JP2015056312A - Nonaqueous electrolyte and nonaqueous electrolyte secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte which improves a capacity maintenance factor at charge and discharge cycle, a capacity maintenance factor at a high temperature, and a resistance increase rate, and also to provide a nonaqueous electrolyte battery using this nonaqueous electrolyte.SOLUTION: A nonaqueous electrolyte containing lithium salt and a nonaqueous organic solvent is related to the nonaqueous electrolyte containing a compound having a structure shown by the formula: Q-O-N (1) (Q represents group 13-16 elements excluding a carbon atom and an oxygen atom).

Description

  The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery using the same, and more specifically, a non-aqueous electrolyte for a lithium secondary battery containing a specific component and the same. 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 up to now, efforts to improve the performance have been repeated.
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.

  In recent years, against the background of global issues such as environmental issues and energy issues, 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, since such a battery is generally expected to be used in an environment exposed to the outside air, in the development, battery characteristics under a low temperature environment such as below freezing point, particularly low temperature resistance characteristics are regarded as important. In addition to this, since a battery having a small characteristic change over a long period of time is demanded from its use, there is a demand for suppression of the rate of increase in resistance associated with durability higher than that of a conventional lithium secondary battery.

As one of efforts to further improve various characteristics of the lithium secondary battery, efforts are being made to add an arbitrary compound to the electrolytic solution.
For example, Patent Document 1 reports a technique in which a negative electrode of a non-aqueous electrolyte battery contains a metal salt or a semimetal salt of nitric acid.

JP 10-233208 A

The present invention improves the low-temperature resistance characteristics in the low-temperature environment of the battery as described above, in particular, the resistance increase rate, and makes it possible to provide a battery with a small change in characteristics over a long period of time. An object is to provide a non-aqueous electrolyte battery.
This invention is made | formed in view of this background art, and it is providing the nonaqueous electrolyte solution for secondary batteries excellent in resistance increase rate, and a secondary battery using the same.

As a result of intensive studies to solve the above problems, the present inventors have found that the rate of increase in resistance of the battery can be improved by incorporating a specific compound as the non-aqueous electrolyte solution. It came to be completed.
That is, the gist of the present invention is as follows.
(A) A non-aqueous electrolyte containing an electrolyte and a non-aqueous solvent, wherein the non-aqueous electrolyte contains at least one compound having a structure represented by the formula (1) liquid.

Q-O-N (1)
(Q represents a group 13-16 element excluding carbon and oxygen atoms)
(B) In the formula (1), Q is any one of a boron atom, an aluminum atom, a silicon atom, a nitrogen atom, a phosphorus atom, and a sulfur atom, and the nonaqueous electrolytic solution according to (a).
(C) The non-aqueous electrolyte solution according to (a), wherein in the formula (1), Q is a phosphorus atom or a sulfur atom.
(D) The non-aqueous electrolyte solution according to (a), wherein the compound having the structure represented by the formula (1) is a compound represented by the following formula (2).

(M represents a Group 13-16 element excluding a carbon atom and an oxygen atom, and R ^{1 to} R ³ each independently represents a hydrogen atom, a halogen atom, or an organic group that may contain a C 1-12 hetero atom. P represents an integer of 1 to 3, q represents an integer of 0 to ^2. R ² and R ³ may be bonded to each other to form a ring, and when M is a group 13 element, p = 2, q = 0, when M is a group 14 element, p = 3 and q = 0, and when M is a group 15 element, 0 ≦ p ≦ 2, 0 ≦ q ≦ 1. (In the case of a group 16 element, p = 1, 1 ≦ q ≦ 2.)
(E) The non-aqueous electrolyte solution according to (d), wherein M is any one of a boron atom, an aluminum atom, a silicon atom, a nitrogen atom, a phosphorus atom, and a sulfur atom in the formula (2).
(F) In the formula (2), M is any one of a phosphorus atom and a sulfur atom, and the nonaqueous electrolytic solution according to (d),
(G) The compound having the structure represented by the formula (1) or the compound represented by the formula (2) is contained in an amount of 0.01 to 10% by mass with respect to the whole non-aqueous electrolyte solution. The nonaqueous electrolytic solution according to any one of (a) to (f).
(H) Non-aqueous electrolyte further Non-aqueous electrolyte further vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, 1,3-propene sultone, ethylene sulfite, ethylene sulfate, adiponitrile, It consists of pimelonitrile, succinonitrile, t-amylbenzene, cyclohexylbenzene, lithium difluorooxalatoborate, lithium bis (oxalato) borate, lithium difluorobis (oxalato) phosphate, lithium tetrafluorooxalatophosphate, lithium tris (oxalato) phosphate. The nonaqueous electrolytic solution according to any one of (a) to (g), wherein at least one compound selected from the group is included.
(I) A non-aqueous electrolyte secondary battery comprising a negative electrode and a positive electrode capable of occluding and releasing metal ions, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte according to any one of (a) to (h) A non-aqueous electrolyte secondary battery characterized by using an aqueous electrolyte.
(J) The non-aqueous electrolyte secondary battery according to (i), wherein the positive electrode capable of inserting and extracting metal ions includes at least one layered transition metal oxide.
(K) The non-aqueous electrolyte secondary battery according to (i), wherein the negative electrode capable of inserting and extracting metal ions contains at least a carbon compound.
(L) A compound represented by the following formula (3).

(M represents a group 13-16 element excluding a carbon atom and an oxygen atom, R ⁴ and R ⁵ each independently represents a hydrogen atom, an organic group that may contain a C 1-12 hetero atom, q Represents an integer of 0 to 2, r represents an integer of 1 to 5, and t represents 1 or 2. R ⁴ and R ⁵ may be bonded to each other to form a ring, and M represents a group 13 element In this case, q = 0, when M is a group 14 element, q = 0, when M is a group 15 element, 0 ≦ q ≦ 1, when M is a group 16 element, 1 ≦ q ≦ 2.)

  The present invention is characterized in that the non-aqueous electrolyte contains a compound having a structure represented by the above formula (1). By using the non-aqueous electrolyte of the present invention for a non-aqueous electrolyte secondary battery, the charge / discharge cycle capacity maintenance rate, the high-temperature capacity maintenance rate, and the resistance increase rate of the battery can be improved.

<1. Non-aqueous electrolyte>
<1-1. Inferred Action Mechanism of Invention>
The estimation mechanism in which the compound having the structure represented by the above formula (1) in the present invention exhibits an excellent resistance increase rate suppressing effect will be described below.
A feature of the present invention is that the non-aqueous electrolyte contains at least one compound having a structure represented by the formula (1).

Q-O-N (1)
(Q represents a group 13-16 element excluding carbon and oxygen atoms)
Examples of Group 13 to 16 elements excluding carbon atoms and oxygen atoms include boron atoms, aluminum atoms, silicon atoms, nitrogen atoms, phosphorus atoms, and sulfur atoms.
Since boron and aluminum have an empty orbit, they have a function as a Lewis acid. This action is expected to deactivate Lewis base sites with high reactive activity present on the positive electrode surface or the negative electrode surface, and suppress side reactions such as electrolytes on the positive electrode surface or the negative electrode surface. Since the side reaction is one of the factors increasing the internal resistance of the battery, it is considered that the rate of increase in resistance can be suppressed by suppressing the side reaction.

A nitrogen atom, a phosphorus atom, and a sulfur atom tend to form a functional group having an unshared electron pair with a high electron donating property. There are crystal structure defects in the structure of the positive electrode surface, and some of these defects may have an unstable structure due to an increase in the valence of the transition metal. An unstable structure promotes deterioration of the positive electrode structure and may increase internal resistance. The above functional group derived from a nitrogen atom, phosphorus atom, or sulfur atom is allowed to act on such a defect site, so that electrons are donated to the defect site, and relaxation of the unstable structure and deterioration of the positive electrode structure are expected. The Thereby, it is thought that the resistance increase rate of a battery is suppressed. In particular, the above-described effects are more effectively exhibited when phosphorus atoms and sulfur atoms are used.

  The structure represented by the above formula (1) is considered to be cleaved at the site of Q—O bond or ON bond in the battery. After the cleavage, it is divided into a component having Q (hereinafter referred to as Q side component) and a component having N atom (hereinafter referred to as N side component). As described above, since both Q and N atoms have an effect of suppressing the resistance increase rate, it is expected that the Q-side component and the N-side component each exhibit an effect of suppressing the resistance increase rate. That is, it is considered that the resistance increase rate can be more effectively and efficiently suppressed by generating a plurality of components that suppress the resistance increase rate from one compound.

<1-2. Example of Invention>
Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments, and can be arbitrarily modified and implemented without departing from the gist of the present invention.
A feature of the present invention is that the non-aqueous electrolyte contains at least one compound having a structure represented by the formula (1) (hereinafter, specific compound).

Q-O-N (1)
(Q represents a group 13-16 element excluding carbon and oxygen atoms)
Specific examples of Q include a boron atom, an aluminum atom, a silicon atom, a nitrogen atom, a phosphorus atom, and a sulfur atom, and among them, a phosphorus atom and a sulfur atom are particularly preferable.
Moreover, it is preferable that the compound which has a structure represented by Formula (1) is a compound represented by following formula (2).

(M represents a Group 13-16 element excluding a carbon atom and an oxygen atom, and R ^{1 to} R ³ each independently represents a hydrogen atom, a halogen atom, or an organic group that may contain a C 1-12 hetero atom. P represents an integer of 1 to 3, q represents an integer of 0 to ^2. R ² and R ³ may be bonded to each other to form a ring, and when M is a group 13 element, p = 2, q = 0, when M is a group 14 element, p = 3 and q = 0, and when M is a group 15 element, 0 ≦ p ≦ 2, 0 ≦ q ≦ 1. (In the case of a group 16 element, p = 1, 1 ≦ q ≦ 2.)
Specific examples of M include a boron atom, an aluminum atom, a silicon atom, a nitrogen atom, a phosphorus atom, and a sulfur atom, and among them, a phosphorus atom and a sulfur atom are particularly preferable.
Preferable specific examples of the peripheral structure of the N atom include the following structures.

  Among the above structures, the following structures are possible in that the cleavage of Q-O-N can be promoted by an electron-withdrawing functional group on the N atom and the film formation reaction of the N-side component after the cleavage is likely to occur. Is particularly preferred.

  Preferable specific examples of Q or M and its peripheral structure include the following structures.

  Among the above structures, phosphorus atoms and sulfur atoms have particularly strong interaction with the positive electrode, and therefore the following structures are particularly preferable.

  From the above, preferable specific examples of the specific compound exist in the number of combinations of the specific example of the peripheral structure of the N atom, Q or M, and specific examples of the peripheral structure. Among them, the following compounds are particularly shown below. Is preferred.

Among the specific compounds, the reason why the above compounds are particularly preferable is that the phosphorus atom and sulfur atom have a particularly effective effect of suppressing the rate of increase in resistance of the battery as compared with other group 13-16 elements, and the N atom. In addition, the point that the cleavage of Q-O-N can be promoted by the electron-withdrawing functional group and the point that the film formation reaction of the N-side component after the cleavage easily occurs can be mentioned.
Moreover, it is preferable that the compound which has a structure represented by Formula (1), or the compound represented by the said Formula (2) is contained 0.01-10 mass% with respect to the whole non-aqueous electrolyte solution, 0 The content is more preferably 0.01 to 8% by mass, and still more preferably 0.01 to 5% by mass. By using in the said range, the effect of this invention is exhibited more.

<1-3. Electrolyte>
<Lithium salt>
As the electrolyte, a lithium salt is usually used. The lithium salt is not particularly limited as long as it is known to be used in this application, and any lithium salt can be used.
Specific examples include the following.

For _{example, LiPF 6, LiBF 4, LiClO} 4, LiAlF 4, LiSbF 6, inorganic lithium salts LiTaF 6, LiWF ₇ and the like;
Lithium tungstates such as LiWOF ₅ ;
HCO ₂ Li, CH ₃ CO ₂ Li, CH ₂ FCO ₂ Li, CHF ₂ CO ₂ Li, CF ₃ CO ₂ Li, CF ₃ CH ₂ CO ₂ Li, CF ₃ CF ₂ CO ₂ Li, CF ₃ CF ₂ CF ₂ Carboxylic acid lithium salts such as CO ₂ Li, CF ₃ CF ₂ CF ₂ CF ₂ CO ₂ Li;
FSO ₃ Li, CH ₃ SO ₃ Li, CH ₂ FSO ₃ Li, CHF ₂ SO ₃ Li, CF ₃ SO ₃ Li, CF ₃ CF ₂ SO ₃ Li, CF ₃ CF ₂ CF ₂ SO ₃ Li, CF ₃ CF ₂ Sulfonic acid lithium salts such as CF ₂ CF ₂ SO ₃ Li;
LiN (FCO) ₂ , LiN (FCO) (FSO ₂ ), LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , Lithium imide salts such as lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) ;
Lithium metide salts such as LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ ;
Lithium oxalatoborate salts such as lithium difluorooxalatoborate and lithium bis (oxalato) borate;
Lithium oxalate phosphate salts such as lithium tetrafluorooxalatophosphate, lithium difluorobis (oxalato) phosphate, lithium tris (oxalato) phosphate;
In addition, 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 C _{2 F 5, LiBF 3 C 3} F 7, 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 Fluorine-containing organic lithium salts such as;

Among them, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiTaF ₆ , FSO ₃ Li, CF ₃ SO ₃ Li, LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiC (FSO ₂ ) ₃ , LiC (CF _{3 SO 2) 3, LiC (C} 2 F 5 SO 2) 3, lithium Bisuo Kisara oxalatoborate, lithium difluoro oxalatoborate, lithium tetrafluoro-oxa Lato phosphate, lithium difluoro bis oxa Lato _phosphate, LiBF ₃ CF _3, LiBF ₃ C ₂ F ₅ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) _{3 and the} like are particularly preferable because they have an effect of improving output characteristics, high-rate charge / discharge characteristics, high-temperature storage characteristics, cycle characteristics, and the like.

These lithium salts may be used alone or in combination of two or more. A preferable example in the case of using two or more types in combination is a combination of LiPF ₆ and LiBF ₄ or LiPF ₆ and FSO ₃ Li, which has an effect of improving load characteristics and cycle characteristics.
In this case, the concentration of LiBF ₄ or FSO ₃ Li with respect to 100% by mass of the entire non-aqueous electrolyte solution is not limited as long as it does not significantly impair the effects of the present invention. On the other hand, it is usually 0.01% by mass or more, preferably 0.1% by mass or more, and usually 30% by mass or less, preferably 20% by mass or less.

Another example is the combined use of an inorganic lithium salt and an organic lithium salt, and the combined use of both has the effect of suppressing deterioration due to high-temperature storage. As an organic lithium salt, CF ₃ SO ₃
Li, LiN (FSO ₂ ) ₂ , LiN (FSO ₂ ) (CF ₃ SO ₂ ), LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethane Disulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , lithium bisoxalatoborate, Lithium difluorooxalatoborate, lithium tetrafluorooxalatophosphate, lithium difluorobisoxalatophosphate, LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) ₃ Etc. are preferred. In this case, the ratio of the organic lithium salt to 100% by mass of the entire non-aqueous electrolyte is preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and preferably 30% by mass or less. Especially preferably, it is 20 mass% or less.

The concentration of these lithium salts in the non-aqueous electrolyte solution is not particularly limited as long as the effects of the present invention are not impaired, but the electric conductivity of the electrolyte solution is in a good range, and good battery performance is ensured. Therefore, the total molar concentration of lithium in the non-aqueous electrolyte is preferably 0.3 mol / L or more, more preferably 0.4 mol / L or more, and further preferably 0.5 mol / L or more. Preferably it is 3 mol / L or less, More preferably, it is 2.5 mol / L or less, More preferably, it is 2.0 mol / L or less.
If the total molar concentration of lithium is too low, the electrical conductivity of the electrolyte may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity, resulting in decreased battery performance. There is a case.

<1-4. Nonaqueous solvent>
The nonaqueous solvent in the present invention is not particularly limited, and a known organic solvent can be used. Examples thereof include cyclic carbonates having no fluorine atom, chain carbonates, cyclic and chain carboxylic acid esters, ether compounds, sulfone compounds, and the like.

<Cyclic carbonate not having fluorine atoms>
Examples of the cyclic carbonate having no fluorine atom include cyclic carbonates having an alkylene group having 2 to 4 carbon atoms.
Specific examples of the cyclic carbonate having an alkylene group having 2 to 4 carbon atoms and having no fluorine atom include ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate and propylene carbonate are particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.

The cyclic carbonate which does not have a fluorine atom may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.
The compounding amount of the cyclic carbonate not having a fluorine atom is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. %, 5% by volume or more, more preferably 10% by volume or more. By setting this range, the decrease in electrical conductivity due to the decrease in the dielectric constant of the non-aqueous electrolyte is avoided, and the high current discharge characteristics, stability against the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery are in a good range. And it will be easier. Moreover, it is 95 volume% or less, More preferably, it is 90 volume% or less, More preferably, it is 85 volume% or less. By setting it as this range, the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, the decrease in ionic conductivity is suppressed, and the load characteristics of the non-aqueous electrolyte battery are easily set in a favorable range.

<Chain carbonate>
As the chain carbonate, a chain carbonate having 3 to 7 carbon atoms is preferable, and a dialkyl carbonate having 3 to 7 carbon atoms is more preferable.
Specific examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate, isobutyl methyl. Examples include carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, t-butyl ethyl carbonate, and the like.

Among them, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, and methyl n-propyl carbonate are preferable, and dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferable. is there.
Further, chain carbonates having a fluorine atom (hereinafter sometimes referred to as “fluorinated chain carbonate”) can also be suitably used.

The number of fluorine atoms contained in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon or may be bonded to different carbons.
Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate and derivatives thereof, fluorinated ethyl methyl carbonate and derivatives thereof, and fluorinated diethyl carbonate and derivatives thereof.

Fluorinated dimethyl carbonate and derivatives thereof include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoro) methyl carbonate, bis (trifluoromethyl) carbonate, and the like. It is done.
Fluorinated ethyl methyl carbonate and derivatives thereof include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2,2 -Trifluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, ethyl trifluoromethyl carbonate, etc. are mentioned.

  Fluorinated diethyl carbonate and its derivatives include ethyl- (2-fluoroethyl) carbonate, ethyl- (2,2-difluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, ethyl- (2,2,2- Trifluoroethyl) carbonate, 2,2-difluoroethyl-2′-fluoroethyl carbonate, bis (2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2′-fluoroethyl carbonate, 2, Examples include 2,2-trifluoroethyl-2 ′, 2′-difluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, and the like.

A chain carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
The amount of the chain carbonate is preferably 5% by volume or more, more preferably 10% by volume or more, and further preferably 15% by volume or more in 100% by volume of the non-aqueous solvent. By setting the lower limit in this way, the viscosity of the non-aqueous electrolyte solution is set in an appropriate range, the decrease in ionic conductivity is suppressed, and the large current discharge characteristics of the non-aqueous electrolyte battery are easily set in a favorable range. Further, the chain carbonate is preferably 90% by volume or less, more preferably 85% by volume or less, in 100% by volume of the nonaqueous solvent. By setting the upper limit in this way, it is easy to avoid a decrease in electrical conductivity resulting from a decrease in dielectric constant of the nonaqueous electrolyte solution, and to make the large current discharge characteristics of the nonaqueous electrolyte solution battery in a favorable range.

<Cyclic carboxylic acid ester>
The cyclic carboxylic acid ester is preferably one having 3 to 12 carbon atoms.
Specific examples include gamma butyrolactone, gamma valerolactone, gamma caprolactone, epsilon caprolactone, and the like. Among these, gamma butyrolactone is particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.

A cyclic carboxylic acid ester may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
The amount of the cyclic carboxylic acid ester is usually 5% by volume or more, more preferably 10% by volume or more, in 100% by volume of the non-aqueous solvent. If it is this range, it will become easy to improve the electrical conductivity of a non-aqueous electrolyte solution, and to improve the large current discharge characteristic of a non-aqueous electrolyte battery. Moreover, the compounding quantity of cyclic carboxylic acid ester becomes like this. Preferably it is 50 volume% or less, More preferably, it is 40 volume% or less. By setting the upper limit in this way, the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, a decrease in electrical conductivity is avoided, an increase in negative electrode resistance is suppressed, and a large current discharge of the non-aqueous electrolyte secondary battery is performed. It becomes easy to make a characteristic into a favorable range.

<Chain carboxylic acid ester>
The chain carboxylic acid ester is preferably one having 3 to 7 carbon atoms. In particular,
Methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, propion Acid-n-butyl, isobutyl propionate, t-butyl propionate, methyl butyrate, ethyl butyrate, butyric acid n-propyl, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, isobutyric acid n-propyl, isopropyl isobutyrate Etc.

Among them, methyl acetate, ethyl acetate, acetate-n-propyl, acetate-n-butyl, methyl propionate, ethyl propionate, propionate-n-propyl, isopropyl propionate, methyl butyrate, ethyl butyrate, etc. It is preferable from the viewpoint of improvement of ionic conductivity.
A chain carboxylic acid ester may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The compounding amount of the chain carboxylic acid ester is usually 10% by volume or more, more preferably 15% by volume or more, in 100% by volume of the non-aqueous solvent. By setting the lower limit in this way, the electrical conductivity of the non-aqueous electrolyte solution is improved, and the large current discharge characteristics of the non-aqueous electrolyte battery are easily improved. Moreover, the compounding quantity of chain | strand-shaped carboxylic acid ester is 60 volume% or less preferably in 100 volume% of nonaqueous solvents, More preferably, it is 50 volume% or less. By setting the upper limit in this way, an increase in negative electrode resistance is suppressed, and the large current discharge characteristics and cycle characteristics of the non-aqueous electrolyte battery are easily set in a favorable range.

<Ether compound>
As the ether compound, a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms in which part of hydrogen may be substituted with fluorine is preferable.
As the chain ether having 3 to 10 carbon atoms,
Diethyl ether, di (2-fluoroethyl) ether, di (2,2-difluoroethyl) ether, di (2,2,2-trifluoroethyl) ether, ethyl (2-fluoroethyl) ether, ethyl (2, 2,2-trifluoroethyl) ether, ethyl (1,
1,2,2-tetrafluoroethyl) ether, (2-fluoroethyl) (2,2,2-trifluoroethyl) ether, (2-fluoroethyl) (1,1,2,2-tetrafluoroethyl) Ether, (2,2,2-trifluoroethyl) (1,1,2,2-tetrafluoroethyl) ether, ethyl-n-propyl ether, ethyl (3-fluoro-n-propyl) ether, ethyl (3 , 3,3-trifluoro-n-propyl) ether, ethyl (2,2,3,3-tetrafluoro-n-propyl) ether, ethyl (2,2,3,3,3-pentafluoro-n- Propyl) ether, 2-fluoroethyl-n-propylether, (2-fluoroethyl) (3-fluoro-n-propyl) ether, (2-fluoroethyl) (3,3 3-trifluoro-n-propyl) ether, (2-fluoroethyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (2-fluoroethyl) (2,2,3,3 (3-pentafluoro-n-propyl) ether, 2,2,2-trifluoroethyl-n-propyl ether, (2,2,2-trifluoroethyl) (3-fluoro-n-propyl) ether, (2 , 2,2-trifluoroethyl) (3,3,3-trifluoro-n-propyl) ether, (2,2,2-trifluoroethyl) (2,2,3,3-tetrafluoro-n- Propyl) ether, (2,2,2-trifluoroethyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, 1,1,2,2-tetrafluoroethyl-n-propyl Ete , (1,1,2,2-tetrafluoroethyl) (3-fluoro-n-propyl) ether, (1,1,2,2-tetrafluoroethyl) (3,3,3-trifluoro-n- Propyl) ether, (1,1,2,2-tetrafluoroethyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (1,1,2,2-tetrafluoroethyl) (2 , 2,3,3,3-pentafluoro-n-propyl) ether, di-n-propylether, (n-propyl) (3-fluoro-n-propyl) ether, (n-propyl) (3,3 , 3-trifluoro-n-propyl) ether, (n-propyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (n-propyl) (2,2,3,3,3 -Pentafluoro-n-propyl) Ether, di (3-fluoro-n-propyl) ether, (3-fluoro-n-propyl) (3,3,3-trifluoro-n-propyl) ether, (3-fluoro-n-propyl) (2 , 2,3,3-tetrafluoro-n-propyl) ether, (3-fluoro-n-propyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di (3,3 , 3-trifluoro-n-propyl) ether, (3,3,3-trifluoro-n-propyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (3,3,3 -Trifluoro-n-propyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di (2,2,3,3-tetrafluoro-n-propyl) ether, (2, 2,3,3-tetrafluoro- -Propyl) (2,2,3,3,3-pentafluoro-n-propyl) ether, di (2,2,3,3,3-pentafluoro-n-propyl) ether, di-n-butyl ether, Dimethoxymethane, methoxyethoxymethane, methoxy (2-fluoroethoxy) methane, methoxy (2,2,2-trifluoroethoxy) methanemethoxy (1,1,2,2-tetrafluoroethoxy) methane, diethoxymethane, ethoxy (2-fluoroethoxy) methane, ethoxy (2,2,2-trifluoroethoxy) methane, ethoxy (1,1,2,2-tetrafluoroethoxy) methane, di (2-fluoroethoxy) methane, (2- Fluoroethoxy) (2,2,2-trifluoroethoxy) methane, (2-fluoroethoxy) (1,1,2,2- Trifluoroethoxy) methanedi (2,2,2-trifluoroethoxy) methane, (2,2,2-trifluoroethoxy) (1,1,2,2-tetrafluoroethoxy) methane, di (1,1, 2,2-tetrafluoroethoxy) methane, dimethoxyethane, methoxyethoxyethane, methoxy (2-fluoroethoxy) ethane, methoxy (2,2,2-trifluoroethoxy) ethane, methoxy (1,1,2,2- Tetrafluoroethoxy) ethane, diethoxyethane, ethoxy (2-fluoroethoxy) ethane, ethoxy (2,2,2-trifluoroethoxy) ethane, ethoxy (1,1,2,2-tetrafluoroethoxy) ethane, di (2-Fluoroethoxy) ethane, (2-Fluoroethoxy) (2,2,2-trifluoroethoxy)
Ethane, (2-fluoroethoxy) (1,1,2,2-tetrafluoroethoxy) ethane, di (2,2,2-trifluoroethoxy) ethane, (2,2,2-trifluoroethoxy) (1 , 1,2,2-tetrafluoroethoxy) ethane, di (1,1,2,2-tetrafluoroethoxy) ethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, etc. Can be mentioned.

Examples of the cyclic ether having 3 to 6 carbon atoms include tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1 , 4-dioxane and the like, and fluorinated compounds thereof.
Among them, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvating ability to lithium ions and improve ion dissociation. Of these, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are preferable because they have low viscosity and give high ionic conductivity.

An ether type compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
The compounding amount of the ether compound is usually in 100% by volume of the non-aqueous solvent, preferably 5% by volume or more, more preferably 10% by volume or more, further preferably 15% by volume or more, and preferably 70% by volume or less. More preferably, it is 60 volume% or less, More preferably, it is 50 volume% or less.

If it is this range, it is easy to ensure the improvement effect of the lithium ion dissociation degree of chain ether, and the improvement of the ionic conductivity derived from a viscosity fall, and when a negative electrode active material is a carbonaceous material, a chain ether with lithium ion It is easy to avoid a situation where the capacity is reduced due to co-insertion.
<Sulfone compound>
As the sulfone compound, a cyclic sulfone having 3 to 6 carbon atoms and a chain sulfone having 2 to 6 carbon atoms are preferable. The number of sulfonyl groups in one molecule is preferably 1 or 2.

As cyclic sulfone having 3 to 6 carbon atoms,
Monosulfone compounds trimethylene sulfones, tetramethylene sulfones, hexamethylene sulfones;
Examples include disulfone compounds such as trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones.

Among these, from the viewpoint of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable.
As the sulfolanes, sulfolane and / or sulfolane derivatives (hereinafter sometimes referred to as “sulfolanes” including sulfolane) are preferable. As the sulfolane derivative, one in which one or more hydrogen atoms bonded to the carbon atom constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group is preferable.

Among them, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,2-difluorosulfolane, 2,3-difluorosulfolane, 2,4-difluorosulfolane, 2,5-difluorosulfolane, 3,4-difluorosulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane, 3-fluoro-3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-
Fluoro-3-methyl sulfolane, 4-fluoro-2-methyl sulfolane, 5-fluoro-3-methyl sulfolane, 5-fluoro-2-methyl sulfolane, 2-fluoromethyl sulfolane, 3-fluoromethyl sulfolane, 2-difluoromethyl Sulfolane, 3-difluoromethyl sulfolane, 2-trifluoromethyl sulfolane, 3-trifluoromethyl sulfolane, 2-fluoro-3- (trifluoromethyl) sulfolane, 3-fluoro-3- (trifluoromethyl) sulfolane, 4- Fluoro-3- (trifluoromethyl) sulfolane, 5-fluoro-3- (trifluoromethyl) sulfolane, and the like are preferable in terms of high ionic conductivity and high input / output characteristics.

In addition, as the chain sulfone having 2 to 6 carbon atoms,
Dimethylsulfone, ethylmethylsulfone, diethylsulfone, n-propylmethylsulfone, n-propylethylsulfone, di-n-propylsulfone, isopropylmethylsulfone, isopropylethylsulfone, diisopropylsulfone, n-butylmethylsulfone, n-butylethyl Sulfone, t-butylmethylsulfone, t-butylethylsulfone, monofluoromethylmethylsulfone, difluoromethylmethylsulfone, trifluoromethylmethylsulfone, monofluoroethylmethylsulfone, difluoroethylmethylsulfone, trifluoroethylmethylsulfone, pentafluoro Ethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, perf Oroethyl methyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, di (trifluoroethyl) sulfone, perfluorodiethyl sulfone, fluoromethyl-n-propyl sulfone, difluoromethyl-n-propyl sulfone, trifluoromethyl- n-propylsulfone, fluoromethylisopropylsulfone, difluoromethylisopropylsulfone, trifluoromethylisopropylsulfone, trifluoroethyl-n-propylsulfone, trifluoroethylisopropylsulfone, pentafluoroethyl-n-propylsulfone, pentafluoroethylisopropylsulfone , Trifluoroethyl-n-butylsulfone, trifluoroethyl-t-butylsulfone, pentafluoroethyl- - butyl sulfone, pentafluoroethyl -t- butyl sulfone, and the like.

  Among them, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, isopropyl methyl sulfone, n-butyl methyl sulfone, t-butyl methyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone , Monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoro Ethyl sulfone, trifluoromethyl-n-propyl sulfone, trifluoromethyl isopropyl sulfone, tri Ruoroechiru -n- butyl sulfone, trifluoroethyl -t- butyl sulfone, trifluoromethyl -n- butyl sulfone, trifluoromethyl -t- butyl sulfone is high ion conductivity, preferable because the input-output characteristic is high.

A sulfone compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
The compounding amount of the sulfone compound is usually 0.3% by volume or more, more preferably 1% by volume or more, still more preferably 5% by volume or more in 100% by volume of the non-aqueous solvent, and preferably 40%. Volume% or less, More preferably, it is 35 volume% or less, More preferably, it is 30 volume% or less.
Within this range, durability improvement effects such as cycle characteristics and storage characteristics can be easily obtained, and the viscosity of the non-aqueous electrolyte can be set within an appropriate range to avoid a decrease in electrical conductivity. When charging / discharging an aqueous electrolyte battery at a high current density, it is easy to avoid a situation in which the charge / discharge capacity retention rate decreases.

<When using a cyclic carbonate having a fluorine atom as a non-aqueous solvent>
In the present invention, when a cyclic carbonate having a fluorine atom is used as a non-aqueous solvent, one of the non-aqueous solvents exemplified above is combined with a cyclic carbonate having a fluorine atom as a non-aqueous solvent other than the cyclic carbonate having a fluorine atom. Two or more kinds may be used in combination with a cyclic carbonate having a fluorine atom.

  For example, one preferred combination of non-aqueous solvents is a combination mainly composed of a cyclic carbonate having a fluorine atom and a chain carbonate. Among them, the total of the cyclic carbonate having a fluorine atom and the chain carbonate in the non-aqueous solvent is preferably 60% by volume or more, more preferably 80% by volume or more, and further preferably 90% by volume or more, and the fluorine atom. The ratio of the cyclic carbonate having a fluorine atom to the total of the cyclic carbonate having a chain and the chain carbonate is 3% by volume or more, preferably 5% by volume or more, more preferably 10% by volume or more, and further preferably 15% by volume or more. Further, it is preferably 60% by volume or less, more preferably 50% by volume or less, still more preferably 40% by volume or less, and particularly preferably 35% by volume or less.

When a combination of these non-aqueous solvents is used, the balance between the cycle characteristics and high-temperature storage characteristics (particularly, the remaining capacity and high-load discharge capacity after high-temperature storage) of a battery produced using the non-aqueous solvent may be improved.
For example, as a specific example of a preferable combination of a cyclic carbonate having a fluorine atom and a chain carbonate,
Monofluoroethylene carbonate and dimethyl carbonate, monofluoroethylene carbonate and diethyl carbonate, monofluoroethylene carbonate and ethyl methyl carbonate, monofluoroethylene carbonate and dimethyl carbonate and diethyl carbonate, monofluoroethylene carbonate and dimethyl carbonate and ethyl methyl carbonate, monofluoro Examples thereof include ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

  Among the combinations of cyclic carbonates having a fluorine atom and chain carbonates, those containing symmetric chain alkyl carbonates as chain carbonates are more preferable, and in particular, monofluoroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, Cycle characteristics include monofluoroethylene carbonate, symmetric chain carbonates and asymmetric chain carbonates such as fluoroethylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. And a large current discharge characteristic are preferable. Among these, the symmetric chain carbonate is preferably dimethyl carbonate, and the alkyl group of the chain carbonate preferably has 1 to 2 carbon atoms.

A combination in which a cyclic carbonate not having a fluorine atom is further added to the combination of the cyclic carbonate having a fluorine atom and the chain carbonate is also a preferable combination. Among them, the total of the cyclic carbonate having a fluorine atom and the cyclic carbonate not having a fluorine atom in the nonaqueous solvent is preferably 10% by volume or more, more preferably 15% by volume or more, and further preferably 20% by volume or more. The ratio of the cyclic carbonate having a fluorine atom to the total of the cyclic carbonate having a fluorine atom and the cyclic carbonate having no fluorine atom is 5% by volume or more, preferably 10% by volume or more, more preferably 15% by volume. % Or more, more preferably 25% by volume or more, preferably 95% by volume or less, more preferably 85% by volume or less, still more preferably 75% by volume or less, and particularly preferably 60% by volume or less.

When a cyclic carbonate having no fluorine atom is contained in this concentration range, the electrical conductivity of the electrolytic solution can be maintained while forming a stable protective film on the negative electrode.
As a specific example of a preferable combination of a cyclic carbonate having a fluorine atom and a cyclic carbonate having no fluorine atom and a chain carbonate,
Monofluoroethylene carbonate and ethylene carbonate and dimethyl carbonate, monofluoroethylene carbonate and ethylene carbonate and diethyl carbonate, monofluoroethylene carbonate and ethylene carbonate and ethyl methyl carbonate, monofluoroethylene carbonate and ethylene carbonate, dimethyl carbonate and diethyl carbonate, monofluoro Ethylene carbonate, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate Monofluoroethylene carbonate and propylene carbonate and dimethyl carbonate, monofluoroethylene carbonate and propylene carbonate and diethyl carbonate, monofluoroethylene carbonate and propylene carbonate and ethyl methyl carbonate, monofluoroethylene carbonate and propylene carbonate, dimethyl carbonate and diethyl carbonate, Monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate and diethyl carbonate Tylmethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, monofluoroethylene Carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate and diethyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate and propylene carbonate Examples include diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

Among the combinations of a cyclic carbonate having a fluorine atom and a cyclic carbonate having no fluorine atom and a chain carbonate, those containing a symmetric chain alkyl carbonate as the chain carbonate are more preferred,
Monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate and ethyl methyl carbonate, monofluoro Ethylene carbonate, ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate Nate, monofluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, monofluoroethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, monofluoroethylene carbonate, ethylene carbonate, propylene carbonate, and dimethyl carbonate It is preferable to use monofluoroethylene carbonate, symmetric chain carbonates, and asymmetric chain carbonates such as sodium carbonate, diethyl carbonate, and ethyl methyl carbonate because the balance between cycle characteristics and large current discharge characteristics is good. Among them, the symmetric chain carbonate is preferably dimethyl carbonate, and the alkyl group of the chain carbonate preferably has 1 to 2 carbon atoms.

  When dimethyl carbonate is contained in the non-aqueous solvent, the proportion of dimethyl carbonate in the total non-aqueous solvent is preferably 10% by volume or more, more preferably 20% by volume or more, and even more preferably 25% by volume or more. Preferably, the content is 30% by volume or more, preferably 90% by volume or less, more preferably 80% by volume or less, still more preferably 75% by volume or less, and particularly preferably 70% by volume or less. The load characteristics may be improved.

Above all, it contains dimethyl carbonate and ethyl methyl carbonate, and by increasing the content ratio of dimethyl carbonate over the content ratio of ethyl methyl carbonate, the electric conductivity of the electrolyte can be maintained, but the battery characteristics after high temperature storage are improved. Therefore, it is preferable.
The volume ratio of dimethyl carbonate to ethyl methyl carbonate in all non-aqueous solvents (dimethyl carbonate / ethyl methyl carbonate) is 1.1 or more in terms of improving the electric conductivity of the electrolyte and improving the battery characteristics after storage. Is preferable, 1.5 or more is more preferable, and 2.5 or more is more preferable.

The volume ratio (dimethyl carbonate / ethyl methyl carbonate) is preferably 40 or less, more preferably 20 or less, still more preferably 10 or less, and particularly preferably 8 or less, from the viewpoint of improving battery characteristics at low temperatures.
In the combination mainly composed of the cyclic carbonate having a fluorine atom and the chain carbonate, in addition to the cyclic carbonate having no fluorine atom, a cyclic carboxylic acid ester, a chain carboxylic acid ester, a cyclic ether, Other solvents such as chain ethers, sulfur-containing organic solvents, phosphorus-containing organic solvents, and fluorine-containing aromatic solvents may be mixed.

<When using a cyclic carbonate having a fluorine atom as an auxiliary agent>
In the present invention, when a cyclic carbonate having a fluorine atom is used as an auxiliary agent, as the non-aqueous solvent other than the cyclic carbonate having a fluorine atom, the above-exemplified non-aqueous solvent may be used alone, or two or more thereof. May be used in any combination and ratio.
For example, one preferred combination of non-aqueous solvents is a combination mainly composed of a cyclic carbonate having no fluorine atom and a chain carbonate.

  Among them, the total of cyclic carbonate and chain carbonate having no fluorine atom in the non-aqueous solvent is preferably 70% by volume or more, more preferably 80% by volume or more, and still more preferably 90% by volume or more, The ratio of the cyclic carbonate having no fluorine atom to the total of the cyclic carbonate and the chain carbonate is preferably 5% by volume or more, more preferably 10% by volume or more, and further preferably 15% by volume or more. Preferably it is 50 volume% or less, More preferably, it is 35 volume% or less, More preferably, it is 30 volume% or less, Most preferably, it is 25 volume% or less.

When a combination of these non-aqueous solvents is used, the balance between the cycle characteristics and high-temperature storage characteristics (particularly, the remaining capacity and high-load discharge capacity after high-temperature storage) of a battery produced using the non-aqueous solvent may be improved.
For example, as a specific example of a preferable combination of a cyclic carbonate having no fluorine atom and a chain carbonate,
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 and diethyl carbonate and ethyl methyl carbonate, ethylene carbonate And dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

  Among the combinations of cyclic carbonates and chain carbonates not having a fluorine atom, those containing asymmetric chain alkyl carbonates as chain carbonates are more preferable, in particular, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, Those containing ethylene carbonate, symmetric chain carbonates and asymmetric chain carbonates such as ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate have cycle characteristics and large current discharge characteristics. This is preferable because of a good balance.

Among them, the asymmetric chain carbonate is preferably ethyl methyl carbonate, and the alkyl group of the chain carbonate preferably has 1 to 2 carbon atoms.
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. Further, the proportion of propylene carbonate in the whole non-aqueous solvent is preferably 0.1% by volume or more, more preferably 1% by volume or more, still more preferably 2% by volume or more, and preferably 20% by volume or less. Preferably it is 8 volume% or less, More preferably, it is 5 volume% or less.

It is preferable to contain propylene carbonate in this concentration range because the low temperature characteristics may be further improved while maintaining the combination characteristics of ethylene carbonate and chain carbonate.
When dimethyl carbonate is contained in the non-aqueous solvent, the proportion of dimethyl carbonate in the total non-aqueous solvent is preferably 10% by volume or more, more preferably 20% by volume or more, and even more preferably 25% by volume or more. Preferably it is 30% by volume or more, preferably 90% by volume or less, more preferably 80% by volume or less, further preferably 75% by volume or less, and particularly preferably 70% by volume or less. The load characteristics of the battery may be improved.

Above all, it contains dimethyl carbonate and ethyl methyl carbonate, and by increasing the content ratio of dimethyl carbonate over the content ratio of ethyl methyl carbonate, the electric conductivity of the electrolyte can be maintained, but the battery characteristics after high temperature storage are improved. This is preferable.
The volume ratio of dimethyl carbonate to ethyl methyl carbonate in all non-aqueous solvents (dimethyl carbonate / ethyl methyl carbonate) is 1.1 or more in terms of improving the electric conductivity of the electrolyte and improving the battery characteristics after storage. Is preferable, 1.5 or more is more preferable, and 2.5 or more is more preferable. The volume ratio (dimethyl carbonate / ethyl methyl carbonate) is preferably 40 or less, more preferably 20 or less, still more preferably 10 or less, and particularly preferably 8 or less, from the viewpoint of improving battery characteristics at low temperatures.

In the combination mainly composed of a cyclic carbonate having no fluorine atom and a chain carbonate, a cyclic carboxylic acid ester, a chain carboxylic acid ester, a cyclic ether, a chain ether, a sulfur-containing organic solvent, You may mix other solvents, such as a phosphorus organic solvent and an aromatic fluorine-containing solvent.
In this specification, the volume of the non-aqueous solvent is a measured value at 25 ° C., but the measured value at the melting point is used for a solid at 25 ° C. such as ethylene carbonate.

<1-5. Auxiliary>
In the non-aqueous electrolyte battery of the present invention, an auxiliary agent may be appropriately used depending on the purpose other than the sulfonic acid ester represented by the formula (1). Examples of auxiliary agents include unsaturated cyclic carbonates having fluorine atoms, overcharge inhibitors, and other auxiliary agents as shown below.

<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 referred to 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 fluorine atom is usually 6 or less, preferably 4 or less, and most preferably 1 or 2.

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.

As the fluorinated ethylene carbonate derivative substituted with a substituent having an aromatic ring or a carbon-carbon double bond,
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-difluoro-4,5-diallylethylene carbonate, 4-fluoro-4-phenylethylene carbonate, 4-fu Oro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate.

Among them, as a fluorinated unsaturated cyclic carbonate particularly preferable for use in combination with the sulfonic acid ester represented by the formula (1),
4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, 4-fluoro-4-vinyl ethylene 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, and 4,5-difluoro-4,5-diallylethylene carbonate are more preferably used because they form a stable interface protective film.

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 this 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 use 2 or more types together by arbitrary combinations and a ratio. 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 compounding amount of the fluorinated unsaturated cyclic carbonate is usually 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, in 100% by mass of the nonaqueous electrolytic solution. Moreover, it is preferably 5% by mass or less, more preferably 4% by mass or less, and further preferably 3% by mass or less.
Within this range, the non-aqueous electrolyte battery tends to exhibit a sufficient cycle characteristics improvement effect, and the high temperature storage characteristics deteriorate, the amount of gas generated increases, and the discharge capacity maintenance ratio decreases. Easy to avoid.

<Overcharge prevention agent>
In the non-aqueous electrolyte solution of the present invention, an overcharge inhibitor can be used in order to effectively prevent the battery from bursting or igniting when the non-aqueous electrolyte battery is overcharged.
As an overcharge prevention agent,
Aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran; 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p -Partially fluorinated product of the above aromatic compound such as cyclohexylfluorobenzene;
Examples thereof include fluorine-containing anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole. Above all,
Aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferred.

  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 preferably 0.1% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. If it is this range, it will be easy to fully express the effect of an overcharge inhibiting agent, and it will be easy to avoid the situation where the characteristics of batteries, such as a high temperature storage characteristic, fall.
The overcharge inhibitor is more preferably 0.2% by mass or more, further preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, and more preferably 3% by mass or less, still more preferably. Is 2% by mass or less.

<Other auxiliaries>
Other known auxiliary agents can be used in the non-aqueous electrolyte solution of the present invention. As other auxiliaries,
Carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride Carboxylic acid anhydrides such as 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, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, sulfolene, diphenylsulfone, N, N-dimethylmethanesulfonamide, N, N-diethylmethanesulfonamide, etc. Sulfur-containing compounds;
Nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide;
Hydrocarbon compounds such as heptane, octane, nonane, decane, cycloheptane;
Fluorine-containing aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene and benzotrifluoride;
Etc. These may be used alone or in combination of two or more. By adding these auxiliaries, capacity maintenance characteristics and cycle characteristics after high temperature storage can be improved.

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 preferably 0.01% by mass or more and 5% by mass or less in 100% by mass of the non-aqueous electrolyte solution. Within this range, the effects of other auxiliaries can be sufficiently exhibited, and it is easy to avoid a situation in which battery characteristics such as high-load discharge characteristics deteriorate.
The blending amount of other auxiliaries is more preferably 0.1% by mass or more, further preferably 0.2% by mass or more, more preferably 3% by mass or less, and further preferably 1% by mass or less. .

As mentioned above, what exists in the inside of the non-aqueous electrolyte battery as described in this invention is also contained in the above-mentioned non-aqueous electrolyte.
Specifically, the components of the non-aqueous electrolyte solution such as lithium salt, solvent, and auxiliary agent are separately synthesized, and the non-aqueous electrolyte solution is prepared from what is substantially isolated 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]
<2-1. 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.

<2-2. Positive electrode>
The positive electrode active material (lithium transition metal compound) used for the positive electrode is described below.
<Lithium transition metal compound>
A lithium transition metal compound is a compound having a structure capable of desorbing and inserting lithium ions. For example, sulfide, phosphate compound, silicic acid compound, boric acid compound, lithium transition metal composite oxidation Such as things. Examples of sulfides include compounds having a two-dimensional layered structure such as TiS ₂ and MoS ₂ , and solid compounds represented by the general formula M _x Mo ₆ S ₈ (M is various transition metals including Pb, Ag, and Cu). Examples thereof include a sugar compound having a three-dimensional skeleton structure. Examples of the phosphate compound include those belonging to the olivine structure, and are generally represented by LiMPO ₄ (M is at least one transition metal), specifically, LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , Examples include LiMnPO ₄ . Examples of the silicic acid compound include LiMSiO ₄ , and examples of the boric acid compound include LiMBO ₄ . Examples of the lithium transition metal composite oxide include spinel structures capable of three-dimensional diffusion and those belonging to a layered structure capable of two-dimensional diffusion of lithium ions. Those having a spinel structure are generally expressed as LiM ₂ O ₄ (M is at least one transition metal), specifically, LiMn ₂ O ₄ , LiCoMnO ₄ , LiNi _0.5 Mn _1.5 O. ₄ , LiCoVO _{4 and the} like. Those having a layered structure are generally expressed as LiMO ₂ (M is at least one transition metal). LiCoO _{2 Specifically, LiNiO 2, LiNi 1-x} Co x O 2, LiNi 1-x-y Co x Mn y O 2, LiNi 0.5 Mn 0.5 O 2, Li 1.2 Cr 0. _{4 Mn 0.4 O 2, Li 1.2} Cr 0.4 Ti 0.4 O 2, such as LiMnO ₂ and the like.

<composition>
The lithium-containing transition metal compound is, for example, a lithium transition metal compound represented by the following composition formula (A) or (B).
1) In the case of a lithium transition metal compound represented by the following composition formula (A)

Li _{1 + x} MO ₂ (A)
However, x is usually 0 or more and 0.5 or less. M is an element composed of Ni and Mn or Ni, Mn and Co, and the Mn / Ni molar ratio is usually 0.1 or more and 5 or less. The Ni / M molar ratio is usually 0 or more and 0.5 or less. The Co / M molar ratio is usually 0 or more and 0.5 or less. In addition, the rich portion of Li represented by x may be replaced with the transition metal site M.

  In the composition formula (A), the atomic ratio of the oxygen amount is described as 2 for convenience, but there may be some non-stoichiometry. Moreover, x in the said compositional formula is the preparation composition in the manufacture stage of a lithium transition metal type compound. Usually, batteries on the market are aged after the batteries are assembled. For this reason, the Li amount of the positive electrode may be deficient with charge / discharge. In this case, x may be measured to be −0.65 or more and 1 or less when discharged to 3 V in composition analysis.

A lithium transition metal-based compound is excellent in battery characteristics when fired at a high temperature in an oxygen-containing gas atmosphere in order to enhance the crystallinity of the positive electrode active material.
Further, the lithium transition metal-based compound represented by the composition formula (A) may be a solid solution with Li ₂ MO ₃ called a 213 layer, as shown in the general formula (A ′) below.

αLi ₂ MO ₃ · (1-α) LiM′O ₂ (A ′)
In the general formula, α is a number satisfying 0 <α <1.

M is at least one metallic element average oxidation number of 4 ^+, specifically, at least one metal element Mn, Zr, Ti, Ru, selected from the group consisting of Re and Pt.
M 'is at least one metallic element average oxidation number of 3 ^+, preferably, V, Mn, Fe, at least one metallic element selected from the group consisting of Co and Ni, more preferably , At least one metal element selected from the group consisting of Mn, Co and Ni.
2) A lithium transition metal compound represented by the following general formula (B).

_{Li [Li a M b Mn 2} -b-a] O 4 + δ ··· (B)
However, M is an element comprised from at least 1 sort (s) of the transition metals chosen from Ni, Cr, Fe, Co, Cu, Zr, Al, and Mg.
The value of b is usually 0.4 or more and 0.6 or less.
When the value of b is within this range, the energy density per unit weight in the lithium transition metal compound is high.

  The value of a is usually 0 or more and 0.3 or less. Moreover, a in the above composition formula is a charged composition in the production stage of the lithium transition metal compound. Usually, batteries on the market are aged after the batteries are assembled. For this reason, the Li amount of the positive electrode may be deficient with charge / discharge. In this case, a may be measured to be −0.65 or more and 1 or less when discharged to 3 V in composition analysis.

When the value of a is within this range, the energy density per unit weight in the lithium transition metal compound is not significantly impaired, and good load characteristics can be obtained.
Furthermore, the value of δ is usually in the range of ± 0.5.
If the value of δ is within this range, the stability as a crystal structure is high, and the cycle characteristics and high-temperature storage of a battery having an electrode produced using this lithium transition metal compound are good.

Here, the chemical meaning of the lithium composition in the lithium nickel manganese composite oxide, which is the composition of the lithium transition metal compound, will be described in more detail below.
In order to obtain a and b in the composition formula of the lithium transition metal compound, each transition metal and lithium are analyzed with an inductively coupled plasma emission spectrometer (ICP-AES) to obtain a ratio of Li / Ni / Mn. It is calculated by the thing.

From a structural point of view, it is considered that lithium related to a is substituted for the same transition metal site. Here, due to the lithium according to a, the average valence of M and manganese becomes larger than 3.5 due to the principle of charge neutrality.
Further, the lithium transition metal based compound may be substituted with fluorine, it is expressed as _{LiMn 2 O 4-x F 2x} .

Specific examples of the lithium transition metal compound having the above composition include, for example, Li _{1 + x} Ni _0.5 Mn _0.5 O ₂ , Li _{1 + x} Ni _0.85 Co _0.10 Al _0.05 O ₂ , Li _{1 + x} Ni _0.33 Mn _0.33 Co _0.33 O ₂ , Li _{1 + x} Ni _0.45 Mn _0.45 Co _0.1 O ₂ , Li _{1 + x} Mn _1.8 Al _0.2 O ₄ , Li _{1 + x} Mn _1.5 Ni _0.5 O ₄ and the like. These lithium transition metal compounds may be used alone or in a blend of two or more.

<Introduction of foreign elements>
Moreover, a different element may be introduce | transduced into a lithium transition metal type compound. As the different elements, B, Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru, Rh, Pd, Ag, In, Sb, Te , Ba, Ta, Mo, W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi , N, F, S, Cl, Br, I, As, Ge, P, Pb, Sb, Si, and Sn. These foreign elements may be incorporated into the crystal structure of the lithium transition metal compound, or may not be incorporated into the crystal structure of the lithium transition metal compound, and may be a single element or compound on the particle surface or grain boundary. May be unevenly distributed.

<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, most preferably 1.7 g / c.
m ³ or more. When the tap density of the positive electrode active material is within the above range, the amount of the dispersion medium and the necessary amount of the conductive material and the binder necessary for forming the positive electrode active material layer can be suppressed. As a result, the filling rate of the positive electrode active material and the 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 high as possible, and there is no particular upper limit, but it is preferably 2.8 g / cm ³ or less, more preferably 2.7 g / cm ³ or less, and even 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.

<Average secondary particle size>
Further, the average secondary particle size of the positive electrode active material is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.2 μm or more, preferably 0.3 μm or more, and usually 20 μm or less, preferably 10 μm or less. It is. If the average secondary particle size is too small, the cycle deterioration of the lithium secondary battery may be increased and handling may be difficult. If the average secondary particle size is too large, the internal resistance of the battery may be increased and output may be difficult to output.

<BET specific surface area>
The BET specific surface area of the positive electrode active material is preferably 0.3 m ² / g or more, more preferably 0.4 m ² / g or more, further preferably 0.5 m ² / g or more, and most preferably 0.6 m ² / g. The upper limit is 50 m ² / g or less, preferably 40 m ² / g or less, more preferably 30 m ² / 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 for 30 minutes at 150 ° C. under a 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>
Although it does not restrict | limit especially as a manufacturing method of a positive electrode active material in the range which does not exceed the summary of this invention, Several methods are mentioned, A general method is used as a manufacturing method of an inorganic compound.
In particular, various methods are conceivable for producing a spherical or elliptical active material. For example, transition metal source materials such as transition metal nitrates and sulfates, and source materials of other elements as necessary. Is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to produce and recover a spherical precursor, which is dried as necessary, and then LiOH, Li ₂ CO ₃ , LiNO There is a method in which an active material is obtained by adding a Li source such as ₃ and baking at a high temperature.

In addition, as an example of another method, transition metal raw materials such as transition metal nitrates, sulfates, hydroxides, oxides and the like, and if necessary, raw materials of other elements are dissolved or pulverized and dispersed in a solvent such as water. Then, it is dry-molded with a spray dryer or the like to obtain a spherical or oval spherical precursor, and a Li source such as LiOH, Li ₂ CO ₃ , LiNO ₃ is added to the precursor and calcined at a high temperature to obtain an active material Is mentioned.

Examples of other methods include transition metal source materials such as transition metal nitrates, sulfates, hydroxides, oxides, Li sources such as LiOH, Li ₂ CO ₃ , LiNO ₃ , and other elements as necessary. The raw material is dissolved or pulverized and dispersed in a solvent such as water, and is then dried by a spray dryer or the like to form a spherical or elliptical precursor, which is fired at a high temperature to obtain an active material. Can be mentioned.

<Blend>
In addition, these positive electrode active materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

<Composition 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. The production of the positive electrode using the 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. Further, for example, the positive electrode active material described above may be roll-formed to form a sheet electrode, or may be formed into a pellet electrode by compression molding.
Hereinafter, a case where the slurry is applied to the positive electrode current collector and dried will be described.

<Active material content>
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. The upper limit is preferably 98% by mass or less, more preferably 95% by mass or less, and particularly preferably 93% by 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 , further preferably 2.2 g / cm ³ or more, and preferably 3.8 g as an upper limit. / Cm ³ or less, more preferably 3.5 g / cm ³ or less, even more preferably 3.0 g / cm ³ or less, and particularly 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 a coating method, the type is not particularly limited as long as it is a material that can be dissolved or dispersed in the liquid medium used during electrode production. However, it is preferable to select in consideration of weather resistance, chemical resistance, heat resistance, flame retardancy, and the like. Specific examples include inorganic compounds such as silicate and water glass, alkane polymers such as polyethylene, polypropylene and poly-1,1-dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; polystyrene and polymethylstyrene. , Polymers having rings such as polyvinyl pyridine, poly-N-vinyl pyrrolidone; polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid, Acrylic derivative polymers such as polyacrylamide; Fluorine resins such as polyvinyl fluoride, polyvinylidene fluoride, and polytetrafluoroethylene; CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide; Polyvinyl chloride, halogen-containing polymers of polyvinylidene chloride; polyvinyl alcohol polymers such as polyvinyl alcohol such as a conductive polymer such as polyaniline can be used.

In addition, mixtures such as the above polymers, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, and the like can also be used. Among these, preferred binders are a fluororesin and a CN group-containing polymer. In addition, a binder may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
When a resin is used as the binder, the weight average molecular weight of the resin is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 10,000 or more, preferably 100,000 or more, and usually 300. 10,000 or less, preferably 1,000,000 or less. If the molecular weight is too low, the strength of the electrode tends to decrease. On the other hand, if the molecular weight is too high, the viscosity becomes high and it may be difficult to form an electrode.

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; N-methylpyrrolidone, dimethylformamide and dimethylacetamide Amides such as aprotic polar solvents such as hexamethylphosphalamide and dimethyl sulfoxide.

<Thickener>
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.
Furthermore, in order to improve the binding effect between the current collector and the active material layer formed on the surface, the surface of these current collectors may be roughened in advance. The surface roughening method includes blasting or rolling with a rough roll, and the surface of the current collector with a wire brush equipped with abrasive cloth paper, grindstone, emery buff, steel wire, etc. to which abrasive particles are fixed. Examples thereof include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method.

  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, in the case of a bottomed square shape, means 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 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 electrode 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.

<Surface coating of positive electrode plate>
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.

<2-3. Negative electrode>
The negative electrode active material used for the negative electrode is not particularly limited as long as it can electrochemically occlude and release metal ions. Specific examples include carbonaceous materials, alloy materials, lithium-containing metal composite oxide materials, and the like. Among these, it is most preferable to use a carbonaceous material in terms of good cycle characteristics and safety and excellent continuous charge characteristics. These may be used individually by 1 type, and may be used together combining 2 or more types arbitrarily.

<Carbonaceous material>
Examples of the carbonaceous material include (1) natural graphite, (2) artificial graphite, (3) amorphous carbon, (4) carbon-coated graphite, (5) graphite-coated graphite, and (6) resin-coated graphite. .
(1) Examples of natural graphite include scaly graphite, scaly graphite, soil graphite, and / or graphite particles obtained by subjecting these graphites to spheroidization or densification. Among these, spherical or ellipsoidal graphite subjected to spheroidizing treatment is particularly preferable from the viewpoints of particle filling properties and charge / discharge rate characteristics.

As an apparatus used for the spheroidization treatment, for example, an apparatus that repeatedly gives mechanical action such as compression, friction, shearing force, etc. including the interaction of particles mainly with impact force to the particles can be used. Specifically, it has a rotor with a large number of blades installed inside the casing, and mechanical action such as impact compression, friction, shearing force, etc. on the carbon material introduced inside the rotor by rotating at high speed. And a device for performing the spheroidizing treatment is preferable. Moreover, it is preferable to have a mechanism that repeatedly gives mechanical action by circulating the carbon material.
For example, when the spheroidizing treatment is performed using the above-described apparatus, the peripheral speed of the rotating rotor is preferably 30 to 100 m / second, more preferably 40 to 100 m / second, and 50 to 100 m / second. More preferably. The treatment can be performed by simply passing a carbonaceous material, but it is preferable to circulate or stay in the apparatus for 30 seconds or longer, and it is preferable to circulate or stay in the apparatus for 1 minute or longer. More preferred.

  (2) Artificial graphite includes coal tar pitch, coal heavy oil, atmospheric residue, petroleum heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride, Organic compounds such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin are usually in the range of 2500 ° C. or higher and usually 3200 ° C. or lower. Examples thereof include those produced by graphitization at a temperature and, if necessary, pulverized and / or classified. At this time, a silicon-containing compound or a boron-containing compound can also be used as a graphitization catalyst. In addition, artificial graphite obtained by graphitizing mesocarbon microbeads separated in the heat treatment process of pitch can be mentioned. Furthermore, the artificial graphite of the granulated particle which consists of primary particles is also mentioned. For example, by mixing mesocarbon microbeads and graphitizable carbonaceous material powders such as coke, graphitizable binders such as tar and pitch, and graphitization catalyst, graphitizing, and pulverizing as necessary Examples of the resulting graphite particles include a plurality of flat particles and aggregated or bonded so that the orientation planes are non-parallel.

  (3) As amorphous carbon, amorphous carbon that has been heat-treated at least once in a temperature range (400 to 2200 ° C.) in which no graphitizable carbon precursor such as tar or pitch is used as a raw material. Examples thereof include amorphous carbon particles that are heat-treated using particles or a non-graphitizable carbon precursor such as a resin as a raw material.

(4) Carbon-coated graphite can be obtained by mixing natural graphite and / or artificial graphite with a carbon precursor that is an organic compound such as tar, pitch, or resin, and heat-treating it at least once in the range of 400 to 2300 ° C. Examples thereof include a carbon graphite composite in which natural graphite and / or artificial graphite is used as nuclear graphite, and amorphous carbon coats the nuclear graphite. The composite form may cover the entire surface or a part thereof, or may be a composite of a plurality of primary particles using carbon originating from the carbon precursor as a binder. Carbon can also be deposited (CVD) by reacting natural graphite and / or artificial graphite with hydrocarbon gases such as benzene, toluene, methane, propane, and aromatic volatiles at a high temperature to deposit carbon on the graphite surface. A graphite composite can also be obtained.

  (5) As graphite-coated graphite, natural graphite and / or artificial graphite and a carbon precursor of an easily graphitizable organic compound such as tar, pitch or resin are mixed and once in a range of about 2400 to 3200 ° C. Examples thereof include graphite-coated graphite in which natural graphite and / or artificial graphite obtained by heat treatment is used as nuclear graphite, and graphitized material covers the whole or part of the surface of nuclear graphite.

(6) As the resin-coated graphite, natural graphite and / or artificial graphite obtained by mixing natural graphite and / or artificial graphite with a resin and drying at a temperature of less than 400 ° C. is used as nuclear graphite, and the resin is nuclear graphite. And resin-coated graphite covering the surface.
Moreover, the carbonaceous material of (1)-(6) may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

Examples of organic compounds such as tar, pitch and resin used in the above (2) to (5) include coal-based heavy oil, direct-current heavy oil, cracked heavy petroleum oil, aromatic hydrocarbon, N-ring compound. , S ring compound, polyphenylene, organic synthetic polymer, natural polymer, thermoplastic resin and carbonizable organic compound selected from the group consisting of thermosetting resins. The raw material organic compound may be used after being dissolved in a low molecular organic solvent in order to adjust the viscosity at the time of mixing.
Moreover, as natural graphite and / or artificial graphite used as a raw material of nuclear graphite, natural graphite subjected to spheroidization treatment is preferable.

<Physical properties of carbonaceous materials>
In addition to the above-described requirements, the carbonaceous material as the negative electrode active material in the present invention further satisfies at least one of the characteristics such as physical properties and shapes shown in the following (1) to (9). It is particularly preferable to satisfy a plurality of items simultaneously.

(1) X-ray parameters The d-value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method of carbonaceous materials is preferably 0.335 nm or more. 360 nm or less, preferably 0.350 nm or less, and more preferably 0.345 nm or less. 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, more preferably 1.5 nm or more, especially 2 nm or more. More preferably it is.

(2) Volume-based average particle diameter 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. It is more preferably 5 μm or more, particularly preferably 7 μm or more, and 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.

(3) Raman R value, Raman half-value 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, 0 .1 or more is more preferable, and it is 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, 60 cm ⁻¹ or less is more preferable, and 40 cm ⁻¹ or less is particularly preferable.
The Raman R value and the Raman half-value width are indices indicating the crystallinity of the surface of the carbonaceous material. The carbonaceous material has an appropriate crystallinity from the viewpoint of chemical stability, but is an interlayer into which lithium 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. The resulting Raman spectrum, the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1, and measuring the intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1, the intensity ratio _{R (R = I B / I} A) 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 P _A in the vicinity of 1580 cm ^-1 of the resulting Raman spectrum was measured, which is defined as the Raman half-value 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

(4) BET specific surface area of the BET specific surface area carbonaceous material is a value of the measured specific surface area using the BET method is usually 0.1 m @ 2 · ^{g -1} or more, 0.7 m ² · ^{g -1} or more 1.0 m ² · g ⁻¹ or more is more preferable, 1.5 m ² · g ⁻¹ or more is particularly preferable, and usually 100 m ² · g ⁻¹ or less, and 25 m ² · g ⁻¹ or less is preferable. Preferably, 15 m ² · g ⁻¹ or less is more preferable, and 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.

(5) Circularity When the circularity is measured as a spherical degree 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 length 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.

(6) 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 is 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 through a sieve having an 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 device (for example, manufactured by Seishin Enterprise Co., Ltd.). Using a tap 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.

(7) 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 molding obtained by filling 0.47 g of the sample into a molding machine with a diameter of 17 mm and compressing it with 58.8 MN · 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

(8) 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.

(9) Secondary material mixing Secondary material mixing means that two or more 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.

<Alloy-based materials>
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. 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.

<Lithium-containing metal composite oxide material>
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.

LixTiyMzO ₄ (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 Li _4/3 Ti _5/3 O ₄ in (a), Li ₁ Ti ₂ O ₄ in (b), and Li _4/5 Ti _11/5 O in (c). ₄ . As for the structure of Z ≠ 0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ is preferable.
Although it does not restrict | limit especially as a manufacturing method of lithium titanium complex oxide in the range which does not exceed the summary of this invention, Several methods are mentioned, A general method is used as a manufacturing method of an inorganic compound.

For example, a method of obtaining an active material by uniformly mixing a titanium source material such as titanium oxide and a source material of another element and a Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ as necessary, and firing at a high temperature. Is mentioned.
In particular, various methods are conceivable for producing a spherical or elliptical active material. As an example, a titanium precursor material such as titanium oxide and, if necessary, a raw material material of another element are dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to create a spherical precursor. There is a method in which the active material is obtained by recovering and drying it as necessary, and then adding a Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ and baking at a high temperature.

As another example, a titanium raw material such as titanium oxide and, if necessary, a raw material of another element are dissolved or pulverized and dispersed in a solvent such as water. A method of obtaining an active material by adding a Li source such as LiOH, Li ₂ CO ₃ , LiNO _{3 and the} like to an elliptical spherical precursor and baking at a high temperature can be mentioned.
As yet another method, a titanium raw material such as titanium oxide, a Li source such as LiOH, Li ₂ CO ₃ and LiNO ₃ and a raw material of another element as necessary are dissolved or pulverized in a solvent such as water. There is a method in which it is dispersed and dried by a spray dryer or the like to obtain a spherical or elliptical precursor, which is then fired at a high temperature to obtain an active material.

  Also, during these steps, elements other than Ti, such as Al, Mn, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, C, Si, Sn , Ag may be present in the metal oxide structure containing titanium and / or in contact with the oxide containing titanium. By containing these elements, the operating voltage and capacity of the battery can be controlled.

<Physical properties of lithium titanium composite oxide>
In addition to the above requirements, the lithium titanium composite oxide as the negative electrode active material in the present invention further satisfies at least one of the characteristics such as physical properties and shapes shown in the following (1) to (7). It is preferable to satisfy a plurality of items at the same time.

(1) BET specific surface area As for the BET specific surface area of the lithium titanium composite oxide used as the negative electrode active material, the specific surface area value measured using the BET method is preferably 0.5 m ² · g ⁻¹ or more. 7 m ² · g ⁻¹ or more is more preferred, 1.0 m ² · g ⁻¹ or more is more preferred, 1.5 m ² · g ⁻¹ or more is particularly preferred, and 200 m ² · g ⁻¹ or less is preferred, 100 m ² · g ⁻¹ or less is more preferred, 50 m ² · g ⁻¹ or less is more preferred, and 25 m ² · g ⁻¹ or less is particularly preferred.

  When the BET specific surface area is less than the above range, the reaction area in contact with the non-aqueous electrolyte when used as the negative electrode material may decrease, and the output resistance may increase. On the other hand, if it exceeds the above range, the surface of the metal oxide crystal containing titanium and the portion of the end face increase, and due to this, crystal distortion also occurs, irreversible capacity cannot be ignored, which is preferable It may be difficult to obtain a battery.

  The specific surface area of the lithium-titanium composite oxide was preliminarily dried at 350 ° C. for 15 minutes under a nitrogen flow using a surface area meter (a fully automatic surface area measuring device manufactured by Rikura Okura) using a surface area meter. Thereafter, a nitrogen adsorption BET one-point method using a gas flow method is performed using a nitrogen helium mixed gas that is accurately adjusted so that the value of the relative pressure of nitrogen with respect to atmospheric pressure is 0.3. The specific surface area determined by the measurement is defined as the BET specific surface area of the lithium titanium composite oxide in the present invention.

(2) Volume-based average particle diameter The volume-based average particle diameter of lithium-titanium composite oxide (secondary particle diameter when primary particles are aggregated to form secondary particles) is determined by laser diffraction / scattering method. It is defined by the obtained volume-based average particle diameter (median diameter).
The volume-based average particle size of the lithium titanium composite oxide is preferably 0.1 μm or more, 0.5
μm or more is more preferable, 0.7 μm or more is more preferable, 50 μm or less is preferable, 40 μm or less is more preferable, 30 μm or less is further preferable, and 25 μm or less is particularly preferable.

  Specifically, the volume-based average particle diameter of the lithium-titanium composite oxide was measured by adding a lithium-titanium composite oxide to a 0.2% by mass aqueous solution (10 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant. The powder is dispersed and the measurement is performed using a laser diffraction / scattering particle size distribution analyzer (LA-700, manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the lithium titanium composite oxide.

  When the volume average particle size of the lithium titanium composite oxide is below the above range, a large amount of binder is required at the time of producing the negative electrode, and as a result, the battery capacity may be reduced. On the other hand, if the above range is exceeded, a non-uniform coating surface tends to be formed when forming the negative electrode plate, which may be undesirable in the battery manufacturing process.

(3) Average primary particle diameter When primary particles are aggregated to form secondary particles, the average primary particle diameter of the lithium titanium composite oxide is preferably 0.01 μm or more, more preferably 0.05 μm or more. Preferably, 0.1 μm or more is more preferable, 0.2 μm or more is particularly preferable, 2 μm or less is preferable, 1.6 μm or less is more preferable, 1.3 μm or less is further preferable, and 1 μm or less is particularly preferable. If the volume-based average primary particle diameter exceeds the above range, it is difficult to form spherical secondary particles, which adversely affects the powder packing property and the specific surface area greatly decreases. There is a possibility that performance is likely to deteriorate. On the other hand, below the above range, there are cases where the performance of the secondary battery is lowered, for example, reversibility of charge / discharge is inferior because crystals are underdeveloped.

  In addition, the primary particle diameter of lithium titanium complex oxide is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification at which particles can be confirmed, for example, a magnification of 10,000 to 100,000 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 determined for any 50 primary particles. Obtained and obtained by taking an average value.

(4) Shape The shape of the lithium-titanium composite oxide particles may be any of lump shape, polyhedron shape, spherical shape, elliptical spherical shape, plate shape, needle shape, columnar shape, etc. as used in the past. Thus, it is preferable to form secondary particles, and the shape of the secondary particles is spherical or elliptical.

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 possible to relieve the stress of expansion and contraction and prevent deterioration when the primary particles are aggregated to form secondary particles, rather than being a single particle active material consisting of only primary particles.
In addition, spherical or oval spherical particles are less oriented during molding of the electrode than plate-like equiaxed particles, so there is less expansion and contraction of the electrode during charge and discharge, and an electrode is produced. The mixing with the conductive material is also preferable because it can be easily mixed uniformly.

(5) Tap Density Tap density lithium-titanium composite oxide is preferably from 0.05 g · ^{cm -3} or more, 0.1 g · ^{cm -3} or more, and more preferably 0.2 g · ^{cm -3} or more, 0.4 g · cm ⁻³ or more is particularly preferable, and 2.8 g · cm ⁻³ or less is preferable and 2.4 g.
· ^{Cm -3} more preferably less, particularly preferably 2 g · ^{cm -3} or less. If the tap density of the lithium-titanium composite oxide is below the above range, the packing density is difficult to increase when used as a negative electrode, and the contact area between the particles decreases, so the resistance between the particles increases, and the output resistance decreases. May increase. On the other hand, if the above range is exceeded, the voids between the particles in the electrode may become too small, and the output resistance may increase due to a decrease in the flow path of the non-aqueous electrolyte solution.

To measure the tap density of the lithium-titanium composite oxide, the sample is passed through a sieve having a mesh size of 300 μm, dropped into a 20 cm ³ tapping cell and filled up to the upper end surface of the cell, and then a powder density measuring device. Using, for example, a tap denser manufactured by Seishin Enterprise Co., Ltd., tapping with a stroke length of 10 mm is performed 1000 times, and the density is calculated from the volume at that time and the weight of the sample. The tap density calculated by the measurement is defined as the tap density of the lithium titanium composite oxide in the present invention.

(6) Circularity When the circularity is measured as the spherical degree of the lithium titanium composite oxide, 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 length of the particle projection shape)”, and is theoretical when the circularity is 1. Become a true sphere.

  The circularity of the lithium-titanium composite oxide is preferably closer to 1. Preferably, it is 0.10 or more, more preferably 0.80 or more, still more preferably 0.85 or more, and particularly preferably 0.90 or more. High current density charge / discharge characteristics generally improve as the circularity increases. Therefore, when the circularity is less than the above range, the filling property of the negative electrode active material is lowered, the resistance between particles is increased, and the high current density charge / discharge characteristics may be lowered for a short time.

  The circularity of the lithium titanium composite oxide is measured using a flow type particle image analyzer (FPIA manufactured by Sysmex Corporation). Specifically, about 0.2 g of a sample is dispersed in a 0.2 mass% aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and an ultrasonic wave of 28 kHz is output at 60 W for 1 After irradiating for minutes, the detection range is specified as 0.6 to 400 μm, and the particle size is measured for particles in the range of 3 to 40 μm. The circularity obtained by the measurement is defined as the circularity of the lithium titanium composite oxide in the present invention.

(7) Aspect ratio The aspect ratio of the lithium titanium composite oxide is preferably 1 or more, preferably 5 or less, more preferably 4 or less, still more preferably 3 or less, and particularly preferably 2 or less. If the aspect ratio exceeds the above range, streaking or a uniform coated surface cannot be obtained when forming an electrode plate, and high current density charge / discharge characteristics may be deteriorated for a short time. The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the lithium titanium composite oxide.

  The aspect ratio of the lithium titanium composite oxide is measured by magnifying and observing the particles of the lithium titanium composite oxide with a scanning electron microscope. When 50 arbitrary lithium-titanium composite oxide particles fixed to the end face of a metal having a thickness of 50 μm or less are selected, and the stage on which the sample is fixed is rotated and tilted, and three-dimensional observation is performed. The longest diameter A of the particles and the shortest diameter B orthogonal to the same are measured, and the average value of A / B is obtained. The aspect ratio (A / B) determined by the measurement is defined as the aspect ratio of the lithium titanium composite oxide in the present invention.

<Configuration and production method of 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.
Further, the current collector of the negative electrode may be roughened in advance.
Furthermore, when the current collector is a metal material, 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. 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, and is 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. but more preferably, particularly 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, 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.

<Area of negative electrode plate>
The area of the negative electrode plate is not particularly limited, but it is preferably designed to be slightly larger than an opposing positive electrode plate, which will be described later, so that the positive electrode plate does not protrude from the negative electrode plate. Further, from the viewpoint of suppressing the life of a cycle in which charge and discharge are repeated and deterioration due to high temperature storage, it is preferable that the area be as close to the positive electrode as possible, because the ratio of electrodes that work more uniformly and effectively is increased and the characteristics are improved. In particular, when used with a large current, the design of the area of the negative electrode plate is important.

<2-4. 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.

<Material>
As materials for the resin and glass fiber separator, for example, polyolefin such as polyethylene and polypropylene, aromatic polyamide, polytetrafluoroethylene, polyethersulfone, polyimide, polyester, polyoxyalkylene, glass filter and the like can be used. Among them, preferred are glass filters and polyolefins, more preferred are polyolefins, and particularly preferred are polyethylene and polypropylene. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. Alternatively, the above materials may be stacked.

<Thickness>
The thickness of the separator is arbitrary, but is usually 1 μm or more, preferably 5 μm or more, more preferably 10 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. On the other hand, if it is thicker than the above range, not only the battery performance such as the rate characteristic may be lowered, but also the energy density of the whole non-aqueous electrolyte secondary battery may be lowered.

<Porosity>
When a porous material such as a porous sheet or nonwoven fabric is used 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, Usually, it is 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

<Average pore diameter>
The average pore diameter of the separator is also arbitrary, but is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm or more. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.

<Inorganic separator>
On the other hand, as the inorganic material, for example, oxides such as alumina, titania and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. Things are used.

<Form>
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-described 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 a fluorine resin such as PVdF as a binder.

<Air permeability>
The characteristic of the separator in the non-aqueous electrolyte secondary battery can be grasped by the Gurley value. The Gurley value indicates the difficulty of air passage in the film thickness direction, and is expressed as the number of seconds required for 100 ml of air to pass through the film. It means that it is harder to go through. That is, a smaller value means better communication in the thickness direction of the film, and a larger value means lower communication in the thickness direction of the film. Communication is the degree of connection of holes in the film thickness direction. If the Gurley value of the separator of the present invention is low, it can be used for various purposes. For example, when used as a separator for a non-aqueous lithium secondary battery, a low Gurley value means that lithium ions can be easily transferred and is preferable because of excellent battery performance. Although the Gurley value of a separator is arbitrary, Preferably it is 10-1000 second / 100ml, More preferably, it is 15-800 second / 100ml, More preferably, it is 20-500 second / 100ml. If the Gurley value is 1000 seconds / 100 ml or less, the electrical resistance is substantially low, which is preferable as a separator.

<Production method>
Specific examples of the method for obtaining the separator main body and the porous film include the following methods.
(1) A low molecular weight material that is compatible with the polyolefin resin and can be extracted in a later step is added to the polyolefin resin, melt kneaded and formed into a sheet, and the low molecular weight material is extracted after stretching or before stretching. (2) Stretching method in which low-temperature stretching and high-temperature stretching are added to a highly elastic sheet prepared by forming a crystalline resin into a sheet with a high draft ratio to make it porous (3) The thermoplastic resin is inorganic or organic. Interfacial exfoliation method in which filler is added to melt knead and form a sheet, and the interface between the resin and filler is exfoliated by stretching to make it porous. The β crystal nucleating agent method in which the sheet on which the β crystal is formed is stretched and made porous by utilizing the crystal transition, and the manufacturing method is not limited to a wet type or a dry type.

<2-5. 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 below the above range, the battery capacity decreases. Also, if the above range is exceeded, the void space is small, the battery expands, and the member expands or the vapor pressure of the electrolyte liquid component increases and the internal pressure rises. In some cases, the gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.

<Current collection structure>
In the case where the electrode group has the laminated structure described above, 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 reduce the resistance by providing a plurality of terminals in the electrode. 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.

<Protective element>
Protection elements such as PTC (Positive Temperature Coefficient), thermal fuse, thermistor, which increases resistance when abnormal heat is generated or excessive current flows, shuts off current flowing through the circuit due to sudden increase in battery internal pressure or internal temperature during 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 (exterior case). There is no restriction | limiting in this exterior body, As long as the effect of this invention is not impaired remarkably, a well-known thing can be employ | adopted arbitrarily.
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 or an aluminum alloy, a magnesium alloy, nickel, titanium, or a metal, 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 the outer case using the above metals, the metal is welded to each other by laser welding, resistance welding, ultrasonic welding, or a sealed sealing structure, or a caulking structure using the above metals through a resin gasket To do. 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.

<Shape>
The shape of the outer case 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 reference example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.
[Production of secondary battery]
<Preparation of positive electrode>
Lithium nickel manganese cobaltate (LiNi _1/3 Mn _1/3 Co _1/3 as a positive electrode active material
90 parts by mass of O ₂ ), 7 parts by mass of carbon black and 3 parts by mass of polyvinylidene fluoride are mixed, and N-methyl-2-pyrrolidone is added to form a slurry, which is uniformly applied to both sides of an aluminum foil having a thickness of 15 μm. After coating and drying so as to be 11.85 mg · cm ⁻² , the positive electrode active material layer was pressed so as to have a density of 2.6 g · cm ⁻³ to obtain a positive electrode.

<Production of negative electrode>
To graphite, an aqueous dispersion of sodium carboxymethylcellulose (concentration of 1% by mass of sodium carboxymethylcellulose) as a thickener and an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber of 50% by mass) as a binder are added. The slurry was mixed with a disperser. The obtained slurry was applied uniformly to one side of a copper foil having a thickness of 12 μm so as to be 6.0 mg · cm ⁻² and dried, and then the density of the negative electrode active material layer was 1.36 g · cm ⁻³ . It pressed so that it might become a negative electrode. The graphite used has a d50 value of 10.9 μm, a specific surface area of 3.41 m ² / g, and a tap density of 0.985 g / cm ³ . Further, the slurry was prepared so that the mass ratio of graphite: sodium carboxymethyl cellulose: styrene-butadiene rubber = 97.5: 1.5: 1 was obtained in the negative electrode after drying.

<Manufacture of non-aqueous electrolyte secondary battery>
The positive electrode, the negative electrode, and the separator were stacked in the order of the negative electrode, the separator, and the positive electrode. The separator was made of polypropylene, had a thickness of 20 μm, and a porosity of 54%. 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]
<Initial charge / discharge test>
In a constant temperature bath at 25 ° C., the sheet-like non-aqueous electrolyte secondary battery was charged at 0.05 C for 10 hours, then rested for 3 hours, and then charged at constant current at 0.2 C to 4.1 V. Further, after a rest of 3 hours, constant current-constant voltage charging was performed at 0.2 C to 4.1 V, and then constant current discharging was performed to 3.0 V at 1/3 C. After that, two charging / discharging cycles were carried out, in which 1 / 3C constant current-constant voltage charging up to 4.1V and subsequent 1 / 3C constant current discharging up to 3.0V were taken as one cycle. Furthermore, after charging at a constant current-constant voltage at 1/3 C to 4.1 V, the battery was stored at 60 ° C. for 12 hours to stabilize the battery. Then, the charge / discharge cycle of 1 / 3C constant current-constant voltage charge up to 4.2V at 25 ° C. and subsequent 1 / 3C constant current discharge up to 3.0V was performed. The last discharge capacity at this time was defined as the initial capacity. In addition, 1C is a current value when discharging the entire capacity of the battery in one hour.

<High temperature storage test>
The battery that had been initially charged and discharged was charged at a constant current-constant voltage to SCO 80% (3880 mV) at 25 ° C., and then stored at 60 ° C. for 4 weeks.

<Charge / discharge cycle test>
The battery that had been initially charged and discharged was charged to 4.2 V by a 2C constant current method at 60 ° C., and then charged and discharged to discharge to 3.0 V by a 2C constant current method. After the charge / discharge cycle, at 25 ° C., a charge / discharge cycle of 1 / 3C constant current-constant voltage charge up to 4.2V and subsequent 1 / 3C constant current discharge up to 3.0V was performed. The discharge capacity was defined as the post-cycle capacity. The ratio of the post-cycle capacity to the initial capacity was defined as the charge / discharge cycle capacity maintenance rate.

<Low-temperature resistance evaluation test>
The battery at the initial stage and after the cycle is adjusted to 3.72 V, and from that state, constant current discharge is performed at −30 ° C. at various current values for 10 seconds. The voltage after 10 seconds is plotted with respect to various current values, and the current value such that the voltage after 10 seconds becomes 3V is obtained. The slope of the straight line obtained by connecting the point thus obtained and the point of the initial value (open circuit state) is defined as the low temperature resistance, and after the high temperature storage test or the charge / discharge cycle test for the initial low temperature resistance. The ratio of the low temperature resistance was defined as the resistance increase rate.

[Example 1]
Under a dry argon atmosphere, fully dried LiPF ₆ 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 solution may be referred to as “reference electrolyte solution”). A compound of the following chemical formula 9 was added to the reference electrolyte so as to be 0.91% by mass with respect to the non-aqueous electrolyte to prepare a non-aqueous electrolyte. A battery was prepared by the above-described method using this electrolytic solution, and the resistance increase rate after the high-temperature storage test was measured. The results thus obtained are shown in Table 1.

[Example 2]
A battery was prepared in the same manner as in Example 1 except that 1.21% by mass of the compound of the following formula 10 was added instead of the compound of the formula 9, and the resistance increase rate after the high-temperature storage test was measured. The results thus obtained are shown in Table 1.

[Example 3]
A battery was prepared in the same manner as in Example 1 except that 0.94% by mass of the compound of the following formula 11 was added instead of the compound of formula 9, and the resistance increase rate after the high-temperature storage test was measured. The results thus obtained are shown in Table 1.

[Example 4]
A battery was prepared in the same manner as in Example 1 except that 0.96% by mass of the compound of the following chemical formula 12 was added instead of the compound of the chemical formula 9, and the resistance increase rate after the high temperature storage test was measured. The results thus obtained are shown in Table 1.

[Reference Example 1]
A battery was prepared in the same manner as in Example 1 except that the reference electrolyte was used as the electrolyte, and the resistance increase rate after the high-temperature storage test was measured. The results thus obtained are shown in Table 1.

From Table 1, it was found that the resistance increase rate after the high-temperature storage test was suppressed in all cases where the specific compound of the present invention was added.
[Example 5]
A battery was prepared in the same manner as in Example 1, and the charge / discharge cycle capacity retention rate and the resistance increase rate after the charge / discharge cycle test were measured. The results thus obtained are shown in Table 2.

[Example 6]
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of vinylene carbonate was further added to the electrolyte solution of Example 1, and the charge / discharge cycle capacity retention rate and the resistance increase rate after the charge / discharge cycle test were determined. It was measured. The results thus obtained are shown in Table 2.
[Reference Example 2]
A battery was prepared in the same manner as in Example 1 except that the reference electrolyte was used as the electrolyte, and the charge / discharge cycle capacity retention rate and the resistance increase rate after the charge / discharge cycle test were measured. The results thus obtained are shown in Table 2.

[Reference Example 3]
A battery was prepared in the same manner as in Example 6 except that the compound of Chemical formula 9 was not added to the electrolytic solution, and the charge / discharge cycle capacity retention rate and the resistance increase rate after the charge / discharge cycle test were measured. The results thus obtained are shown in Table 2.
[Reference Example 4]
A battery was prepared in the same manner as in Example 1 except that 0.54% by mass of the compound of the following chemical formula 13 was added to the electrolytic solution instead of the chemical formula 9 and the charge / discharge cycle capacity retention rate and the charge / discharge cycle test were The resistance increase rate was measured. The results thus obtained are shown in Table 2.

[Reference Example 5]
A battery was prepared in the same manner as in Example 6 except that 0.54% by mass of the compound of Chemical Formula 10 was added to the electrolytic solution instead of the compound of Chemical Formula 9, and after the charge / discharge cycle capacity maintenance rate and the charge / discharge cycle test The resistance increase rate was measured. The results thus obtained are shown in Table 2.

  From the comparison between Reference Example 2 and Reference Example 4 and the comparison between Reference Example 3 and Reference Example 5, when a sulfonic acid ester not having the characteristics of the specific compound in the present invention was added, the charge / discharge cycle capacity retention rate, A decrease in characteristics was confirmed in one or both of the resistance increase rates. However, from the comparison between Reference Example 2 and Example 5 and the comparison between Reference Example 3 and Example 6, the addition of the specific compound in the present invention improves both the charge / discharge cycle capacity retention rate and the resistance increase rate. The effect was recognized. As described above, the electrolyte containing the specific compound in the present invention not only suppresses the resistance increase rate of the non-aqueous electrolyte battery, but also realizes the charge / discharge cycle capacity maintenance rate and the resistance increase rate at a higher level than before. I also found out that In addition, since the charge / discharge cycle test is performed at a high temperature of 60 ° C., the technology of the present invention shows an improvement effect on the capacity retention rate when the battery is left in a high temperature environment. Suggests.

According to the non-aqueous electrolyte solution of the present invention, it is possible to improve capacity deterioration during charge / discharge cycles and high-temperature storage of a non-aqueous electrolyte battery. Therefore, the non-aqueous electrolyte solution of the present invention and the non-aqueous electrolyte battery using the same 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, etc. , Walkie Talkie, 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, Load Examples include leveling power sources and natural energy storage power sources.

Claims (12)

A non-aqueous electrolyte containing an electrolyte and a non-aqueous solvent, wherein the non-aqueous electrolyte contains at least one compound having a structure represented by the formula (1).
Q-O-N (1)
(Q represents a group 13-16 element excluding carbon and oxygen atoms)   The non-aqueous electrolyte solution according to claim 1, wherein Q in the formula (1) is any one of a boron atom, an aluminum atom, a silicon atom, a nitrogen atom, a phosphorus atom, and a sulfur atom.   In the said Formula (1), Q is a phosphorus atom and a sulfur atom, The non-aqueous electrolyte solution of Claim 1 characterized by the above-mentioned. The non-aqueous electrolyte solution according to claim 1, wherein the compound having a structure represented by the formula (1) is a compound represented by the following formula (2).

(M represents a Group 13-16 element excluding a carbon atom and an oxygen atom, and R ^{1 to} R ³ each independently represents a hydrogen atom, a halogen atom, or an organic group that may contain a C 1-12 hetero atom. P represents an integer of 1 to 3, q represents an integer of 0 to ^2. R ² and R ³ may be bonded to each other to form a ring, and when M is a group 13 element, p = 2, q = 0, when M is a group 14 element, p = 3 and q = 0, and when M is a group 15 element, 0 ≦ p ≦ 2, 0 ≦ q ≦ 1. (In the case of a group 16 element, p = 1, 1 ≦ q ≦ 2.)   The non-aqueous electrolyte solution according to claim 4, wherein in the formula (2), M is any one of a boron atom, an aluminum atom, a silicon atom, a nitrogen atom, a phosphorus atom, and a sulfur atom.   In the said Formula (2), M is either a phosphorus atom or a sulfur atom, The non-aqueous electrolyte solution of Claim 4 characterized by the above-mentioned.   The compound having the structure represented by the formula (1) or the compound represented by the formula (2) is contained in an amount of 0.01 to 10% by mass with respect to the whole non-aqueous electrolyte solution. Item 7. The nonaqueous electrolytic solution according to any one of Items 1 to 6.   In addition to non-aqueous electrolytes, non-aqueous electrolytes further include vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, 1,3-propane sultone, 1,3-propene sultone, ethylene sulfite, ethylene sulfate, adiponitrile, pimelonitrile, Selected from the group consisting of sinonitrile, t-amylbenzene, cyclohexylbenzene, lithium difluorooxalatoborate, lithium bis (oxalato) borate, lithium difluorobis (oxalato) phosphate, lithium tetrafluorooxalatophosphate, lithium tris (oxalato) phosphate The non-aqueous electrolyte solution according to any one of claims 1 to 7, wherein at least one kind of compound is contained. It is a non-aqueous electrolyte secondary battery provided with the negative electrode and positive electrode which can occlude and discharge | release metal ion, and a non-aqueous electrolyte solution, Comprising: The non-aqueous electrolyte solution of any one of Claims 1-8 is used. A non-aqueous electrolyte secondary battery characterized by the above.   The non-aqueous electrolyte secondary battery according to claim 9, wherein the positive electrode capable of inserting and extracting metal ions includes at least one layered transition metal oxide.   The non-aqueous electrolyte secondary battery according to claim 9, wherein the negative electrode capable of inserting and extracting metal ions contains at least a carbon compound. A compound represented by the following formula (3).

(M represents a group 13-16 element excluding a carbon atom and an oxygen atom, R ⁴ and R ⁵ each independently represents a hydrogen atom, an organic group that may contain a C 1-12 hetero atom, q Represents an integer of 0 to 2, r represents an integer of 1 to 5, and t represents 1 or 2. R ⁴ and R ⁵ may be bonded to each other to form a ring, and M represents a group 13 element In this case, q = 0, when M is a group 14 element, q = 0, when M is a group 15 element, 0 ≦ q ≦ 1, when M is a group 16 element, 1 ≦ q ≦ 2.)