JP2010044938A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery which has high energy density by including a stabilized radical compound and is excellent in conservation and cycle characteristics. <P>SOLUTION: The secondary battery includes at least a positive electrode, a negative electrode, and an electrolyte as a constituent, and includes an organic compound which accompanies radical reaction on at least one process of charging and discharging as an active material (radical compound). The organic compound is a compound indicated by general formula (1). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a secondary battery including a positive electrode, a negative electrode, and an electrolyte as constituent elements, and more particularly to a secondary battery having a large energy density, excellent storage stability, and excellent cycle characteristics.

  Batteries are used to convert chemical energy into electrical energy using the redox reaction that occurs at the positive and negative electrodes, or to store electrical energy converted into chemical energy. It is used as. In recent years, with the rapid market expansion of notebook personal computers and mobile phones, there is an increasing demand for small high-capacity batteries with high energy density. In order to meet this demand, a battery has been developed that uses an alkali metal ion such as lithium ion as a charge carrier and uses an electrochemical reaction associated with charge transfer.

  However, since this lithium ion battery uses a metal oxide having a large specific gravity as the positive electrode active material, there is a problem that the battery capacity per unit mass is not sufficient. Thus, attempts have been made to develop large-capacity batteries using lighter electrode materials. For example, a battery using an organic compound having a disulfide bond as an active material for a positive electrode is disclosed (for example, see Patent Documents 1 and 2). However, since this battery uses an organic compound mainly composed of an element having a small specific gravity such as sulfur or carbon as an electrode material, a certain effect can be obtained in terms of constituting a high-capacity battery having a high energy density. However, there is a problem that the recombination efficiency of the dissociated disulfide bond is small and the stability in the charged state or the discharged state is insufficient.

  Similarly, a battery using a conductive polymer as an electrode material has been proposed as a battery using an organic compound as an active material (see, for example, Patent Document 3). However, in a battery using such a conductive polymer as an electrode material, a certain effect can be obtained in terms of reducing the weight of the battery, but it is still insufficient in terms of increasing the capacity of the battery.

On the other hand, a secondary battery using a radical compound as an active material has been disclosed (for example, see Patent Document 4). This battery has a high capacity density and stable charge / discharge, so the rate characteristics are good. However, the active material shown here has problems such as stability against temperature and a decrease in life, and a solution is desired. ing.
US Pat. No. 4,833,048 Japanese Patent No. 2715778 U.S. Pat. No. 4,442,187 JP 2002-151084 A

  In order to solve the above-described problems, an object of the present invention is to provide a secondary battery having a large energy density, storage stability and good cycle characteristics by including a stabilized radical compound. And

  The above object of the present invention can be achieved by the following configuration.

  1. In a secondary battery having at least a positive electrode, a negative electrode, and an electrolyte as constituents, and an organic compound accompanied by a radical reaction in at least one of charging and discharging processes as an active material (radical compound), the organic compound has the following general formula ( A secondary battery comprising the compound represented by 1).

[Wherein, X represents —N—Y or —CR ₁ (R ₂ ), and at least one of X is —N—Y, and Y represents a hydrogen atom, an alkyl group, an aryl group, or —O ·. And at least one of all Y is —O., Ra to Rc and R ₁ and R ₂ represent a hydrogen atom or a substituent, m represents an integer of 1 to 4, and when m = 1, L represents a hydrogen atom or a substituent, and when m is 2 to 4, L represents a 2 to 4 valent linking group. ]
2. At least two of X in the general formula (1) are —N—Y, Y represents a hydrogen atom, an alkyl group, an aryl group, or —O ·, and at least one of all Y is —O. The secondary battery as described in 1 above, wherein

  3. Of the groups corresponding to -N-Y in X of the general formula (1), Z, which represents the ratio of -NH and -NO. 3. The secondary battery as described in 1 or 2 above.

  4). Of the groups corresponding to —N—Y in X of the general formula (1), Z, which represents the ratio of —NH and —NO · in the above formula (1), is 0.8 or more and 1.0 or less. 3. The secondary battery as described in 1 or 2 above.

  5. A secondary battery comprising the radical compound according to any one of the above 1 to 4 in a positive electrode.

  According to the present invention, it is possible to provide a secondary battery including a stabilized radical compound, having a large energy density, storage stability and good cycle characteristics.

  The present invention will be described in more detail. The present invention is a secondary battery that includes at least a positive electrode, a negative electrode, and an electrolyte as constituents and includes an organic compound that undergoes a radical reaction in at least one of a charging reaction and a discharging reaction. A stabilized secondary battery was obtained by using an organic compound incorporating a nitroxy radical in the adamantane skeleton represented by the general formula (1) as the organic compound accompanied by the radical reaction.

  By using an organic compound in which a nitroxy radical is incorporated in the adamantane skeleton, the secondary battery can be provided in which decomposition due to disproportionation is suppressed and stabilized, and the energy density is further improved.

  The embodiment of the secondary battery of the present invention has, for example, a configuration in which a negative electrode layer 1 and a positive electrode layer 2 are superposed via a separator 5 containing an electrolyte, as shown in the front sectional view of FIG. Yes. In the present invention, the active material used for the negative electrode layer 1 or the positive electrode layer 2 is an organic compound that generates a radical compound by a radical reaction, and the generated radical compound is stabilized. In addition, it is considered that the reason why the generated radical is stabilized becomes an active material of the battery is that the stabilized radical can further perform electrochemical oxidation-reduction. The assembled structure is sealed with a sealing material 6.

  FIG. 2 shows a cross-sectional view of the secondary battery. The structure is such that the negative electrode current collector 3, the negative electrode layer 1, the separator 5 containing the electrolyte, the positive electrode layer 2, and the positive electrode current collector 4 are sequentially stacked. It has a structure.

  In the present invention, the method for laminating the positive electrode layer and the negative electrode layer is not particularly limited, and a multi-layered laminate, a combination of laminates on both sides of a current collector, a wound one, or the like can be used.

(1) Active material (compound represented by general formula (1))
In General Formula 1, the substituents represented by Ra to Rc and R ₁ and R ₂ are not particularly limited, and examples thereof include alkyl groups (methyl, ethyl, i-propyl, hydroxyethyl, stearyl, dodecyl, eicosyl, Docosyl, oleyl, etc.), cycloalkyl groups (cyclopropyl, cyclohexyl, etc.), aryl groups (phenyl, p-tetradecanyloxyphenyl, o-octadecanylaminophenyl, naphthyl, hydroxyphenyl, etc.), hydroxyl groups, carboxyl groups Nitro group, trifluoromethyl group, amide group (acetamide, benzamide, etc.), carbamoyl group (methylcarbamoyl, butylcarbamoyl, phenylcarbamoyl etc.), ester group (ethyloxycarbonyl, i-propyloxycarbonyl, phenyloxycarboni) ), Carbonyloxy groups (methylcarbonyloxy, propylcarbonyloxy, phenylcarbonyloxy, etc.), cyano groups, halogen atoms (chlorine, bromine, iodine, fluorine), alkoxy groups (methoxy, ethoxy, butoxy, etc.), aryloxy groups (Phenoxy, naphthyloxy, etc.), sulfonyl groups (methanesulfonyl, p-toluenesulfonyl, etc.), alkylthio groups (methylthio, ethylthio, butylthio, etc.), arylthio (phenylthio, etc.), sulfonamide groups (methanesulfonamide, dodecylsulfonamide, p-toluenesulfonamide etc.), sulfamoyl group (methylsulfamoyl, phenylsulfamoyl etc.), amino group, alkylamino group (ethylamino, dimethylamino, hydroxyamino etc.), arylamino group Phenylamino, naphthylamino and the like).

Examples of the divalent to tetravalent linking group represented by L include an alkylene group (for example, methylene, ethylene, 2,2-dimethylpropylene, propylene, 1,4-cyclohexylene, dodecylene, hexadecylene, 2-ethylhexene). Xylene, 2-hexyldecalene, etc.), arylene groups (eg, phenylene, naphthylene, etc.), —C (═O) —, —SO ₂ —, —O—, —S—, —NR ₂₁ (R ₂₂ ) or the like And the like. R ₂₁ and R ₂₂ represent a hydrogen atom, an alkyl group or an aryl group. Or the group etc. which are represented by the following are mentioned.

  Preferably, a combination of alkylene and at least one of -C (= O) O-, -OC (= O)-, -O-, -C (= O) NH-, -NHC (= O)- A linking group consisting of a combination of at least one of —C (═O) O—, —O—C (═O) —, and —O— and alkylene is more preferable.

In the general formula (1), Z can be obtained from the conversion rate to radicals, and the conversion rate to radicals can be calculated by obtaining the spin concentration from the ESR spectrum. The spin concentration means the number of unpaired electrons (radicals) per unit mass, and is a value obtained by the following method from the absorption area intensity of an electron spin resonance spectrum (hereinafter referred to as ESR spectrum), for example. First, a sample to be measured for ESR spectrum is ground with a mortar or the like and pulverized. By this treatment, the skin effect (a phenomenon in which the microwave does not pass through to the inside) can be pulverized into particles having a size that can be ignored. A certain amount of the pulverized sample is filled in a quartz glass capillary having an inner diameter of 2 mm or less, preferably 1 to 0.5 mm, degassed to 10 ⁻⁵ mmHg (1 mmHg is 133.322 Pa) or less, and sealed. The ESR spectrum is measured. The ESR spectrum is measured using, for example, a JEOL-JES-FR30 type ESR spectrometer. The spin concentration can be obtained by integrating the obtained ESR signal twice and comparing it with a calibration curve. However, in the present invention, any measuring machine and measurement conditions are applicable as long as the spin concentration can be measured correctly. For example, when the conversion rate to radicals is 80%, Z = 0.8 from the following.

  Hereinafter, although the compound represented by General formula (1) is described, it is not limited to these.

  In the present invention, a radical compound other than the compound of the present invention can be used in combination, and the type of the radical compound is not particularly limited. Examples of such radical compounds include organic compounds such as oxy radical compounds, nitroxyl radical compounds, nitrogen radical compounds, carbon radical compounds, boron radical compounds, and sulfur radical compounds.

  Specific examples of the radical compound include compounds such as the following general formulas (RA-1) to (RA-14), but are not limited thereto.

  Although the synthesis example of the compound represented by General formula (1) is shown below, it can synthesize | combine by another well-known prescription.

  <Synthesis Example 1 Exemplary Compound (A-25)>

  While 12 g of compound (a) was dissolved in 120 ml of dry dichloromethane and stirred, a solution of 39.4 g of m-chloroperbenzoic acid dissolved in 120 ml of dry dichloromethane was slowly added dropwise over 1 hour at room temperature. It stirred for 6 hours after completion | finish of dripping. The precipitate was filtered, the filtrate was washed with an aqueous sodium carbonate solution and water, and the solvent of the obtained organic layer was removed under reduced pressure. The residue was separated and purified by thin layer chromatography to obtain 8.1 g (yield 59%) of (A-25a).

  8.0 g of (A-25a) was dissolved in 80 ml of dichloromethane, cooled to 0 to 5 ° C., and 2.8 g of pyridine was slowly added dropwise with stirring. While maintaining 0 to 5 ° C, 3.6 g of adipic acid chloride was slowly added dropwise. After completion of the dropwise addition, the temperature was gradually raised to room temperature and stirred for 4 hours. After completion of the reaction, water was added for extraction, and the solvent of the organic layer was removed under reduced pressure. The obtained residue was separated and purified by thin layer chromatography to obtain 8.1 g (yield 59%) of (A-25a).

The spin concentration determined from ESR was 4.05 × 10 ²¹ spins / g, the conversion rate of NH groups to NO · was 100%, and Z = 1.0.

  <Synthesis Example 2 Exemplary Compound (A-28)>

  While 15 g of compound (b) was dissolved in 150 ml of dry dichloromethane and stirred, a solution of 46.1 g of m-chloroperbenzoic acid dissolved in 150 ml of dry dichloromethane was slowly added dropwise over 1 hour at room temperature. It stirred for 6 hours after completion | finish of dripping. The precipitate was filtered, the filtrate was washed with an aqueous sodium carbonate solution and water, and the solvent of the obtained organic layer was removed under reduced pressure. The residue was separated and purified by thin layer chromatography to obtain 12.2 g (yield 72%) of (A-28a).

  12.0 g of (A-28a) was dissolved in 120 ml of dichloromethane, 1.8 g of 1,3-propanediol and 0.55 g of 4- (dimethylamino) pyridine were added, and the mixture was cooled to 0 to 5 ° C. and stirred. . While maintaining 0 to 5 ° C, 10.8 g of DCC was slowly added. After 5 minutes, the ice bath was removed, the temperature was raised to room temperature, and the mixture was stirred for 4 hours. Dicyclohexylurea precipitated from the reaction mixture was filtered, the filtrate was washed with dilute hydrochloric acid, aqueous sodium hydrogen carbonate solution and water, and the solvent was removed under reduced pressure. The obtained residue was separated and purified by thin layer chromatography to obtain 8.2 g (yield 64%) of (A-28).

The spin concentration determined from ESR was 1.95 × 10 ²¹ spins / g, the conversion rate of NH groups to NO · was 89%, and Z = 0.89.

(Other than radical compounds)
In the present invention, a material that generates a radical compound in the course of the charge / discharge reaction can be used as an active material for the positive electrode and / or the negative electrode. It is preferable to use as.

In addition, when using these materials as an active material of any one of a positive electrode and a negative electrode, the material listed below can be used as an active material of another electrode. That is, when a material that generates a radical compound is used as the active material of the negative electrode layer, metal oxide particles, a disulfide compound, a conductive polymer, and the like are used as the active material of the positive electrode layer. Here, examples of the metal oxide include lithium manganate such as LiMnO ₂ and Li _x Mn ₂ O ₄ (0 <x <2) or lithium manganate having a spinel structure, MnO ₂ , LiCoO ₂ , LiNiO ₂ , Or Li _x V ₂ O ₅ (0 <x <2) and the like, and disulfide compounds include dithioglycol, 2,5-dimercapto-1,3,4-thiadiazole, S-triazine-2,4,6-trithiol. In addition, examples of the conductive polymer include polyacetylene, polyphenylene, polyaniline, and polypyrrole. In the present invention, these positive electrode layer materials can be used singly or in combination of two or more, and it is also preferable to mix a conventionally known active material and these materials to use as a composite active material.

  On the other hand, when a material that generates a radical compound is used as the active material of the positive electrode layer, graphite, amorphous carbon, lithium metal, lithium alloy, lithium ion storage carbon, and conductive polymer are used as the active material of the negative electrode layer. These are used alone or in combination of two or more. These shapes are not particularly limited. For example, in addition to a thin film of lithium metal, a bulk shape, a powdered shape, a fiber shape, a flake shape, or the like can be used.

(2) Binder In the present invention, a binder can also be used in order to strengthen the bond between the constituent materials. Examples of such binders include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene / butadiene copolymer rubber, polypropylene, polyethylene, polyimide, and various polyurethanes. And a resin binder.

(3) Catalyst In the present invention, a catalyst that promotes the oxidation-reduction reaction can also be used in order to perform the electrode reaction more smoothly. 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. Is mentioned.

(4) Current collector The current collector in the present invention is formed of a conductor and collects electric charges generated from battery electrodes. In the present invention, as the negative electrode current collector 3 and the positive electrode current collector 4, a metal foil such as nickel, aluminum, copper, gold, silver, aluminum alloy, and stainless steel, a metal flat plate, a mesh electrode, a carbon electrode, or the like is used. be able to. Further, such a current collector may have a catalytic effect, or the active material and the current collector may be chemically bonded.

(5) Separator and Sealing Agent The separator 5 in the present invention prevents the positive electrode layer and the negative electrode layer from contacting each other, and a material such as a porous film or a nonwoven fabric can be used. Further, such a separator is preferably configured to contain an electrolyte. However, when an ion conductive polymer is used as the electrolyte, the separator itself can be omitted. Further, the sealing material 6 in the present invention is not particularly limited, and a conventionally known material used for a battery exterior is used.

(6) Electrolyte In the present invention, the electrolyte performs charge carrier transport between both the negative electrode layer 1 and the positive electrode layer 2, and generally has an ionic conductivity of 10 ⁻⁵ to 10 ⁻¹ S / cm at room temperature. Have. In the present invention, for example, an electrolyte solution in which an electrolyte salt is dissolved in a solvent can be used as the electrolyte. Examples of such an 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, and Li (CF ₃ Conventionally known materials such as SO ₂ ) ₃ C and Li (C ₂ F ₅ SO ₂ ) ₃ C can be used.

  Examples of the electrolyte salt solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, tetrahydrofuran, dioxolane, sulfolane, dimethylformamide, dimethylacetamide, and N-methyl-2-pyrrolidone. An organic solvent such as can be used. In the present invention, these solvents can be used alone or as a mixed solvent of two or more.

  Furthermore, in the present invention, a solid electrolyte can be used as the electrolyte. Examples of the polymer compound used in such a solid electrolyte include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-monofluoroethylene copolymer, and fluorine. Vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, etc., and acrylonitrile-methyl Methacrylate copolymer, acrylonitrile-methyl acrylate copolymer, acrylonitrile-ethyl methacrylate copolymer, acrylonitrile-ethyl acrylate copolymer, acrylonitrile-methacrylic acid copolymer, acrylonitrile- Acrylic acid copolymers, acrylonitrile - acrylonitrile polymers such as vinyl acetate copolymer, further polyethylene oxide, ethylene oxide - propylene oxide copolymers, and polymers of these acrylates body or methacrylate body thereof. The solid electrolyte may be a gel obtained by adding an electrolytic solution to these polymer compounds, or may be used as it is with only the polymer compound.

(7) Shape In addition, the shape of the battery is not particularly limited, and can be applied to shapes of a cylindrical battery, a coin battery, a square battery, a film battery, a button battery, and the like.

  The present invention will be described more specifically below, but the present invention is not limited to these examples.

Example 1
(1) Production of battery In a dry box equipped with a gas purifier, under a argon atmosphere, 50 mg of a radical compound represented by compound (A-1) in a glass container and 60 mg of graphite powder as an auxiliary conductive material After mixing, 20 mg of vinylidene fluoride-hexafluoropropylene copolymer and 1 g of tetrahydrofuran were further added thereto, and further mixed for several minutes until the whole became uniform, and a black slurry was obtained.

  Subsequently, 200 mg of the obtained slurry was dropped on the surface of an aluminum foil (area: 1.5 cm × 1.5 cm, thickness: 100 μm) provided with lead wires, so that the entire thickness was uniform with a wire bar. When the mixture was allowed to stand at room temperature for 60 minutes, the solvent tetrahydrofuran evaporated, and an electrode layer was formed on the aluminum foil.

Next, 600 mg of vinylidene fluoride-hexafluoropropylene copolymer and 1,400 mg of an electrolyte solution made of a propylene carbonate solution having an acceptor number of 18.9 containing 1 mol / l LiPF ₆ as an electrolyte salt were mixed. To the mixture, 11.3 g of tetrahydrofuran was further added and stirred at room temperature. After the vinylidene fluoride-hexafluoropropylene copolymer is dissolved, this solution is applied onto a stepped glass plate, and allowed to stand at room temperature for 1 hour to naturally dry tetrahydrofuran, and a gel electrolyte membrane having a thickness of 1 mm A cast film was obtained.

  Next, a gel electrolyte film cut out to 2.0 cm × 2.0 cm is laminated on the aluminum foil on which the electrode layer is formed, and further a lithium-laminated copper foil (lithium film thickness 30 μm, copper foil film) provided with a lead wire After stacking 20 μm thick), the whole was sandwiched between 5 mm thick polytetrafluoroethylene sheets, and pressure was applied to produce a battery 101.

  Batteries 102 to 115 were produced in the same manner as described above except that the radical compounds listed in Table 1 were used instead of the compound (A-1).

  The weight average molecular weight Mw of the comparative compound 1 was 89000, and dispersion degree Mw / Mn was 3.3.

(2) Evaluation of Battery The battery 101 manufactured as described above was charged and discharged at a constant current (0.1 mA), with a cut-off voltage of 4.2 V for charging and 2.5 V for discharging. As a result, a flat voltage portion was observed in the vicinity of 2.9 V, and it was confirmed that the device was operating as a battery. Furthermore, when this battery was repeatedly charged / discharged, it was confirmed that it could be charged / discharged over 10 cycles or more and operated as a secondary battery. It was confirmed that the other batteries 102 to 115 also operate as secondary batteries.

(3) Evaluation of preservability Many batteries having the same structure as the obtained batteries 101 to 115 were produced, and initial charge / discharge was performed 10 cycles. Subsequently, after charging under the same conditions as described above, five batteries were stored in a thermostatic chamber having an explosion-proof structure set to 60 ° C. Seven days later, the battery was taken out, discharged under the same conditions as described above, and the “discharge capacity after storage” was measured. For each battery, “self-discharge rate (%)” was calculated according to the following calculation formula.

  Next, charging and discharging were performed under the same conditions. Thus, the obtained discharge capacity was set as “recovery discharge capacity”, and the ratio of each battery to the “discharge capacity before storage” was obtained and set as “recovery capacity ratio (%)”.

  The obtained results are shown in Table 2.

  As is apparent from Table 2, the secondary battery of the present invention using at least the positive electrode, the negative electrode, and the electrolyte as constituent elements and using the compound of the present invention as an active material has good cycleability at the time of charge and discharge, and the stability thereof is also high. It turns out that it is improving.

It is front sectional drawing of the secondary battery which concerns on this invention. It is sectional drawing of the secondary battery which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Negative electrode layer 2 Positive electrode layer 3 Negative electrode collector 4 Positive electrode collector 5 Separator 6 Sealing material

Claims (5)

In a secondary battery having at least a positive electrode, a negative electrode, and an electrolyte as constituents, and an organic compound accompanied by a radical reaction in at least one of charging and discharging processes as an active material (radical compound), the organic compound has the following general formula ( A secondary battery comprising the compound represented by 1).

[Wherein, X represents —N—Y or —CR ₁ (R ₂ ), and at least one of X is —N—Y, and Y represents a hydrogen atom, an alkyl group, an aryl group, or —O ·. And at least one of all Y is —O., Ra to Rc and R ₁ and R ₂ represent a hydrogen atom or a substituent, m represents an integer of 1 to 4, and when m = 1, L represents a hydrogen atom or a substituent, and when m is 2 to 4, L represents a 2 to 4 valent linking group. ] At least two of X in the general formula (1) are —N—Y, Y represents a hydrogen atom, an alkyl group, an aryl group, or —O ·, and at least one of all Y is —O. The secondary battery according to claim 1, wherein: Of the groups corresponding to -N-Y in X of the general formula (1), Z, which represents the ratio of -NH and -NO. The secondary battery according to claim 1, wherein the secondary battery is a battery.

Of the groups corresponding to —N—Y in X of the general formula (1), Z, which represents the ratio of —NH and —NO · in the above formula (1), is 0.8 or more and 1.0 or less. The secondary battery according to claim 1, wherein the secondary battery is a battery. A secondary battery comprising the radical compound according to any one of claims 1 to 4 in a positive electrode.

Images