JP2005228640A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery having high energy density, high capacity, and high stability in charge/discharge cycles. <P>SOLUTION: In the secondary battery having at least a positive electrode, a negative electrode, and an electrolyte as a constituting element, an active material of at least one electrode of the positive electrode and the negative electrode contains a nitroxyl radical compound having a unit represented by formula (1). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a secondary battery, and more particularly to a secondary battery having high energy density, high capacity and excellent stability.

  In recent years, with the rapid market expansion of small-sized or portable electronic devices such as notebook computers and mobile phones, there is an increasing demand for weight reduction and capacity increase for batteries used in these. In order to meet this demand, secondary batteries using an alkali metal ion such as lithium ion as a charge carrier and utilizing an electrochemical reaction associated with charge exchange have been actively developed. Among these, lithium ion secondary batteries are used in various electronic devices as high-capacity batteries having excellent stability and large energy density. Such a lithium ion secondary battery uses, as an active material, a lithium-containing transition metal oxide such as lithium manganate or lithium cobaltate as a positive electrode, and carbon as a negative electrode. Charging / discharging is performed using a separation reaction.

  However, this lithium-ion secondary battery uses a metal oxide with a large specific gravity for the positive electrode in particular, so the battery capacity per unit mass is not sufficient, and a high-capacity battery is developed using a lighter electrode material. Attempts to do so have been considered. For example, Patent Documents 1 and 2 disclose batteries using an organic compound having a disulfide bond as a positive electrode. This is an electrochemical redox reaction involving generation and dissociation of disulfide bonds, which is used as a battery principle. Since this battery is composed of an electrode material mainly composed of an element having a small specific gravity such as sulfur or carbon, it has a certain effect in terms of a high-capacity battery having a high energy density. However, due to the low efficiency with which the dissociated bonds are recombined and the diffusion of the active material into the electrolyte, there are drawbacks in that the capacity tends to decrease with repeated charge / discharge cycles.

  On the other hand, as a battery using an organic compound, a battery using a conductive polymer as an electrode material has been proposed. This is a battery based on the principle of doping and dedoping of electrolyte ions with respect to a conductive polymer. The dope reaction described here is a reaction that stabilizes excitons such as charged solitons and polarons generated by oxidation or reduction of a conductive polymer with a counter ion. On the other hand, the de-doping reaction corresponds to the reverse reaction and indicates a reaction in which exciton stabilized by a counter ion is electrochemically oxidized or reduced. Patent Document 3 discloses a battery using such a conductive polymer as a positive electrode or negative electrode material. This battery is composed only of elements having a low specific gravity such as carbon and nitrogen, and is expected to be developed as a high capacity battery. However, conductive polymers have the property that excitons generated by redox are delocalized over a wide range of π-electron conjugated systems and interact with each other. This places a limit on the concentration of excitons generated and limits the capacity of the battery. For this reason, a battery using a conductive polymer as an electrode material has a certain effect in terms of weight reduction, but is insufficient in terms of a large capacity.

  As described above, various batteries that do not use a transition metal-containing active material have been proposed in order to realize a high-capacity battery. However, a battery having high energy density, high capacity and excellent stability has not yet been obtained.

As described above, in a lithium ion battery that uses a transition metal oxide for the positive electrode, the specific gravity of the element is large, and thus it is theoretically difficult to manufacture a high-capacity battery that exceeds the current level. For this reason, in order to realize a high-capacity battery, various batteries that do not use a transition metal-containing active material have been proposed, but batteries having high energy density, high capacity, and excellent stability have not yet been obtained. Absent.
U.S. Pat. No. 4,833,048 Japanese Patent No. 2715778 U.S. Pat. No. 4,442,187

  Accordingly, an object of the present invention is to provide a novel secondary battery having high energy density, high capacity, and excellent charge / discharge cycle stability.

  The inventors have found that the above problem can be solved by using a nitroxyl radical compound having a unit represented by the formula (1) as an active material of an electrode.

  That is, according to the present invention, in a secondary battery including at least a positive electrode, a negative electrode, and an electrolyte, at least one of the positive electrode and the negative electrode includes a nitroxyl radical compound having a unit represented by the formula (1). Is a secondary battery characterized by

(In the formula (1), R ^{1 to} R ⁴ may be the same or different and each represents a hydrogen atom, an alkyl group, an alkoxy group, a cyano group, a halogen atom or a fluoroalkyl group. R ^{5 to} R ⁶ may be the same or different and each represents an alkyl group, a halogen atom or a fluoroalkyl group.
The active material is preferably a positive electrode active material. At this time, it is preferable that the negative electrode active material is any one of graphite, amorphous carbon, lithium metal, lithium alloy, lithium ion storage carbon, and a conductive polymer.

  Further, the present invention provides a secondary battery that utilizes an electrode reaction of an active material, wherein at least one of the positive electrode and the negative electrode reacts with a nitroxyl radical compound having a unit represented by formula (1) as a reactant or product. It is a secondary battery which is an electrode reaction.

(In Formula (1), R < ¹ > -R < ⁴ > may be the same or different and represents a hydrogen atom, an alkyl group, an alkoxy group, a cyano group, a halogen atom, or a fluoroalkyl group. R < ⁵ >- R ⁶ may be the same or different, and represents an alkyl group, a halogen atom or a fluoroalkyl group.)
In the present invention, the active material is preferably a positive electrode active material, and the electrode reaction is preferably an electrode reaction at the positive electrode.

  When the electrode reaction is an electrode reaction at the positive electrode, the electrode reaction can be a discharge reaction that generates a bond between the nitroxyl radical compound and an electrolyte cation, and a charge reaction that is a reverse reaction of the discharge reaction. At this time, it is preferable that the electrolyte cation is a lithium ion.

  When the electrode reaction is an electrode reaction at the positive electrode, the electrode reaction may be a discharge reaction that cleaves the bond between the nitroxyl radical compound and the electrolyte anion, and a charge reaction that is the reverse reaction of the discharge reaction. it can.

  This invention is made | formed based on having discovered that said compound was excellent as an electrode active material. These compounds consist of carbon, nitrogen, hydrogen, oxygen, etc., and can be composed of only elements having a small mass. For this reason, since the mass of an active material can be made small, when a secondary battery is produced using this, a secondary battery with a large energy density per mass can be obtained. The electrode reaction of the secondary battery of the present invention is an oxidation-reduction reaction of a nitroxyl radical compound having a unit represented by the formula (1) (hereinafter sometimes simply referred to as a nitroxyl radical compound). A stable reaction with almost no reaction and reversible at a rate of almost 100%, and further, it is difficult for the active material to decrease due to diffusion of the active material into the electrolyte. Can be obtained.

  In the battery, since the electrode active material is oxidized or reduced by an electrode reaction, the electrode active material takes two states, a starting state and an oxidized or reduced state. In the present invention, the active material takes a nitroxyl radical structure represented by the formula (1) in either a starting state or an oxidized or reduced state.

  As a charging / discharging mechanism, the nitroxyl radical compound, which is an active material, reversibly changes between a radical state and an ion state by an electrode reaction, and charges are accumulated and released. In the present invention, the nitroxyl radical compound directly contributes to the electrode reaction at the positive electrode or the negative electrode, and the electrode using these as an active material is not limited to either the positive electrode or the negative electrode. . However, from the viewpoint of energy density, it is particularly preferable to use the positive electrode active material. In the present invention, the electrolyte cation is not particularly limited, but lithium ion is particularly preferable from the viewpoint of obtaining a high capacity.

  According to the present invention, it is possible to provide a novel secondary battery having high energy density, high capacity, and excellent charge / discharge cycle stability.

  Embodiments of the present invention will be described below.

The secondary battery of the present invention can be configured as follows.
(I) A secondary battery including at least one of a positive electrode, a negative electrode, and an electrolyte, wherein at least one active material of the positive electrode and the negative electrode includes a nitroxyl radical compound having a unit represented by the formula (1) .
(Ii) In a secondary battery using an electrode reaction of an active material, at least one of the positive electrode and the negative electrode uses a nitroxyl radical compound having a unit represented by formula (1) as a reactant or a product. A secondary battery that is an electrode reaction.

In the formula (1), R ^{1 to} R ⁴ may be the same or different and each represents a hydrogen atom, an alkyl group, an alkoxy group, a cyano group, a halogen atom, or a fluoroalkyl group. The alkyl group is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, the alkoxy group is preferably an alkoxy group consisting of a linear or branched alkyl group having 1 to 6 carbon atoms, and the halogen atom is a fluorine atom or chlorine. An atom or a bromine atom is preferred. Moreover, when R < ¹ > -R < ⁴ > is an alkyl group, an alkoxy group, or a fluoroalkyl group, it is more preferable that the carbon number is 1. This is because setting the number of carbon atoms to 1 is advantageous in that the molecular weight per unit structure is reduced and the battery capacity density per mass of the active material is increased. In particular, a methyl group or a methoxy group is preferable. For the same reason, when R ^{1 to} R ⁴ are halogen atoms, they are more preferably fluorine atoms.

In formula (1), R ^{5 to} R ⁶ may be the same or different and each represents an alkyl group, a halogen atom or a fluoroalkyl group. The alkyl group is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, and the halogen atom is preferably a fluorine atom, a chlorine atom or a bromine atom. For the same reason as R ^{1 to} R ⁴ above, when R ^{5 to} R ⁶ are an alkyl group or a fluoroalkyl group, the number of carbon atoms is more preferably 1. A methyl group is particularly preferable. For the same reason, when R ^{5 to} R ⁶ are halogen atoms, fluorine atoms are more preferable.

When said nitroxyl radical compound has multiple units represented by Formula (1), R < ¹ > -R < ⁶ > may differ between units. Furthermore, you may have another unit in a molecule | numerator.

  The above nitroxyl radical compound may be a low molecule or a polymer, but in the case of a polymer, there is an advantage that elution from the electrode to the electrolytic solution hardly occurs. The number average molecular weight is preferably from 1,000 to 1,000,000, and more preferably from 5,000 to 1,000,000 from the viewpoint that elution into the electrolytic solution hardly occurs. Moreover, since the solubility to electrolyte solution becomes low even if it is a low molecule, it is preferable that the unit represented by Formula (1) is two or more. Examples of terminal atoms of both low and high molecules include a hydrogen atom and a methyl group. It may be a homopolymer composed of one of the units represented by the formula (1), a copolymer composed of a plurality of the units represented by the formula (1), or one of the units represented by the formula (1) or A copolymer composed of a plurality of types and other units may be used.

  Specific examples of the unit represented by the formula (1) include units represented by the formulas (2) to (4).

A unit wherein R ^{1 to} R ⁴ are hydrogen atoms and R ^{5 to} R ⁶ are methyl groups [formula (2)]:

A unit wherein R ¹ is a fluorine atom, R ^{2 to} R ⁴ are hydrogen atoms, and R ^{5 to} R ⁶ are methyl groups [formula (3)]:

A unit wherein R ¹ is a methoxy group, R ^{2 to} R ⁴ are hydrogen atoms, and R ^{5 to} R ⁶ are methyl groups [formula (4)]:

  The nitroxyl radical compounds (1) to (4) can be synthesized by applying a generally known organic synthesis reaction. For example, a nitroxyl radical compound can be obtained by synthesizing a corresponding amine compound and oxidizing it with an oxidizing agent such as perbenzoic acid such as m-chloroperbenzoic acid or hydrogen peroxide (reaction). Formula (I), literature (1964, Tetrahydron Letter, 3945)). Other compounds represented by the general formula (1) can be obtained by oxidation of corresponding amines as well, but it can be obtained by a similar method (LB Voldarsky et al., Synthetic Chemistry of Stable Nitroxides, CRC Press Inc). The method for synthesizing a nitroxyl radical described in Roca Baton, Florida (1994) can be applied. For example, a nitroxy radical compound can be obtained by synthesizing a corresponding hydroxyamine compound and oxidizing it using an oxidizing agent such as silver oxide or lead oxide.

  In the secondary battery of the present invention, the active material may be in a solid state or may be dissolved or dispersed in an electrolyte. However, when it is used in a solid state, it is preferably insoluble or lowly soluble in the electrolytic solution in order to reduce a decrease in capacity due to dissolution in the electrolytic solution.

  In the secondary battery of the present invention, the nitroxyl radical compound which is an active material can be used alone, but two or more kinds may be used in combination. Moreover, you may use in combination with another active material.

In the present invention, there are a case where a secondary battery is manufactured using the nitroxyl radical compound itself as an active material and a case where a secondary battery is manufactured using a compound which changes to the nitroxyl radical compound by an electrode reaction. is there. Examples of compounds that change the nitroxyl radical compound by the electrode reaction, the anion and the lithium and sodium salts such as lithium ions or sodium ions consisting of the electrolyte cation or a cation and PF ₆ ^- or BF ₄ ^- like electrolyte anions And a salt composed of

  The secondary battery of the present invention uses the nitroxyl radical compound as an active material in one electrode reaction of the positive electrode or the negative electrode, or both electrode reactions. A conventionally well-known thing can be utilized for one electrode as an active material of a secondary battery.

For example, when the nitroxyl radical compound is used as the negative electrode active material, metal oxide particles, disulfide compounds, conductive polymers, and the like are used as the positive electrode active material. Here, examples of the metal oxide include lithium manganate such as LiMnO ₂ and Li _x Mn ₂ O ₄ (0 <x <2), lithium manganate having a spinel structure, MnO ₂ , LiCoO ₂ , LiNiO ₂ , Li _{x V 2 O 5 (0 <} x <2) . Examples of the disulfide compounds, e.g. dithioglycol, 2,5-dimercapto-1,3,4-thiadiazole, S- triazine-2,4,6-trithiol and the like, Examples of the conductive polymer include polyacetylene, polyphenylene, polyaniline, and polypyrrole. In the present invention, these positive electrode active materials can be used alone or in combination. Further, a conventionally known active material and the nitroxyl radical compound may be mixed and used as a composite active material.

  On the other hand, when the nitroxyl radical compound is used as the positive electrode active material, graphite, amorphous carbon, lithium metal, lithium alloy, lithium ion storage carbon, conductive polymer, etc. can be used as the negative electrode active material. . These shapes are not particularly limited. For example, lithium metal is not limited to a thin film shape, but may be a bulk shape, a powdered shape, a fiber shape, a flake shape, or the like. These negative electrode active materials can be used alone or in combination. Moreover, you may use combining a conventionally well-known active material and the said nitroxyl radical compound.

  In the present invention, the active material containing the nitroxyl radical compound is preferably used as the active material for the electrode reaction in the positive electrode. At this time, the electrode reaction at the positive electrode can be a discharge reaction that generates a bond between the nitroxyl radical compound and the electrolyte cation, and a charge reaction by reverse reaction of the discharge reaction. Alternatively, it may be a discharge reaction for cleaving the bond between the nitroxyl radical compound and the electrolyte anion, and a charge reaction by reverse reaction of the discharge reaction. The electrolyte cation is preferably lithium ion.

  When the electrode is formed using the nitroxyl radical compound, an auxiliary conductive material or an ion conduction auxiliary material can be mixed for the purpose of reducing impedance. Examples of these materials include carbonaceous fine particles such as graphite, carbon black, and acetylene black, and conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyacene as auxiliary conductive materials. Examples thereof include a polymer gel electrolyte and a polymer solid electrolyte.

  In order to strengthen the connection between the constituent materials of the electrode, a binder can also be used. Examples of such binders include polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene / butadiene copolymer rubber, polypropylene, and polyethylene. Resin binders such as polyimide and various polyurethanes.

  In order to perform the electrode reaction more smoothly, a catalyst that assists the oxidation-reduction reaction can also be used. Examples of such catalysts include conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyacene, basic compounds such as pyridine derivatives, pyrrolidone derivatives, benzimidazole derivatives, benzothiazole derivatives, and acridine derivatives, and metal ion complexes. Can be mentioned.

  As the negative electrode current collector and the positive electrode current collector in the present invention, a metal foil such as nickel, aluminum, copper, gold, silver, aluminum alloy, stainless steel, a metal flat plate, a mesh electrode, a carbon electrode, or the like can be used. Further, the current collector may have a catalytic effect, or the active material and the current collector may be chemically bonded. On the other hand, a separator made of a porous film, a nonwoven fabric or the like can be used so that the positive electrode and the negative electrode are not in contact with each other.

In the present invention, the electrolyte performs charge carrier transport between the negative electrode and the positive electrode, and generally has an ionic conductivity of 10 ⁻⁵ to 10 ⁻¹ S / cm or more at room temperature. . As the electrolyte, for example, an electrolytic solution in which an electrolyte salt is dissolved in a solvent can be used. Examples of the electrolyte salt include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, Li (CF ₃ SO ₂ ) ₃ C Conventionally known materials such as Li (C ₂ F ₅ SO ₂ ) ₃ C can be used. As the solvent, for example, an organic solvent such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, tetrahydrofuran, dioxolane, sulfolane, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone is used. Can do. These solvents can be used alone or in admixture of two or more.

  Furthermore, in the present invention, a solid electrolyte can be used as the electrolyte. Polymer compounds used in these solid electrolytes include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-monofluoroethylene copolymer, and vinylidene fluoride. -Vinylidene fluoride polymers such as trifluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer; acrylonitrile-methyl methacrylate copolymer Polymers, acrylonitrile-methyl acrylate copolymer, acrylonitrile-ethyl methacrylate copolymer, acrylonitrile-ethyl acrylate copolymer, acrylonitrile-methacrylic acid copolymer, acrylonitrile-acrylic Acid copolymer, an acrylonitrile - acrylonitrile polymers such as vinyl acetate copolymer; and polyethylene oxide, ethylene oxide - propylene oxide copolymers, and polymers of these acrylates body or methacrylate body thereof. These polymer compounds may be used in the form of a gel containing an electrolytic solution, or only a polymer compound containing an electrolyte salt may be used as it is.

  In the present invention, the shape of the secondary battery is not particularly limited, and a conventionally known battery can be used. Examples of the shape of the secondary battery include a case in which an electrode laminate or a wound body is sealed with a metal case, a resin case, or a laminate film composed of a metal foil such as an aluminum foil and a synthetic resin film, etc. A mold, a square, a coin, a sheet, etc. are used, but the present invention is not limited to these.

  The method for producing the secondary battery is not particularly limited, and various methods can be used depending on the material. For example, a solvent is added to the active material to form a slurry, which is applied to the electrode current collector, and the solvent is volatilized by heating or at room temperature, and then laminated or wound with a counter electrode and a separator sandwiched between and wrapped in an outer package. Is injected and sealed. Solvents for slurrying include ether solvents such as tetrahydrofuran and diethyl ether; amine solvents such as N-methylpyrrolidone; aromatic hydrocarbon solvents such as benzene, toluene and xylene; aliphatics such as hexane and heptane. Hydrocarbon type: Halogen type hydrocarbons such as chloroform and dichloromethane.

  In the present invention, a conventionally known method can be used as a method of manufacturing a secondary battery for other manufacturing conditions such as taking out a lead from an electrode and packaging.

  Although there is no restriction | limiting in particular in the kind of secondary battery of this invention, It is preferable that it is a lithium ion secondary battery.

  Hereinafter, the details of the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

(Example 1)
50 mg of a nitroxyl radical compound (number average molecular weight 8300) comprising a unit represented by the formula (2), 200 mg of graphite powder, and 25 mg of a polytetrafluoroethylene resin binder were weighed and kneaded using an agate mortar. The mixture obtained by dry-mixing for about 10 minutes was made into a thin film having a thickness of about 200 μm by applying pressure and roller stretching. This was dried overnight at 80 ° C. in a vacuum, and then punched into a circle having a diameter of 12 mm to form a coin battery electrode.

Next, a coin-type battery having the configuration shown in FIG. 1 was produced using the obtained electrode. First, the obtained electrode was immersed in an electrolytic solution so that the electrolytic solution was infiltrated into voids in the electrode. As the electrolytic solution, an ethylene carbonate / diethyl carbonate mixed solution (mixing ratio 3: 7 (volume ratio)) containing 1 mol / l LiN (C ₂ F ₅ SO ₂ ) ₂ electrolyte salt was used. The electrode impregnated with the electrolytic solution was placed on the positive electrode current collector 6 as the positive electrode 5, and the separator 4 made of a porous film impregnated with the electrolytic solution was laminated thereon. Further, a lithium-bonded copper foil to be the negative electrode 3 was laminated, and the negative electrode current collector 1 covered with the insulating packing 2 was superposed. The laminated body thus produced was pressed with a caulking machine to form a sealed coin-type battery.

  A battery using the nitroxyl radical compound composed of the unit represented by the formula (2) as the positive electrode active material and the metal lithium as the negative electrode active material, produced as described above, has a voltage of 4. mA at a constant current of 0.1 mA. The battery was charged until it reached 0V. Subsequently, discharging was performed at a constant current of 0.1 mA. As a result, the voltage became constant for 2 hours near 3.2 V, and then dropped rapidly. When the voltage dropped to 2.5V, charging was performed again, and charging / discharging was repeated 10 times in the range of 4.0 to 2.5V. The evaluation temperature was 20 ° C. As a result, it was confirmed that the voltage was constant at around 3.2 V during discharge even after repeated charge and discharge. As a result of continuing this test up to 50 cycles, the first discharge capacity (per active material mass of the positive electrode) was 170 mAh / g, the 50th discharge capacity was 169 mAh / g, and the (50th discharge capacity) / ( The first discharge capacity) was 99.4%.

(Example 2)
As the electrolytic solution, a closed coin type was used in the same manner as in Example 1 except that an ethylene carbonate / diethyl carbonate mixed solution (mixing ratio 3: 7 (volume ratio)) containing 1 mol / l LiPF ₆ electrolyte salt was used. I built a battery.

  A battery using the nitroxyl radical compound composed of the unit represented by the formula (2) as the positive electrode active material and the metal lithium as the negative electrode active material, produced as described above, has a voltage of 4. mA at a constant current of 0.1 mA. The battery was charged until it reached 0V. Subsequently, discharging was performed at a constant current of 0.1 mA. As a result, the voltage became constant around 3.2 V and then dropped rapidly. When the voltage dropped to 2.5V, charging was performed again, and charging / discharging was repeated 10 times in the range of 4.0 to 2.5V. The evaluation temperature was 20 ° C. As a result, it was confirmed that the voltage was constant at around 3.2 V during discharge even after repeated charge and discharge.

(Example 3)
A sealed coin-type battery was assembled in the same manner as in Example 1, except that graphite was used as the negative electrode active material.

  A battery using the nitroxyl radical compound composed of the unit represented by the formula (2) as the positive electrode active material and graphite as the negative electrode active material, prepared as described above, and a voltage of 4.0 V at a constant current of 0.1 mA. Charged until Subsequently, discharging was performed at a constant current of 0.1 mA. As a result, the voltage became constant around 3.0 V and then dropped rapidly. When the voltage dropped to 2.5 V, the battery was charged again, and further a cycle test was performed by repeating charge and discharge. The charge / discharge range was 4.0 to 2.5 V, and the evaluation temperature was 20 ° C. As a result of this test, the first discharge capacity (per active material mass of the positive electrode) was 160 mAh / g, and the 50th discharge capacity was 158 mAh / g. (50th discharge capacity) / (1st discharge capacity) was 98.8%.

(Comparative Example 1)
225 mg of graphite powder and 25 mg of polytetrafluoroethylene resin binder were measured and kneaded using an agate mortar. The mixture obtained by dry-mixing for about 10 minutes was roller-stretched under pressure to obtain a thin electrode plate having a thickness of 215 μm. The thin electrode plate was dried overnight at 80 ° C. in a vacuum, and then punched into a circle having a diameter of 12 mm to produce an electrode for a coin battery containing no nitroxyl radical compound.

Next, a coin-type battery having the configuration shown in FIG. 1 was produced using the obtained electrode. First, the obtained electrode was immersed in an electrolytic solution so that the electrolytic solution was infiltrated into voids in the electrode. As the electrolytic solution, an ethylene carbonate / diethyl carbonate mixed solution (mixing ratio 3: 7 (volume ratio)) containing 1 mol / l LiN (C ₂ F ₅ SO ₂ ) ₂ electrolyte salt was used. The electrode impregnated with the electrolytic solution was placed on the positive electrode current collector 6 as the positive electrode 5, and the separator 4 made of a porous film impregnated with the electrolytic solution was laminated thereon. Further, a lithium-bonded copper foil to be the negative electrode 3 was laminated, and the negative electrode current collector 1 covered with the insulating packing 2 was superposed. The laminate thus produced was pressed by a caulking machine to obtain a sealed coin type battery.

  The battery produced as described above was charged with a constant current of 0.1 mA until the voltage reached 4.0V. Subsequently, when discharging was performed at a constant current of 0.1 mA, the voltage dropped rapidly to 0.8 V in about 30 minutes. Immediately after that, when the battery was charged with a constant current of 0.1 mA, the voltage increased rapidly. When the voltage reached 4.0V, the voltage dropped sharply to 0.8V even after discharging again. As mentioned above, the voltage flat part seen in above-mentioned Examples 1-3 was not able to be confirmed in charging / discharging.

  As described above, the present invention proposes a novel secondary battery using a nitroxyl radical compound having a unit represented by the formula (1) as an active material. This makes it possible to produce a secondary battery composed of light and safe elements that do not contain heavy metals as an electrode active material, and has a high energy density, high capacity, and excellent stability. A secondary battery can be realized.

It is a conceptual diagram which shows the structure of the battery produced in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Negative electrode collector 2 Insulation packing 3 Negative electrode 4 Separator 5 Positive electrode 6 Positive electrode collector

Claims (8)

A secondary battery having at least a positive electrode, a negative electrode, and an electrolyte as constituent elements, wherein at least one of the active material of the positive electrode and the negative electrode includes a nitroxyl radical compound having a unit represented by the formula (1). Next battery.

(In the formula (1), R ^{1 to} R ⁴ may be the same or different and each represents a hydrogen atom, an alkyl group, an alkoxy group, a cyano group, a halogen atom or a fluoroalkyl group. R ^{5 to} R ⁶ may be the same or different and each represents an alkyl group, a halogen atom or a fluoroalkyl group.   The secondary battery according to claim 1, wherein the active material is a positive electrode active material. In a secondary battery using an electrode reaction of an active material, at least one of the positive electrode and the negative electrode is an electrode reaction in which a nitroxyl radical compound having a unit represented by the formula (1) is used as a reactant or a product. A secondary battery characterized by being.

(In the formula (1), R ^{1 to} R ⁴ may be the same or different and each represents a hydrogen atom, an alkyl group, an alkoxy group, a cyano group, a halogen atom or a fluoroalkyl group. R ^{5 to} R ⁶ may be the same or different and each represents an alkyl group, a halogen atom or a fluoroalkyl group.   The secondary battery according to claim 3, wherein the active material is a positive electrode active material, and the electrode reaction is an electrode reaction at a positive electrode.   The secondary battery according to claim 4, wherein the electrode reaction at the positive electrode is a discharge reaction that generates a bond between the nitroxyl radical compound and an electrolyte cation, and a charge reaction that is a reverse reaction of the discharge reaction.   The secondary battery according to claim 4, wherein the electrode reaction at the positive electrode is a discharge reaction that cleaves a bond between the nitroxyl radical compound and an electrolyte anion, and a charge reaction that is a reverse reaction of the discharge reaction.   The secondary battery according to claim 5, wherein the electrolyte cation is lithium ion.   The secondary battery according to claim 2, wherein the negative electrode active material is any one of graphite, amorphous carbon, lithium metal, lithium alloy, lithium ion storage carbon, and a conductive polymer.

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