JP5906915B2 - Non-aqueous electrolyte for secondary battery and non-aqueous electrolyte secondary battery using the same - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte for a secondary battery and a secondary battery using the same, and more specifically, a non-aqueous electrolyte for a lithium secondary battery containing a specific component and the use thereof. The present invention relates to a lithium secondary battery.

Along with the downsizing of electronic equipment due to the rapid development of modern industry, there has been a strong demand for higher capacity of secondary batteries. Therefore, lithium secondary batteries having higher energy density than nickel / cadmium batteries and nickel / hydrogen batteries have been developed, and efforts to improve performance have been repeated until now.
On the other hand, in recent years, with the background of global issues such as environmental problems and energy problems, great expectations have been placed on the application of lithium secondary batteries to large-scale power sources such as in-vehicle power sources and stationary power sources. However, in general, it is indispensable to ensure the stability of such batteries against repeated charging and discharging over a long period of time, and further, they are expected to be used in an environment exposed to the outside air. In particular, battery characteristics under particularly low temperature environments, particularly low temperature discharge characteristics, are regarded as important.

Components constituting the lithium secondary battery are mainly classified into a positive electrode, a negative electrode, a separator, and an electrolytic solution. Of these, electrolytes generally include electrolytes such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiCF ₃ (CF ₂ ) ₃ SO ₃ , Cyclic carbonates such as ethylene carbonate and propylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; cyclic esters such as γ-butyrolactone and γ-valerolactone; chain esters such as methyl acetate and methyl propionate A non-aqueous electrolyte solution dissolved in a non-aqueous solvent such as a liquid is used.

As one of the efforts to improve the long-term durability of lithium secondary batteries, by adding a specific compound to the above electrolyte, a passive film is formed on the negative electrode at the initial use of the battery, which is a major cause of deterioration. Efforts are being made to suppress side reactions such as reductive decomposition of solvents.
Examples of such compounds include compounds containing an isocyanate group in the molecule. Patent Document 1, Patent Document 2 and Patent Document 3 disclose that cycle stability is improved by adding a low-molecular compound having an isocyanate group, a chain isocyanate compound or a diisocyanate compound to the electrolyte solution, respectively. Yes.

  Patent Document 4 proposes to use a specific sulfone compound and an isocyanate compound in combination as a compound to be added to the electrolytic solution for improving the cycle characteristics. However, with the isocyanate compounds as described above, it is difficult to satisfy the long-term durability performance required for large batteries for automobiles in recent years. Furthermore, further improvements are required to achieve sufficient battery characteristics including low temperature discharge characteristics.

On the other hand, some lithium secondary batteries may be used by immobilizing the electrolytic solution by impregnating the non-aqueous electrolytic solution into the higher order structure formed by the polymer matrix. As a result, it is possible to provide a lithium secondary battery having a high degree of freedom in battery shape design and almost no liquid leakage. In such so-called gel polymer electrolytes, isocyanate compounds are sometimes used. For example, Patent Documents 5, 6 and 7 disclose that a polymer matrix is formed by curing in combination with a polymer capable of binding to an isocyanate group such as a polyol.

  For the purpose of the crosslinking agent, the isocyanate compound may be a low molecular weight aliphatic diisocyanate or alicyclic diisocyanate as described above, or may be a polyisocyanate produced using these as a main raw material. Usually, cured resins obtained by curing polyisocyanates have excellent mechanical properties such as flexibility and chemical resistance, and are widely used in paints, adhesives, sealing materials, waterproof materials, foams, elastomers, etc. For the same reason, it is also preferably used in gel electrolyte polymers.

  As polyisocyanates, those having a skeleton such as carbodiimide, uretdione, oxadiaditrione, biuret, urethane, allophanate, isocyanurate and the like are known. The biuret type polyisocyanate is disclosed in Patent Document 8, Patent Document 9, and the like. The isocyanurate type polyisocyanate is disclosed in Patent Document 10 and Patent Document 11. The allophanate type polyisocyanate is disclosed in Patent Document 12 and the like.

  However, when the electrolyte solution is solidified, the polymer matrix hinders the movement of ions, and the resistance of the battery is remarkably increased. For example, it is not suitable for a battery that requires a large current. Therefore, depending on the use of the battery, it may not be preferable to coexist an isocyanate compound and a compound that cures with the isocyanate compound in the electrolytic solution, and to cure them to solidify the electrolytic solution.

JP 2005-259641 A JP 2006-164759 A JP 2007-242411 A JP 2010-225522 A JP 2005-158703 A JP 2005-294020 A JP 2004-214041 A JP-A 63-174961 JP-A-8-225511 JP-A-63-57577 JP 57-47319 A JP-A-7-304724

This invention is made | formed in view of this background art, and is providing the nonaqueous electrolyte solution for secondary batteries excellent in long-term durability and load characteristics.
As a result of intensive studies in view of the above problems, the present inventor has found that in a non-aqueous electrolyte solution composed of an electrolyte and a non-aqueous solvent, one or more partial structures represented by the following general formula (1) in the molecule and an isocyanate group By including a specific amount of a compound having 2 or more, it was found that a non-aqueous electrolyte secondary battery with extremely excellent long-term durability and load characteristics can be realized, and the present invention has been completed.

That is, the gist of the present invention is a non-aqueous electrolyte solution for a non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of occluding and releasing metal ions, and a separator,
Wherein together with the non-aqueous electrolyte is an electrolyte and a nonaqueous solvent, the following formula in the molecule (1) a partial structure of one or more indicated, and a compound having two or more isocyanate groups 0.01% by mass or more, 1 It is a non-aqueous electrolyte solution for non-aqueous electrolyte secondary batteries characterized by containing 0.0 mass% or less .

Here, R represents an arbitrary element or group.
Another gist of the present invention is a non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting metal ions, and a separator, wherein the non-aqueous electrolyte is the non-aqueous electrolyte. A non-aqueous electrolyte secondary battery is provided.
One of the excellent effects of the present invention is to have two or more isocyanate groups. By blending such a compound into the electrolytic solution, a passive film derived from this partial structure is formed on the negative electrode surface, and the film is firmly bound on the negative electrode surface. As a result, reductive decomposition of the solvent can be effectively suppressed, and the effect can be maintained for a long time. In addition, since the partial structure represented by the formula (1) is included in the molecule, the above-described film becomes a film having a relatively high lithium ion conductivity, so that the charge transfer resistance is low, and excellent low-temperature discharge characteristics are obtained. Is possible. As described above, by blending the compound of the present invention in the electrolytic solution so that the electrolytic solution does not solidify, it is possible to achieve superior durability and load characteristics than using other disclosed isocyanate compounds. It becomes possible.

  According to the present invention, a passive film having a low resistance is formed on the electrode surface, the chemical stability of the substance in the battery is improved, and a secondary battery having excellent cycle characteristics and low-temperature discharge characteristics over a long period of time. It is possible to provide a non-aqueous electrolyte solution and a secondary battery for use.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of constituent elements described below is an example (representative example) of an embodiment of the present invention, and is not specified by these contents. Various modifications can be made within the scope of the gist.

<1-1. Electrolyte>
There is no restriction | limiting in the electrolyte used for the non-aqueous electrolyte of this invention, The well-known thing used as an electrolyte can be arbitrarily employ | adopted and contained in the target non-aqueous electrolyte secondary battery. When the non-aqueous electrolyte solution of the present invention is used in a non-aqueous electrolyte secondary battery, the electrolyte is preferably a lithium salt.

Specific examples of the electrolyte include inorganic lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , Li ₂ CO ₃ , and LiBF ₄ ;
LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄ (CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₃ (CF ₃ ), LiBF ₃ ( Fluorine-containing organic compounds such as C ₂ F ₅ ), LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ Lithium salt;

Lithium bis (oxalato) borate, lithium difluoro (oxalato) borate,
Dicarboxylic acid complex lithium salts such as lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate;
Sodium salts or potassium salts such as KPF ₆ , NaPF ₆ , NaBF ₄ , CF ₃ SO ₃ Na;
Etc.

Of these, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ or lithium bis (oxalato) borate are preferable, and LiPF ₆ or LiBF ₄ is preferred.
One type of electrolyte may be used alone, or two or more types of electrolytes may be used in any combination and ratio. In particular, when two types of specific inorganic lithium salts are used in combination, or when an inorganic lithium salt and a fluorine-containing organic lithium salt are used in combination, gas generation during continuous charging is suppressed, or deterioration after high-temperature storage is suppressed. preferable.

  The concentration of the lithium salt in the final composition of the non-aqueous electrolyte of the present invention is arbitrary as long as the effects of the present invention are not significantly impaired, but usually 0.5 mol / L or more, preferably 0.6 mol / L or more. More preferably, it is 0.8 mol / L or more, usually 3 mol / L or less, preferably 2 mol / L or less, more preferably 1.5 mol / L or less. If it is the said range, lithium which is a charged particle is not too little, and the viscosity of electrolyte solution can be made into a suitable range, and the electrical conductivity of electrolyte solution can fully be ensured.

<1-2. Non-aqueous solvent>
The non-aqueous solvent contained in the non-aqueous electrolyte of the present invention is not particularly limited as long as it is a solvent that does not adversely affect battery characteristics when used as a battery, but is used in the following non-aqueous electrolytes. One or more of the solvents are preferable. Examples of commonly used non-aqueous solvents include linear and cyclic carbonates, linear and cyclic carboxylic acid esters, linear and cyclic ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and the like.

  There is no restriction | limiting in the kind of chain carbonate, As an example of what is used normally, a dialkyl carbonate is preferable and carbon number of the alkyl group to comprise is preferable 1-5, respectively, Most preferably, it is 1-4. Specific examples include dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate and the like. Among these, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate are preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.

  There is no restriction | limiting in the kind of cyclic carbonate, As what is normally used, carbon number of the alkylene group which comprises cyclic carbonate has preferable 2-6, Most preferably, it is 2-4. Specific examples include ethylene carbonate, propylene carbonate, butylene carbonate (2-ethylethylene carbonate, cis and trans-2,3-dimethylethylene carbonate). Among these, ethylene carbonate or propylene carbonate is preferable in that various characteristics in the non-aqueous electrolyte secondary battery are good.

The type of chain carboxylate ester is not limited, and examples of commonly used ones include methyl acetate, ethyl acetate, acetic acid-n-propyl, acetic acid-i-propyl, acetic acid-n-butyl, acetic acid-i-butyl. , Acetate-t-butyl, methyl propionate, ethyl propionate, propionate-n-propyl, propionate-i-propyl, propionate-n-butyl, propionate-i-butyl, propionate-t-butyl, etc. Is mentioned. Among these, methyl acetate, ethyl acetate, methyl propionate, or ethyl propionate are preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.

Also, the type of cyclic carboxylic acid ester is not limited, but examples of commonly used ones include γ-butyrolactone, γ-valerolactone, δ-valerolactone, and the like. Among these, γ-butyrolactone is preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.
The type of chain ether is not limited, but examples of commonly used ones include dimethoxymethane, dimethoxyethane, diethoxymethane, diethoxyethane, ethoxymethoxymethane, and ethoxymethoxyethane. Among these, dimethoxyethane or diethoxyethane is preferable in terms of industrial availability and various characteristics in the non-aqueous electrolyte secondary battery.

Moreover, although there is no restriction | limiting in the kind of cyclic ether, Tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran etc. are mentioned as an example of what is used normally.
Although there is no restriction | limiting in particular also in the kind of phosphorus-containing organic solvent, As an example of what is used normally, phosphate esters, such as a trimethyl phosphate, a triethyl phosphate, and a triphenyl phosphate;
Phosphites such as trimethyl phosphite, triethyl phosphite and triphenyl phosphite; phosphine oxides such as trimethyl phosphine oxide, triethyl phosphine oxide and triphenyl phosphine oxide; and the like.

  The type of sulfur-containing organic solvent is not particularly limited, but examples of commonly used solvents include ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, sulfolane, and sulfolene. Dimethylsulfone, diphenylsulfone, methylphenylsulfone, dibutyldisulfide, dicyclohexyldisulfide, tetramethylthiuram monosulfide, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide and the like.

  Among these, chain and cyclic carbonates or chain and cyclic carboxylic acid esters are preferable in terms of various characteristics in the non-aqueous electrolyte secondary battery, and among them, ethylene carbonate, propylene carbonate, dimethyl carbonate, More preferred are ethyl methyl carbonate, diethyl carbonate, ethyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, methyl propionate, γ- Butyrolactone is more preferred.

  These may be used alone or in combination of two or more, but it is preferable to use two or more compounds in combination. For example, it is preferable to use a high dielectric constant solvent of cyclic carbonates in combination with a low viscosity solvent such as chain carbonates or chain esters. One preferred combination of non-aqueous solvents is a combination mainly composed of cyclic carbonates and chain carbonates. Among them, the total of the cyclic carbonates and the chain carbonates in the whole non-aqueous solvent is usually 80% by volume or more, preferably 85% by volume or more, more preferably 90% by volume or more, and the cyclic carbonates The capacity of the cyclic carbonates relative to the total of the chain carbonates is usually 5% by volume or more, preferably 10% by volume or more, more preferably 15% or more by volume, usually 50% capacity or less, preferably 40% or less, more Preferably it is 35% or less. Use of a combination of these non-aqueous solvents is preferable because the balance between cycle characteristics and high-temperature storage characteristics (particularly, remaining capacity and high-load discharge capacity after high-temperature storage) of a battery produced using the non-aqueous solvent is improved.

Specific examples of preferred combinations of cyclic carbonates and chain carbonates include ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate And ethyl methyl carbonate, ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

  A combination in which propylene carbonate is further added to the combination of these ethylene carbonates and chain carbonates is also a preferable combination. In the case of containing propylene carbonate, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99: 1 to 40:60, particularly preferably 95: 5 to 50:50. Furthermore, the amount of propylene carbonate in the whole non-aqueous solvent is usually 0.1% by volume or more, preferably 1% by volume, more preferably 2% by volume or more, usually 10% by volume or less, preferably 8% by volume or less, more Preferably, it is preferably 5% by volume or less because the discharge load characteristics are further excellent while maintaining the combination characteristics of ethylene carbonate and chain carbonates.

  Among these, those containing asymmetric chain carbonates are more preferable, particularly ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl. Those containing ethylene carbonate such as methyl carbonate, symmetric chain carbonates and asymmetric chain carbonates, or further containing propylene carbonate are preferred because of a good balance between cycle characteristics and discharge load characteristics. Among these, those in which the asymmetric chain carbonate is ethyl methyl carbonate are preferable, and the alkyl group constituting the dialkyl carbonate preferably has 1 to 2 carbon atoms.

  Another example of a preferable mixed solvent is one containing a chain ester. In particular, those containing a chain ester in the mixed solvent of cyclic carbonates and chain carbonates are preferable from the viewpoint of improving the discharge load characteristics of the battery. Examples of the chain esters include ethyl acetate and methyl propionate. Is particularly preferred. The volume of the chain ester in the non-aqueous solvent is usually 5% or more, preferably 8% or more, more preferably 15% or more, usually 50% or less, preferably 35% or less, more preferably Is 30% by volume or less, more preferably 25% by volume or less.

  Examples of other preferable non-aqueous solvents include one organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate and butylene carbonate, γ-butyrolactone and γ-valerolactone, or two or more selected from the group A mixed solvent composed of an organic solvent occupies 60% by volume or more of the whole. Such a mixed solvent preferably has a flash point of 50 ° C. or higher, and particularly preferably 70 ° C. or higher. A non-aqueous electrolyte using this solvent reduces evaporation of the solvent and leakage even when used at high temperatures. Among them, the total of ethylene carbonate and γ-butyrolactone in the non-aqueous solvent is usually 80% by volume or more, preferably 90% by volume or more, and the volume ratio of ethylene carbonate and γ-butyrolactone is 5:95 to 45%. Or a total of ethylene carbonate and propylene carbonate is usually 80% by volume or more, preferably 90% by volume or more, and the volume ratio of ethylene carbonate to propylene carbonate is 30:70 to 80:20 Use of a certain material generally improves the balance between cycle characteristics and discharge load characteristics.

<1-3. Compound having at least one partial structure represented by formula (1) and two or more isocyanate groups in the molecule>
The compound blended in the electrolytic solution used in the present invention has one or more partial structures represented by the following general formula (1) and two or more isocyanate groups in the molecule (hereinafter referred to as an isocyanate compound). Is).

Here, R represents an arbitrary element or group.
Furthermore, from the stability as an organic substance, it is preferable that one of the ends of the structure of the general formula (1) is bonded to a carbon atom, and the other is bonded to a nitrogen atom or an oxygen atom. preferable. R is preferably a group having hydrogen or an isocyanate group. From the viewpoint of ease of production, the compound of the present invention more preferably has one or more skeletons selected from uretdione, oxadiaditrione, biuret, urethane, allophanate and isocyanurate. Two or more of each skeleton may be contained in the molecule.

The compound of the present invention is characterized by having two or more isocyanate groups in the molecule, preferably 3 or more, and usually 15 or less, preferably 10 or less, more preferably 8
It is as follows. When the number of isocyanate groups in the molecule is in the above range, the stability of the film can be increased, and the increase in charge transfer resistance of the positive electrode due to the increase in functional groups can be prevented.

  In the manufacturing process, when the polyfunctionalization is promoted by reacting raw materials, the molecular weight is inevitably increased. However, there are several cases where the conventional simple compound has a higher molecular weight than conventional isocyanate compounds with a low molecular weight. The average molecular weight is usually 200 or more, preferably 300 or more, and usually 10,000 or less, preferably 5000 or less, more preferably 3000 or less, and still more preferably 2000 or less. When the number average molecular weight is in the above range, dissolution in the electrolytic solution tends to be ensured. For the same reason as above, the average number of functional groups is 2 or more, preferably 3 or more, and usually 12 or less, preferably 10 or less, more preferably 8 or less.

The terminal of the isocyanate group of the compound of the present invention is preferably bonded to an alkylene group from the viewpoint of cost of raw materials during production, ease of production, and durability of the film formed and bound, Is preferably 4 or more, preferably 12 or less, more preferably 8 or less.
The isocyanate compound used in the present invention also includes so-called blocked isocyanate, which is blocked with a blocking agent to enhance storage stability. Examples of the blocking agent include alcohols, phenols, organic amines, oximes, and lactams. Specific examples include n-butanol, phenol, tributylamine, diethylethanolamine, methyl ethyl ketoxime, and ε-caprolactam. Etc.
For the purpose of accelerating the reaction based on the isocyanate compound and obtaining a higher effect, a metal catalyst such as dibutyltin dilaurate or an amine catalyst such as 1,8-diazabicyclo [5.4.0] undecene-7 is used. Use in combination is also preferred.

The compound of this invention may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. Moreover, the aliphatic unisocyanate etc. which are unreacted raw materials may be contained. Some of these monomer components are undesirable in terms of worker safety and health, and it is preferable to use them by removing them within a range that does not adversely affect the human body. Furthermore, the compound of the present invention may contain a monoisocyanate compound. In particular, the addition of alkyl monoisocyanates has the effect of improving the low-temperature discharge characteristics.

  The concentration of the isocyanate compound in the composition of the non-aqueous electrolyte solution of the present invention is 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and less than 3% by mass, Preferably it is 2.7 mass% or less, More preferably, it is 2.5 mass% or less, More preferably, it is 1.5 mass% or less, Most preferably, it is the range of 0.8 mass% or less. If it is the said range, while being able to fully improve the chemical and physical stability in a battery, the excessive increase in resistance by film formation can be suppressed.

<1-4. Auxiliary>
In addition to the above-described electrolyte, non-aqueous solvent, and the compounds (A) and (B), an auxiliary may be appropriately added to the non-aqueous electrolyte of the present invention depending on the purpose. Examples of the auxiliary agent include cyclic carbonates having an unsaturated bond shown below, cyclic carbonates having fluorine atoms, unsaturated cyclic carbonates having fluorine atoms, overcharge inhibitors, and other auxiliary agents.

(Cyclic carbonate having an unsaturated bond)
The cyclic carbonate having an unsaturated bond (hereinafter sometimes abbreviated as “unsaturated cyclic carbonate”) also has an effect of improving the battery life because it forms a film on the negative electrode surface.
The unsaturated cyclic carbonate is not particularly limited as long as it is a cyclic carbonate having a carbon-carbon double bond and / or a carbon-carbon triple bond, and any unsaturated carbonate can be used. The cyclic carbonate having an aromatic ring is also included in the unsaturated cyclic carbonate.

Examples of the unsaturated cyclic carbonate include vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring, a carbon-carbon double bond or a carbon-carbon triple bond, phenyl carbonates, vinyl carbonates, allyl carbonates, Catechol carbonates, ethynyl carbonates, propargyl carbonate and the like can be mentioned.
As vinylene carbonates, vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate, 4 , 5-diallyl vinylene carbonate and the like.

  Specific examples of the ethylene carbonate substituted with a substituent having an aromatic ring, a carbon-carbon double bond or a carbon-carbon triple bond include vinyl ethylene carbonate, 4,5-divinylethylene carbonate, 4-methyl-5- Vinylethylene carbonate, 4-allyl-5-vinylethylene carbonate, phenylethylene carbonate, 4,5-diphenylethylene carbonate, 4-phenyl-5-vinylethylene carbonate, 4-allyl-5-phenylethylene carbonate, allylethylene carbonate, Examples include 4,5-diallyl ethylene carbonate, 4-methyl-5-allyl ethylene carbonate, ethynyl ethylene carbonate, propargyl ethylene carbonate, and the like.

Among them, particularly preferable unsaturated cyclic carbonates for use in combination with the compound of the present invention include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, vinyl vinylene carbonate, 4,5-vinyl vinylene carbonate, allyl vinylene carbonate. 4,5-diallyl vinylene carbonate, vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, 4-methyl-5-vinyl ethylene carbonate, allyl ethylene carbonate, 4,5-diallyl ethylene carbonate, 4-
Since methyl-5-allylethylene carbonate, 4-allyl-5-vinylethylene carbonate, and ethynylethylene carbonate form a stable interface protective film, they are more preferably used.

  The molecular weight of the unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 250 or less. If it is in the said range, it will be easy to ensure the solubility of the unsaturated cyclic carbonate with respect to non-aqueous electrolyte solution, and the effect of this invention will fully be easy to be expressed. The molecular weight of the unsaturated cyclic carbonate is more preferably 80 or more and 150 or less. The production method of the unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method.

  An unsaturated cyclic carbonate may be used individually by 1 type, or may have 2 or more types by arbitrary combinations and ratios. Moreover, the compounding quantity of unsaturated cyclic carbonate is not restrict | limited in particular, As long as the effect of this invention is not impaired remarkably, it is arbitrary. The blending amount of the unsaturated cyclic carbonate is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more in 100% by mass of the non-aqueous electrolyte solution. 5% by mass or less, preferably 4% by mass or less, more preferably 3% by mass or less. Within the above range, the cycle characteristics of the non-aqueous electrolyte secondary battery can be improved, and further, the decrease in the discharge capacity retention rate due to the decrease in the high temperature storage characteristics can be suppressed, while the resistance due to excessive film formation is reduced. Increase can be suppressed.

(Cyclic carbonate having a fluorine atom)
The number of fluorine atoms contained in the cyclic carbonate having fluorine atoms is not particularly limited as long as it is 1 or more. Among them, the number of fluorine atoms is usually 6 or less, preferably 4 or less, and most preferably 1 or 2 atoms.
Specific examples of the cyclic carbonate derivatives include fluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene. Carbonate, 4-fluoro-5-methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (trifluoromethyl) ) -Ethylene carbonate, 4- (fluoromethyl) -4-fluoroethylene carbonate, 4- (fluoromethyl) -5-fluoroethylene carbonate, 4-fluoro-4,5-dimethylethylene carbonate, 4,5 Difluoro-4,5-dimethylethylene carbonate, 4,4-difluoro-5,5-dimethylethylene carbonate,
Among them, particularly preferred fluorinated cyclic carbonates for use in combination with the compound of the present invention include fluoroethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4,4-difluoroethylene carbonate, and 4,5-difluoroethylene carbonate. Since an interface protective film is formed, it is more preferably used.

  The molecular weight of the fluorinated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 250 or less. If it is the said range, it will be easy to ensure the solubility of the fluorinated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention will be easy to be expressed. The production method of the fluorinated cyclic carbonate is not particularly limited, and any known method can be selected and produced. The molecular weight is more preferably 100 or more, and more preferably 200 or less.

A fluorinated cyclic carbonate may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios. Moreover, the compounding quantity of a fluorinated cyclic carbonate is not restrict | limited in particular, Unless the effect of this invention is impaired remarkably, it is arbitrary. The compounding amount of the fluorinated cyclic carbonate is usually 0.01% by mass or more, preferably 0.1% in 100% by mass of the non-aqueous electrolyte.
1 mass% or more, More preferably, it is 0.2 mass% or more, and is 90 mass% or less normally, Preferably it is 85 mass% or less, More preferably, it is 80 mass% or less. Within the above range, the cycle characteristics of the non-aqueous electrolyte secondary battery can be improved, and further, the decrease in the discharge capacity retention rate due to the decrease in the high temperature storage characteristics can be suppressed, while the excessive increase in resistance is suppressed. be able to.

  In particular, when fluorinated cyclic carbonate is used as a solvent, the blending amount is usually 5% by mass or more, preferably 7% by mass or more, more preferably 10% by mass or more, in 100% by mass of the nonaqueous electrolytic solution. Usually, it is 90 mass% or less, Preferably it is 70 mass% or less, More preferably, it is 50 mass% or less. By being in the above range, when the battery is operated at a high voltage, the secondary decomposition reaction of the non-aqueous electrolyte can be suppressed, the battery durability can be enhanced, and the electrical conductivity of the non-aqueous electrolyte is extremely low. Decline can be prevented.

(Fluorinated unsaturated cyclic carbonate)
As the fluorinated cyclic carbonate, it is also preferable to use a cyclic carbonate having an unsaturated bond and a fluorine atom (hereinafter sometimes abbreviated as “fluorinated unsaturated cyclic carbonate”). The number of fluorine atoms contained in the fluorinated unsaturated cyclic carbonate is not particularly limited as long as it is 1 or more. Among them, the number of fluorine atoms is usually 6 or less, preferably 4 or less, and most preferably 1 or 2 atoms.

Examples of the fluorinated unsaturated cyclic carbonate include fluorinated vinylene carbonate derivatives, fluorinated ethylene carbonate derivatives substituted with an aromatic ring or a substituent having a carbon-carbon double bond.
Fluorinated vinylene carbonate derivatives include 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, 4-fluoro-5- And vinyl vinylene carbonate.

  Examples of the fluorinated ethylene carbonate derivative substituted with an aromatic ring or a substituent having a carbon-carbon double bond include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5. -Vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4,4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate 4,5-difluoro-4-allylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4-fluoro-4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate 4,5-diflu B-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4- Examples thereof include phenylethylene carbonate.

Among them, particularly preferred fluorinated unsaturated cyclic carbonates for use in combination with the compounds of the present invention include 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, 4- Allyl-5-fluorovinylene carbonate, 4-fluoro-4-vinylethylene carbonate, 4-fluoro-4-allylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, 4-fluoro-5-allylethylene carbonate, 4, 4-difluoro-4-vinylethylene carbonate, 4,4-difluoro-4-allylethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4,5-difluoro-4-allylethylene carbonate, 4-fluoro- , 5-vinyl ethylene carbonate, 4-fluoro -
Since 4,5-diallylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-diallylethylene carbonate forms a stable interface protective film, it is more preferable. Used.

  The molecular weight of the fluorinated unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is preferably 50 or more and 250 or less. If it is the said range, it will be easy to ensure the solubility of the fluorinated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention will be easy to be expressed. The production method of the fluorinated unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method. The molecular weight is more preferably 100 or more, and more preferably 200 or less.

  A fluorinated unsaturated cyclic carbonate may be used individually by 1 type, and may have 2 or more types by arbitrary combinations and ratios. Moreover, the compounding quantity of a fluorinated unsaturated cyclic carbonate is not restrict | limited in particular, As long as the effect of this invention is not impaired remarkably, it is arbitrary. The blending amount of the fluorinated unsaturated cyclic carbonate is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more in 100% by mass of the non-aqueous electrolyte. Moreover, it is 5 mass% or less normally, Preferably it is 4 mass% or less, More preferably, it is 3 mass% or less. Within the above range, the cycle characteristics of the non-aqueous electrolyte secondary battery can be improved, and further, the decrease in the discharge capacity retention rate due to the decrease in the high temperature storage characteristics can be suppressed, while the resistance increase due to excessive film formation Can be suppressed.

(Overcharge prevention agent)
In the non-aqueous electrolyte solution of the present invention, an overcharge inhibitor can be used in order to effectively suppress battery explosion / ignition when the non-aqueous electrolyte secondary battery is in an overcharged state or the like. .
As an overcharge inhibitor, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; 2-fluorobiphenyl, Partially fluorinated products of the above aromatic compounds such as o-cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and the like And a fluorine-containing anisole compound. Of these, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, terphenyl partially hydrogenated, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferable. These may be used alone or in combination of two or more. When two or more kinds are used in combination, in particular, a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene, biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, Using at least one selected from aromatic compounds not containing oxygen, such as t-amylbenzene, and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether, dibenzofuran, and the like is an overcharge prevention property and a high temperature storage property. From the standpoint of balance.

  The amount of the overcharge inhibitor is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The overcharge inhibitor is usually 0.1% by mass or more and usually 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. Further, it is preferably 0.2% by mass or more, more preferably 0.3% by mass or more, further preferably 0.5% by mass or more, and preferably 3% by mass or less, more preferably 2% by mass or less. is there. If it is the said range, the overcharge prevention effect can fully be aimed at, On the other hand, battery characteristics, such as a high temperature storage characteristic, can be ensured.

<Other auxiliaries>
Other known auxiliary agents can be used in the non-aqueous electrolyte solution of the present invention. Other auxiliary agents include lithium monofluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, lithium fluorosulfonate, trifluoromethanesulfonic acid Examples of the lithium salt include lithium, lithium bis (oxalato) borate, lithium difluorooxalatoborate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, and lithium tetrafluorooxalatophosphate. By adding these auxiliaries, cycle characteristics and low-temperature discharge characteristics can be improved.

  Further, as an auxiliary capable of improving capacity maintenance characteristics and cycle characteristics after high temperature storage, carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; succinic anhydride, anhydrous glutar Carboxylic anhydrides such as acid, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride and phenylsuccinic anhydride; Spiro compounds such as 2,4,8,10-tetraoxaspiro [5.5] undecane and 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane; ethylene sulfite; 1,3-propane sultone, 1-fluoro-1,3-propa Sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-propene-1,3-sultone, 1-fluoro-1-propene-1,3-sultone, 2- Fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1,4-butane sultone, 1-butene-1,4-sultone, 3-butene-1,4- Sulfur, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, sulfolene, diphenylsulfone, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide, etc. Compound: 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazo Ninone-containing compounds such as dinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide, succinonitrile, adiponitrile, and pimelonitrile; hydrocarbon compounds such as heptane, octane, nonane, decane, cycloheptane, fluorobenzene And fluorine-containing aromatic compounds such as difluorobenzene, hexafluorobenzene and benzotrifluoride. These auxiliary agents may be used alone or in combination of two or more.

  The blending amount of other auxiliary agents is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The other auxiliary agent is usually 0.01% by mass or more and usually 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. The blending amount of other auxiliaries is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and preferably 3% by mass or less, more preferably 1% by mass or less. If it is the said range, the bad influence to a battery can be suppressed, fully exhibiting the effect of an adjuvant.

  The non-aqueous electrolyte solution described above includes those existing inside the non-aqueous electrolyte battery according to the present invention. Specifically, the components of the non-aqueous electrolyte such as lithium salt, solvent, and auxiliary agent are separately synthesized, and the non-aqueous electrolyte is prepared from the substantially isolated one by the method described below. In the case of a nonaqueous electrolyte solution in a nonaqueous electrolyte battery obtained by pouring into a separately assembled battery, the components of the nonaqueous electrolyte solution of the present invention are individually placed in the battery, In order to obtain the same composition as the non-aqueous electrolyte solution of the present invention by mixing in a non-aqueous electrolyte battery, the compound constituting the non-aqueous electrolyte solution of the present invention is further generated in the non-aqueous electrolyte battery. The case where the same composition as the aqueous electrolyte is obtained is also included.

[2. Non-aqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery of the present invention comprises a negative electrode and a positive electrode that can occlude and release ions, and the non-aqueous electrolyte of the present invention.
<2-1. Battery configuration>
The non-aqueous electrolyte secondary battery of the present invention is the same as the conventionally known non-aqueous electrolyte secondary battery except for the non-aqueous electrolyte, and is usually impregnated with the non-aqueous electrolyte of the present invention. The positive electrode and the negative electrode are laminated via a porous film (separator), and these are housed in a case (exterior body). Therefore, the shape of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

<2-2. Non-aqueous electrolyte>
As the non-aqueous electrolyte, the above-described non-aqueous electrolyte of the present invention is used. In addition, in the range which does not deviate from the meaning of this invention, it is also possible to mix | blend and use other nonaqueous electrolyte solutions with respect to the nonaqueous electrolyte solution of this invention.
<2-3. Negative electrode>
The negative electrode active material used for the negative electrode is described below. The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and the like. These may be used individually by 1 type, and may be used together combining 2 or more types arbitrarily.

(Negative electrode active material)
Examples of the negative electrode active material include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and the like.
As a carbonaceous material used as a negative electrode active material,
(1) natural graphite,
(2) a carbonaceous material obtained by heat-treating an artificial carbonaceous material and an artificial graphite material at least once in the range of 400 to 3200 ° C;
(3) a carbonaceous material in which the negative electrode active material layer is made of carbonaceous materials having at least two or more different crystallinities and / or has an interface in contact with the different crystalline carbonaceous materials,
(4) A carbonaceous material in which the negative electrode active material layer is made of carbonaceous materials having at least two or more different orientations and / or has an interface in contact with the carbonaceous materials having different orientations,
Is preferably a good balance between initial irreversible capacity and high current density charge / discharge characteristics. Moreover, the carbonaceous materials (1) to (4) may be used alone or in combination of two or more in any combination and ratio.

  Examples of the artificial carbonaceous material and artificial graphite material of (2) above include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, those obtained by oxidizing these pitches, needle coke, pitch coke and Carbon materials that are partially graphitized, furnace black, acetylene black, organic pyrolysis products such as pitch-based carbon fibers, carbonizable organic materials and their carbides, or carbonizable organic materials are benzene, toluene, xylene, quinoline And a solution dissolved in a low-molecular organic solvent such as n-hexane, and carbides thereof.

  As an alloy material used as the negative electrode active material, as long as lithium can be occluded / released, lithium alone, simple metals and alloys forming lithium alloys, or oxides, carbides, nitrides, silicides, sulfides thereof Any of compounds such as products or phosphides may be used and is not particularly limited. The single metal and alloy forming the lithium alloy are preferably materials containing group 13 and group 14 metal / metalloid elements (that is, excluding carbon), more preferably aluminum, silicon and tin (hereinafter referred to as “ Simple metals) and alloys or compounds containing these atoms (sometimes abbreviated as “specific metal elements”). These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  As a negative electrode active material having at least one kind of atom selected from a specific metal element, a metal simple substance of any one specific metal element, an alloy composed of two or more specific metal elements, one type or two or more specific types Alloys comprising metal elements and one or more other metal elements, as well as compounds containing one or more specific metal elements, and oxides, carbides, nitrides and silicides of the compounds And composite compounds such as sulfides or phosphides. By using these simple metals, alloys or metal compounds as the negative electrode active material, the capacity of the battery can be increased.

  In addition, a compound in which these complex compounds are complexly bonded to several kinds of elements such as a simple metal, an alloy, or a nonmetallic element is also included. Specifically, for example, in silicon and tin, an alloy of these elements and a metal that does not operate as a negative electrode can be used. For example, in the case of tin, a complex compound containing 5 to 6 kinds of elements in combination with a metal that acts as a negative electrode other than tin and silicon, a metal that does not operate as a negative electrode, and a nonmetallic element may be used. it can.

  Among these negative electrode active materials, since the capacity per unit mass is large when a battery is formed, any one simple metal of a specific metal element, an alloy of two or more specific metal elements, oxidation of a specific metal element In particular, silicon and / or tin metal simple substance, alloy, oxide, carbide, nitride and the like are preferable from the viewpoint of capacity per unit mass and environmental load.

  The lithium-containing metal composite oxide material used as the negative electrode active material is not particularly limited as long as it can occlude and release lithium, but a material containing titanium and lithium is preferable from the viewpoint of high current density charge / discharge characteristics, A lithium-containing composite metal oxide material containing titanium is more preferable, and a composite oxide of lithium and titanium (hereinafter sometimes abbreviated as “lithium titanium composite oxide”) is more preferable. That is, it is particularly preferable to use a lithium titanium composite oxide having a spinel structure in a negative electrode active material for a non-aqueous electrolyte secondary battery because the output resistance is greatly reduced.

  In addition, lithium or titanium of the lithium titanium composite oxide is at least selected from the group consisting of other metal elements such as Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. Those substituted with one element are also preferred. The metal oxide is a lithium titanium composite oxide represented by the general formula (A). In the general formula (A), 0.7 ≦ x ≦ 1.5, 1.5 ≦ y ≦ 2.3, It is preferable that 0 ≦ z ≦ 1.6 because the structure upon doping and dedoping of lithium ions is stable.

LixTiyMzO4 (A)
[In the general formula (A), M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. ]
Among the compositions represented by the general formula (A),
(A) 1.2 ≦ x ≦ 1.4, 1.5 ≦ y ≦ 1.7, z = 0
(B) 0.9 ≦ x ≦ 1.1, 1.9 ≦ y ≦ 2.1, z = 0
(C) 0.7 ≦ x ≦ 0.9, 2.1 ≦ y ≦ 2.3, z = 0
This structure is particularly preferable because of a good balance of battery performance.
Particularly preferred representative compositions of the above compounds are Li4 / 3Ti5 / 3O4 in (a), Li1Ti2O4 in (b), and Li4 / 5Ti11 / 5O4 in (c). As for the structure of Z ≠ 0, for example, Li4 / 3Ti4 / 3Al1 / 3O4 is preferable.

<Physical properties of carbonaceous materials>
When using a carbonaceous material as a negative electrode active material, it is desirable to have the following physical properties.

(X-ray parameters)
The d value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction by the Gakushin method of carbonaceous materials is preferably 0.335 nm or more, and is usually 0.360 nm or less. 350 nm or less is preferable, and 0.345 nm or less is more preferable. Further, the crystallite size (Lc) of the carbonaceous material obtained by X-ray diffraction by the Gakushin method is preferably 1.0 nm or more, and more preferably 1.5 nm or more.

(Volume-based average particle size)
The volume-based average particle diameter of the carbonaceous material is a volume-based average particle diameter (median diameter) obtained by a laser diffraction / scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and 7 μm. The above is particularly preferable, and is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, further preferably 30 μm or less, and particularly preferably 25 μm or less.

When the volume-based average particle size is in the above range, the loss of the initial battery capacity due to the increase in irreversible capacity can be suppressed, and uniform electrode application is possible when the electrode preparation step by application is included.
The volume-based average particle size is measured by dispersing carbon powder in a 0.2% by weight aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction / scattering particle size distribution. This can be performed using a meter (LA-700 manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the carbonaceous material of the present invention.

(Raman R value, Raman half width)
The Raman R value of the carbonaceous material is a value measured using an argon ion laser Raman spectrum method, and is usually 0.01 or more, preferably 0.03 or more, more preferably 0.1 or more, and usually 1.5 or less, preferably 1.2 or less, more preferably 1 or less, and particularly preferably 0.5 or less.

Further, the Raman half-width in the vicinity of 1580 cm −1 of the carbonaceous material is not particularly limited, but is usually 10 cm −1 or more, preferably 15 cm −1 or more, and usually 100 cm −1 or less, and 80 cm −1 or less. Preferably, it is more preferably 60 cm-1 or less, and particularly preferably 40 cm-1 or less.
The Raman R value and the Raman half-value width are indices indicating the crystallinity of the surface of the carbonaceous material, but the carbonaceous material has an appropriate crystallinity from the viewpoint of chemical stability, while the interlayer in which Li enters by charge / discharge. It is preferable that the crystallinity is such that it does not disappear. In the case where the density of the negative electrode is increased by press after applying to the current collector, it is preferable to take account of this because crystals tend to be oriented in a direction parallel to the electrode plate.

When the Raman R value or the Raman half-value width is in the above range, the reaction between the carbonaceous material and the nonaqueous electrolytic solution can be suppressed, and the deterioration of the load characteristics due to the disappearance of the site can be suppressed.
The measurement of the Raman spectrum, using a Raman spectrometer (manufactured by JASCO Corporation Raman spectrometer), the sample is naturally dropped into the measurement cell and filled, and while irradiating the sample surface in the cell with argon ion laser light, This is done by rotating the cell in a plane perpendicular to the laser beam. For the obtained Raman spectrum, the intensity IA of the peak PA near 1580 cm −1 and the intensity IB of the peak PB near 1360 cm −1 are measured, and the intensity ratio R (R = IB / IA) is calculated. The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material of the present invention. Further, the half width of the peak PA near 1580 cm −1 of the obtained Raman spectrum is measured, and this is defined as the Raman half width of the carbonaceous material of the present invention.

Moreover, said Raman measurement conditions are as follows.
Argon ion laser wavelength: 514.5nm
・ Laser power on the sample: 15-25mW
・ Resolution: 10-20cm-1
Measurement range: 1100 cm-1 to 1730 cm-1
・ Raman R value, Raman half width analysis: Background processing
-Smoothing processing: Simple average, 5 points of convolution

(BET specific surface area)
The BET specific surface area of the carbonaceous material is a value of the specific surface area measured using the BET method, and is usually 0.1 m 2 · g −1 or more, preferably 0.7 m 2 · g −1 or more, and 1.0 m 2. g-1 or more is more preferable, 1.5 m2 · g-1 or more is particularly preferable, and usually 100 m2 · g-1 or less, preferably 25 m2 · g-1 or less, more preferably 15 m2 · g-1 or less. 10 m 2 · g −1 or less is particularly preferable.

When the value of the BET specific surface area is in the above range, precipitation of lithium on the electrode surface can be suppressed, while gas generation due to reaction with the non-aqueous electrolyte can be suppressed.
The specific surface area was measured by the BET method using a surface area meter (a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 350 ° C. for 15 minutes under nitrogen flow, Using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure becomes 0.3, the nitrogen adsorption BET one-point method by the gas flow method is used. The specific surface area determined by the measurement is defined as the BET specific surface area of the carbonaceous material of the present invention.

(Roundness)
When the circularity is measured as the degree of the sphere of the carbonaceous material, it is preferably within the following range. The circularity is defined as “circularity = (peripheral length of an equivalent circle having the same area as the particle projection shape) / (actual perimeter of the particle projection shape)”, and is theoretical when the circularity is 1. Become a true sphere. The circularity of the particles having a particle size of 3 to 40 μm in the range of the carbonaceous material is desirably closer to 1, and is preferably 0.1 or more, more preferably 0.5 or more, and more preferably 0.8 or more, 0.85 or more is more preferable, and 0.9 or more is particularly preferable.

The greater the degree of circularity of the carbonaceous material, the better the filling property and the resistance between particles, so that the high current density charge / discharge characteristics are improved. Therefore, it is preferable that the circularity is as high as the above range.
The circularity is measured using a flow type particle image analyzer (FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample was dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. The detection range is specified as 0.6 to 400 μm, and the particle size is measured in the range of 3 to 40 μm. The circularity determined by the measurement is defined as the circularity of the carbonaceous material of the present invention.

  The method for improving the circularity is not particularly limited, but a sphere-shaped sphere is preferable because the shape of the interparticle void when the electrode body is formed is preferable. Examples of spheroidizing treatment include a method of mechanically approaching a sphere by applying a shearing force and a compressive force, a mechanical / physical processing method of granulating a plurality of fine particles by the binder or the adhesive force of the particles themselves, etc. Is mentioned.

(Tap density)
The tap density of the carbonaceous material is usually 0.1 g · cm −3 or more, preferably 0.5 g · cm −3 or more, more preferably 0.7 g · cm −3 or more, and 1 g · cm −3 or more. Particularly preferable, 2 g · cm −3 or less is preferable, 1.8 g · cm −3 or less is more preferable, and 1.6 g · cm −3 or less is particularly preferable. When the tap density is in the above range, battery capacity can be ensured and increase in resistance between particles can be suppressed.

  The tap density is measured by passing a sieve having a mesh opening of 300 μm, dropping the sample onto a 20 cm 3 tapping cell and filling the sample to the upper end surface of the cell, and then measuring a powder density measuring instrument (for example, a tap manufactured by Seishin Enterprise Co., Ltd.). Using a denser, tapping with a stroke length of 10 mm is performed 1000 times, and the tap density is calculated from the volume at that time and the mass of the sample. The tap density calculated by the measurement is defined as the tap density of the carbonaceous material of the present invention.

(Orientation ratio)
The orientation ratio of the carbonaceous material is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less. When the orientation ratio is in the above range, excellent high-density charge / discharge characteristics can be ensured. The upper limit of the above range is the theoretical upper limit value of the orientation ratio of the carbonaceous material.
The orientation ratio is measured by X-ray diffraction after pressure-molding the sample. Set the molded body obtained by filling 0.47 g of the sample into a molding machine with a diameter of 17 mm and compressing it with 58.8MN · m-2 so that it is flush with the surface of the sample holder for measurement. X-ray diffraction is measured. From the (110) diffraction and (004) diffraction peak intensities of the obtained carbon, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated. The orientation ratio calculated by the measurement is defined as the orientation ratio of the carbonaceous material of the present invention.

The X-ray diffraction measurement conditions are as follows. “2θ” indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator ・ Slit:
Divergence slit = 0.5 degree Light receiving slit = 0.15 mm
Scattering slit = 0.5 degree / measurement range and step angle / measurement time:
(110) plane: 75 degrees ≦ 2θ ≦ 80 degrees 1 degree / 60 seconds (004) plane: 52 degrees ≦ 2θ ≦ 57 degrees 1 degree / 60 seconds

(Aspect ratio (powder))
The aspect ratio of the carbonaceous material is usually 1 or more and usually 10 or less, preferably 8 or less, and more preferably 5 or less. When the aspect ratio is in the above range, streaking at the time of forming an electrode plate is suppressed, and further uniform coating becomes possible, so that excellent high current density charge / discharge characteristics can be ensured. The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the carbonaceous material.

  The aspect ratio is measured by magnifying and observing the carbonaceous material particles with a scanning electron microscope. Carbonaceous material particles when three-dimensional observation is performed by selecting arbitrary 50 graphite particles fixed to the end face of a metal having a thickness of 50 μm or less and rotating and tilting the stage on which the sample is fixed. The longest diameter A and the shortest diameter B orthogonal thereto are measured, and the average value of A / B is obtained. The aspect ratio (A / B) obtained by the measurement is defined as the aspect ratio of the carbonaceous material of the present invention.

(Mixed with secondary materials)
The sub-material mixing means that two or more types of carbonaceous materials having different properties are contained in the negative electrode and / or the negative electrode active material. The properties referred to here are selected from the group consisting of X-ray diffraction parameters, median diameter, aspect ratio, BET specific surface area, orientation ratio, Raman R value, tap density, true density, pore distribution, circularity, and ash content. Shows more than one characteristic.
As a particularly preferred example of mixing these secondary materials, the volume-based particle size distribution is not symmetrical when centered on the median diameter, containing two or more carbonaceous materials having different Raman R values, And X-ray parameters are different.
As an example of the effect of the admixture of secondary materials, carbonaceous material such as graphite (natural graphite, artificial graphite), carbon black such as acetylene black, and amorphous carbon such as needle coke is contained as a conductive material. Reducing electrical resistance.

  When mixing a conductive material as a secondary material mixture, one type may be mixed alone, or two or more types may be mixed in any combination and ratio. The mixing ratio of the conductive material to the carbonaceous material is usually 0.1% by mass or more and 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 45% by mass or less. Yes, 40 mass% or less is preferable. When the mixing ratio is in the above range, the effect of reducing electric resistance can be secured and an increase in initial irreversible capacity can be suppressed.

<2-4. Structure of Negative Electrode and Preparation Method Negative Electrode>
Any known method can be used for producing the electrode as long as the effects of the present invention are not significantly impaired. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to a negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can do.
In the case of using an alloy-based material, a method of forming a thin film layer (negative electrode active material layer) containing the above-described negative electrode active material by a technique such as vapor deposition, sputtering, or plating is also used.

(Current collector)
As the current collector for holding the negative electrode active material, a known material can be arbitrarily used. Examples of the current collector for the negative electrode include metal materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. Copper is particularly preferable from the viewpoint of ease of processing and cost.
In addition, the shape of the current collector may be, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, or the like when the current collector is a metal material. Among them, a metal thin film is preferable, a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable, and both can be used as a current collector.
The thickness of the current collector is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less, from the viewpoint of securing battery capacity and handling properties.

(Thickness ratio between current collector and negative electrode active material layer)
The ratio of the thickness of the current collector to the negative electrode active material layer is not particularly limited, but the value of “(the thickness of the negative electrode active material layer on one side immediately before the nonaqueous electrolyte injection) / (thickness of the current collector)” However, 150 or less is preferable, 20 or less is more preferable, 10 or less is particularly preferable, 0.1 or more is preferable, 0.4 or more is more preferable, and 1 or more is particularly preferable. When the ratio of the thickness of the current collector to the negative electrode active material layer is in the above range, battery capacity can be secured and heat generation of the current collector during high current density charge / discharge can be suppressed.

(Binder)
The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used in manufacturing the electrode.
Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, polyimide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, Rubber polymers such as NBR (acrylonitrile / butadiene rubber) and ethylene / propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / Thermoplastic elastomeric polymers such as ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers or hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate , Soft resinous polymers such as ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer, etc. And a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions). These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  The ratio of the binder to the negative electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, particularly preferably 0.6% by mass or more, and preferably 20% by mass or less, 15% by mass. The following is more preferable, 10% by mass or less is further preferable, and 8% by mass or less is particularly preferable. When the ratio of the binder with respect to a negative electrode active material exceeds the said range, the binder ratio from which the amount of binders does not contribute to battery capacity may increase, and the fall of battery capacity may be caused. On the other hand, below the above range, the strength of the negative electrode may be reduced.

  In particular, when a rubbery polymer typified by SBR is contained as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and 0 .6% by mass or more is more preferable, usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. When the main component contains a fluorine-based polymer typified by polyvinylidene fluoride, the ratio to the negative electrode active material is usually 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more. It is preferably 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

(Slurry forming solvent)
The solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive material used as necessary. Alternatively, either an aqueous solvent or an organic solvent may be used.
Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N, N- Examples include dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, and the like.
In particular, when an aqueous solvent is used, it is preferable to add a dispersant or the like in addition to the thickener and slurry it using a latex such as SBR. In addition, these solvents may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

(Thickener)
A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  Further, when using a thickener, the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, Moreover, it is 5 mass% or less normally, 3 mass% or less is preferable, and 2 mass% or less is more preferable. When the ratio of the thickener to the negative electrode active material is within the above range, it is possible to suppress a decrease in battery capacity and an increase in resistance, and it is possible to ensure appropriate applicability.

(Electrode density)
The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g · cm −3 or more, and 1.2 g · cm −3 or more. Is more preferably 1.3 g · cm −3 or more, preferably 2.2 g · cm −3 or less, more preferably 2.1 g · cm −3 or less, and 2.0 g · cm −3 or less. Further preferred is 1.9 g · cm −3 or less. When the density of the negative electrode active material existing on the current collector is in the above range, the negative electrode active material particles are prevented from being destroyed, and an increase in initial irreversible capacity or to the vicinity of the current collector / negative electrode active material interface. While the deterioration of the high current density charge / discharge characteristics due to the reduced permeability of the non-aqueous electrolyte solution can be suppressed, the decrease in battery capacity and the increase in resistance can be suppressed.

(Thickness of negative electrode plate)
The thickness of the negative electrode plate is designed according to the positive electrode plate to be used, and is not particularly limited. However, the thickness of the composite layer obtained by subtracting the thickness of the metal foil of the core is usually 15 μm or more, preferably 20 μm or more. More preferably, it is 30 μm or more, and usually 300 μm or less, preferably 280 μm or less, more preferably 250 μm or less.

(Surface coating of negative electrode plate)
Moreover, you may use what adhered the substance of the composition different from this to the surface of the said negative electrode plate. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.

<2-5. Positive electrode>
(Positive electrode active material)
The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. For example, a material containing lithium and at least one transition metal is preferable. Specific examples include lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.

  V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable as the transition metal of the lithium transition metal composite oxide. Specific examples include lithium-cobalt composite oxides such as LiCoO2 and lithium- Nickel composite oxides, lithium manganese composite oxides such as LiMnO2, LiMn2O4, Li2MnO4, and some of transition metal atoms that are the main components of these lithium transition metal composite oxides are Al, Ti, V, Cr, Mn, Fe, Examples include those substituted with other metals such as Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and Si. Specific examples of the substituted ones include, for example, LiNi0.5Mn0.5O2, LiNi0.85Co0.10Al0.05O2, LiNi0.33Co0.33Mn0.33O2, LiMn1.8Al0.2O4, LiMn1.5Ni0.5O4, and the like.

As the transition metal of the lithium-containing transition metal phosphate compound, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable. Specific examples include, for example, LiFePO4, Li3F.
e2 (PO4) 3, iron phosphates such as LiFeP2O7, cobalt phosphates such as LiCoPO4, and some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn , Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and the like substituted with other metals.

(Surface coating)
Moreover, you may use what the substance of the composition different from this adhered to the surface of the said positive electrode active material. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

  For example, these surface adhering substances are dissolved or suspended in a solvent, impregnated and added to the positive electrode active material, and dried. After the surface adhering substance precursor is dissolved or suspended in a solvent and impregnated and added to the positive electrode active material, It can be made to adhere to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing simultaneously. In addition, when making carbon adhere, the method of making carbonaceous adhere mechanically later in the form of activated carbon etc. can also be used, for example.

The amount of the surface adhering substance is by mass with respect to the positive electrode active material, preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, and the upper limit, preferably 20% or less, more preferably, as the lower limit. Is used at 10% or less, more preferably 5% or less. The surface adhering substance can suppress the oxidation reaction of the electrolytic solution on the surface of the positive electrode active material, and can improve the battery life. Within the above range, the resistance associated with the inhibition of the entry and exit of lithium ions can be suppressed, while the above effect can be sufficiently exhibited.
In the present invention, a material in which a material having a different composition is attached to the surface of the positive electrode active material is also referred to as “positive electrode active material”.

(shape)
Examples of the shape of the positive electrode active material particles include a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, and a column shape, which are conventionally used. It is preferable that the secondary particles have a spherical shape or an elliptical shape. In general, an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken. Therefore, it is preferable that the primary particles are aggregated to form secondary particles, rather than a single particle active material having only primary particles, in order to relieve expansion and contraction stress and prevent deterioration. In addition, spherical or oval spherical particles are less oriented during molding of the electrode than plate-like equiaxed particles, so that the expansion and contraction of the electrode during charging and discharging is small, and the electrode is produced. The mixing with the conductive material is also preferable because it is easy to mix uniformly.

(Tap density)
The tap density of the positive electrode active material is preferably 0.5 g / cm 3 or more, more preferably 1.0 g / cm 3 or more, still more preferably 1.5 g / cm 3 or more, and most preferably 1.7 g / cm 3 or more. When the tap density of the positive electrode active material is within the above range, it is possible to suppress the amount of dispersion medium and the necessary amount of conductive material and binder required at the time of forming the positive electrode active material layer. Battery capacity can be secured. . By using a complex oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. In general, the tap density is preferably as large as possible, and there is no particular upper limit, but it is preferably 2.7 g / cm 3 or less, more preferably 2.5 g / cm 3 or less. When it is within the above range, it is possible to suppress a decrease in load characteristics.
In the present invention, the tap density is defined as the powder packing density (tap density) g / cc when 5 to 10 g of the positive electrode active material powder is put in a 10 ml glass measuring cylinder and tapped 200 times with a stroke of about 20 mm. Ask.

(Median diameter d50)
The median diameter d50 of the positive electrode active material particles (secondary particle diameter when primary particles are aggregated to form secondary particles) is preferably 0.3 μm or more, more preferably 1.2 μm or more, and even more preferably. Is 1.5 μm or more, most preferably 2 μm or more, and the upper limit is preferably 20 μm or less, more preferably 18 μm or less, still more preferably 16 μm or less, and most preferably 15 μm or less. Within the above range, a high tap density product can be obtained and the battery performance can be prevented from decreasing. On the other hand, when forming a positive electrode for a battery, that is, when slurrying an active material, a conductive material, a binder, etc. with a solvent, It is possible to prevent problems such as drawing streaks. Here, by mixing two or more kinds of the positive electrode active materials having different median diameters d50, it is possible to further improve the filling property when forming the positive electrode.
In the present invention, the median diameter d50 is measured by a known laser diffraction / scattering particle size distribution measuring device. When LA-920 manufactured by HORIBA is used as a particle size distribution meter, a 0.1% by mass sodium hexametaphosphate aqueous solution is used as a dispersion medium for measurement, and a measurement refractive index of 1.24 is set after ultrasonic dispersion for 5 minutes. Measured.

(Average primary particle size)
When primary particles are aggregated to form secondary particles, the average primary particle diameter of the positive electrode active material is preferably 0.05 μm or more, more preferably 0.1 μm or more, and still more preferably 0.8 μm. The upper limit is preferably 2 μm or less, more preferably 1.6 μm or less, still more preferably 1.3 μm or less, and most preferably 1 μm or less. When it is in the above range, powder filling property and specific surface area can be secured and deterioration of battery performance can be suppressed, while reversibility of charge and discharge can be secured by obtaining appropriate crystallinity. .
In the present invention, the primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done.

(BET specific surface area)
The BET specific surface area of the positive electrode active material is preferably 0.4 m 2 / g or more, more preferably 0.5 m 2 / g or more, still more preferably 0.6 m 2 / g or more, and the upper limit is 50 m 2 / g or less, preferably 40 m 2. / G or less, more preferably 30 m2 / g or less. When the BET specific surface area is in the above range, the battery performance can be secured and the applicability of the positive electrode active material can be kept good.
In the present invention, the BET specific surface area is determined by using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 150 ° C. for 30 minutes under nitrogen flow, and then atmospheric pressure. This is defined as a value measured by a nitrogen adsorption BET one-point method using a gas flow method, using a nitrogen-helium mixed gas accurately adjusted so that the value of the relative pressure of nitrogen to 0.3 is 0.3.

(Method for producing positive electrode active material)
As a manufacturing method of the positive electrode active material, a general method is used as a manufacturing method of the inorganic compound. In particular, various methods are conceivable for producing a spherical or elliptical active material. For example, a phosphorus raw material such as phosphoric acid and a raw material M of the composition formula (1) are dissolved in a solvent such as water. Or, pulverize and disperse, adjust the pH while stirring, create and recover a spherical precursor, dry it if necessary, and then add Li source such as LiOH, Li2CO3, LiNO3 and calcinate at high temperature To obtain an active material.

  For the production of the positive electrode, the positive electrode active material of the composition formula (1) and / or the positive electrode active material of the composition formula (1) coated with the surface adhesion material may be used alone, or one or more of different compositions And may be used in any combination or ratio. Preferred combinations in this case include LiMn2O4 or a combination with a part of this Mn substituted with another transition metal or the like, or LiCoO2 or a part of this Co substituted with another transition metal or the like Combinations are listed. Here, the positive electrode active material of the composition formula (1) and / or the positive electrode active material of the composition formula (1) coated with the surface adhesion material is preferably 30% by mass or more of the whole positive electrode active material, More preferably, it is at least mass%. When the usage rate of the positive electrode active material of the composition formula (1) and / or the positive electrode active material of the composition formula (1) coated with the surface adhering material decreases, the battery capacity may be reduced. The “positive electrode active material of composition formula (1) and / or the positive electrode active material of composition formula (1) coated with the surface adhering material” and “the positive electrode active material of composition formula (1) and / or the surface adhering”. The “positive electrode active material other than the positive electrode active material of the composition formula (1) coated with the material” is collectively referred to as “positive electrode active material”.

<2-6. Structure and manufacturing method of positive electrode>
The structure of the positive electrode will be described below. In the present invention, the positive electrode can be produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector. Manufacture of the positive electrode using a positive electrode active material can be performed by a conventional method. That is, a positive electrode active material and a binder, and if necessary, a conductive material and a thickener mixed in a dry form into a sheet form are pressure-bonded to the positive electrode current collector, or these materials are liquid media A positive electrode can be obtained by forming a positive electrode active material layer on the current collector by applying it to a positive electrode current collector and drying it as a slurry by dissolving or dispersing in a slurry.

The content of the positive electrode active material in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more. Moreover, an upper limit becomes like this. Preferably it is 95 mass% or less, More preferably, it is 93 mass% or less. Within the above range, the electric capacity of the positive electrode active material in the positive electrode active material layer can be secured, and the strength of the positive electrode can be maintained.
The positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer is preferably 1.5 g / cm 3 or more as a lower limit, more preferably 2 g / cm 3 or more, further preferably 2.2 g / cm 3 or more, and the upper limit is preferably 3.5 g / cm 3 or less. More preferably, it is 3 g / cm 3 or less, and still more preferably 2.8 g / cm 3 or less. If it exceeds this range, the permeability of the electrolyte solution to the vicinity of the current collector / active material interface decreases, and the charge / discharge characteristics particularly at a high current density decrease, and a high output may not be obtained. On the other hand, if it is lower, the conductivity between the active materials is lowered, the battery resistance is increased, and a high output may not be obtained.

(Conductive material)
A known conductive material can be arbitrarily used as the conductive material. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbon materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. The conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more in the positive electrode active material layer, and the upper limit is usually 50% by mass or less, preferably It is used so as to contain 30% by mass or less, more preferably 15% by mass or less. Sufficient electrical conductivity and battery capacity can be ensured within the above range.

(Binder)
The binder used in the production of the positive electrode active material layer is not particularly limited, and in the case of the coating method, any material that can be dissolved or dispersed in the liquid medium used during electrode production may be used. Resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluorine rubber, isoprene rubber , Rubber polymers such as butadiene rubber and ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / Ethylene copolymer, styrene Thermoplastic elastomeric polymer such as isoprene / styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer Soft resinous polymers such as polymers; Fluoropolymers such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers; alkali metal ions (especially lithium ions) And a polymer composition having ion conductivity. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and the upper limit is usually 80% by mass or less, preferably 60%. It is not more than mass%, more preferably not more than 40 mass%, most preferably not more than 10 mass%. Within the above range, the mechanical strength of the positive electrode can be ensured, and deterioration of battery performance such as cycle characteristics can be suppressed, while decrease in battery capacity and conductivity can be suppressed.

(Slurry forming solvent)
As the solvent for forming the slurry, the positive electrode active material, the conductive material, the binder, and a solvent capable of dissolving or dispersing the thickener used as necessary may be used. There is no restriction, and either an aqueous solvent or an organic solvent may be used. Examples of the aqueous medium include water, a mixed medium of alcohol and water, and the like. Examples of the organic medium include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone. Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) Amides such as dimethylformamide and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide.

  In particular, when an aqueous medium is used, it is preferable to make a slurry using a thickener and a latex such as styrene-butadiene rubber (SBR). A thickener is usually used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios. When a thickener is further added, the ratio of the thickener to the active material is 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more. The upper limit is 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. When it is in the above range, good coatability can be obtained, and a decrease in battery capacity and an increase in resistance can be suppressed.

(Current collector)
The material of the positive electrode current collector is not particularly limited, and a known material can be arbitrarily used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.

  Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal in the case of a metal material. A thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred. In addition, you may form a thin film suitably in mesh shape. Although the thickness of the thin film is arbitrary, from the viewpoint of strength and handleability as a current collector, it is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and the upper limit is usually 1 mm or less, preferably 100 μm or less. More preferably, it is 50 μm or less.

Moreover, it is also preferable from the viewpoint of reducing the electronic contact resistance between the current collector and the positive electrode active material layer that a conductive additive is applied to the surface of the current collector. Examples of the conductive assistant include noble metals such as carbon, gold, platinum, and silver.
The ratio of the thickness of the current collector to the positive electrode active material layer is not particularly limited, but the value of (thickness of the positive electrode active material layer on one side immediately before electrolyte injection) / (thickness of the current collector) is 20 The lower limit is preferably 15 or less, most preferably 10 or less, and the lower limit is preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. Within the above range, heat generation of the current collector during high current density charge / discharge can be suppressed, and battery capacity can be secured.

(Electrode area)
When using the non-aqueous electrolyte of the present invention, it is preferable that the area of the positive electrode active material layer is larger than the outer surface area of the battery outer case from the viewpoint of increasing the stability at high output and high temperature. Specifically, the sum of the electrode areas of the positive electrode with respect to the surface area of the exterior of the secondary battery is preferably 15 times or more, and more preferably 40 times or more. The outer surface area of the outer case is the total area obtained by calculation from the vertical, horizontal, and thickness dimensions of the case part filled with the power generation element excluding the protruding part of the terminal in the case of a bottomed square shape. . In the case of a bottomed cylindrical shape, the geometric surface area approximates the case portion filled with the power generation element excluding the protruding portion of the terminal as a cylinder. The total electrode area of the positive electrode is the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material, and in the structure in which the positive electrode mixture layer is formed on both sides via the current collector foil. , The sum of the areas where each surface is calculated separately.

(Thickness of positive plate)
The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the composite layer obtained by subtracting the metal foil thickness of the core material is preferably as a lower limit with respect to one side of the current collector. Is 10 μm or more, more preferably 20 μm or more, and the upper limit is preferably 500 μm or less, more preferably 450 μm or less.

(Positive electrode surface coating)
Moreover, you may use what adhered the substance of the composition different from this to the surface of the said positive electrode plate. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate, and carbon.

<2-7. Separator>
Usually, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the nonaqueous electrolytic solution of the present invention is usually used by impregnating the separator.
The material and shape of the separator are not particularly limited, and known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Among them, a resin, glass fiber, inorganic material, etc. formed of a material that is stable with respect to the non-aqueous electrolyte solution of the present invention is used, and a porous sheet or a nonwoven fabric-like material having excellent liquid retention properties is used. Is preferred.

  As materials for the resin and glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used. Of these, glass filters and polyolefins are preferred, and polyolefins are more preferred. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The thickness of the separator is arbitrary, but is usually 1 μm or more, preferably 5 μm or more, more preferably 8 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. Moreover, when it is the said range, while ensuring insulation and mechanical strength, battery performance and energy density, such as a rate characteristic, can be ensured.

  Furthermore, when using a porous material such as a porous sheet or nonwoven fabric as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Further, it is usually 90% or less, preferably 8 ^ 5% or less, and more preferably 75% or less. When the porosity is in the above range, insulation and mechanical strength can be secured, while film resistance can be suppressed and good rate characteristics can be obtained.

  Moreover, although the average pore diameter of a separator is also arbitrary, it is 0.5 micrometer or less normally, 0.2 micrometer or less is preferable, and it is 0.05 micrometer or more normally. When the average pore diameter is in the above range, the film resistance can be suppressed and good rate characteristics can be obtained while preventing a short circuit. On the other hand, as inorganic materials, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. Used.

  As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the above-mentioned independent thin film shape, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. For example, a porous layer may be formed by using alumina particles having a 90% particle size of less than 1 μm on both surfaces of the positive electrode and using a fluororesin as a binder.

<2-8. Battery design>
(Electrode group)
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed through the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape through the separator. Either is acceptable. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. .
When the electrode group occupancy is in the above range, the battery capacity can be secured and the deterioration of characteristics such as charge / discharge repetition performance and high temperature storage accompanying the increase in internal pressure can be suppressed, and further the operation of the gas release valve can be prevented. Can do.

(Current collection structure)
The current collecting structure is not particularly limited, but in order to more effectively realize the high current density charge / discharge characteristics by the non-aqueous electrolyte solution of the present invention, a structure that reduces the resistance of the wiring part and the joint part is used. It is preferable. Thus, when internal resistance is reduced, the effect of using the non-aqueous electrolyte solution of this invention is exhibited especially favorable.
In the case where the electrode group has the above laminated structure, a structure formed by bundling the metal core portions of the electrode layers and welding them to the terminals is preferably used. When the area of one electrode increases, the internal resistance increases. Therefore, it is also preferable to provide a plurality of terminals in the electrode to reduce the resistance. When the electrode group has the winding structure described above, the internal resistance can be lowered by providing a plurality of lead structures for the positive electrode and the negative electrode, respectively, and bundling the terminals.

(Exterior case)
The material of the outer case is not particularly limited as long as it is a substance that is stable with respect to the non-aqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a metal such as a magnesium alloy, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.

  In an exterior case using metals, the metal is welded to each other by laser welding, resistance welding, or ultrasonic welding to form a sealed sealed structure, or a caulking structure using the above metals via a resin gasket. Things. Examples of the outer case using the laminate film include a case where a resin-sealed structure is formed by heat-sealing resin layers. In order to improve sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when a resin layer is heat-sealed through a current collecting terminal to form a sealed structure, a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used. Resins are preferably used.

(Protective element)
As a protective element, PTC (Positive Temperature Coefficient), thermal fuse, thermistor, whose resistance increases when abnormal heat or excessive current flows, cut off current flowing in the circuit due to sudden rise in battery internal pressure or internal temperature at abnormal heat generation A valve (current cutoff valve) or the like can be used. It is preferable to select a protective element that does not operate under normal use at a high current, and it is more preferable that the protective element is designed so as not to cause abnormal heat generation or thermal runaway even without the protective element.

(Exterior body)
The non-aqueous electrolyte secondary battery of the present invention is usually configured by housing the non-aqueous electrolyte, the negative electrode, the positive electrode, the separator, and the like in an exterior body. This exterior body is not particularly limited, and any known one can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Specifically, the material of the exterior body is arbitrary, but usually, for example, nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like is used.
The shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.
<< First Example >>
[Production of secondary battery]
<Preparation of positive electrode>
Using 90 parts by mass of lithium nickel manganese cobaltate (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) as a positive electrode active material, 7 parts by mass of carbon black and 3 parts by mass of polyvinylidene fluoride were mixed, and N-methyl 2-Pyrrolidone was added to form a slurry, which was uniformly coated on both sides of an aluminum foil having a thickness of 15 μm and dried, and then the density of the positive electrode active material layer was 2.6 g · c.
The positive electrode was pressed to m- ³ .

<Production of negative electrode>
Raman R value, defined as the ratio of the peak intensity of 1360 cm ^-1 to the peak intensity of 1580 cm ^-1 in the argon ion laser Raman spectroscopy is 0. Graphite No. 33, aqueous dispersion of sodium carboxymethylcellulose as a thickener (concentration of 1% by mass of sodium carboxymethylcellulose) and aqueous dispersion of styrene-butadiene rubber as a binder (concentration of styrene-butadiene rubber of 50% by mass) And mixed with a disperser to form a slurry. The obtained slurry was uniformly applied to one side of a 12 μm thick copper foil and dried, and then pressed so that the density of the negative electrode active material layer was 1.4 g · cm ⁻³ to obtain a negative electrode. In addition, in the negative electrode after drying, it created so that it might become mass ratio of graphite: sodium carboxymethylcellulose: styrene-butadiene rubber = 98: 1: 1.

<Manufacture of non-aqueous electrolyte secondary battery>
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, the positive electrode, the separator, and the negative electrode. The battery element thus obtained was wrapped in a cylindrical aluminum laminate film, injected with an electrolyte described later, and then vacuum sealed to produce a sheet-like non-aqueous electrolyte secondary battery. Furthermore, in order to improve the adhesion between the electrodes, the sheet-like battery was sandwiched between glass plates and pressurized.

[Battery evaluation]
<Run-in operation>
In a constant temperature bath at 25 ° C., the sheet-like non-aqueous electrolyte secondary battery was charged at constant current-constant voltage to 4.1 V at 0.2 C, and then discharged to 3.0 V at 0.2 C. This was performed for 5 cycles to stabilize the battery. In addition, 1C is a current value when discharging the entire capacity of the battery in one hour.

<Cycle characteristic evaluation>
The lithium secondary battery was charged with a constant current corresponding to 2C at 60 ° C., and then discharged with a constant current of 2C as one cycle, and 500 cycles were performed.
The discharge capacity at the 500th cycle of the battery when using the non-aqueous electrolyte solution (reference electrolyte solution) not containing the compound of the present invention is 1, and the 500th cycle of the battery when using the non-aqueous electrolyte solution of the present invention. The discharge capacities of were compared. That is,
It is the comparison of the value calculated | required from the formula of (discharge capacity of the 500th cycle of the non-aqueous electrolyte solution of this invention) / (discharge capacity of the 500th cycle of a reference | standard electrolyte solution). The results are shown in Table 1.

<Low-temperature discharge characteristics evaluation>
For a battery charged by an amount of electricity corresponding to 50% of the initial capacity, 0.3C, 0.5C, 1.0C, 1.5C, 2.0C, and 2.5C under an environment of −30 ° C. Each was discharged for 10 seconds, and the voltage at the 10th second was measured. In the current-voltage curve thus obtained, a current value at 3 V was calculated, and this value was used as a low temperature discharge characteristic. Here, the current value when using the reference electrolyte was set to 1, and the current values of the batteries when using the non-aqueous electrolyte of the present invention were compared. That is,
It is the comparison of the value calculated | required from the formula of (current value of the non-aqueous electrolyte solution of this invention) / (current value of a reference | standard electrolyte solution). The results are shown in Table 1.

[Example 1-1]
Under a dry argon atmosphere, fully dried LiPF6 was dissolved in a mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate (volume ratio 3: 3: 4) so that the total amount of the non-aqueous electrolyte was 1 mol / L. (This electrolyte may be referred to as a “reference electrolyte”). Duranate ^TM TPA-100 (manufactured by Asahi Kasei Chemicals Co., Ltd.) having an isocyanurate skeleton was added to the reference electrolyte so as to be 0.5 mass% to prepare a non-aqueous electrolyte.

[Example 1-2]
An electrolyte solution was prepared in the same manner as in Example 1-1 except that Duranate ^TM 24A-100 (manufactured by Asahi Kasei Chemicals) having a biuret skeleton was used instead of Duranate ^TM TPA-100.
[Example 1-3]
An electrolyte solution was prepared in the same manner as in Example 1-1 except that Duranate ^TM D101 (manufactured by Asahi Kasei Chemicals) having a urethane skeleton was used as the compound.

[Example 1-4]
An electrolyte solution was prepared in the same manner as in Example 1-3, except that the content of Duranate ^TM D101 was 1.0% by mass with respect to the total amount of the non-aqueous electrolyte solution.
[Example 1-5]
An electrolyte solution was prepared in the same manner as in Example 1-1 except that the content of Duranate ^TM TPA-100 with respect to the total amount of the non-aqueous electrolyte solution was 1.0% by mass.

[ Reference Example 1 ]
An electrolyte solution was prepared in the same manner as in Example 1-1 except that the content of Duranate ^TM TPA-100 was 2.5% by mass with respect to the total amount of the non-aqueous electrolyte solution.
[Comparative Example 1-1]
An electrolyte solution was prepared in the same manner as in Example 1-1 except that the reference electrolyte solution not containing the compound of the present invention was used, and a battery was produced, cycled, and low-temperature discharge tested in the same manner as in Example 1. . The results thus obtained are shown in Table 1.

[Comparative Example 1-2]
An electrolyte solution was prepared in the same manner as in Example 1-1 except that 1,6-diisocyanatohexane (HDI) was used in place of Duranate ^TM TPA-100.
[Comparative Example 1-3]
An electrolyte solution was prepared in the same manner as Comparative Example 1-2, except that the content of HDI with respect to the total amount of the non-aqueous electrolyte solution was 1.0% by mass.
[Comparative Example 1-4]
An electrolyte solution was prepared in the same manner as in Example 1-1, except that the content of Duranate ^TM TPA-100 with respect to the total amount of the non-aqueous electrolyte solution was 3.0% by mass.

  From Table 1, it can be seen that the compound of the present invention and the comparative example 1,6-diisocyanatohexane (HDI) have the property that the cycle characteristics are improved when the blending amount is increased, but the low-temperature discharge characteristics are lowered. However, it was confirmed that the decrease of the compound of the present invention was clearly smaller than that of the compound of the comparative example, when the addition amount was increased, the low temperature discharge characteristics were remarkably decreased. That is, by using the compound of the present invention, it is possible to design a battery that distributes both the cycle characteristics and the low-temperature discharge characteristics in a balanced manner.

<< Second embodiment >>
In this example, the following battery configuration and reference electrolyte different from those in the first example were evaluated.
[Production of secondary battery]
<Preparation of positive electrode>
72 parts by mass of lithium manganate (Li _1.1 Mn _1.9 Al _0.1 O ₄ ) as the first positive electrode active material, lithium nickel manganese cobalt composite oxide (Li _{1. 15} Ni _0.45 Mn _0.45 Co _0.10 O ₂ ), 18 parts by mass, 5 parts by mass of carbon black as a conductive agent, 5 parts by mass of polyvinylidene fluoride (PVdF) as a binder, N -After mixing and slurrying in methyl-2-pyrrolidone, this was uniformly applied to an aluminum foil having a thickness of 15 μm and dried, and then roll-pressed to obtain a positive electrode.

<Production of negative electrode>
93 parts by mass of graphite powder, 1 part by mass of carbon black, and 6 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed and slurried in N-methyl-2-pyrrolidone, and this was thickened. It was uniformly applied to 12 μm copper foil, dried, and roll-pressed to obtain a negative electrode.

<Manufacture of non-aqueous electrolyte secondary battery>
The positive electrode, the negative electrode, and the polyolefin separator were laminated in the order of the negative electrode, the separator, and the positive electrode. The battery element thus obtained was wrapped in an aluminum laminate film, injected with an electrolyte solution described later, and then vacuum sealed to produce a sheet-like non-aqueous electrolyte secondary battery.

[Battery evaluation]
<Initial charge / discharge>
In a thermostatic bath at 25 ° C., the sheet-like non-aqueous electrolyte secondary battery is 4 at 0.1 C (the rated capacity due to the discharge capacity at 1 hour rate is 1 C. The same applies hereinafter). After constant current-constant voltage charge to 2 V, the battery was discharged to 3.0 V at 0.1 C. Subsequently, the battery was charged at a constant current-constant voltage to 4.2 V at 0.3 C, and then discharged to 3.0 V at 0.3 C. This was carried out for 2 cycles for a total of 3 cycles to stabilize the non-aqueous electrolyte secondary battery. Thereafter, the battery was kept at 60 ° C. for 24 hours to perform aging. Thereafter, charge and discharge were performed at 0.3 C, and the discharge capacity was measured to obtain an initial capacity.

<Cycle characteristic evaluation>
At 55 ° C., a constant current-constant voltage charge to 4.2 V with a constant current corresponding to 1 C, and then a process of discharging to 3.0 V with a constant current of 1 C was performed as 30 cycles. Here, the cycle maintenance ratio was calculated from the following calculation formula.
(Discharge capacity at 30th cycle) / (Discharge capacity at 1st cycle)
The results are shown in Table 2.

[Example 2-1]
Under a dry argon atmosphere, fully dried LiPF6 was dissolved in a mixture of ethylene carbonate and diethyl carbonate (volume ratio 3: 7) so that the total amount of the non-aqueous electrolyte was 1 mol / L (this electrolyte was “Second reference electrolyte”. Duranate ^TM TPA-100 and fluoroethylene carbonate (FEC) were added to the second reference electrolyte so as to be 0.5% by mass and 2.0% by mass, respectively, to prepare a non-aqueous electrolyte.

[Example 2-2]
To the second reference electrolyte, Duranate ^TM TPA-100 and vinylene carbonate (VC) were added so as to be 0.5% by mass and 1.0% by mass, respectively, and the non-aqueous electrolyte was added in the same manner as in Example 2-1. Prepared.
[Example 2-3]
To the second reference electrolyte solution, Duranate ^TM TPA-100, FEC and vinylene carbonate (VC) were added so as to be 0.5% by mass, 1.0% by mass and 1.0% by mass, respectively, and Example 2-1 A non-aqueous electrolyte solution was prepared in the same manner as described above.

[Example 2-4]
To the second reference electrolyte solution, Duranate ^TM TPA-100, FEC and succinic anhydride (SUC) were added so as to be 0.5% by mass, 1.0% by mass and 0.2% by mass, respectively. A non-aqueous electrolyte solution was prepared in the same manner as in 1.
[Example 2-5]
To the second reference electrolyte, Duranate ^TM TPA-100, VC and SUC were added to 0.5% by mass, 1.0% by mass and 0.2% by mass, respectively, and the same as in Example 2-1. An aqueous electrolyte was prepared.

[Comparative Example 2-1]
An electrolyte solution was prepared in the same manner as in Example 2-1, except that the second reference electrolyte solution containing no compound of the present invention or other auxiliary agent was used, and a battery was manufactured and a cycle test was performed.
[Comparative Example 2-2]
An electrolyte solution was prepared in the same manner as in Example 2-3 except that it did not contain Duranate ^TM TPA-100, and a battery was manufactured and a cycle test was performed. The results thus obtained are shown in Table 2.

  From this result, when the battery configuration is different, and also when the type and composition of the non-aqueous solvent and auxiliary agent constituting the electrolyte are different, the cycle characteristics are improved by the configuration of the present invention as in the first embodiment described above. It was confirmed that it could be improved.

<< Third embodiment >>
In this example, the following battery configuration and reference electrolyte different from those in the first and second examples were evaluated.
[Production of secondary battery]
<Preparation of positive electrode>
94% by mass of lithium cobalt oxide (LiCoO2) as a positive electrode active material, 3% by mass of acetylene black as a conductive material, and 3% by mass of polyvinylidene fluoride (PVdF) as a binder in an N-methylpyrrolidone solvent And mixed with a disperser to form a slurry. This was uniformly applied to both sides of a 21 μm thick aluminum foil, dried, and then pressed to obtain a positive electrode.

<Production of negative electrode>
100 parts by weight of graphite powder as the negative electrode active material, 1 part by weight of aqueous dispersion of sodium carboxymethyl cellulose (concentration of 1% by weight of sodium carboxymethyl cellulose) as the thickener and binder, respectively, and aqueous dispersion of styrene-butadiene rubber 1 part by mass (concentration of styrene-butadiene rubber 50% by mass) was added and mixed with a disperser to form a slurry. This slurry was uniformly applied to one side of a 12 μm thick copper foil, dried, and then pressed to obtain a negative electrode.

<Manufacture of non-aqueous electrolyte secondary battery>
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, the positive electrode, the separator, and the negative electrode to produce a battery element. This battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness 40 μm) were coated with a resin layer while projecting positive and negative terminals, and a nonaqueous electrolyte solution described later was injected into the bag. Then, vacuum sealing was performed to produce a sheet-like non-aqueous electrolyte battery.

[Battery evaluation]
<Initial capacity evaluation>
A non-aqueous electrolyte battery is pressed between glass plates at 25 ° C. and charged at a constant current of up to 4.1 V at a current equivalent to 0.2 C, and then discharged to 3 V at a constant current of 0.2 C. The battery is further charged to a constant current-constant voltage charge (hereinafter referred to as “CCCV charge” where appropriate) (0.05C cut) to 4.33V at a current corresponding to 0.2C and then discharged to 3V at 0.2C. Stabilized. Next, after CCCV charge (0.05 C cut) to 4.33 V at 0.2 C, the battery was discharged again to 3 V at 0.2 C, and the initial discharge capacity was determined. Here, 1C represents a current value for discharging the reference capacity of the battery in one hour, and for example, 0.2C represents a current value of 1/5 thereof.

<High temperature storage characteristics evaluation test>
After performing CCCV charge (0.05C cut) to 4.33V again, high temperature preservation | save was performed on the conditions of 85 degreeC and 24 hours. After sufficiently cooling the battery, the volume was measured by immersion in an ethanol bath, and the amount of gas generated from the volume change before and after storage was determined. Next, discharge at 25 ° C. to 3 V at 0.2 C, measure the remaining capacity after the high temperature storage characteristics test, determine the ratio of the remaining capacity to the initial discharge capacity, this is the remaining capacity (%) after high temperature storage did. Again, CCCV charge (0.05C cut) to 4.33V, discharge to 3V at 0.2C, measure 0.2C discharge capacity after high temperature storage characteristics test, 0.2C discharge capacity relative to initial discharge capacity The ratio was determined as the recovery capacity (%) after high-temperature storage. The evaluation results are shown in Table 3. In addition, the numerical value in a table | surface is a relative value when Comparative Example 3-1 is set to 100%.

[Example 3-1]
Under a dry argon atmosphere, fully dried LiPF6 was dissolved in a mixture of ethylene carbonate, monofluoroethylene carbonate and dimethyl carbonate (volume ratio 15:15:70) so that the total amount of the non-aqueous electrolyte was 1 mol / L. (This electrolyte is referred to as “third reference electrolyte”). Duranate ^TM TPA-100, VC, and adiponitrile (AdpCN) were added to the third reference electrolyte solution so as to be 0.3% by mass, 1.0% by mass, and 1.0% by mass, respectively, to prepare a non-aqueous electrolyte. did.

[Example 3-2]
An electrolyte solution was prepared in the same manner as in Example 3-1, except that the content of Duranate ^TM TPA-100 was 0.5 mass%.
[Comparative Example 3-1]
An electrolyte solution was prepared in the same manner as in Example 3-1, except that it did not contain Duranate ^TM TPA-100, and a battery was manufactured and high-temperature storage characteristics were evaluated. The results thus obtained are shown in Table 3.

  From this result, it was confirmed that the configuration of the present invention can suppress not only the cycle characteristics in the first and second embodiments described above but also the swelling and capacity reduction of the battery during high temperature storage.

According to the non-aqueous electrolyte solution of the present invention, a non-aqueous electrolyte secondary battery excellent in cycle characteristics and low-temperature discharge characteristics can be produced, so that any electronic device or the like in which the non-aqueous electrolyte secondary battery is used can be manufactured. It can be suitably used in the field.
The application of the non-aqueous electrolyte solution or the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and can be used for various known applications. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. , Electronic notebook, calculator, memory card, portable tape recorder, radio, backup power supply, motor, automobile, motorcycle, motorbike, bicycle, lighting equipment, toy, game equipment, clock, electric tool, strobe, camera, etc. Can do.

Claims (6)

A non-aqueous electrolyte solution for a non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode capable of occluding and releasing metal ions, and a separator,
Wherein together with the non-aqueous electrolyte is an electrolyte and a nonaqueous solvent, the following formula in the molecule (1) a partial structure of one or more indicated, and a compound having two or more isocyanate groups 0.01% by mass or more, 1 A non-aqueous electrolyte solution for a non-aqueous electrolyte secondary battery, comprising 0.0 mass% or less .

Here, R represents an arbitrary element or group.   2. The nonaqueous electrolytic solution according to claim 1, wherein the structure of the compound has one or more skeletons selected from uretdione, oxadiaditrione, biuret, urethane, allophanate, and isocyanurate.   3. The non-aqueous electrolyte solution according to claim 1, wherein the compound has a number average molecular weight of 300 or more and 5000 or less.   The non-aqueous electrolyte further contains at least one selected from the group consisting of unsaturated cyclic carbonates, fluorinated cyclic carbonates and nitrogen-containing compounds. Aqueous electrolyte.   The said separator contains at least 1 sort (s) chosen from polyethylene and a polypropylene, The nonaqueous electrolyte solution as described in any one of Claims 1-4 characterized by the above-mentioned.   A non-aqueous electrolyte secondary battery comprising a negative electrode and a positive electrode capable of inserting and extracting metal ions, and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution is a non-aqueous electrolyte according to any one of claims 1 to 5. A non-aqueous electrolyte secondary battery characterized by being a liquid.