JP2016110970A - Aqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery using an electrolyte that is safe even when the battery is broken in use and the electrolyte is leaked from the battery housing.SOLUTION: The aqueous secondary battery includes: a positive electrode containing as an active material a metallocene compound; a negative electrode containing as an active material an orthoquinone compound; and an aqueous electrolyte.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an aqueous secondary battery.

  In recent years, secondary batteries have been widely used as power sources for IT devices such as mobile phones and notebook computers and electric vehicles. In particular, lithium ion secondary batteries are widely used from the viewpoints of high battery characteristics such as electromotive force, energy density, charge / discharge energy efficiency, and low self-discharge. Lithium ion secondary batteries use a non-aqueous electrolyte solution containing an organic solvent, for example, as an electrolyte solution in order to enable high voltage charge / discharge. For the electrode, for example, a lithium transition metal oxide or the like is used for either the positive electrode or the negative electrode.

  In order to improve battery characteristics, materials used for lithium ion secondary batteries are being researched daily. Patent Document 1 discloses a technique of an electrode active material for an electricity storage device using a lithium ion secondary battery as an electricity storage device as a technique used for an electrode of a lithium ion secondary battery. Specifically, in a lithium ion secondary battery, an electrode active material containing a tetraketone compound is used for the electrode in order to increase the energy density.

International Publication No. 2011/111401

  However, an electrolytic solution containing an organic solvent used for a lithium ion secondary battery is flammable and harmful to the human body. The lithium ion secondary battery has a problem that it is dangerous for the user if it is damaged in use and the electrolyte solution leaks out of the battery casing.

  Therefore, an object of the present invention is to provide a secondary battery that uses an electrolytic solution that is safe even if it is damaged during use and leaks from the battery casing.

  The gist of the present invention for solving the above problems is as follows.

  An aqueous secondary battery comprising a positive electrode containing a metallocene compound as an active material, a negative electrode containing an orthoquinone compound as an active material, and an aqueous electrolyte.

  An aqueous secondary battery in which at least one of the positive electrode and the negative electrode contains a conductive additive.

  An aqueous secondary battery, wherein the aqueous electrolyte contains at least one salt selected from the group consisting of a salt of an alkali metal element and a salt of a Group 2 element.

  An aqueous secondary battery in which the aqueous electrolyte contains a sodium salt.

  An aqueous secondary battery in which the amount of dissolved oxygen in the aqueous electrolytic solution is 7.3 ppm or less.

  An aqueous secondary battery in which the orthoquinone compound is an oligomer including a structural unit derived from a compound represented by the following formula (1) or a compound represented by the following formula (1).

（式中、Ｒ^１〜Ｒ^４は、それぞれ独立して、水素原子、ハロゲン原子、複素環基、アミノ基、ニトロ基、ホルミル基、シアノ基、ヒドロキシ基、アルコキシ基、チオール基、アルキルチオ基、アルキルカルボニル基、アリールカルボニル基、アルキルスルホニル基、アリールスルホニル基、若しくは炭化水素基である。複素環基、アミノ基、アルコキシ基、アルキルチオ基、アルキルカルボニル基、アリールカルボニル基、アルキルスルホニル基、アリールスルホニル基、及び炭化水素基は、置換されていてもよい。Ｒ^１〜Ｒ^４のいずれか２つ以上の基が一緒になって、それぞれが結合している炭素原子と共に、置換されていてもよい環構造を形成してもよい。）

(In the formula, R ^{1 to} R ⁴ are each independently a hydrogen atom, a halogen atom, a heterocyclic group, an amino group, a nitro group, a formyl group, a cyano group, a hydroxy group, an alkoxy group, a thiol group, an alkylthio group, Alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl group, or hydrocarbon group, heterocyclic group, amino group, alkoxy group, alkylthio group, alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl The group and the hydrocarbon group may be substituted, and any two or more groups of R ^{1 to} R ⁴ may be substituted together with the carbon atom to which each is bonded. A ring structure may be formed.)

  An aqueous secondary battery in which the orthoquinone compound is an oligomer including a structural unit derived from a compound represented by the following formula (2) or a compound represented by the following formula (2).

（式中、Ｒ^１１〜Ｒ^１８は、それぞれ独立して、水素原子、ハロゲン原子、複素環基、アミノ基、ニトロ基、ホルミル基、シアノ基、ヒドロキシ基、アルコキシ基、チオール基、アルキルチオ基、アルキルカルボニル基、アリールカルボニル基、アルキルスルホニル基、アリールスルホニル基、若しくは炭化水素基である。複素環基、アミノ基、アルコキシ基、アルキルチオ基、アルキルカルボニル基、アリールカルボニル基、アルキルスルホニル基、アリールスルホニル基、及び炭化水素基は、置換されていてもよい。Ｒ^１１〜Ｒ^１８のいずれか２つ以上の基が一緒になって、それぞれが結合している炭素原子と共に、置換されていてもよい環構造を形成してもよい。）

(Wherein R ^{11 to} R ¹⁸ are each independently a hydrogen atom, halogen atom, heterocyclic group, amino group, nitro group, formyl group, cyano group, hydroxy group, alkoxy group, thiol group, alkylthio group, Alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl group, or hydrocarbon group, heterocyclic group, amino group, alkoxy group, alkylthio group, alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl The group and the hydrocarbon group may be substituted, and any two or more groups of R ^{11 to} R ¹⁸ may be substituted together with the carbon atom to which each is bonded. A ring structure may be formed.)

  An aqueous secondary battery in which the metallocene compound is an oligomer including a structural unit derived from a compound represented by the following formula (3) or a compound represented by the following formula (3).

（式中、Ｒ^２１〜Ｒ^３０は、それぞれ独立して、水素原子、ハロゲン原子、複素環基、アミノ基、ニトロ基、ホルミル基、シアノ基、ヒドロキシ基、アルコキシ基、チオール基、アルキルチオ基、アルキルカルボニル基、アリールカルボニル基、アルキルスルホニル基、アリールスルホニル基、若しくは炭化水素基である。複素環基、アミノ基、アルコキシ基、アルキルチオ基、アルキルカルボニル基、アリールカルボニル基、アルキルスルホニル基、アリールスルホニル基、及び炭化水素基は、置換されていてもよい。Ｍは、遷移金属原子である。）

(In the formula, R ^{21 to} R ³⁰ are each independently a hydrogen atom, a halogen atom, a heterocyclic group, an amino group, a nitro group, a formyl group, a cyano group, a hydroxy group, an alkoxy group, a thiol group, an alkylthio group, Alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl group, or hydrocarbon group, heterocyclic group, amino group, alkoxy group, alkylthio group, alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl The group and the hydrocarbon group may be substituted, and M is a transition metal atom.)

  An aqueous secondary battery in which the metallocene compound is ferrocene.

  The aqueous secondary battery of the present invention uses an aqueous electrolyte. Thereby, the secondary battery of this invention is safe even if it should be damaged by any chance at the time of use. Furthermore, by using an orthoquinone compound as an active material for the negative electrode, a secondary battery having high safety, high output, and high charge / discharge cycle characteristics can be provided.

It is a figure which shows schematic structure of the water-system secondary battery which is one Embodiment of this invention. 10 is a cyclic voltammogram of the aqueous secondary battery of Example 9. FIG. 10 is a cyclic voltammogram of the aqueous secondary battery of Example 10. FIG. 2 is a cyclic voltammogram of an aqueous secondary battery of Example 11. FIG. 14 is a cyclic voltammogram of the aqueous secondary battery of Example 12. FIG.

Hereinafter, the water-based secondary battery of the present invention will be described in detail.
The aqueous secondary battery of the present invention includes a positive electrode containing a metallocene compound as an active material, a negative electrode containing an orthoquinone compound as an active material, and an aqueous electrolyte. In addition to these, other configurations may be provided as needed within the scope of solving the above-described problems. Each will be described below.

[Structure of water-based secondary battery]
First, the shape and structure of an embodiment of the aqueous secondary battery of the present invention will be described with reference to FIG. The aqueous secondary battery 10 of the present embodiment includes a positive electrode sheet 13 in which a positive electrode active material layer 12 containing a metallocene compound is formed on a positive electrode current collector 11 and a negative electrode active material layer containing an orthoquinone compound on the surface of the negative electrode current collector 14. 17, a separator 19 provided between the positive electrode sheet 13 and the negative electrode sheet 18, and an aqueous electrolyte solution 20 that fills between the positive electrode sheet 13 and the negative electrode sheet 18. . In this aqueous secondary battery 10, the separator 19 is sandwiched between the positive electrode sheet 13 and the negative electrode sheet 18, and these are wound and inserted into the cylindrical case 22, and the positive electrode terminal 24 and the negative electrode sheet 18 connected to the positive electrode sheet 13. And a negative electrode terminal 26 connected to each other. The positive electrode sheet 13 of this embodiment is an example of the positive electrode of the present invention. The negative electrode sheet 18 of this embodiment is an example of the negative electrode of the present invention. In the water-based secondary battery of this embodiment, the case containing the positive electrode sheet 13, the negative electrode sheet 18, and the aqueous electrolyte solution 20 is a cylindrical shape using the cylindrical case 22. Good. There are various types of cases such as a laminate type and a coin type. Examples of the shape include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, and a square type. Moreover, you may apply to the large sized thing etc. which are used for an electric vehicle etc.

  As the material of the positive electrode current collector 11 and the negative electrode current collector 14, a material that does not cause a side reaction at the potentials of the positive electrode and the negative electrode is used. More specifically, the positive electrode current collector 11 and the negative electrode current collector 14 may be made of a material having corrosion resistance that does not cause a reaction such as dissolution at the potential of the positive electrode and the negative electrode. As a material of the positive electrode current collector 11 and the negative electrode current collector 14, for example, a metal material, an alloy, a carbon material, an inorganic conductive oxide material, or the like can be used. Examples of the metal material include copper, nickel, brass, zinc, aluminum, stainless steel, tungsten, gold, and platinum. The alloy is, for example, SUS. Examples of the carbon material include graphite, hard carbon, and glassy carbon.

(Negative electrode active material)
The negative electrode of the aqueous secondary battery shown in the negative electrode sheet 18 of FIG. 1 described above is formed, for example, by providing a negative electrode active material layer containing a negative electrode active material on a negative electrode current collector. The negative electrode active material of the water-based secondary battery includes an orthoquinone compound. Here, the orthoquinone compound refers to a compound having an aromatic ring containing an orthoquinone structure having two adjacent carbonyl groups.

  As the orthoquinone compound, an oligomer containing a structural unit derived from a compound represented by the following formula (1) or a compound represented by the following formula (1) is preferable.

In the formula (1), R ^{1 to} R ⁴ are each independently a hydrogen atom, a halogen atom, a heterocyclic group, an amino group, a nitro group, a formyl group, a cyano group, a hydroxy group, an alkoxy group, a thiol group, An alkylthio group, an alkylcarbonyl group, an arylcarbonyl group, an alkylsulfonyl group, an arylsulfonyl group, or a hydrocarbon group; The heterocyclic group, amino group, alkoxy group, alkylthio group, alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl group, and hydrocarbon group may be substituted. Any two or more groups of R ^{1 to} R ⁴ may be combined to form an optionally substituted ring structure together with the carbon atom to which each is bonded. In addition, it is preferable that the number of carbon atoms contained in the groups R ^{1 to} R ⁴ is small.

Examples of the halogen atom of R ^{1 to} R ⁴ in the formula (1) include fluorine, chlorine, bromine, iodine and the like. Of these, chlorine and bromine are preferable, and bromine is more preferable.

  Examples of the heterocyclic group include pyridyl group, pyrimidyl group, furyl group, chenyl group, tetrahydrofuryl group, dioxolanyl group, benzoxazol-2-yl group, tetrahydropyranyl group, pyrrolidyl group, imidazolicyl group, pyrazolysyl group, thiazolysyl group 5- to 6-membered aromatic heterocyclic groups containing a nitrogen atom, an oxygen atom, a sulfur atom, etc. as a heteroatom such as a group, inch azolysyl group, oxazolyl group, isoxazolyl group, piperidyl group, piperazyl group, morpholinyl group and the like Group heterocyclic group.

  The alkyl group, alkenyl group and alkynyl group may be either linear or branched.

  Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group. Specific examples of the alkenyl group include a vinyl group, a propenyl group, a 3-butenyl group, a 3-pentenyl group, and a 3-hexenyl group. Specific examples of the alkynyl group include ethynyl group, 2-propynyl group, and 2-butynyl group. Specific examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of the cycloalkenyl group include a cyclopentenyl group, a cyclohexenyl group, and a cyclohexenyl group. Specific examples of the aryl group include a phenyl group, a naphthyl group, and an anthranyl group.

  The heterocyclic group, amino group, alkoxy group, alkylthio group, alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl group, and hydrocarbon group may further have a substituent. Examples of the substituent include a hydroxy group, a carboxy group, an amino group, a cyano group, a nitro group, a sulfonamide group, a halogen atom, an acyl group, an acyloxy group, an alkoxycarbonyl group, and an oxo group.

Among the orthoquinone compounds represented by the above formula (1), any two or more groups of R ^{1 to} R ⁴ may be combined and each may be substituted with the carbon atom to which each is bonded. The compound which forms is preferable. The ring structure may be either an aromatic ring such as a benzene ring or an aliphatic ring. Examples of the substituent in the ring structure include a hydrocarbon group, a hydroxy group, a carboxy group, an amino group, a cyano group, a nitro group, a sulfonamide group, a halogen atom, an acyl group, an acyloxy group, an alkoxycarbonyl group, and an oxo group. Can be mentioned. The ring structure may contain a hetero atom such as an oxygen atom, a nitrogen atom, or a sulfur atom in at least a part of the ring structure.

The orthoquinone compound represented by the formula (1) is preferably a compound in which R ¹ and R ² and R ³ and R ⁴ are bonded to each other to form an aromatic ring, among which the following formula (2) is preferred. Orthoquinone compounds are more preferred.

In the formula (2), R ^{11 to} R ¹⁸ are each independently a hydrogen atom, a halogen atom, a heterocyclic group, an amino group, a nitro group, a formyl group, a cyano group, a hydroxy group, an alkoxy group, a thiol group, An alkylthio group, an alkylcarbonyl group, an arylcarbonyl group, an alkylsulfonyl group, an arylsulfonyl group, or a hydrocarbon group; The heterocyclic group, amino group, alkoxy group, alkylthio group, alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl group, and hydrocarbon group may be substituted. Any two or more groups of R ^{11 to} R ¹⁸ may be combined together to form an optionally substituted ring structure together with the carbon atom to which each is bonded.

Regarding the halogen atom, heterocyclic group, alkoxy group, alkylthio group, alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl group and hydrocarbon group of R ^{11 to} R ¹⁸ , R in the above formula (1) It can be applied to the description of the ¹ to R ^4.

  Examples of the orthoquinone compound include orthobenzoquinone or its halide, 9,10-phenanthrenequinone or its halide, pyrene-4,5-dione or its halide, or pyrene-4,5,9,10-tetraone or its halogen. Or oligomers containing structural units derived from these compounds are more preferred, 9,10-phenanthrenequinone, 2,7-dibromo-9,10-phenanthrenequinone, pyrene-4,5,9,10-tetraone or 2,7-dibromopyrene-4,5,9,10-tetraone is particularly preferred, and 9,10-phenanthrenequinone or 2,7-dibromo-9,10-phenanthrenequinone is most preferred.

  The orthoquinone compound is also preferably an oligomer containing a structural unit derived from the compound represented by the formula (1). The structural unit derived from the compound represented by the formula (1) means a group constituted by removing at least one hydrogen atom from the compound represented by the formula (1). The position at which the hydrogen atom is removed is not particularly limited, and may be on an aromatic ring or on a substituent that the aromatic ring has.

  The oligomer in the present invention may be a homo-oligomer containing a structural unit derived from the compound represented by formula (1) or formula (2), or a hetero-oligomer containing a structural unit derived from these and other compounds. The bonds between the structural units may be ordinary chemical bonds such as single bonds, phenylene bonds, sulfide bonds, ether bonds, ester bonds, carbonate bonds, amide bonds, and imide bonds.

  The orthoquinone compound as the negative electrode active material may be contained in the negative electrode active material layer in the form of a salt formed with an alkali metal ion or alkaline earth metal ion as an anion having a reduced quinone moiety.

  The negative electrode active material layer may contain an orthoquinone compound alone or in combination of two or more.

(Positive electrode active material)
The positive electrode of the water-based secondary battery shown in the positive electrode sheet 13 of FIG. 1 described above includes, for example, a positive electrode active material layer containing a metallocene compound on a positive electrode current collector. The active material in the positive electrode of the water-based secondary battery includes a metallocene compound. Here, the metallocene compound is a sandwich-type bis (cyclopentadienyl) complex in which two cyclopentadienyl rings are arranged in parallel and a transition metal ion is inserted between them.

As a metallocene compound preferable as the positive electrode active material, an oligomer including a structural unit derived from a compound represented by the following formula (3) or a compound represented by the following formula (3) can be given. In formula (3), a structural formula of D _5d symmetry is shown, but D _5h symmetry may be used.

In the formula (3), R ^{21 to} R ³⁰ each independently represent a hydrogen atom, a halogen atom, a heterocyclic group, an amino group, a nitro group, a formyl group, a cyano group, a hydroxy group, an alkoxy group, a thiol group, An alkylthio group, an alkylcarbonyl group, an arylcarbonyl group, an alkylsulfonyl group, an arylsulfonyl group, or a hydrocarbon group; The heterocyclic group, amino group, alkoxy group, alkylthio group, alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl group, and hydrocarbon group may be substituted. M is a transition metal atom.

Examples of the halogen atom of R ^{21 to} R ³⁰ in the formula (3) include fluorine, chlorine, bromine, iodine and the like. For the heterocyclic group, alkoxy group, alkylthio group, alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl group, and hydrocarbon group, the description of R ^{1 to} R ⁴ in the formula (1) is applied. it can.

  As M in the formula (3), Fe (iron), Ni (nickel), Sc (scandium), Ti (titanium), V (vanadium), Cr (chromium), Mn (manganese), Co (cobalt), Cu (copper), Zn (zinc), etc. are mentioned. From the viewpoint of improving the cycle characteristics of the aqueous secondary battery, Fe and Ni are preferable, and Fe is more preferable. That is, more preferred metallocene compounds are ferrocene compounds and oligoferrocene compounds in which M is Fe in the formula (3). Most preferred is ferrocene. Further, other molecules such as halides may be added to M.

  It is also preferable that the metallocene compound is an oligomer containing a structural unit derived from the compound represented by the formula (3). The structural unit derived from the compound represented by the formula (3) means a group constituted by removing at least one hydrogen atom from the compound represented by the formula (3). The position at which the hydrogen atom is removed is not particularly limited, and may be on a cyclopentadienyl ring or a substituent of the cyclopentadienyl ring. Specific examples of the structural unit derived from the compound represented by the formula (3) include the following structural units. In addition, other molecules such as halides may be added to M as in the formula (3).

（式中、Ｍは、遷移元素である。）

(In the formula, M is a transition element.)

  The metallocene compound that is a positive electrode active material may be contained in the positive electrode active material layer in the form of a salt formed with a halogen ion, a sulfate ion, a hydroxide ion, or the like as a cation in which the transition metal atom portion is oxidized.

  The positive electrode active material layer may contain one or more metallocene compounds in combination.

  Thus, the negative electrode includes a negative electrode active material layer including an orthoquinone compound, and the positive electrode includes a positive electrode active material layer including a metallocene compound. In addition, the negative electrode may include a conductive additive, a binder, and the like in addition to the orthoquinone compound that is the negative electrode active material described above, in the negative electrode active material layer. In the positive electrode active material layer, in addition to the metallocene compound that is the positive electrode active material described above, a conductive additive, a binder, and the like may be included.

  As the conductive auxiliary agent contained in the positive electrode and the negative electrode, a carbon material, a conductive polymer, a powder metal, an inorganic conductive oxide, or the like can be used. Examples of the carbon material include activated carbon, activated carbon fiber, porous carbon, graphite, carbon black, carbon nanotube, carbon nanofiber, carbon nanohorn, and graphene. Examples of the conductive polymer include polyaniline, polyacetylene, polyfluorene, polypyrrole, and polythiophene. Examples of the powder metal include aluminum, gold, and platinum. Of these, carbon materials are preferable, and activated carbon is particularly preferable.

  As the binder contained in the positive electrode and the negative electrode, a material suitable for the application that does not decompose in the potential region to be used can be selected and used. For example, polyvinylidene fluoride, polytetrafluoroethylene, carboxymethyl cellulose, styrene butadiene rubber, polyacrylic acid, polyimide resin, polyamide resin, fluorine rubber, and the like.

  Each of the conductive additive and the binder contained in the positive electrode active material layer and the negative electrode active material layer may be used alone or in combination of two or more.

  In each of the electrode active material layers of the negative electrode active material layer and the positive electrode active material layer, the composition ratios of the positive electrode or negative electrode electrode active material, the conductive additive and the binder are 5 to 100% by mass, 0 to 0%, respectively. What is necessary is just to adjust suitably in the range of 90 mass% and 0-30 mass%. The conductive auxiliary agent and the binder may not be added. Moreover, the thickness of the negative electrode active material layer and the positive electrode active material layer is not particularly limited. The mass ratio of the positive electrode active material to the negative electrode active material is not particularly limited. For example, the positive electrode / negative electrode is preferably 0.5 to 10.0, and preferably 1.0 to 5.0. Is more preferable.

(Aqueous electrolyte)
The aqueous electrolytic solution in the present invention contains water and at least one water-soluble salt. The water-soluble salt is preferably at least one salt selected from the group consisting of alkali metal element salts and Group 2 element salts, and includes sodium salts, magnesium salts, calcium salts, lithium salts, and beryllium salts. It is more preferably at least one salt selected from the group, more preferably a sodium salt or magnesium salt, and particularly preferably a sodium salt.

  The kind of anion contained in the water-soluble salt is not particularly limited. Examples of anions include halide ions, sulfate ions, nitrate ions, phosphate ions, and the like. Specifically, the halide ions are chloride ions, bromide ions, iodide ions and the like.

  The water-soluble salt is preferably a neutral salt at 25 ° C., among which at least one neutral sodium salt selected from the group consisting of sodium chloride, sodium bromide, sodium iodide, sodium sulfate, sodium nitrate and the like. At least one neutral magnesium salt selected from the group consisting of magnesium chloride, magnesium bromide, magnesium iodide, magnesium sulfate, magnesium nitrate, etc., at least selected from the group consisting of lithium chloride, lithium bromide, etc. One neutral lithium salt is more preferable, sodium chloride, sodium sulfate, magnesium chloride and the like are more preferable, and sodium chloride and sodium sulfate are particularly preferable.

  The concentration of the water-soluble salt in the aqueous electrolyte is appropriately selected according to the type of the water-soluble salt. The concentration of the water-soluble salt in the aqueous electrolytic solution varies depending on the temperature and solute. For example, when the aqueous electrolytic solution is 20 ° C. and the water-soluble salt is sodium chloride, 0.1 mol / L to 6 It is preferably in the range of 1 mol / L, and if the water-soluble salt is magnesium chloride, it is preferably in the range of 0.1 mol / L to 5.7 mol / L. The concentration of the water-soluble salt in the aqueous electrolytic solution may be equal to or lower than the saturation solubility, and a higher concentration is preferable.

  The aqueous electrolytic solution may contain a water-soluble organic solvent. Examples of the organic solvent include acetonitrile and acetone.

  When the aqueous electrolyte contains an organic solvent, the content is 50% by mass or less with respect to water, and preferably 10% by mass or less.

  The aqueous electrolyte may contain various additives as required. Examples of the additive include sodium sulfite.

  The aqueous electrolyte preferably has a dissolved oxygen content of 7.3 ppm or less. When the dissolved oxygen amount is 7.3 ppm or less, the cycle characteristics of the secondary battery tend to be further improved. A more preferable dissolved oxygen amount is 5 ppm or less, and a most preferable dissolved oxygen amount is 4 ppm or less.

  Generally, the saturated dissolved oxygen content at room temperature (22 ° C. to 23 ° C.) of the aqueous electrolyte is 8.2 to 8.6 ppm, and the dissolved oxygen content can be reduced to 7.3 ppm or less by a commonly used operation. . For example, the amount of dissolved oxygen can be maintained in a desired range by degassing at least once at the time of battery manufacture, or by providing a structure for suppressing an increase in the amount of oxygen by providing packing at the time of battery manufacture. The degassing method is appropriately selected from commonly used methods, and can be performed, for example, by reducing pressure, heating, or the like.

  In an open battery, the amount of dissolved oxygen can be reduced by providing an insertion tube in the aqueous electrolyte and constantly bubbling nitrogen gas.

(Separator)
The aqueous secondary battery may include a separator. The separator is disposed so as to separate the positive electrode and the negative electrode, and is required to pass ions and prevent a short circuit between the positive and negative electrodes. The separator is not particularly limited, and a conventionally known separator can be used. For example, a polyolefin fiber nonwoven fabric, a microporous membrane made of polyolefin, a glass filter, a ceramic porous material, or the like can be used.

[Method for producing water-based secondary battery]
The aqueous secondary battery of the present invention is manufactured by enclosing a negative electrode, a positive electrode, and an electrolyte in a housing case such as the cylindrical case 22 of FIG. A specific manufacturing procedure will be described below.

  Next, specific embodiments of the present invention will be described with reference to examples, but the present invention is not limited to these examples.

<Production of water-based secondary battery>
(Preparation of positive electrode)
A positive electrode active material was supported on activated carbon as a conductive aid. In a mortar, the activated carbon supporting the positive electrode active material and polytetrafluoroethylene (PTFE) as a binder were mixed and kneaded. A positive electrode was produced by providing a positive electrode active material layer formed by rolling the mixture on a current collector.

(Preparation of negative electrode)
A negative electrode active material was supported on activated carbon as a conductive aid. In a mortar, the activated carbon supporting the negative electrode active material and polytetrafluoroethylene (PTFE) as a binder were mixed and kneaded. A negative electrode was produced by providing a negative electrode active material layer formed by rolling the mixture on a current collector.

  Examples of a method for supporting each electrode active material on the conductive assistant in each electrode include a method of uniformly attaching each electrode active material to the conductive assistant via a liquid phase. The rolling is performed by roll rolling using a roller press or the like. By this roll rolling, each of the electrode active material layers of the positive electrode and the negative electrode can be made into an electrode having a flat surface that is further compressed to a predetermined thickness and smoothed.

(Battery assembly method 1)
The obtained positive electrode and negative electrode were cut into a quadrilateral shape, and the current collector was attached to the end of the surface on which the electrode was not formed by spot welding using nickel metal foil as the positive electrode or the negative electrode terminal. The separator which consists of the said electrode and a regenerated cellulose nonwoven fabric was attached to the lamination cell. An electrolytic solution (3M-NaCl aqueous solution or 1M-MgCl ₂ aqueous solution) was injected into the cell, the electrode was impregnated with the electrolytic solution under a vacuum environment, and the laminate cell was sealed using a vacuum sealer device.

(Battery assembly method 2)
In addition to the structure manufactured by sealing with the laminate cell described above, the structure may be manufactured using a glass sample bottle cell or the like. A manufacturing method in a structure using a glass sample bottle cell or the like is as follows. First, the obtained positive electrode and negative electrode are cut into a quadrilateral shape, and the current collector is attached to the end of the surface on which the electrode is not formed by using a nickel metal foil as a positive electrode or a negative electrode terminal by spot welding. It was. Then, the glass sample bottle cell, attaching the electrode, electrolyte (3M-NaCl aqueous solution or 1M-MgCl ₂ solution) was added. The sample bottle cell was sealed with a lid, an insertion tube was provided in the electrolyte, and nitrogen gas was constantly bubbled.

  The water-system secondary battery of Examples 1-8 was produced by the said method. Table 1 below shows the positive electrode active material, the negative electrode active material, the conductive additive, the type and mass of the binder, and the type of the electrolyte used in Examples 1 to 8. Table 1 also shows the different battery assembly methods.

正極活物質：フェロセン
負極活物質：２，７−ジブロモ−９，１０−フェナントレンキノン
導電助剤：活性炭
結着材：ポリテトラフルオロエチレン（ＰＴＦＥ）

Positive electrode active material: Ferrocene negative electrode active material: 2,7-dibromo-9,10-phenanthrenequinone conductive additive: activated carbon binder: polytetrafluoroethylene (PTFE)

(Measurement of dissolved oxygen)
The amount of dissolved oxygen in the electrolytic solution was measured at room temperature (about 23 ° C.) immediately before injecting the electrolytic solution into the laminate cell using a dissolved oxygen meter (OM-71-L1; manufactured by HORIBA, Ltd.). As a result, the dissolved oxygen content of the aqueous secondary battery of Example 1 was 0.37 ppm. The dissolved oxygen content of the aqueous secondary battery of Example 2 was 3.09 ppm. The amount of dissolved oxygen of the aqueous secondary battery of Example 3 was 7.27 ppm. The dissolved oxygen content of the aqueous secondary battery of Example 7 was 0.6 ppm, and the dissolved oxygen content of the aqueous secondary battery of Example 8 was 3.1 ppm.

(Assembly of cyclic voltammetry cell)
The obtained positive electrode was attached to a platinum mesh provided with a platinum wire to obtain a working electrode. An electrode made of activated carbon and PTFE was press bonded to the electrode with a platinum wire attached to the counter electrode. An electrolyte (3M-NaCl aqueous solution) was added to a glass sample bottle cell. The sample bottle cell was sealed with a lid, an insertion tube was provided in the electrode, and nitrogen gas was constantly bubbled. The negative electrode also has the same cell configuration as the positive electrode.

(Cyclic voltammetry)
Table 2 shows the production conditions of the working electrode and the counter electrode produced by the method described above. In Examples 9 and 11, a positive electrode was produced as a working electrode. In Examples 10 and 12, a negative electrode was produced as a working electrode. In Examples 9 and 10, 3M-NaCl aqueous solution was used as the electrolyte. In Examples 11 and 12, 1M-MgCl ₂ aqueous solution was used as the electrolytic solution.

正極活物質：フェロセン
負極活物質：２，７−ジブロモ−９，１０−フェナントレンキノン
導電助剤：活性炭
結着材：ポリテトラフルオロエチレン（ＰＴＦＥ）

Positive electrode active material: Ferrocene negative electrode active material: 2,7-dibromo-9,10-phenanthrenequinone conductive additive: activated carbon binder: polytetrafluoroethylene (PTFE)

  The aqueous secondary battery using the positive electrode obtained in Example 9 as a working electrode was subjected to cyclic voltammetry. A cyclic voltammogram is shown in FIG. Ag / AgCl was used for the reference electrode, and the sweep range was −0.5 to 0.5 V and the sweep speed was 1 mV / s. Similarly, the aqueous secondary battery using the negative electrode obtained in Example 10 as a working electrode was subjected to cyclic voltammetry. A cyclic voltammogram is shown in FIG. Ag / AgCl was used for the reference electrode, and the sweep range was −0.7 to 0.7 V and the sweep speed was 1 mV / s. The aqueous secondary battery using the positive electrode obtained in Example 11 as a working electrode was subjected to cyclic voltammetry. A cyclic voltammogram is shown in FIG. Ag / AgCl was used for the reference electrode, and the sweep range was −0.7 to 0.6 V and the sweep speed was 1 mV / s. The aqueous secondary battery using the negative electrode obtained in Example 12 as a working electrode was subjected to cyclic voltammetry. A cyclic voltammogram is shown in FIG. Ag / AgCl was used for the reference electrode, and the sweep range was −0.7 to 0.5 V and the sweep speed was 1 mV / s.

(Charge / discharge cycle characteristics evaluation)
The aqueous secondary batteries obtained in Examples 1 to 3, 7, and 8 were subjected to a charge / discharge test. The charge / discharge conditions of the charge / discharge test were a current value at a rate of 20 C relative to the theoretical capacity of the battery, and a voltage range of 0 to 1.1V. The charge / discharge test was started 1000 times and repeated 1000 times. The capacity maintenance rate was expressed as a percentage of the 100th, 500th, 700th, and 1000th discharge capacities with respect to the initial discharge capacity. The results are shown in Table 3. Table 3 also shows the amount of dissolved oxygen in each of the aqueous secondary batteries of Examples 1 to 3, 7, and 8 described above.

  As shown in Table 3, from the amount of dissolved oxygen in the electrolyte solutions of Examples 1 to 3, 7, and 8, and the value of the repetitive capacity retention rate of the secondary battery, the aqueous secondary battery of the present invention has a dissolved oxygen amount. It was found that the repetition capacity retention rate increased and the cycle characteristics improved as the value decreased. It was confirmed that the aqueous secondary batteries of Examples 1 to 3, 7, and 8 were excellent in cycle characteristics.

(Rate test)
Moreover, the water-system secondary battery obtained in Examples 4-6 was used for the charging / discharging test. The charge / discharge conditions of the charge / discharge test were set to a voltage range of 0 to 1.1 V with current values of 20C, 15C, 10C, 5C, and 2C with respect to the theoretical capacity of the battery. Table 4 shows the discharge capacity at each rate when the discharge capacity of 2C is set to 100 for the results obtained under the charge / discharge conditions together with Comparative Example 1. In Comparative Example 1, lithium iron phosphate (LiFePO ₄ ) was used as the positive electrode active material, artificial graphite was used as the negative electrode active material, and ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at the same weight as the electrolyte. In the mixed solvent, LiPF ₆ was dissolved so as to be 1 mol / L, and further 0.05 wt% of tris (pentafluorophenyl) borane (TPFPB) and 4-fluoro-1,3-dioxolan-2-one (FEC) A lithium secondary battery using 0.05 wt% was used.

  From the charge / discharge curves of the water-based secondary batteries of Examples 4 to 6 shown in Table 4, even when the rate is high, there is little decrease in capacity, and high output performance is confirmed.

  From the cyclic voltammograms of the aqueous secondary batteries of Examples 9 and 10 shown in FIGS. 2 and 3, it was confirmed that a reversible charge / discharge reaction proceeds. Moreover, when compared with the charge / discharge curve of the lithium secondary battery of Comparative Example 1 shown in Table 4, it was confirmed that the reversibility of the aqueous secondary batteries of Examples 4 to 6 was good.

  The water-based secondary battery of the present invention has few resource problems and cost problems, greatly improves safety because it does not use organic solvents, and has high output and excellent cycle characteristics. It is suitably used for a power failure power supply device.

DESCRIPTION OF SYMBOLS 10 Water-system secondary battery 11 Positive electrode collector 12 Positive electrode active material layer 13 Positive electrode sheet 14 Negative electrode collector 17 Negative electrode active material layer 18 Negative electrode sheet 19 Separator 20 Aqueous electrolyte 22 Cylindrical case 24 Positive electrode terminal 26 Negative electrode terminal

Claims (9)

  An aqueous secondary battery comprising a positive electrode containing a metallocene compound as an active material, a negative electrode containing an orthoquinone compound as an active material, and an aqueous electrolyte.   The aqueous secondary battery according to claim 1, wherein at least one of the positive electrode and the negative electrode contains a conductive additive.   The aqueous secondary battery according to claim 1 or 2, wherein the aqueous electrolyte contains at least one salt selected from the group consisting of a salt of an alkali metal element and a salt of a second metal element.   The aqueous secondary battery according to claim 3, wherein the aqueous electrolyte contains a sodium salt.   The aqueous secondary battery according to any one of claims 1 to 4, wherein an amount of dissolved oxygen in the aqueous electrolytic solution is 7.3 ppm or less. The said orthoquinone compound is an oligomer containing the structural unit derived from the compound represented by the compound represented by the following formula (1), or the following formula (1). Water-based secondary battery.

(In the formula, R ^{1 to} R ⁴ are each independently a hydrogen atom, a halogen atom, a heterocyclic group, an amino group, a nitro group, a formyl group, a cyano group, a hydroxy group, an alkoxy group, a thiol group, an alkylthio group, Alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl group, or hydrocarbon group, heterocyclic group, amino group, alkoxy group, alkylthio group, alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl The group and the hydrocarbon group may be substituted, and any two or more groups of R ^{1 to} R ⁴ may be substituted together with the carbon atom to which each is bonded. A ring structure may be formed.) The aqueous secondary battery according to claim 6, wherein the orthoquinone compound is an oligomer including a structural unit derived from a compound represented by the following formula (2) or a compound represented by the following formula (2).

(Wherein R ^{11 to} R ¹⁸ are each independently a hydrogen atom, halogen atom, heterocyclic group, amino group, nitro group, formyl group, cyano group, hydroxy group, alkoxy group, thiol group, alkylthio group, Alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl group, or hydrocarbon group, heterocyclic group, amino group, alkoxy group, alkylthio group, alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl The group and the hydrocarbon group may be substituted, and any two or more groups of R ^{11 to} R ¹⁸ may be substituted together with the carbon atom to which each is bonded. A ring structure may be formed.) The metallocene compound is an oligomer including a structural unit derived from a compound represented by the following formula (3) or a compound represented by the following formula (3). Water-based secondary battery.

(In the formula, R ^{21 to} R ³⁰ are each independently a hydrogen atom, a halogen atom, a heterocyclic group, an amino group, a nitro group, a formyl group, a cyano group, a hydroxy group, an alkoxy group, a thiol group, an alkylthio group, Alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl group, or hydrocarbon group, heterocyclic group, amino group, alkoxy group, alkylthio group, alkylcarbonyl group, arylcarbonyl group, alkylsulfonyl group, arylsulfonyl The group and the hydrocarbon group may be substituted, and M is a transition metal atom.)   The aqueous secondary battery according to claim 8, wherein the metallocene compound is ferrocene.

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