction between the air electrode catalyst and the separator can be used. 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 like flaky graphite, artificial graphite, and expanded graphite; conductive fibers such as carbon fibers and metal fibers; metal powders such as copper, silver, nickel, and aluminum; organic electron conductive materials such as polyphenylene derivatives; and any mixtures thereof. The shape of the electron conductive material may be particulate or other shapes. The electron conductive material may be used in a form that provides a continuous phase in the thickness direction in the air electrode. For example, the electron conductive material may be a porous material. Further, the electron conductive material may be in the form of a mixture or composite with the air electrode catalyst, and as described above, it 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 based on the total amount of the air electrode.

[0080] As the silver oxide electrode of the silver-zinc battery, a known silver oxide electrode used in silver-zinc batteries can be used. The silver oxide electrode contains, for example, silver(I) oxide.

Examples

[0081] Hereinafter, the present disclosure will be specifically described by way of examples. However, the present disclosure is not limited to the following examples.

[0082] <Preparation of Electrolyte Solution> (Examples 1 to 5) Ionic-exchanged water, potassium hydroxide (KOH), lithium hydroxide (LiOH), the chelating agent shown in Table 1, a nonionic surfactant (polyoxyethylene octyl phenyl ether (Triton X-100, manufactured by Sigma-Aldrich)), and an anionic surfactant (a mixture of polyoxyethylene alkyl ether phosphate esters (monoester and diester), manufactured by Rhodafac, trade name: RA-600) were mixed to prepare an electrolytic solution (potassium hydroxide concentration: 30% by mass, lithium hydroxide concentration: 1% by mass, chelating agent content: 2% by mass, nonionic surfactant: 0.005% by mass, anionic surfactant: 0.005% by mass). Note that the content of the above components is based on the total mass of the electrolytic solution. When a hydrate is used as the chelating agent, the content of the chelating agent indicates the amount of the hydrate used.

[0083] (Comparative Example 1) An electrolytic solution (potassium hydroxide concentration: 30% by mass, lithium hydroxide concentration: 1% by mass, nonionic surfactant: 0.005% by mass, anionic surfactant: 0.005% by mass) was prepared in the same manner as in Examples 1 to 5 except that no chelating agent was used.

[0084] <Fabrication of Positive Electrode> A lattice body made of foamed nickel with a porosity of 95% was prepared, and a positive electrode current collector was obtained by pressure-molding the lattice body. Next, a positive electrode material paste was prepared by weighing a predetermined amount of cobalt-coated nickel hydroxide powder, metallic cobalt, cobalt hydroxide, yttrium oxide, CMC (carboxymethyl cellulose), PTFE (polytetrafluoroethylene), and ionic-exchanged water and then mixing them. At this time, the mass ratio of the solid content was adjusted to "nickel hydroxide: metallic cobalt: yttrium oxide: cobalt hydroxide: CMC: PTFE = 88: 10.3: 1: 0.3: 0.3: 0.1". The water content of the positive electrode material paste was adjusted to 27.5% by mass based on the total mass of the positive electrode material paste. Next, the positive electrode material paste was applied onto the positive electrode current collector and then dried at 80 ° C for 30 minutes. Thereafter, it was pressure-molded by a roll press to obtain an unformed positive electrode having a positive electrode material (positive electrode material layer) on both sides.

[0085] <Fabrication of Negative Electrode> As the negative electrode current collector, copper punching metal (aperture ratio: 50%, thickness: 0.10 mm) plated with tin was prepared. Next, a negative electrode material paste was prepared by weighing predetermined amounts of zinc oxide, metallic zinc, HEC (hydroxyethyl cellulose, manufactured by Sumitomo Seika Chemical Co., Ltd., trade name: AV-15F), surfactant (manufactured by BASF, trade name: Dispex AA 4140), and ion-exchanged water and then mixing them. At this time, the mass ratio of the solid content was adjusted to "zinc oxide: metallic zinc: HEC: surfactant = 84.5:11.5:3.5:0.5". The water content of the negative electrode material paste was adjusted to 32.5% by mass based on the total mass of the negative electrode material paste. Next, after applying the negative electrode material paste onto the negative electrode current collector, it was dried at 80°C for 30 minutes. Then, it was pressure-molded by a roll press to obtain an unformed negative electrode having negative electrode materials (negative electrode material layers) on both sides.

[0086] <Fabrication of Nickel-Zinc Battery> Before battery assembly, a porous membrane (manufactured by Ube Industries, Ltd., trade name: UP3355, air permeability: 440 sec / 100 mL) was hydrophilized with a surfactant (manufactured by Sigma-Aldrich Japan K.K., trade 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 and then drying it at room temperature for 1 hour. The air permeability of the porous membrane indicates the value after the hydrophilization treatment. After cutting the porous membrane into 3.0 cm × 10.0 cm and folding it in half, a porous membrane A (3.0 cm × 5.0 cm) was obtained. After obtaining a bag-shaped porous member by heat-sealing a pair of both side surfaces (long sides) of this porous membrane A, a positive electrode body was obtained by accommodating one unformed positive electrode in this bag-shaped porous member. Also, after obtaining a bag-shaped porous member by heat-sealing a pair of both side surfaces (long sides) of the porous membrane A, a negative electrode body was obtained by accommodating one unformed negative electrode in this bag-shaped porous member.

[0087] A non-woven fabric (3.0 cm × 5.0 cm) obtained by cutting VL100 manufactured by Nippon Kodo Paper Industry Co., Ltd. (material: cellulose, thickness: 100 μm, air permeability: 0.3 sec / 100 mL) into 3.0 cm × 10.0 cm and then folding it in half was sandwiched between the positive electrode body and the negative electrode body, and two positive electrode bodies and three negative electrode bodies were alternately laminated. Then, the electrode plates of the same polarity were connected with a strap to produce an electrode group (electrode plate group). After placing this electrode group in a battery case, a lid was adhered to the upper surface of the battery case to obtain an unformed nickel-zinc battery. Next, an electrolytic solution was injected into the battery case of the unformed nickel-zinc battery and then left for 24 hours. Thereafter, charging was performed under the conditions of 32 mA for 15 hours to produce a nickel-zinc battery after formation (nominal capacity: 320 mAh).

[0088] <Characteristic Evaluation> Using the nickel-zinc batteries of Examples 1 to 5 and Comparative Example 1, the life performance (cycle life performance) of the nickel-zinc battery was evaluated. The specific evaluation method is shown below, and the results are shown in Table 1.

[0089] At 40°C, after charging the nickel-zinc battery at a constant voltage of 105.7 mA (0.33C) and 1.88V until the current value decays to 16 mA (0.05C), a test was conducted with one cycle being to discharge the nickel-zinc battery at a constant current of 105.7 mA (0.33C) until the battery voltage reaches 1.1V. When the discharge capacity fell below 60% of the discharge capacity in the first cycle, the test was terminated, and the life performance was evaluated based on the number of cycles performed until the end of the test.

[0090]

Table 1

Claims

1. containing an alkali metal hydroxide and a chelating agent, wherein the chelating agent includes at least one selected from the group consisting of aminocarboxylic acid chelating agents, hydroxamic acid chelating agents, and phosphonic acid chelating agents, an electrolyte solution for a zinc battery (excluding an electrolyte solution for a zinc battery containing an alkali metal hydroxide and ethylenediaminetetraacetic acid).

2. The electrolyte solution for a zinc battery according to Claim 1, wherein the alkali metal hydroxide contains potassium hydroxide.

3. The electrolyte solution for a zinc battery according to Claim 1 or 2, wherein the chelating agent includes at least one selected from the group consisting of iminodiacetic acid, nitrilotriacetic acid, and salts thereof.

4. The electrolyte solution for a zinc battery according to any one of Claims 1 to 3, wherein the chelating agent includes at least one selected from the group consisting of acetohydroxamic acid and salts thereof.

5. The electrolyte solution for a zinc battery according to any one of Claims 1 to 4, wherein the chelating agent includes at least one selected from the group consisting of etidronic acid and salts thereof.

6. The electrolyte solution for a zinc battery according to any one of Claims 1 to 5, further containing a surfactant.

7. The electrolyte solution for a zinc battery according to Claim 6, wherein the surfactant includes at least one selected from the group consisting of nonionic surfactants and anionic surfactants.

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

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