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 compound represented by a general formula (1) in the figure excluding polyoxyethylene octylphenyl ether. [In the formula (1), n represents an integer from 1 to 10; and R1 and R2 each independently represent an organic group, a hydrogen atom or a metal atom, where if n=1 then at least one of R1 and R2 represents an organic group.]SELECTED DRAWING: None

Description

Technical Field

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

Background 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 that, due to the combination of a zinc electrode and a nickel electrode, it has a high electromotive force as an aqueous battery. Further, since the nickel-zinc battery is low-cost in addition to excellent input / output performance, 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 formula (discharge reaction: rightward, charge reaction: leftward). (Positive electrode) 2NiOOH + 2H2O + 2e - → 2Ni(OH)2 + 2OH - (Negative electrode) Zn + 2OH - → Zn(OH)2 + 2e -

[0004] As shown in the above formula, in 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, tetrahydroxozincate 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] For zinc batteries such as nickel-zinc batteries, further improvement in life performance is required.

[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 compound represented by the following general formula (1) (excluding polyoxyethylene octyl phenyl ether).

[0009]

Chemical Formula

[0010] Another aspect of the present disclosure provides a zinc battery including a positive electrode, a negative electrode, and the above-described electrolyte for a zinc battery.

[0011] According to the above-described electrolyte for a zinc battery and the zinc battery, excellent life performance can be obtained.

Advantages of the Invention

[0012] 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

[0013] "A or more" in a numerical range means A and the range exceeding A. "A or less" in a numerical range means A and the 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 either A or B, or both. The materials exemplified in this specification can be used alone or in combination of two or more, unless otherwise specified. In this specification, the amount of each component in the composition means the total amount of the plurality of substances corresponding to each component in the composition, unless otherwise specified when there are a plurality of substances corresponding to each component in the composition. In this specification, the terms "film" or "layer" include not only the structure formed over the entire surface but also the structure formed partially when observed as a plan view. In this specification, the term "step" includes not only an independent step but also a step in which the intended action of the step is achieved even if 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".

[0014] 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.

[0015] 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.

[0016] The electrolyte according to this embodiment contains an alkali metal hydroxide and a compound represented by the following general formula (1) (excluding polyoxyethylene octyl phenyl ether). According to the electrolyte according to this embodiment, excellent life performance can be obtained. Further, according to the electrolyte according to this embodiment, excellent high-rate discharge performance can be obtained in a zinc battery.

Chemical formula

[0017] Examples of the factors for obtaining such effects include, but are not limited to, the following factors. That is, when an alkali metal hydroxide (M-OH, where M represents an alkali metal element) and a compound represented by the general formula (1) coexist, the compound represented by the general formula (1) forms a complex with the metal cation M + . As a result, the reactivity of hydroxide ions in the electrolyte is increased, so that the uneven distribution of the reaction between zinc and hydroxide ions at the negative electrode is alleviated, and the deterioration of battery performance due to morphological changes is suppressed.

[0018] Examples of the alkali metal hydroxide include potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), etc. 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 and easily obtaining excellent high-rate discharge 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.

[0019] The content of the alkali metal hydroxide in the electrolyte (total amount of the alkali metal hydroxide) may be in the following range based on the total amount of the electrolyte from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge 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.

[0020] The content of potassium hydroxide in the electrolyte may be in the following range based on the total amount of the electrolyte from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge 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.

[0021] The content of lithium hydroxide in the electrolyte may be in the following range based on the total amount of the electrolyte from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge 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.

[0022] The electrolyte according to this embodiment contains a compound represented by the following general formula (1) (excluding polyoxyethylene octylphenyl ether). R in the following general formula (1) 1 and R 2 do not combine with each other to form a cyclic structure. Note that the electrolyte according to this embodiment may contain a compound represented by the general formula (1) and polyoxyethylene octylphenyl ether. [Chemical formula] [In formula (1), n represents an integer from 1 to 10, and R 1 and R 2 each independently represent an organic group, a hydrogen atom, or a metal atom. However, when n = 1, at least one of R 1 and R 2 represents an organic group.]

[0023] n in the general formula (1) may be in the following range from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge performance. n may be 8 or less, 6 or less, 4 or less, 3 or less, or 2 or less. n may be 2 or more, 3 or more, or 4 or more. From these viewpoints, n may be 1 to 8, 1 to 6, or 1 to 4.

[0024] The number of ether groups in the compound represented by the general formula (1) may be in the following ranges from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge performance. The number of ether groups may be 9 or less, 7 or less, 5 or less, 4 or less, or 3 or less. The number of ether groups may be 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. From these viewpoints, the number of ether groups may be 1 to 9, 2 to 7, or 2 to 5.

[0025] R in the general formula (1) 1 and R 2 may both be organic groups from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge performance. Examples of the organic group include an alkyl group, an aryl group, an ester group, a carboxyl group, a carboxylate group (such as a sodium salt and a potassium salt). The organic group may be an alkyl group or an aryl group, and may be an alkyl group from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge performance.

[0026] The organic group may have a substituent. Examples of the substituent include a halogen atom, a carboxyl group, a carboxylate group, a hydroxyl group (excluding the OH structure included in the carboxyl group), an epoxy group, an ether group, an alkoxide group, an ester group, a ketone group, an aldehyde group, etc. The organic group may be an organic group having no substituent, an alkyl group having no substituent, or an aryl group having no substituent, and may be an alkyl group having no substituent from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge performance.

[0027] The carbon number of the organic group (including the carbon of the substituent possessed by the organic group) may be 8 or less, 6 or less, 4 or less, 3 or less, 2 or less, or 1 from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge performance. The carbon number of the organic group may be 1 or more. From these viewpoints, the carbon number of the organic group may be 1 to 8.

[0028] The alkyl group may be linear or branched. From the viewpoint of easily obtaining excellent life performance and the viewpoint of easily obtaining excellent high-rate discharge performance, the alkyl group may be a linear alkyl group, and may be a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and may be a methyl group.

[0029] R 1 and R 2 may be the same as each other from the viewpoint of easily obtaining excellent life performance and the viewpoint of easily obtaining excellent high-rate discharge performance, and may be the same organic group, may be the same alkyl group, and may be a methyl group.

[0030] Examples of the compound represented by the general formula (1) include polyethylene glycol; polyoxyethylene monoalkyl ethers, polyoxyethylene dialkyl ethers (glyme compounds), polyoxyethylene alkyl phenyl ethers, and other polyoxyethylene alkyl ether compounds. From the viewpoint of easily obtaining excellent life performance and the viewpoint of easily obtaining excellent high-rate discharge performance, the compound represented by the general formula (1) may contain a polyoxyethylene alkyl ether compound and may contain a glyme compound.

[0031] Examples of the polyoxyethylene monoalkyl ether include polyoxyethylene methyl ether, polyoxyethylene ethyl ether, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene heptyl ether, polyoxyethylene octyl ether, polyoxyethylene nonyl ether, 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.

[0032] Examples of glyme compounds include polyoxyethylene dimethyl ether, polyoxyethylene diethyl ether, polyoxyethylene dipropyl ether, polyoxyethylene dibutyl ether, polyoxyethylene dipentyl ether, polyoxyethylene dihexyl ether, polyoxyethylene diheptyl ether, polyoxyethylene dioctyl ether, polyoxyethylene methyl ethyl ether, and the like.

[0033] Glyme compounds may be monoglyme compounds such as monoglyme (ethylene glycol dimethyl ether), ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether; diglyme compounds such as diglyme (diethylene glycol dimethyl ether), diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether; triglyme compounds such as triglyme (triethylene glycol dimethyl ether), triethylene glycol diethyl ether, triethylene glycol dipropyl ether, triethylene glycol dibutyl ether; tetraglyme compounds such as tetraglyme (tetraethylene glycol dimethyl ether), tetraethylene glycol diethyl ether, tetraethylene glycol dipropyl ether, tetraethylene glycol dibutyl ether, and the like. From the viewpoint of easily obtaining excellent life performance and the viewpoint of easily obtaining excellent high-rate discharge performance, the compound represented by the general formula (1) may contain at least one selected from the group consisting of monoglyme compounds, diglyme compounds, triglyme compounds, and tetraglyme compounds, may contain at least one selected from the group consisting of monoglyme, diglyme, triglyme, and tetraglyme, may contain at least one selected from the group consisting of diglyme and triglyme, and may contain diglyme.

[0034] Examples of polyoxyethylene alkyl phenyl ethers include polyoxyethylene methyl phenyl ether, polyoxyethylene ethyl phenyl ether, polyoxyethylene propyl phenyl ether, polyoxyethylene butyl phenyl ether, polyoxyethylene pentyl phenyl ether, polyoxyethylene hexyl phenyl ether, polyoxyethylene heptyl phenyl ether, polyoxyethylene nonyl phenyl ether, and the like.

[0035] When the compound represented by the general formula (1) contains a glyme compound, the content of the glyme compound in the compound represented by the general formula (1) is 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 compound represented by the general formula (1) (total amount of the compound represented by the general formula (1)), from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge performance. The compound represented by the general formula (1) may be in a form consisting essentially of a glyme compound (substantially 100% by mass of the compound represented by the general formula (1) is a glyme compound).

[0036] The molecular weight of the compound represented by the general formula (1) may be in the following ranges from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge performance. The molecular weight of the compound represented by the general formula (1) may be 50 or more, 60 or more, 70 or more, 80 or more, or 90 or more. The molecular weight of the compound represented by the general formula (1) may be 2000 or less, 1500 or less, 1000 or less, 500 or less, 300 or less, 250 or less, or 230 or less. From these viewpoints, the molecular weight of the compound represented by the general formula (1) may be 50 to 2000. The molecular weight of the compound represented by the general formula (1) may be 120 or more, 140 or more, 160 or more, 180 or more, 200 or more, or 220 or more, and may be 220 or less, 200 or less, 180 or less, 160 or less, 140 or less, 120 or less, or 100 or less.

[0037] The content of the compound represented by the general formula (1) in the electrolyte (the total amount of the compound represented by the general formula (1)) may be in the following ranges based on the total amount of the electrolyte from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge performance. The content of the compound represented by the general formula (1) 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 compound represented by the general formula (1) 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 compound represented by the general formula (1) 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.

[0038] The content of the compound represented by the general formula (1) may be in the following ranges with respect to 100 parts by mass of the alkali metal hydroxide from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge performance. The content of the compound represented by the general formula (1) 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 compound represented by the general formula (1) 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 compound represented by the general formula (1) may be 1 to 30 parts by mass.

[0039] The electrolytic solution according to this embodiment may further contain a surfactant (excluding the compound represented by the general formula (1)) from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge performance. The reasons why the electrolytic solution containing a surfactant makes it easier to obtain excellent life performance and excellent high-rate discharge performance are speculated as follows, but are 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.

[0040] Examples of the surfactant include nonionic surfactants (non-ionic surfactants), anionic surfactants, cationic surfactants, amphoteric surfactants, and the like. From the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge 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.

[0041] 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 viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge 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 ether.

[0042] 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.

[0043] Examples of polyoxyethylene alkyl phenyl ethers include polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, and the like.

[0044] An anionic surfactant has an anionic hydrophilic group and a hydrophobic group. Examples of anionic surfactants include polyoxyalkylene alkyl ether phosphates (such as polyoxyethylene alkyl ether phosphates), polyoxyethylene alkyl ether sulfates, sodium dodecylbenzenesulfonate, alkali salts of styrene-acrylic acid copolymers, sodium alkylnaphthalenesulfonate, sodium alkyl diphenyl 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 viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge performance, the anionic surfactant may contain polyoxyalkylene alkyl ether phosphates and may contain polyoxyethylene alkyl ether phosphates.

[0045] 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, alkylamidoamine salts, monoalkyltrimethylammonium salts, dialkyldimethylammonium salts, alkylbenzyldimethylammonium salts, alkylpyridinium salts, and benzethonium chloride salts. From the viewpoint of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge 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.

[0046] 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, octadecyltrimethylammonium chloride, and the like.

[0047] 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.

[0048] 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 viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge 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).

[0049] 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 viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge 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.

[0050] The content (total amount of surfactant) of the surfactant in the electrolytic solution may be in the following range based on the total amount of the electrolytic solution from the viewpoints of easily obtaining excellent life performance and easily obtaining excellent high-rate discharge 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.

[0051] The electrolytic solution according to the present embodiment can contain a liquid medium such as water (for example, ion-exchanged water).

[0052] Hereinafter, as an example of a zinc battery in which the electrolytic solution according to the above embodiment is used, a nickel-zinc battery will be described.

[0053] The zinc battery according to the present embodiment includes, for example, an electrolytic cell, an electrode group (for example, a plate group) housed in the electrolytic cell, and an electrolytic solution. The zinc battery according to the present embodiment may be either after formation or before formation.

[0054] The electrode group includes, for example, a positive electrode (for example, a positive electrode plate), a negative electrode (for example, a negative electrode plate), and a separator disposed between the positive electrode and the negative electrode. The positive electrode and the negative electrode are, for example, alternately laminated via the separator 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, for example, by a strap.

[0055] 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 or after formation.

[0056] The current collector (positive electrode current collector or negative electrode current collector) constitutes a current conduction path from the electrode material (positive electrode material or negative electrode material). The current collector has, for example, a shape such as a flat plate shape or a sheet shape. The current collector may be a current collector having a three-dimensional network structure formed of a foamed metal, an expanded metal, a punched metal, a felt-like material of metal fibers, or the like.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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, etc. 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.

[0061] 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), etc. Examples of the binder include hydrophilic or hydrophobic polymers, etc., such as hydroxyethyl cellulose (HEC), hydroxypropyl methylcellulose (HPMC), carboxymethyl cellulose (CMC), sodium polyacrylate (SPA), fluorine-based polymers (such as polytetrafluoroethylene (PTFE)), etc. 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, cobalt hydroxide, etc.). 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, etc. 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.

[0062] The negative electrode material contains a negative electrode active material containing zinc. Examples of the negative electrode active material include metallic zinc, zinc oxide, zinc hydroxide, etc. The negative electrode active material may contain one of these components alone or may contain a plurality of components. The negative electrode material contains, for example, metallic zinc in a fully charged state and zinc oxide and zinc hydroxide in a discharged state. The negative electrode active material may be, for example, in a particulate form and may contain metallic zinc particles, zinc oxide particles, zinc hydroxide particles, etc. The content of the negative electrode active material is, for example, 50 to 99% by mass based on the total mass of the negative electrode material.

[0063] 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 binders 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.

[0064] 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 membrane or a laminate of a plurality of porous membranes.

[0065] Examples of the material of the separator include organic materials (such as resin materials), inorganic materials, etc. 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.

[0066] 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.

[0067] The manufacturing method of the nickel-zinc battery described above includes, for example, a component manufacturing process for obtaining the components of the zinc battery and an assembly process for assembling the components to obtain a zinc battery. In the component manufacturing process, at least electrodes (positive electrode and negative electrode) are obtained.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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).

[0072] Subsequently, after injecting the electrolytic solution according to the present embodiment into the battery case of an unformed zinc battery, it is left for a certain period of time. Then, charging is performed under predetermined conditions to form 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).

[0073] 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.

[0074] As the air electrode of the air-zinc battery, a known air electrode used for 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.

[0075] 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 that can utilize 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.

[0076] As the electronic conductive material, those having conductivity and enabling electron conduction between the air electrode catalyst and the separator can be used. Examples of the electronic 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 electronic conductive materials such as polyphenylene derivatives; and any mixtures thereof. The shape of the electronic conductive material may be particulate or other shapes. The electronic conductive material may be used in a form that provides a continuous phase in the thickness direction in the air electrode. For example, the electronic conductive material may be a porous material. Also, the electronic 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 electronic conductive material. The content of the electronic 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.

[0077] 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

[0078] Hereinafter, the present disclosure will be specifically described by way of examples. However, the present disclosure is not limited to the following examples.

[0079] <Preparation of electrolyte solution> (Examples 1 to 4) Ionic-exchanged water, potassium hydroxide (KOH), lithium hydroxide (LiOH), an additive shown in Table 1 (compound represented by General Formula (1)), a nonionic surfactant (polyoxyethylene octyl phenyl ether (Triton X-100, manufactured by Sigma-Aldrich)), and an anionic surfactant (mixture of polyoxyethylene alkyl ether phosphate ester (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, additive 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.

[0080] (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 4, except that the additive (compound represented by General Formula (1)) was not used.

[0081] <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, followed by stirring. 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.

[0082] <Fabrication of Negative Electrode> As the negative electrode current collector, copper punching metal (opening ratio: 50%, thickness: 0.10 mm) plated with tin was prepared. Next, a negative electrode material paste was prepared by stirring a mixed solution obtained by weighing a predetermined amount 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 a negative electrode material (negative electrode material layer) on both sides.

[0083] <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.

[0084] The 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 arranging this electrode group in the battery case, a lid was adhered to the upper surface of the battery case to obtain an unformed nickel-zinc battery. Next, after injecting the electrolyte into the battery case of the unformed nickel-zinc battery, it was left for 24 hours. Then, charging was performed under the conditions of 32 mA for 15 hours to produce a nickel-zinc battery after formation (nominal capacity: 320 mAh).

[0085] <Characteristic Evaluation> Using the nickel-zinc batteries of Examples 1 to 4 and Comparative Example 1, the life performance (cycle life performance) and high-rate discharge performance of the nickel-zinc batteries were evaluated. The specific evaluation methods are shown below, and the results are shown in Table 1.

[0086] (Evaluation of Life Performance) 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 discharging 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 dropped 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.

[0087] (Evaluation of High-Rate Discharge Performance) At 25°C, after charging the nickel-zinc battery at a constant voltage of 320 mA (1C) and 1.88V until the current value decays to 16 mA (0.05C), the nickel-zinc battery was discharged at a constant current of 3200 mA (10.0C) until the battery voltage reaches 1.1V, and the discharge capacity was measured. The high-rate discharge performance was evaluated based on the measured discharge capacity.

[0088]

Table 1

Claims

1. An electrolyte for a zinc battery, containing an alkali metal hydroxide and a compound represented by the following general formula (1) (excluding polyoxyethylene octyl phenyl ether). 【Chemical 1】 In formula (1), n represents an integer from 1 to 10, and R １ represents an organic group selected from the group consisting of an alkyl group, an aryl group, an ester group, a carboxyl group, and a carboxylate group, and R ２ represents an organic group selected from the group consisting of an alkyl group, an aryl group, an ester group, a carboxyl group, and a carboxylate group, a hydrogen atom, or a metal atom.]

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

3. The electrolyte for a zinc battery according to Claim 1 or 2, wherein the compound represented by the general formula (1) contains a glyme compound.

4. The electrolyte for a zinc battery according to any one of Claims 1 to 3, wherein the compound represented by the general formula (1) contains at least one selected from the group consisting of monoglyme, diglyme, triglyme, and tetraglyme.

5. The electrolyte for a zinc battery according to any one of Claims 1 to 4, further containing a surfactant (excluding the compound represented by the general formula (1)).

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

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

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