JP2010129279A - Electrode for secondary battery and secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for secondary battery having a high energy density and superior cycle characteristics, and also to provide a secondary battery. <P>SOLUTION: The electrode for secondary battery forms at least one of a positive electrode and a negative electrode of the secondary battery, and has an organic compound having a π electron conjugated cloud, and a compound the conductivity of which decreases 50% or more when the electric potential rises exceeding a prescribed potential. The secondary battery uses this electrode for secondary battery. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrode for a secondary battery and a secondary battery in which elution of an in-electrode material at a high potential is suppressed.

  With the recent spread of portable electronic devices such as portable personal computers and handy video cameras, non-aqueous electrolyte secondary batteries having high voltage and high energy density are widely used as power sources. From the viewpoint of environmental problems, electric vehicles and hybrid vehicles using electric power as a part of power have been put into practical use.

  Among these non-aqueous electrolyte secondary batteries, lithium ion secondary batteries using a lithium-containing metal oxide for the positive electrode and a carbon material for the negative electrode are used in various electronic devices as secondary batteries having a high energy density. Yes.

  Further, lithium ion secondary batteries are expected to have higher performance such as further weight reduction and higher energy density.

  As a secondary battery that achieves this high performance, for example, Patent Document 1 discloses a secondary battery using an organic compound having a disulfide bond as an electrode.

  Patent Document 2 discloses an organic compound having a π-electron conjugated cloud as a new active material that can be expected to be charged and discharged at high speed, and a reaction mechanism thereof.

  However, when an organic compound having a disulfide bond is used as an active material, an effect of increasing the capacity can be obtained, but there is a problem that cycle characteristics and output characteristics are poor. This is because charge / discharge of organic compounds uses dissociation / recombination of disulfide bonds. That is, the molecules that have been separated by the electrode reaction migrate in the electrode and are eluted in the electrolyte. And the molecule | numerator once eluted cannot perform a battery reaction. For this reason, the cycle characteristics deteriorate due to the gradual loss of the function of the active material in the electrode.

  Further, when an organic compound having a π-electron conjugated cloud is used as an active material, the organic compound is eluted into the organic electrolyte, so that there is a problem that cycle characteristics are low.

  Furthermore, in recent years, an electrode having an organic compound having a π-electron conjugated cloud or a radical and a compound having an ion binding site has been proposed in order to suppress elution of the organic compound from the electrode. For example, it is disclosed in Patent Document 3.

  However, since a compound having an ion binding site does not contribute to charging / discharging, when a compound having an ion binding site is added, the cycle characteristics of the battery are improved, but there is a problem that the energy density is lowered.

  Moreover, even if it has a compound which has an ion binding site | part, since elution cannot be suppressed completely, it has received restrictions that 90% of capacity | capacitance is utilized. This is disclosed in Patent Document 4, for example.

When a material having a small potential change due to charging / discharging of the active material is used, there is a problem that if the potential is controlled, sufficient capacity cannot be used or 90% or more is charged.
Japanese Patent Laid-Open No. 11-214008 JP 2004-111374 A JP 2006-324179 A JP 2007-305461 A

  This invention is made | formed in view of the said actual condition, and makes it a subject to provide the electrode for secondary batteries excellent in cycling characteristics, and a secondary battery by suppressing the elution of the in-electrode material in a high potential. .

  In order to solve the above-mentioned problems, the present inventors have conducted extensive studies, and as a result of repeatedly studying a method for suppressing elution of an organic compound in an electrode having an organic compound having a π-electron conjugated cloud, the present invention It came to make.

  That is, the secondary battery electrode according to the first aspect of the present invention is a secondary battery electrode that forms at least one of a positive electrode and a negative electrode of a secondary battery. And a compound whose conductivity decreases by 50% or more when the potential rises beyond the potential.

  The electrode for a secondary battery of the present invention according to claim 1 has an organic compound having a π-electron conjugated cloud and a compound whose conductivity decreases by 50% or more when the potential increases beyond a predetermined potential. is doing. By including a compound whose conductivity changes (decreases) when the potential rises, the conductivity of the compound whose conductivity changes (decreases) when the electrode reaches a potential exceeding the predetermined potential decreases, The conductivity of the electrode also decreases (resistance to the current flowing through the electrode increases). When the conductivity of the electrode decreases, the potential of the electrode increases due to overvoltage (the voltage of electricity flowing through the electrode increases), and immediately reaches a potential at which the capacity can be charged 100% by the electrode reaction. That is, when the potential of the electrode changes during charging and discharging, the time during which the electrode is in the potential range where the organic compound having the π-electron conjugated cloud is decomposed (potential greater than a predetermined potential) is shortened. As a result, it is possible to suppress the organic compound having the π electron conjugated cloud from being separated and eluted. That is, the electrode for a secondary battery of the present invention suppresses elution of an organic compound from the electrode at a high potential, and is an electrode excellent in cycle characteristics.

  Note that in claim 1, the organic compound having a π-electron conjugated cloud is a compound that is separated and eluted when the potential of the organic compound increases.

  Further, when the potential rises above the predetermined potential, the predetermined potential of the compound whose conductivity decreases by 50% or more is a potential lower than the potential at which the organic compound having a π-electron conjugated cloud starts to be disconnected. More preferably, specifically, the potential is 80% or less of the potential at which the organic compound is released, and more preferably 50% or less of the potential at which the organic compound is released.

  And when the electrical conductivity of a compound whose electrical conductivity changes (decreases) decreases by 50% or more, when the electrical potential of the electrode changes, when the electrical conductivity of the compound before and after exceeding a predetermined potential is compared, It shows that the electrical conductivity after the decrease is less than 50% of the electrical conductivity before the decrease.

  In the secondary battery electrode according to the second aspect of the present invention, the organic compound having a π-electron conjugated cloud has a structure represented by the following chemical formula 4.

(Here, R1-4 are chain or cyclic aliphatic groups, each of which may be the same or different, and X may be a sulfur atom, an oxygen atom, or a carbon. (At least one selected from the group consisting of an atom, a silicon atom, a phosphorus atom, a boron atom, and a halogen atom.)
According to the second aspect, the structure of the organic compound having a π-electron conjugated cloud is represented by the chemical formula (4), whereby the effect of the first aspect can be exhibited.

  In the secondary battery electrode of the present invention according to claim 3, the organic compound having a π-electron conjugated cloud contains bisethylenedithiotetrathiafulvalene or a derivative thereof.

  According to claim 3, the organic compound having a π-electron conjugated cloud has bisethylenedithiotetrathiafulvalene or a derivative thereof, whereby the effects of claims 1-2 can be exhibited.

In the secondary battery electrode of the present invention according to claim 4, the compound whose conductivity is changed has a conductivity of 1 S / cm or less at a potential of 3.7 V (Li / Li ⁺ ) or more.

According to the fourth aspect, the predetermined potential is 3.7 V (Li / Li ⁺ ), and the reduced electric conductivity is 1 S / cm or less, whereby the effects of the first to third aspects can be exhibited.

  In the secondary battery electrode according to the fifth aspect of the present invention, the compound whose conductivity is changed is a polyaniline compound represented by the following chemical formula 5.

  According to the fifth aspect, when the compound whose conductivity is changed is represented by the chemical formula 5, the effects of the first to fourth aspects can be exhibited.

  In the secondary battery electrode according to the sixth aspect of the present invention, the compound whose conductivity is changed is a polyaniline derivative represented by the following chemical formula (6).

(Here, R5 to R12 are substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted aromatic groups, substituted or unsubstituted aralkyl groups. , Hydroxyl group, substituted or unsubstituted alkoxy group, substituted or unsubstituted acyl group, carboxyl group, substituted or unsubstituted alkoxycarbonyl group, cyano group, substituted or unsubstituted amino group, substituted or unsubstituted aryloxy A group, a substituted or unsubstituted aryloxycarbonyl group, a nitro group, a nitroso group, a halogen atom, or a hydrogen atom, and R5 to R12 may be the same group or different groups. However, when R5 to R12 are groups containing an aliphatic group, the aliphatic group may be substituted or substituted, either saturated or unsaturated. Any one of unsubstituted, chain-like, cyclic or branched may be contained, and it may contain one or more oxygen, nitrogen, sulfur, silicon, phosphorus, boron or halogen atoms, and R5 to R12 contain an aromatic group. In this case, the aromatic group may be either substituted or unsubstituted and may contain one or more oxygen, nitrogen, sulfur, silicon, phosphorus, boron, or halogen atoms. This hydroxyl group may form a salt with a metal atom, and when R5 to R12 contain any one of an alkoxy group, an alkoxycarbonyl group, and an amino group, these functional groups may be substituted or unsubstituted. It may contain one or more oxygen, nitrogen, sulfur, silicon, phosphorus, boron or halogen atoms, and R5 to R12 may form a ring between the respective functional groups. It has.)
According to the sixth aspect, the compound of which conductivity is changed becomes a polyaniline derivative represented by the following chemical formula 6, so that the effects of the first to fifth aspects can be exhibited.

  As substituted or unsubstituted alkyl groups of R5 to R12 in the chemical formula 6, methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, isobutyl, amyl, isoamyl, tert-amyl, hexyl, Heptyl, isoheptyl, tertiary heptyl, n-octyl, isooctyl, tertiary octyl, 2-ethylhexyl, nonyl, isononyl, decyl, dodecyl (lauryl), tridecyl, tetradecyl (myristyl), pentadecyl, hexadecyl (palmityl), peptadecyl, octadecyl (Stearyl) etc. can be mentioned.

  Examples of the substituted or unsubstituted alkenyl group or alkoxy group represented by R5 to R12 in Formula 6 include an alkenyl group or an alkoxy group derived from the above alkyl group.

  Examples of the substituted or unsubstituted cycloalkyl group represented by R5 to R12 in the chemical formula 6 include cyclopentyl, cyclobutyl, cyclohexyl, cycloheptyl and the like.

  Examples of the halogen atom of R5 to R12 in the chemical formula 6 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

  As substituted or unsubstituted acyl groups of R5 to R12 in the chemical formula 6, acetyl, propionyl, octanoyl, acryloyl, methacryloyl, phenylcarbonyl (benzoyl), phthaloyl, 4-trifluoromethylbenzoyl, salicyloyl, oxaloyl, 1 , 4-butanedicarbonyl, dibutylcarbamoyl, tolylenecarbamoyl, hexamethylenedicarbamoyl and the like.

  As substituted or unsubstituted aromatic groups of R5 to R12 in the chemical formula 6, phenyl group, 1-naphthyl group, 2-naphthyl group, 9-fluorenyl group, 1-anthryl group, 2-anthryl group, 9 -Anthryl group, 1-phenanthryl group, 2-phenanthryl group, 3-phenanthryl group, 4-phenanthryl group, 9-phenanthryl group, 1-naphthacenyl group, 2-naphthacenyl group, 9-naphthacenyl group, 1-pyrenyl group, 2 -Pyrenyl group, 4-pyrenyl group, 2-biphenylyl group, 3-biphenylyl group, 4-biphenylyl group, p-terphenyl-4-yl group, p-terphenyl-3-yl group, p-ter Phenyl-2-yl group, m-terphenyl-4-yl group, m-terphenyl-3-yl group, m-terphenyl-2-yl group, o-tolyl group, m-tol Group, p-tolyl group, p-t-butylphenyl group, p- (2-phenylpropyl) phenyl group, 3-methyl-2-naphthyl group, 4-methyl-1-naphthyl group, 4-methyl-1 -Anthryl group, 4′-methylbiphenylyl group, aromatic hydrocarbon group such as 4 ″ -t-butyl-p-terphenyl-4-yl group, 1-pyrrolyl group, 2-pyrrolyl group, 3-pyrrolyl Group, pyrazinyl group, 2-pyridinyl group, 3-pyridinyl group, 4-pyridinyl group, 1-indolyl group, 2-indolyl group, 3-indolyl group, 4-indolyl group, 5-indolyl group, 6-indolyl group, 7-indolyl group, 1-isoindolyl group, 2-isoindolyl group, 3-isoindolyl group, 4-isoindolyl group, 5-isoindolyl group, 6-isoindolyl group, 7-isoindolyl group 2-furyl group, 3-furyl group, 2-benzofuranyl group, 3-benzofuranyl group, 4-benzofuranyl group, 5-benzofuranyl group, 6-benzofuranyl group, 7-benzofuranyl group, 1-isobenzofuranyl group, 3 -Isobenzofuranyl group, 4-isobenzofuranyl group, 5-isobenzofuranyl group, 6-isobenzofuranyl group, 7-isobenzofuranyl group, 2-quinolyl group, 3-quinolyl group, 4 -Quinolyl group, 5-quinolyl group, 6-quinolyl group, 7-quinolyl group, 8-quinolyl group, 1-isoquinolyl group, 3-isoquinolyl group, 4-isoquinolyl group, 5-isoquinolyl group, 6-isoquinolyl group, 7 -Isoquinolyl group, 8-isoquinolyl group, 2-quinoxalinyl group, 5-quinoxalinyl group, 6-quinoxalinyl group, 1-carbazolyl group, 2-carba Zolyl group, 3-carbazolyl group, 4-carbazolyl group, 9-carbazolyl group, 1-phenanthridinyl group, 2-phenanthridinyl group, 3-phenanthridinyl group, 4-phenanthridinyl group, 6-phenanthridinyl group, 7-phenanthridinyl group, 8-phenanthridinyl group, 9-phenanthridinyl group, 10-phenanthridinyl group, 1-acridinyl group, 2-acridinyl group, 3-acridinyl group, 4-acridinyl group, 9-acridinyl group, 1,7-phenanthrolin-2-yl group, 1,7-phenanthrolin-3-yl group, 1,7-phenanthrolin-4 -Yl group, 1,7-phenanthrolin-5-yl group, 1,7-phenanthrolin-6-yl group, 1,7-phenanthrolin-8-yl group, 1,7-phenanthroline -9-I Group, 1,7-phenanthroline-10-yl group, 1,8-phenanthrolin-2-yl group, 1,8-phenanthrolin-3-yl group, 1,8-phenanthrolin-4 -Yl group, 1,8-phenanthrolin-5-yl group, 1,8-phenanthrolin-6-yl group, 1,8-phenanthrolin-7-yl group, 1,8-phenanthroline -9-yl group, 1,8-phenanthrolin-10-yl group, 1,9-phenanthrolin-2-yl group, 1,9-phenanthrolin-3-yl group, 1,9-phen group Nansulolin-4-yl group, 1,9-phenanthrolin-5-yl group, 1,9-phenanthrolin-6-yl group, 1,9-phenanthrolin-7-yl group, 1,9 -Phenanthrolin-8-yl group, 1,9-phenanthrolin-10-yl group, 1,10 Phenanthrolin-2-yl group, 1,10-phenanthrolin-3-yl group, 1,10-phenanthrolin-4-yl group, 1,10-phenanthrolin-5-yl group, 2, 9-phenanthrolin-1-yl group, 2,9-phenanthrolin-3-yl group, 2,9-phenanthrolin-4-yl group, 2,9-phenanthrolin-5-yl group, 2,9-phenanthrolin-6-yl group, 2,9-phenanthrolin-7-yl group, 2,9-phenanthrolin-8-yl group, 2,9-phenanthrolin-10-yl Group, 2,8-phenanthrolin-1-yl group, 2,8-phenanthrolin-3-yl group, 2,8-phenanthrolin-4-yl group, 2,8-phenanthrolin-5 -Yl group, 2,8-phenanthrolin-6-yl group, 2,8-phenanthro Phosphorin-7-yl group, 2,8-phenanthrolin-9-yl group, 2,8-phenanthrolin-10-yl group, 2,7-phenanthrolin-1-yl group, 2,7- Phenanthrolin-3-yl group, 2,7-phenanthrolin-4-yl group, 2,7-phenanthrolin-5-yl group, 2,7-phenanthrolin-6-yl group, 2, 7-phenanthrolin-8-yl group, 2,7-phenanthrolin-9-yl group, 2,7-phenanthrolin-10-yl group, 1-phenazinyl group, 2-phenazinyl group, 1-pheno Thiazinyl group, 2-phenothiazinyl group, 3-phenothiazinyl group, 4-phenothiazinyl group, 10-phenothiazinyl group, 1-phenoxazinyl group, 2-phenoxazinyl group, 3-phenoxazinyl group, 4-phenoxazinyl group, 10- Enoxazinyl group, 2-oxazolyl group, 4-oxazolyl group, 5-oxazolyl group, 2-oxadiazolyl group, 5-oxadiazolyl group, 3-flazanyl group, 2-thienyl group, 3-thienyl group, 2-methylpyrrole-1- Yl group, 2-methylpyrrol-3-yl group, 2-methylpyrrol-4-yl group, 2-methylpyrrol-5-yl group, 3-methylpyrrol-1-yl group, 3-methylpyrrol-2-yl Yl group, 3-methylpyrrol-4-yl group, 3-methylpyrrol-5-yl group, 2-t-butylpyrrol-4-yl group, 3- (2-phenylpropyl) pyrrol-1-yl group, 2-methyl-1-indolyl group, 4-methyl-1-indolyl group, 2-methyl-3-indolyl group, 4-methyl-3-indolyl group, 2-t-butyl-1-india Le group, 4-t-butyl-1-indolyl group, 2-t-butyl-3-indolyl group, and a 4-t-butyl-3-indolyl group and the like.

  As the substituted or unsubstituted aralkyl group of R5 to R12 in the formula 6, benzyl group, 1-phenylethyl group, 2-phenylethyl group, 1-phenylisopropyl group, 2-phenylisopropyl group, phenyl-t -Butyl group, α-naphthylmethyl group, 1-α-naphthylethyl group, 2-α-naphthylethyl group, 1-α-naphthylisopropyl group, 2-α-naphthylisopropyl group, β-naphthylmethyl group, 1- β-naphthylethyl group, 2-β-naphthylethyl group, 1-β-naphthylisopropyl group, 2-β-naphthylisopropyl group, 1-pyrrolylmethyl group, 2- (1-pyrrolyl) ethyl group, p-methylbenzyl group M-methylbenzyl group, o-methylbenzyl group, p-chlorobenzyl group, m-chlorobenzyl group, o-chlorobenzyl group, p-bromine Benzyl group, m-bromobenzyl group, o-bromobenzyl group, p-iodobenzyl group, m-iodobenzyl group, o-iodobenzyl group, p-hydroxybenzyl group, m-hydroxybenzyl group, o-hydroxybenzyl group P-aminobenzyl group, m-aminobenzyl group, o-aminobenzyl group, p-nitrobenzyl group, m-nitrobenzyl group, o-nitrobenzyl group, p-cyanobenzyl group, m-cyanobenzyl group, o -Cyanobenzyl group, 1-hydroxy-2-phenylisopropyl group, 1-chloro-2-phenylisopropyl group and the like can be mentioned.

  The substituted or unsubstituted alkoxycarbonyl group of R5 to R12 in Chemical Formula 6 is a group represented by —COOX, and the substituent X is the above substituted or unsubstituted alkyl group, the above substituted or unsubstituted group. Examples thereof include a substituted cycloalkyl group and the above-described substituted or unsubstituted aralkyl group.

  The substituted or unsubstituted amino groups represented by R5 to R12 in Formula 6 are each independently a hydrogen atom, the substituted or unsubstituted alkyl group, the substituted or unsubstituted alkenyl group, and the substituted or unsubstituted group. Examples thereof include a substituted cycloalkyl group, the above substituted or unsubstituted aromatic group, and the above substituted or unsubstituted aralkyl group.

  In the substituted or unsubstituted aryloxy group represented by R5 to R12 in the chemical formula 6, examples of the substituent X include the substituted or unsubstituted aromatic groups described above.

  The substituted or unsubstituted aryloxycarbonyl group of R5 to R12 in Formula 6 is a group represented by —COOX, and examples of the substituent X include the substituted or unsubstituted aromatic group. it can.

  The electrode for a secondary battery of the present invention according to claim 7 comprises a current collector, a compound formed on the surface of the current collector, the conductivity of which varies depending on the potential, and an organic compound having a π electron conjugated cloud. And an organic compound having a π-electron conjugated cloud at 2 to 100 mass% when the mass of the entire electrode mixture layer is 100 mass%.

  According to the seventh aspect, the effects of the first to sixth aspects can be exhibited by including an organic compound having a π-electron conjugated cloud at 2 to 100 mass%. Here, 100 mass% is not included about the ratio in which an organic compound is contained. More preferably, it is 3-75 mass%, More preferably, it is the range of 5-50 mass%.

  Moreover, about the compound from which electrical conductivity changes with an electric potential, 2-100 mass% is preferable when the mass of the whole electrode mixture layer shall be 100 mass%, More preferably, it is 3-75 mass%, More preferably, it is 5-50 mass%. Range. Here, the proportion of the compound whose conductivity changes depending on the potential does not include 100 mass%, as in the case of the organic compound.

  Furthermore, the ratio between the organic compound having a π-electron conjugated cloud and the compound whose conductivity varies with potential is preferably 50 to 100: 2 to 50, more preferably 60 to 100: 2 in terms of mass ratio. It is -20, More preferably, it is 70-100: 2-20.

  The electrode for a secondary battery of the present invention according to claim 8 is used as a positive electrode for a lithium battery.

  According to claim 8, when the electrode for a secondary battery of the present invention is used as a positive electrode of a lithium battery, it exhibits an effect of becoming a lithium battery (lithium ion secondary battery) having excellent cycle characteristics and a long life.

  A secondary battery according to a ninth aspect of the present invention includes a positive electrode and a negative electrode each including the secondary battery electrode according to any one of the first to eighth aspects, and an electrolytic solution. Features.

  According to the ninth aspect, the secondary battery of the present invention uses a secondary battery electrode that can obtain a secondary battery having excellent cycle characteristics and a long life, and therefore, a secondary battery having excellent cycle characteristics and a long life. Demonstrates the effect of obtaining a battery.

  A secondary battery electrode according to a tenth aspect of the present invention is a positive electrode comprising the secondary battery electrode according to any one of the first to eighth aspects, a negative electrode, and the positive electrode and the negative electrode. And a non-aqueous electrolyte.

  According to the tenth aspect, the secondary battery of the present invention uses the electrode for a secondary battery capable of obtaining a secondary battery having excellent cycle characteristics and a long life as a positive electrode, and thus has excellent cycle characteristics and a long life. Demonstrates the effect of obtaining a secondary battery.

  In the secondary battery electrode of the present invention, an organic compound having a π-electron conjugated cloud functions as an active material, and the organic compound is separated and eluted by a change in the conductivity of the compound in which the conductivity changes (decreases). Is suppressed. Thereby, the electrode for secondary batteries of the present invention is lightweight, has a high energy density, and can provide a secondary battery with good cycle characteristics.

  Moreover, the secondary battery of this invention has the electrode for secondary batteries of this invention, is a secondary battery which is lightweight, has a high energy density, and has favorable cycle characteristics.

  The electrode for a secondary battery of the present invention is characterized by having an organic compound having a π-electron conjugated cloud and a compound whose conductivity is changed (decreased). It can be set as the structure similar to the electrode for secondary batteries.

Moreover, it is preferable that the electrode for secondary batteries of this invention has the active material used in the conventionally well-known electrode for secondary batteries. Examples of the active material include an active material (positive electrode active material) for a lithium ion secondary battery, and specifically, a lithium having a layered structure or a spinel structure that is a compound that inserts and desorbs lithium ions. - the metal composite oxide can Ageraru, and more _{specifically, Li (1-X) NiO} 2, Li (1-X) MnO 2, Li (1-X) Mn 2 O4, Li (1 _{-X) CoO 2, Li (1} -X) can be mentioned FeO 2, LiFePO _4, or the like. X in these chemical formulas represents a number from 0 to 1. In addition, each compound may be a compound in which a transition metal such as Li, Mg, Al, or Co, Ti, Nb, or Cr is added or at least partially substituted. In addition to using these lithium-metal composite oxides alone, a plurality of these may be mixed and used. Among these, the lithium-metal composite oxide is preferably at least one of a lithium manganese-containing composite oxide having a layered structure or a spinel structure, a lithium nickel-containing composite oxide, and a lithium cobalt-containing composite oxide.

  An electrode for a secondary battery according to the present invention includes a current collector, an electrode mixture layer formed on the surface of the current collector, and having an organic compound having a compound whose conductivity varies with potential and a π-electron conjugated cloud The electrode mixture layer may further include a known additive such as a binder or a conductive material. Examples of the conductive material include ketjen black, acetylene black, carbon black, graphite, carbon nanotube, and amorphous carbon. In addition, conductive polymer polyaniline, polypyrrole, polythiophene, polyacetylene, polyacene, and the like can be given. Polyvinylidene fluoride, polytetrafluoroethylene, EPDM, SBR, NBR, fluorine rubber and the like can be mentioned. Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, EPDM, SBR, NBR, and fluororubber. In addition, examples of the current collector include aluminum, stainless steel, nickel-plated steel, and the like.

  As a method for forming an electrode mixture layer on the surface of the current collector, an organic compound, a compound whose conductivity is changed, an active material, a binder, or an electrode mixture having a conductive material is dispersed in an appropriate dispersion medium. A method of coating and drying on the surface of the current collector after dissolution is exemplified.

  The secondary battery electrode of the present invention is preferably used for a lithium ion secondary battery, but may be used for other batteries.

  When the secondary battery of the present invention is a lithium ion secondary battery and the electrode for a secondary battery of the present invention is a positive electrode, the configuration of the negative electrode other than the positive electrode, the separator, the non-aqueous electrolyte, etc. is a conventionally known configuration It can be.

  The negative electrode also preferably includes a current collector and an electrode mixture layer having a negative electrode active material formed on the surface of the current collector. The electrode mixture layer further includes a binder, a conductive material, and the like. These known additives may be included.

As the negative electrode active material, a compound that occludes lithium ions during charging and releases them during discharging can be used. The negative electrode active material is not particularly limited in its material configuration, and known materials and configurations can be used. Examples thereof include carbon materials such as lithium metal, graphite or amorphous carbon, alloy materials containing silicon and tin, and oxide materials such as Li ₄ Ti ₅ O ₁₂ and Nb ₂ O ₅ . In addition to using these oxide materials alone, a plurality of these oxide materials may be mixed and used. Examples of the current collector include copper, nickel, stainless steel, nickel plated steel and the like.

  As a method for forming an electrode mixture layer on the surface of the current collector, an organic compound, a compound whose conductivity is changed, an active material, a binder, or an electrode mixture having a conductive material is dispersed in an appropriate dispersion medium. A method of coating and drying on the surface of the current collector after dissolution is exemplified.

  The electrolytic solution is not particularly limited, and an electrolytic solution in which a supporting salt is dissolved in a solvent such as an organic solvent, an ionic liquid that is liquid itself, or a supporting salt that is further dissolved in the ionic liquid. I can give you.

  As the organic solvent, those usually used for non-aqueous electrolytes can be used alone or in combination of two or more kinds, but cyclic carbonate compounds, cyclic ester compounds, sulfone or sulfoxide compounds, amide compounds, chain carbonates. It is preferable to contain at least one selected from the group consisting of a compound, a chain or cyclic ether compound, and a chain ester compound. In particular, it is preferable to contain at least one cyclic carbonate compound and a chain carbonate compound, and by using this combination, not only the cycle characteristics are excellent, but also the viscosity of the electrolyte, the electric capacity / output of the obtained battery, etc. A non-aqueous electrolyte with a good balance can be provided.

  In the organic solvent, the cyclic carbonate compound, the cyclic ester compound, the sulfone or sulfoxide compound, and the amide compound have a high relative dielectric constant, and thus play a role of increasing the dielectric constant of the electrolytic solution. Examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), 1,2-butylene carbonate, isobutylene carbonate, and the like. Examples of the cyclic ester compound include γ-butyrolactone and γ-valerolactone. Examples of the sulfone or sulfoxide compound include sulfolane, sulfolene, tetramethylsulfolane, diphenyl sulfone, dimethyl sulfone, dimethyl sulfoxide, and the like. Among these, sulfolanes are preferable. Examples of the amide compound include N-methylpyrrolidone, dimethylformamide, dimethylacetamide and the like.

  The chain carbonate compound, the chain or cyclic ether compound, and the chain ester compound can lower the viscosity of the non-aqueous electrolyte. Therefore, battery characteristics such as power density can be improved, such as the mobility of electrolyte ions can be increased. Moreover, since it is low-viscosity, the performance of the non-aqueous electrolyte at low temperatures can be increased.

  Specifically, as the chain carbonate compound, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethyl-n-butyl carbonate, methyl-t-butyl carbonate, di-i-propyl Examples thereof include carbonate and t-butyl-i-propyl carbonate. Examples of the linear or cyclic ether compounds include dimethoxyethane (DME), ethoxymethoxyethane, diethoxyethane, tetrahydrofuran, dioxolane, dioxane, 1,2-bis (methoxycarbonyloxy) ethane, 1,2-bis (ethoxycarbonyloxy). ) Ethane, 1,2-bis (ethoxycarbonyloxy) propane, ethylene glycol bis (trifluoroethyl) ether, i-propylene glycol (trifluoroethyl) ether, ethylene glycol bis (trifluoromethyl) ether, diethylene glycol bis (tri Fluoroethyl) ether and the like. Among these, dioxolanes are preferable. Examples of the chain ester compound include carboxylic acid ester compounds represented by the following chemical formula 7.

(Here, R represents an alkyl group having 1 to 4 carbon atoms. N represents 0, 1 or 2.)
Examples of the alkyl group having 1 to 4 carbon atoms in Chemical Formula 7 include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl and tert-butyl. Specifically, methyl formate, ethyl formate, methyl acetate, Examples include ethyl acetate, propyl acetate, sec-butyl acetate, butyl acetate, methyl propionate, and ethyl propionate. In addition, acetonitrile, propionitrile, nitromethane, and derivatives thereof can also be used.

Further, the ionic liquid is not particularly limited as long as it is an ionic liquid usually used for an electrolyte of a lithium secondary battery. For example, as a cation component, 1-methyl-3-ethylimidazolium having high conductivity is used. cation, dimethyl ethyl methoxy ammonium cation and the like, and an anionic ^{_{component, BF 4 -, LiN (SO}} 2 C 2 F 5) 2 - and the like.

The kind of the supporting salt (electrolyte salt) is not particularly limited, but an inorganic salt selected from LiPF ₆ , LiBF ₄ , LiClO ₄ and LiAsF ₆ , a derivative of the inorganic salt, LiCF ₃ SO ₃ , LiC ( An organic salt selected from CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) _2, LiN (CF ₃ SO ₂ ) (SO ₂ C ₄ F ₉ ), and the like, and The organic salt is preferably at least one of its derivatives. There is no particular limitation on the concentration of the supporting salt, and it is preferable to select appropriately in consideration of the types of the supporting salt and the solvent according to the use. The supporting salt is preferably dissolved in the organic solvent so that the concentration in the electrolytic solution is 0.1 to 3.0 mol / liter, particularly 0.5 to 2.0 mol / liter. If the concentration of the supporting salt is less than 0.1 mol / liter, a sufficient current density may not be obtained. If the concentration is greater than 3.0 mol / liter, the stability of the non-aqueous electrolyte may be impaired. .

  The separator plays a role of electrically insulating the positive electrode and the negative electrode and holding the electrolytic solution. As the separator, for example, a porous synthetic resin film, particularly a porous film of a polyolefin polymer (polyethylene, polypropylene) may be used. Note that the separator is preferably larger than the positive electrode and the negative electrode in order to ensure insulation between the positive electrode and the negative electrode.

  As the separator, a commonly used polymer microporous film can be used without any particular limitation. Examples of the film include polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene chloride, polyacrylonitrile, polyacrylamide, polytetrafluoroethylene, polysulfone, polyethersulfone, polycarbonate, polyamide, polyimide, polyethylene oxide and polypropylene oxide. Films composed of ethers, various celluloses such as carboxymethylcellulose and hydroxypropylcellulose, polymer compounds mainly composed of poly (meth) acrylic acid and various esters thereof, derivatives thereof, copolymers and mixtures thereof. Etc. These films may be used alone or may be used as a multilayer film by superimposing these films. Furthermore, various additives may be used for these films, and the type and content thereof are not particularly limited. Among these films, films made of polyethylene, polypropylene, polyvinylidene fluoride, and polysulfone are preferably used.

  These films are microporous so that the electrolyte can penetrate and ions can easily pass therethrough. The microporosity method includes a phase separation method in which a polymer compound and a solvent solution are formed into a film while microphase separation is performed, and the solvent is extracted and removed to make it porous. The film is extruded and then heat-treated, the crystals are aligned in one direction, and a gap is formed between the crystals by stretching to make it porous, and so on.

  The secondary battery according to the present invention includes elements other than the above elements as required. The shape of the secondary battery of the present invention is not particularly limited, and batteries of various shapes such as a coin shape, a cylindrical shape, and a square shape can be used.

  Hereinafter, the present invention will be described using examples.

  As an example of the present invention, a positive electrode for a lithium ion secondary battery and a lithium ion secondary battery were manufactured.

Example 1
(Preparation of positive electrode)
Mix 0.9 g of bisethylenedithiotetrathiafulvalene, an organic compound having a π-conjugated structure, 0.05 g of polyaniline, 0.05 g of acetylene black (conductive material) until uniform, add 5 mL of water as a solvent, and mix thoroughly did.

  The mixed solution was applied on an aluminum foil (current collector) and dried at 80 ° C. for 30 minutes. After drying, this was punched into a disk shape having a diameter of 14 mm.

  Thus, the positive electrode of this example was manufactured.

  In the positive electrode of this example, the conductivity of polyaniline was measured. The measurement results are shown in FIG. As shown in FIG. 1, the electrical conductivity at 0.4 V (vs SHE) was 1 S / cm, and the electrical conductivity at 0.6 V (vs SHE) was 0.001 S / cm. That is, the conductivity at 0.6V is reduced by 50% or more from the conductivity at 0.4V. The conductivity at 0.6 V (vs SHE) or higher was 0.001 S / cm or lower.

  The polyaniline used in this example is polypyrrole containing PTS (paratoluenesulfonic acid) as a 40 mass% dopant.

(Negative electrode)
As the negative electrode, disc-shaped metallic lithium having a diameter of 15 mm was used.

(Electrolyte adjustment)
Ethylene carbonate (EC) and dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) 4: 3: were mixed at a mass ratio of 3, LiPF ₆ was dissolved in this mixed organic solvent at a concentration of 1 mole / liter, the electrolyte A liquid was used.

(Battery assembly)
A coin battery was manufactured using the manufactured positive electrode of this example. The coin battery 1 of the present embodiment is shown in a sectional view in FIG. The coin battery of this example has a positive electrode 2, a negative electrode 3, an electrolyte solution 4, and a separator 7. The negative electrode 3 was made of metallic lithium, the electrolytic solution 4 was the prepared electrolytic solution, and the separator 7 was a 25 μm thick polyethylene porous membrane. The positive electrode 2 has a positive electrode current collector 2a, and the negative electrode 3 has a negative electrode current collector 3a.

  These power generation elements were housed in a stainless steel case (consisting of a positive electrode case 50 and a negative electrode case 51). The positive electrode case 50 and the negative electrode case 51 serve as a positive electrode terminal and a negative electrode terminal. A gasket 6 made of polypropylene is interposed between the positive electrode case 50 and the negative electrode case 51 to ensure sealing and insulation between the positive electrode case 50 and the negative electrode case 51.

  First, the positive electrode 2 was placed on the positive electrode case 50 in a state where the positive electrode current collector 2a was in contact with the positive electrode case 50, and a separator 7 made of a porous polyethylene sheet was placed thereon. Next, the electrolytic solution 3 prepared by the above method was poured into the case.

  And the negative electrode case 51 which accommodated the negative electrode 2 inside and fitted the gasket 6 to the peripheral part was covered, and the outer periphery was crimped, and the lithium ion secondary battery (coin battery) of the present Example was manufactured.

(Comparative example)
0.9 g of bisethylenedithiotetrathiafulvalene, which is an organic compound having a π-conjugated structure, and 0.1 g of acetylene black (conductive material) were mixed until uniform, and 5 mL of water was added as a solvent and mixed thoroughly.

  The mixed solution was applied on an aluminum foil (current collector) and dried at 80 ° C. for 30 minutes. After drying, this was punched into a disk shape having a diameter of 14 mm.

  The positive electrode of this comparative example was manufactured by the above.

  Thereafter, using the positive electrode of the comparative example, the lithium ion secondary battery (coin battery) of the comparative example was manufactured in the same manner as in the example.

(Evaluation)
As evaluation of the batteries manufactured in Examples and Comparative Examples, cycle characteristics and initial charge capacity were examined.

(Test method)
First, constant current charging to 4.1V at a charging current 0.10mA / cm ^2, was constant current discharge to 3.0V at a discharge current 0.10mA / cm ^2. The discharge capacity at this time was defined as the initial discharge capacity.

After initial charge and discharge, a constant current charging to 4.1V at a charging current 0.10mA / cm ^2, was repeated cycles of constant current discharge to 3.0V at a discharge current 0.10mA / cm ^2. The discharge capacities at the 20th and 50th charge / discharge cycles were measured and are shown in Table 1 as discharge capacity ratios. In Table 1, the initial discharge capacity was set to 100, and the discharge capacity ratio was determined from the following formula using the discharge capacity at the 20th and 50th cycles and the initial discharge capacity. In addition, the measurement of charging / discharging and discharge capacity was performed in 25 degreeC atmosphere.

  Discharge capacity ratio = [(discharge capacity in a predetermined cycle) / (initial discharge capacity)] × 100

  As shown in Table 1, it can be confirmed that the coin battery of the example has a higher discharge capacity ratio than the coin battery of the comparative example in both the 20th cycle and the 50th cycle. That is, it was confirmed that the coin battery of the present example was a battery having better cycle characteristics than the coin battery of the comparative example.

  Subsequently, after the first charge / discharge, the charge capacity was measured up to 90% of the capacity (from 3.0 V to 4.1 V in the example, from 3.0 V to 3.7 V in the comparative example), The charge / discharge capacity ratio is shown in Table 2. In Table 2, as in the case of Table 1, it is expressed as a ratio to the capacity at full charge (4.1 V in the example and 3.7 V in the comparative example).

  As shown in Table 2, it was confirmed that the coin battery of the example can use almost all of the capacity of the coin battery, which is 98%. On the other hand, it was confirmed that the coin battery of the comparative example can use only 90% lower capacity than the example. That is, it was confirmed that the coin battery of this example was a battery having a battery capacity superior to that of the coin battery of the comparative example.

  As described above, in the coin battery of the example, when the positive electrode having an organic compound (bisethylenedithiotetrathiafulvalene) having a π-conjugated structure as an active material rises above a predetermined potential, its conductivity is increased. By having a compound (polyaniline) whose rate is reduced by 50% or more, even when the battery is charged / discharged, the electrical conductivity of polyaniline is low even when the bisethylenedithiotetrathiafulvalene is disconnected at a high potential (3.7 V or more). As a result, the conductivity of the electrode decreases. And the electric potential of an electrode becomes high and reaches | attains immediately to the electric potential which shows the voltage capacity of an electrode reaction. That is, the period during which the electrode is in the potential range (potential greater than or equal to a predetermined potential) in which the organic compound having the π electron conjugated cloud is decomposed is shortened. As a result, it is possible to suppress the organic compound having the π electron conjugated cloud from being separated and eluted. As a result, the coin battery of this example suppresses elution of the organic compound from the electrode at a high potential, and is an electrode having excellent cycle characteristics.

It is the graph which showed the measurement result of the electrical conductivity of the polyaniline of an Example. It is a longitudinal cross-sectional view which shows roughly the structure of the coin battery manufactured in the Example.

Explanation of symbols

1: Coin battery 2: Positive electrode 2a: Positive electrode current collector 3: Negative electrode 3a: Negative electrode current collector 4: Electrolytic solution 50: Positive electrode case 51: Negative electrode case 6: Gasket 7: Separator

Claims (10)

In the secondary battery electrode forming at least one of the positive electrode and the negative electrode of the secondary battery,
an organic compound having a π-electron conjugated cloud;
A compound whose conductivity decreases by 50% or more when the potential rises above a predetermined potential;
An electrode for a secondary battery, comprising: 2. The electrode for a secondary battery according to claim 1, wherein the organic compound having the π-electron conjugated cloud has a structure represented by the following chemical formula 1.

(Here, R1-4 are chain or cyclic aliphatic groups, each of which may be the same or different, and X may be a sulfur atom, an oxygen atom, or a carbon. (At least one selected from the group consisting of an atom, a silicon atom, a phosphorus atom, a boron atom, and a halogen atom.)   The secondary battery electrode according to claim 1, wherein the organic compound having the π-electron conjugated cloud contains bisethylenedithiotetrathiafulvalene or a derivative thereof. The electrode for a secondary battery according to any one of claims 1 to 3, wherein the compound in which the conductivity changes has a conductivity at a potential of 3.7 V (Li / Li ⁺ ) or more of 1 S / cm or less. The electrode for a secondary battery according to any one of claims 1 to 4, wherein the compound whose electrical conductivity changes is a polyaniline compound represented by the following chemical formula 2.

The electrode for a secondary battery according to any one of claims 1 to 5, wherein the compound that changes the conductivity is a polyaniline derivative represented by the following chemical formula 3.

(Here, R5 to R12 are substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted aromatic groups, substituted or unsubstituted aralkyl groups. , Hydroxyl group, substituted or unsubstituted alkoxy group, substituted or unsubstituted acyl group, carboxyl group, substituted or unsubstituted alkoxycarbonyl group, cyano group, substituted or unsubstituted amino group, substituted or unsubstituted aryloxy A group, a substituted or unsubstituted aryloxycarbonyl group, a nitro group, a nitroso group, a halogen atom, or a hydrogen atom, and R5 to R12 may be the same group or different groups. However, when R5 to R12 are groups containing an aliphatic group, the aliphatic group may be substituted or substituted, either saturated or unsaturated. Any one of unsubstituted, chain-like, cyclic or branched may be contained, and it may contain one or more oxygen, nitrogen, sulfur, silicon, phosphorus, boron or halogen atoms, and R5 to R12 contain an aromatic group. In this case, the aromatic group may be either substituted or unsubstituted and may contain one or more oxygen, nitrogen, sulfur, silicon, phosphorus, boron, or halogen atoms. This hydroxyl group may form a salt with a metal atom, and when R5 to R12 contain any one of an alkoxy group, an alkoxycarbonyl group, and an amino group, these functional groups may be substituted or unsubstituted. It may contain one or more oxygen, nitrogen, sulfur, silicon, phosphorus, boron or halogen atoms, and R5 to R12 may form a ring between the respective functional groups. It has.) The secondary battery electrode is:
A current collector,
An electrode mixture layer formed on the surface of the current collector and having a compound whose conductivity varies with the potential and an organic compound having the π-electron conjugated cloud;
Have
The electrode for a secondary battery according to any one of claims 1 to 6, wherein an organic compound having the π-electron conjugated cloud is contained at 2 to 100 mass% when the mass of the entire electrode mixture layer is 100 mass%.   The secondary battery electrode according to any one of claims 1 to 7, which is used as a positive electrode for a lithium battery.   A secondary battery comprising: a positive electrode and a negative electrode each using at least one of the electrodes for a secondary battery according to claim 1; and an electrolytic solution.   The positive electrode which consists of the electrode for secondary batteries in any one of Claims 1-8, a negative electrode, the separator distribute | arranged between this positive electrode and this negative electrode, and a non-aqueous electrolyte. The secondary battery as described.

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