JP6780450B2 - Non-aqueous electrolyte and non-aqueous electrolyte secondary batteries - Google Patents

Description

The present invention relates to a non-aqueous electrolyte solution and a non-aqueous electrolyte solution secondary battery. Specifically, the present invention relates to a non-aqueous electrolyte solution containing a specific solvent and a specific compound, and a non-aqueous electrolyte solution using the non-aqueous electrolyte solution. Regarding liquid secondary batteries.

Non-aqueous electrolyte secondary such as lithium secondary batteries in a wide range of applications such as power supplies for mobile phones such as smartphones, so-called consumer small devices such as laptop computers, and in-vehicle power supplies for driving such as electric vehicles. Batteries have been put into practical use.
Above all, in the case of an in-vehicle power supply for an electric vehicle or the like, high output characteristics are required when starting in a cold region (-20 ° C to -30 ° C), so improvement of low temperature output is important.

So far, as a means for improving the low temperature output of non-aqueous electrolyte secondary batteries, there are many ways to improve the active materials of positive and negative electrodes and various battery components such as non-aqueous electrolyte. Technology is being considered.

For example, Patent Document 1 discloses a technique for improving the ion conductivity at a low temperature by optimizing the composition ratio of the cyclic carbonate and the chain carbonate in the non-aqueous electrolyte solution for a low temperature.

Patent Document 2 discloses a non-aqueous electrolyte solution having improved cycle characteristics by adding tricredil phosphate (tricresyl phosphate) to the electrolyte solution. Further, Patent Document 2 describes that lactones, ethers, carboxylic acids, nitriles, amides, nitros, sulfolanes and the like may be used.

In Patent Document 3, in a lithium battery composed of a positive electrode containing a lithium phosphoric acid compound having an olivine structure, a negative electrode, and a non-aqueous electrolytic solution, an electrolytic solution in which 1,2-dimethoxyethane and a cyclic carbonate ester derivative are used in combination is described. , It is disclosed that it is excellent in ion conductivity.

Patent Document 4 discloses that in a lithium battery composed of a positive electrode, a negative electrode, and a non-aqueous electrolytic solution, an electrolytic solution using methyl propionate and ethynyl ethylene carbonate in combination improves charge / discharge characteristics at low temperatures. There is.

Japanese Unexamined Patent Publication No. 10-0276225 Japanese Unexamined Patent Publication No. 2006-221972 Japanese Unexamined Patent Publication No. 2010-86722 Japanese Unexamined Patent Publication No. 2013-171758

As described above, when a non-aqueous electrolyte battery is used as an in-vehicle power source for an electric vehicle, high output characteristics are required when starting in a cold region, so it is important to improve the low temperature output.
However, the types of non-aqueous solvents that can be used in the non-aqueous electrolyte solution are limited, and the effect of improving the low temperature output characteristics is insufficient only by preparing the composition of the non-aqueous solvent as in Patent Document 1. ..

Although Patent Document 2 discloses that a battery using an electrolytic solution containing tricredyl phosphate is excellent in cycle characteristics, the effect of improving the low temperature output characteristics of the battery is insufficient.

Further, Patent Document 3 describes that the use of dimethoxyethane improves the ionic conductivity, but dimethoxyethane is easily oxidatively decomposed and can be used only in combination with a specific positive electrode and a specific compound. There was a problem that it could only be used.
In particular, since the positive electrode potential containing the lithium phosphoric acid compound having an olivine structure is low, there is a problem that sufficient output cannot be obtained as an in-vehicle power supply, and the low-temperature output characteristics are insufficient for in-vehicle power supply. there were.
Patent Document 4 is an invention that solves the problem that a carboxylic acid ester is easily decomposed by using a carboxylic acid ester such as methyl propionate in combination with a specific compound. However, the low temperature output characteristics are insufficient to use the battery using the non-aqueous electrolyte solution described in Patent Document 4 as it is as an in-vehicle power source.

The present invention solves the problem that an ether compound such as 1,2-dimethoxyethane and a carboxylic acid ester such as methyl propionate cannot be used alone because they are easily decomposed in an electrolytic solution. It is an invention found that the low temperature output characteristic is improved by using it together with the phosphoric acid ester compound represented by the formula (1).

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a non-aqueous electrolyte solution and a non-aqueous electrolyte secondary battery having excellent low temperature output characteristics.

The present inventor is keen to solve the problem that ether compounds such as 1,2-dimethoxyethane and carboxylic acid esters such as methyl propionate cannot be used alone because they are easily decomposed in an electrolytic solution. As a result of repeated studies, a non-aqueous electrolyte solution capable of obtaining excellent low-temperature output characteristics can be obtained by using the ether compound and / or the carboxylic acid ester in combination with the phosphoric acid ester compound represented by the general formula (1) described later. It is an invention found to be obtained.
Patent Document 3 is a non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent, which is a non-aqueous electrolyte solution containing a specific compound represented by the general formula (1) described later and a chain ether and / or a carboxylic acid ester. We have found that the low temperature output characteristics are significantly improved by using the electrolytic solution, and have completed the present invention.

That is, the present invention provides the specific embodiments shown in the following [1] to [16].
[1] A non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent, which contains at least one compound selected from the group consisting of the compound of the following general formula (1) and a chain ether and a carboxylic acid ester. Aqueous electrolyte.

(In the formula (1), R ^{1 to} R ³ represent hydrogen atoms or chain hydrocarbon groups having 1 to 10 carbon atoms, respectively. In the formula, a, b, and c represent integers from 0 to 5. a + b + c indicates an integer of ^{1 to} 9. R ^{1 to} R ³ may be the same or different.)
[2] The non-aqueous electrolyte solution according to [1], wherein in the general formula (1), R ^{1 to} R ³ are hydrogen atoms or methyl groups.
[3]
The non-aqueous electrolyte solution according to [1] or [2], wherein R ^{1 to} R ³ are methyl groups in the general formula (1) and a = b = c = 1 or 2.
[4]
The non-aqueous electrolyte solution according to [1] to [3], wherein the compound represented by the general formula (1) contains any of the following structural formulas (2) to (4).

[5] The non-aqueous electrolytic solution according to [4], which contains two or more of the structural formulas (2) to (4) in the non-aqueous electrolytic solution.
[6] When two or more compounds represented by the general formula (1) are contained, the ratio of the substitution positions of R ^{1 to} R ³ is the sum of the ortho-position, meta-position, and para-position. The non-aqueous electrolyte solution according to [4], wherein the meta-positional substituent is 50% or more.
[7] Of [1] to [6], the content of the compound represented by the general formula (1) is 0.001% by mass or more and 10% by mass or less with respect to the total amount of the non-aqueous electrolyte solution. The non-aqueous electrolyte solution according to any one item.
[8] At least one compound selected from the group consisting of the chain ether or the carboxylic acid ester is contained in an amount of 0.5% by volume or more and 80% by volume or less based on the total amount of the solvent of the non-aqueous electrolyte solution [1]. ] To [7]. The non-aqueous electrolyte solution according to any one of the items.
[9] The non-aqueous electrolyte solution according to [1] to [8], wherein the chain ether is at least one of dimethoxyethane, ethoxymethoxyethane, and diethoxyethane.
[10] The carboxylic acid ester is at least one of methyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and gamma butyrolactone, [1] to [9]. The non-aqueous electrolyte solution described in 1.
[11] The non-aqueous electrolyte solution according to [1] to [10], which further contains a carbon-carbon unsaturated bond or a carbonate containing at least one of fluorine atoms.
[12] The carbonate containing at least one of the early carbon-carbon unsaturated bond or the fluorine atom is at least one selected from the group consisting of vinylene carbonate, vinylethylene carbonate, ethynylethylene carbonate, and fluoroethylene carbonate. 11] The non-aqueous electrolyte solution.
[13] A non-aqueous electrolyte secondary battery containing a negative electrode and a positive electrode capable of storing and releasing lithium ions, and the non-aqueous electrolyte solution according to [1] to [12].
[14] The negative electrode has a negative electrode active material layer on a current collector, and the negative electrode active material layer includes a simple substance metal of silicon, an alloy and a compound, a simple substance metal of tin, an alloy and a compound, a carbonaceous material, and the like. The non-aqueous electrolyte secondary battery according to [13], which contains at least one selected from the group consisting of lithium titanium composite oxides.
[15] The positive electrode has a positive electrode active material layer on a current collector, and the positive electrode active material layer includes a lithium-cobalt composite oxide, a lithium-cobalt-nickel composite oxide, and a lithium-manganese composite oxide. It contains at least one selected from the group consisting of lithium-cobalt-manganese composite oxide, lithium-nickel composite oxide, lithium-nickel-manganese composite oxide, and lithium-cobalt-nickel-manganese composite oxide. 13] The non-aqueous electrolyte secondary battery.
[16] The positive electrode has a positive electrode active material layer on a current collector, and the positive electrode active material layer is a group consisting of LixMPO ₄ (M is a group of transition metals of groups 4 to 11 of the 4th period of the periodic table. The non-aqueous electrolyte secondary battery according to [15], wherein x contains at least one element selected from the above, 0 <x <1.2).

According to the present invention, it is possible to provide a non-aqueous electrolyte solution and a non-aqueous electrolyte secondary battery which are suitable for in-vehicle use and have excellent low temperature output characteristics.

Hereinafter, embodiments of the present invention will be described in detail. The following embodiments are examples (representative examples) of embodiments of the present invention, and the present invention is not limited thereto. Further, the present invention can be arbitrarily modified and implemented without departing from the gist thereof.

<1. Non-aqueous electrolyte>
<1-1. Compound of general formula (1)>
The non-aqueous electrolyte solution of the present invention is characterized by containing a compound represented by the following general formula (1).

In the formula (1), R ^{1 to} R ³ represent hydrogen atoms or chain hydrocarbon groups having 1 to 10 carbon atoms, respectively. In the formula, a, b, and c represent integers from 0 to 5, and a + b + c represent integers from 1 to 9. a, b, c or R ^{1 to} R ³ may be the same or different.

Specific examples of the chain hydrocarbon group include an alkyl group, an alkenyl group and an alkynyl group, preferably an alkyl group and an alkenyl group, and more preferably an alkyl group. With the above-mentioned chain hydrocarbon group, a composite film of the compound represented by the general formula (1) and the chain ether or carboxylic acid ester described later is likely to be formed, and the solvent is not water in a non-aqueous electrolyte solution. The solvent, chain ether, carboxylic acid ester, etc. are decomposed, and the increase in resistance of the non-aqueous electrolytic solution can be suppressed.
Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group and the like. Since an increase in viscosity (decrease in output) is suppressed, a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, a hexyl group, and more preferably a methyl group, an ethyl group, or n. -Propyl group, n-butyl group, n-pentyl group, hexyl group, more preferably methyl group, ethyl group, n-propyl group, n-butyl group, particularly preferably methyl group, ethyl group.
Specific examples of the alkenyl group include a vinyl group, an allyl group, a metharyl group, a 2-butenyl group, a 3-methyl2-butenyl group, a 3-butenyl group, a 4-pentenyl group and the like, and an increase in the solution viscosity ( From the viewpoint of suppressing the decrease in output), a vinyl group, an allyl group, a metalyl group, a 2-butenyl group, more preferably a vinyl group, an allyl group, a metallic group, and further preferably an allyl group.
Specific examples of the alkynyl group include an ethynyl group, a 2-propynyl group, a 2-butynyl group, a 3-butynyl group, a 4-pentynyl group, a 5-hexynyl group and the like, and an increase in solution viscosity (decrease in output). From the viewpoint of suppressing the above, preferred are ethynyl groups, 2-propynyl groups, 2-butynyl groups, 3-butynyl groups, more preferably 2-propynyl groups, 3-butynyl groups, and even more preferably 2-propynyl groups. Be done.

From the viewpoint of forming a film on the electrode of the compound represented by the general formula (1), in the general formula (1), R ^{1 to} R ³ are preferably hydrogen atoms or methyl groups. Among ^them, more preferably one of R 1 to R ³ is a methyl ^group, and more preferably all R 1 to R ³ is a methyl group.

From the viewpoint of forming a film on the electrode of the compound represented by the general formula (1), it is preferable that a, b, and c are 1 or 2, respectively, in the general formula (1). Further, for the same reason, it is more preferable that a = b = c = 1 or 2, and it is further preferable that a = b = c = 1.

Examples of the specific structure of the compound represented by the general formula (1) in the compound used in the present invention include the following structures.
In the following structural formula, Et and Bu represent an ethyl group and a butyl group, respectively.

Preferably, a compound having the following structure is mentioned. This is because having an alkyl group on the aromatic ring facilitates the formation of a film on the positive electrode.

More preferably, a compound having the following structure can be mentioned. This is because the positive electrode coating produced by the compound having the following structure has high lithium ion permeability. Then, it is particularly preferable that the non-aqueous electrolyte solution contains two kinds of compounds having the following structures from the viewpoint of low temperature output characteristics.

The blending amount of the compound represented by the general formula (1) with respect to the total amount of the non-aqueous electrolyte solution of the present invention is not limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but the total amount of the non-aqueous electrolyte solution of the present invention. On the other hand, it is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 10.0% by mass or less, preferably 5.0% by mass or less. It is more preferably blended with the electrolytic solution at a concentration of 4.0% by mass or less, more preferably 3.0% by mass or less. At the above concentration, the viscosity of the non-aqueous electrolyte solution is in an appropriate range, and tends to have excellent low temperature output characteristics.
The compound represented by the general formula (A) may be used alone or in combination of two or more, and preferably contains two or more.
In the present invention, when two or more compounds represented by the general formula (A) are contained, tri (p-tolyl) phosphine, tri (m-tolyl) phosphine, and tri (o-tolyl) phosphine are used in combination. Alternatively, tricresyl phosphate produced from a cresol containing a plurality of isomers may be used, and it is preferable to use tricresyl phosphate produced from a cresol containing a plurality of isomers.

When two or more compounds represented by the general formula (1) are contained, the ratio of the substitution positions of R _{1 to} R ₃ is para to the sum of the ortho-position, meta-position, and para-position from the viewpoint of low-temperature output characteristics. position substituents body goes usually 10% or more, preferably 20% or more, more preferably 30% or more, the upper limit is not particularly limited, but good Mashiku is at 40% or less.

When two or more compounds represented by the general formula (1) are contained, the ratio of the substitution positions of R ^{1 to} R ³ is meta to the sum of the ortho-position, meta-position, and para-position from the viewpoint of low-temperature output characteristics. The position substitution product is usually 50% or more, preferably 60% or more, more preferably 65% or more, and the upper limit is not particularly limited, but is usually 90% or less, preferably 80% or less.

When two or more compounds represented by the general formula (1) are contained, the ratio of the substitution positions of R ^{1 to} R ³ is the ortho position, the meta position, and the para position from the viewpoint of reducing the film formation rate due to steric hindrance. The ortho position substitution product is usually 40% or less, preferably 30% or less, more preferably 10% or less, still more preferably 1% or less, and particularly preferably not containing the ortho position substitution product with respect to the sum of the positions. ..

The substitution positions of R ^{1 to} R ³ of the compound represented by the above general formula (1) can be analyzed by using ^{1 1} H-NMR. For example, when an equimolar mixture of tri (o-tolyl) phosphine and tri (p-tolyl) phosphine is used, the ortho position substitution product is 50%, (p-tolyl) (m-tolyl) (o-tolyl). The ortho position substitution when using only phosphine is calculated to be 33%.
Further, when R ^{1 to} R ³ of the general formula (1) have a chain alkyl group at the para position and the ortho position, or a structure having a chain alkyl group at the meta position and the ortho position is also used as an ortho position substitution product, and para. A structure having a chain alkyl group at the position and the meta position shall be a meta position substitution product.

The method of containing the compound represented by the general formula (1) in the electrolytic solution of the present invention is not particularly limited. In addition to the method of directly adding the compound to the electrolytic solution, a method of generating the compound in a battery or an electrolytic solution can be mentioned. Examples of the method for generating the above compound include a method in which phosphorus oxytrichloride and cresol are added to a non-aqueous electrolytic solution and the compound is generated by oxidation, reduction, hydrolysis or the like. Further, a method of producing a battery and generating it by applying an electric load such as charging / discharging can be mentioned.
When the cresol is a mixture of a para-position-substituted product, a meta-position-substituted product, and an ortho-position-substituted product, a compound represented by the general formula (1) is produced in the battery according to the cresol substitution product ratio. ..

When the compound represented by the general formula (1) is contained in a non-aqueous electrolyte solution and actually used for producing a non-aqueous electrolyte secondary battery, it is consumed as a positive electrode film after charging and discharging. Even if the non-aqueous electrolyte solution is extracted again after disassembling the battery, the content in the solution may be significantly reduced. Therefore, the inclusion of the compound represented by the general formula (1) in the present invention also includes the detection of the compound derived from the general formula (1) in the electrolytic solution or on the surface of the positive electrode.
For example, in order to detect the compound derived from the general formula (1) from the surface of the positive electrode, pyrolysis gas chromatography or the like can be used.
Further, the content of the compound represented by the general formula (1) in the present invention means at the time of producing the non-aqueous electrolyte solution, at the time of injecting the non-aqueous electrolyte solution into the battery, or at the time of shipment as the battery. Means the content of.

<1-2. Chain ether, carboxylic acid ester>
The second feature of the non-aqueous electrolyte solution of the present invention is that it further contains a chain ether and / or a carboxylic acid ester in addition to the compound of the following general formula (1).

The content of the chain ether and / or the carboxylic acid ester is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired. However, the chain ether and / or the carboxylic acid ester is a non-aqueous electrolyte solution. Usually 0.5% by volume or more, preferably 1% by volume or more, more preferably 2% by volume or more, and usually 80% by volume or less, preferably 45% by volume or less, more preferably 30% by volume, based on the total amount of the solvent. % Or less, more preferably 20% by volume or less, and particularly preferably 10% by volume or less. When the chain ether and the carboxylic acid ester are contained, the low temperature output characteristic tends to be improved when the sum of the contents of the chain ether and the carboxylic acid ester is in the above range.
The volume% and volume ratio in the present invention mean values measured at 25 ° C. and 1 atm, and the following description is also treated in the same manner.
Further, in the present invention, the total amount of the solvent in the non-aqueous electrolyte solution is defined as <1-2. Chain ether, carboxylic acid ester> and <1-4. It means the sum of the compounds described in Non-aqueous solvent>.

It is not clear whether the problem of the present invention could be solved by containing the compound of the general formula (1) and further containing the chain ether and / or the carboxylic acid ester, but it is presumed as follows. ..

The compound represented by the general formula (1) has an aromatic ring in which a chain hydrocarbon group, which is an easily oxidizing site, is substituted in the molecule. Therefore, it is known that the above-mentioned site undergoes an oxidation reaction on the positive electrode to generate cation species and form a film.
However, when the compound of the general formula (1) is added, the viscosity of the non-aqueous electrolyte solution increases and the ionic conductivity decreases, which has a drawback that the output characteristics deteriorate. Further, when a film made of the compound of the general formula (1) is formed on the positive electrode, the speed of insertion and desorption of lithium ions on the surface of the positive electrode becomes slow, so that there is a drawback that the output characteristics are rather deteriorated.

Further, a non-aqueous electrolyte solution using a chain ether or a carboxylic acid ester as a solvent has a low electrochemical oxidation potential, and therefore tends to cause a side reaction on the surface of the positive electrode. For this reason, after durability such as after high temperature storage or after a cycle, the charge transfer reaction resistance increases, the output characteristics decrease, the battery capacity decreases, gas is generated by decomposition at the positive electrode, and the battery swells. There was a tendency to increase.
That is, there is a problem that the output characteristics of the compound represented by the general formula (1) are lowered when both the chain ether and the carboxylic acid ester are used alone.

However, when the compound represented by the general formula (1) is used in combination with a chain ether or a carboxylic acid ester as in the present invention, the compound represented by the general formula (1) produces a cation species and a chain. The polar groups (for example, ether groups and ester groups) of the ether and carboxylic acid ester in the molecule chemically react to form a complex film on the positive electrode, thereby suppressing the deterioration of output characteristics. It is thought that it was possible. Since these composite coatings have electron insulating properties, the output decrease due to the subsequent oxidation reaction of the chain ether or carboxylic acid ester is suppressed, and the coating portion derived from the chain ether or carboxylic acid ester is highly permeable to lithium ions. It is presumed that excellent output characteristics were obtained because of the properties.

<1-2-1. Chain ether>
Examples of the chain ether include chain ethers in which the ether oxygen in one molecule usually has 3 to 10 carbon atoms, and from the viewpoint of battery output, chain ethers having 3 to 7 carbon atoms are preferable, and chain ethers having 3 to 5 carbon atoms are preferable. Chain ethers are more preferred.
The chain ether may be used alone or in combination of two or more.

Examples of the chain ether include diethyl ether, di (2-fluoroethyl) ether, di (2,2-difluoroethyl) ether, di (2,2,2-trifluoroethyl) ether, and 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-propyl ether, (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 ether, (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-propyl ether, (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-tri) Fluoro-n-propyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (3,3,3-trifluoro-n-propyl) (2,2,3,3,3-penta) Fluoro-n-propyl) ether, di (2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,3,3-tetrafluoro-n-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-tetrafluoroethoxy) methanedi (2,2,2-trifluoroethoxy) methane, (2,2,2-trifluoroethoxy) (1,1,2,2-tetrafluoroethoxy) methane, di (1,1,2,2-tetrafluoroethoxy) methane, dimethoxyethane, methoxyethoxy ethane, methoxy (2-fluoroethoxy) ethane, methoxy (2) , 2,2-Trifluoroethoxy) ether, methoxy (1,1,2,2-tetrafluoroethoxy) ether, di Ethoxyethane, 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-tri) Fluoroethoxy) ethane, (2,2,2-trifluoroethoxy) (1,1,2,2-tetrafluoroethoxy) ethane, di (1,1,2,2-tetrafluoroethoxy) ethane, ethylene glycol di Examples thereof include -n-propyl ether, ethylene glycol di-n-butyl ether and diethylene glycol dimethyl ether.

Among these, dimethoxymethane, dimethoxyethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvation ability to lithium ions and are ions. It is more preferable in terms of improving dissociability.

Among these, dimethoxymethane, dimethoxyethane, diethoxymethane, and ethoxymethoxymethane are more preferable because they have a low viscosity and give high ionic conductivity.

The content of the chain ether is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.5% by volume or more, preferably 1 volume, based on the total amount of the solvent of the non-aqueous electrolyte solution. % Or more, more preferably 2% by volume or more, and usually 80% by volume or less, preferably 45% by volume or less, more preferably 30% by volume or less, still more preferably 20% by volume or less, particularly preferably 10% by volume or less. When the content of a certain chain ether is within the above preferable range, it is easy to secure the effect of improving the lithium ion dissociation degree of the chain ether and the effect of improving the ionic conductivity due to the decrease in viscosity. Further, when the negative electrode active material is a carbonaceous material, the phenomenon that the chain ether is co-inserted together with the lithium ion can be suppressed, so that a non-aqueous electrolyte solution having more excellent low temperature output characteristics tends to be obtained.

<1-2-2. Carboxylate ester>
Carboxylate esters are classified into chain carboxylic acid esters and cyclic carboxylic acid esters, and chain carboxylic acid esters are preferably used in relation to battery output.
As the carboxylic acid ester, one type may be used, or two or more types may be mixed and used. When two or more kinds are mixed, the chain carboxylic acid ester may be mixed with each other or the cyclic carboxylic acid ester with each other, or the chain carboxylic acid ester and the cyclic carboxylic acid ester may be mixed with each other.

<1-2-2-1. Chain carboxylic acid ester>
Examples of the chain carboxylic acid ester usually include those having 3 to 10 carbon atoms, and from the viewpoint of battery output, the chain carboxylic acid ester having 3 to 6 carbon atoms is preferable, and the chain carboxylic acid ester having 3 to 5 carbon atoms is preferable. Is more preferable.

Specifically, 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, -n-butyl propionate, isobutyl propionate, -t-butyl propionate, methyl butyrate, ethyl butyrate, -n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, -n-isobutyrate Examples thereof include propyl, isopropyl isobutyrate, methyl pivalate, ethyl pivalate and the like.

Among these, methyl acetate, ethyl acetate, -n-propyl acetate, -n-butyl acetate, methyl propionate, ethyl propionate, -n-propyl propionate, isopropyl propionate, methyl butyrate, methyl isobutyrate, pivalic acid Methyl or the like is preferable from the viewpoint of improving the ionic conductivity due to the decrease in viscosity, suppressing the decomposition reaction at the positive electrode, and improving the low temperature output characteristics.

Among these, methyl acetate, -n-propyl acetate, methyl propionate, ethyl propionate, -n-propyl propionate, methyl isobutyrate, and methyl pivalate are more preferable from the viewpoint of greatly improving the low temperature output. ..

Among these, methyl acetate, -n-propyl acetate, methyl propionate, ethyl propionate, -n-propyl propionate, methyl isobutyrate, and methyl pivalate are isobutyric acid, especially from the viewpoint of stability during high-temperature storage. Methyl butyrate and methyl pivalate are more preferred.

The content of the chain carboxylic acid ester is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.5% by volume or more, preferably 0.5% by volume or more, based on the total amount of the solvent of the non-aqueous electrolyte solution. 1% by volume or more, more preferably 2% by volume or more, and usually 80% by volume or less, preferably 45% by volume or less, more preferably 30% by volume or less, still more preferably 20% by volume or less, particularly preferably 10% by volume. It is as follows. When the content of the chain carboxylic acid ester is within the above range, the electric conductivity of the non-aqueous electrolyte solution is improved, and the low temperature output characteristics can be easily improved.

<1-2-2-2. Cyclic carboxylic acid ester>
Examples of the cyclic carboxylic acid ester usually include a cyclic carboxylic acid ester having 3 to 12 carbon atoms, preferably a cyclic carboxylic acid ester having 3 to 10 carbon atoms from the viewpoint of battery output, and a cyclic carboxylic acid ester having 3 to 8 carbon atoms. Is more preferable.

Specific examples thereof include gamma-butyrolactone, gamma valerolactone, gamma caprolactone, and epsilon caprolactone. Of these, gamma-butyrolactone is particularly preferable from the viewpoint of improving low-temperature output characteristics resulting from an improvement in the degree of lithium ion dissociation.

The content of the cyclic carboxylic acid ester is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.5% by volume or more, preferably 1 by volume, based on the total amount of the solvent of the non-aqueous electrolyte solution. By volume or more, more preferably 2% by volume or more, and usually 80% by volume or less, preferably 45% by volume or less, more preferably 30% by volume or less, still more preferably 20% by volume or less, particularly preferably 10% by volume or less. Is. When the content of the cyclic carboxylic acid ester is within the above range, the viscosity of the non-aqueous electrolyte solution is within an appropriate range, the decrease in electrical conductivity is avoided, and the increase in negative electrode resistance is suppressed, so that the non-aqueous electrolyte solution secondary It is easy to set the battery output low temperature characteristic in a good range.

<1-3. Electrolyte>
<Lithium salt>
A lithium salt is usually used as the electrolyte in the non-aqueous electrolyte solution of the present invention. The lithium salt is not particularly limited as long as it is known to be used for this purpose, and any lithium salt can be used, and specific examples thereof include the following.

For example, inorganic lithium salts such as LiBF ₄ , LiClO ₄ , LiAlF ₄ , LiSbF ₆ , LiTaF ₆ , LiWF ₇ ;
Lithium fluorophosphates other than LiPF ₆ such as LiPF ₆ , LiPO ₃ F, LiPO ₂ F ₂ ;
Lithium tungstic acid salts 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 Lithium carboxylic acid 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 Lithium sulfonic acid salts such as CF ₂ CF ₂ SO ₃ Li;
LiN (FCO ₂ ) 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₎ Lithium imides such as SO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) salts;
Lithiummethide salts such as LiC (FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ ;
Lithium oxalate salts such as lithium difluorooxalatobolate, lithium bis (oxalate) borate, lithium tetrafluorooxalat oxalate, lithium difluorobis (oxalate) phosphate, lithium tris (oxalat) 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; and the like.

Inorganic lithium salts, lithium fluorophosphates, lithium sulfonic acid salts, lithium imide salts, lithium oxa from the viewpoint of further enhancing the effect of improving charge / discharge rate charge / discharge characteristics and impedance characteristics in addition to the low temperature output characteristics obtained by the present invention. Those selected from lat salts are preferable.

Among them, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiTaF ₆ , LiPO ₃ F, LiPO ₂ F ₂ , 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-perfluoropropanedisulfonylimide, LiC ( FSO ₂ ) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , Lithium difluorooxalatobolate, Lithium bis (oxalate) borate, Lithium tetrafluorooxalatphosphate, Lithium difluorobis ( Oxalato) phosphate, lithium tris (oxalat) phosphate and the like are particularly preferable because they have the effect of improving low temperature output characteristics, high rate charge / discharge characteristics, impedance characteristics, high temperature storage characteristics, cycle characteristics and the like. Further, the above-mentioned electrolyte salt may be used alone or in combination of two or more.

The total concentration of these electrolytes in the non-aqueous electrolyte solution is not particularly limited, but is usually 8% by mass or more, preferably 8.5% by mass or more, more preferably 9% by mass, based on the total amount of the non-aqueous electrolyte solution. % Or more. The upper limit thereof is usually 18% by mass or less, preferably 17% by mass or less, and more preferably 16% by mass or less. When the total concentration of the electrolyte is within the above range, the electric conductivity becomes appropriate for battery operation, so that sufficient low temperature output characteristics tend to be obtained.

<1-4. Non-aqueous solvent>
Like a general non-aqueous electrolyte solution, the non-aqueous electrolyte solution of the present invention usually contains a non-aqueous solvent that dissolves the above-mentioned electrolyte as its main component. The non-aqueous solvent used here is not particularly limited, and a known organic solvent can be used. Examples of the organic solvent include saturated cyclic carbonates, chain carbonates, cyclic ethers, sulfones and the like, but are not particularly limited thereto. These can be used individually by 1 type or in combination of 2 or more types.

<1-4-1. Saturated cyclic carbonate>
Examples of the saturated cyclic carbonate usually include those having an alkylene group having 2 to 4 carbon atoms, and a saturated cyclic carbonate having 2 to 3 carbon atoms is preferably used from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation. ..

Examples of the saturated cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate and the like. Of these, ethylene carbonate and propylene carbonate are preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation. As the saturated cyclic carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio.

The content of the saturated cyclic carbonate is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but the lower limit of the content when one of them is used alone is based on the total amount of the solvent in the non-aqueous electrolyte solution. It is usually 3% by volume or more, preferably 5% by volume or more. By setting this range, it is possible to avoid a decrease in electrical conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte solution, and to improve the large current discharge characteristics, stability with respect to the negative electrode, and cycle characteristics of the non-aqueous electrolyte secondary battery. It will be easier to set the range. The upper limit is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. By setting this range, the viscosity of the non-aqueous electrolyte solution can be set to an appropriate range, the decrease in ionic conductivity can be suppressed, and the low temperature output characteristics of the non-aqueous electrolyte secondary battery can be further improved. is there.

<1-4-2. Chain carbonate>
As the chain carbonate, one having 3 to 7 carbon atoms is usually used, and from the viewpoint of cycle characteristics and battery output, a chain carbonate having 3 to 5 carbon atoms is preferably used.

Specifically, as the chain carbonate, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propylisopropyl carbonate, ethylmethyl carbonate, methyl-n-propyl carbonate, n-butylmethyl carbonate, etc. Examples thereof include isobutylmethyl carbonate, t-butylmethyl carbonate, ethyl-n-propyl carbonate, n-butylethyl carbonate, isobutylethyl carbonate, t-butylethyl carbonate and the like.

Among them, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propylisopropyl carbonate, ethylmethyl carbonate and methyl-n-propyl carbonate are preferable, and dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate are particularly preferable. is there.

In addition, chain carbonates having a fluorine atom (hereinafter, may be abbreviated as "fluorinated chain carbonate") can also be preferably 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 different carbons. Examples of the fluorinated chain carbonate include a fluorinated dimethyl carbonate derivative, a fluorinated ethyl methyl carbonate derivative, and a fluorinated diethyl carbonate derivative.

Examples of the fluorinated dimethyl carbonate derivative include fluoromethylmethyl carbonate, difluoromethylmethyl carbonate, trifluoromethylmethyl carbonate, bis (fluoromethyl) carbonate, bis (difluoro) methyl carbonate, bis (trifluoromethyl) carbonate and the like.

Examples of the fluorinated ethyl methyl carbonate derivative include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, and 2,2,2-tri. Examples thereof include fluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, ethyl trifluoromethyl carbonate and the like.

Examples of the fluorinated diethyl carbonate derivative include ethyl- (2-fluoroethyl) carbonate, ethyl- (2,2-difluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, and ethyl- (2,2,2-trifluoro). Ethyl) carbonate, 2,2-difluoroethyl-2'-fluoroethyl carbonate, bis (2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2'-fluoroethyl carbonate, 2,2 Examples thereof include 2-trifluoroethyl-2', 2'-difluoroethyl carbonate and bis (2,2,2-trifluoroethyl) carbonate.

As the chain carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio.

The content of the chain carbonate is not particularly limited, but is usually 15% by volume or more, preferably 20% by volume or more, and more preferably 25% by volume or more with respect to the total amount of the solvent of the non-aqueous electrolyte solution. Further, it is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. By setting the content of the chain carbonate in the above range, the viscosity of the non-aqueous electrolyte solution is set in an appropriate range, the decrease in ionic conductivity is suppressed, and the low temperature output characteristics of the non-aqueous electrolyte secondary battery are improved. It becomes easier to make a range.

Further, by combining ethylene carbonate with a specific chain carbonate at a specific content, the battery performance can be remarkably improved.

For example, when dimethyl carbonate and ethyl methyl carbonate are selected as the specific chain carbonate, the content of ethylene carbonate is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but the non-aqueous electrolyte solution It is usually 15% by volume or more, preferably 20% by volume, and usually 45% by volume or less, preferably 40% by volume or less with respect to the total amount of the solvent, and the content of dimethyl carbonate is based on the total amount of the solvent of the non-aqueous electrolyte solution. It is usually 20% by volume or more, preferably 30% by volume or more, and usually 50% by volume or less, preferably 45% by volume or less, and the content of ethylmethyl carbonate is usually 20% by volume or more, preferably 30% by volume or more. In addition, it is usually 50% by volume or less, preferably 45% by volume or less. By setting the content within the above range, it is possible to improve the ionic conductivity by lowering the viscosity of the non-aqueous electrolyte solution while lowering the low temperature precipitation temperature of the electrolyte, and to obtain high output characteristics even at low temperatures.

<1-4-3. Cyclic ether>
As the cyclic ether, a cyclic ether having 3 to 6 carbon atoms is usually used, and a cyclic ether having 3 to 5 carbon atoms is preferably used because it has a high solvation ability with lithium ions and improves ionic dissociation.

Examples of the cyclic ether 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 these fluorinated compounds.

Among these, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 1,4-dioxane and the like are preferable because they have high solvation ability to lithium ions and improve ionic dissociation.

The content of the cyclic ether is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1% by volume or more, preferably 2% by volume or more, based on the total amount of the solvent of the non-aqueous electrolyte solution. It is more preferably 3% by volume or more, and usually 30% by volume or less, preferably 25% by volume or less, and more preferably 20% by volume or less. When the content of the ether compound is within the above-mentioned preferable range, it is easy to secure the effect of improving the lithium ion dissociation degree of the chain ether and improving the ionic conductivity due to the decrease in viscosity.

<1-4-4. Sulfone compounds>
The sulfone compound is not particularly limited even if it is a cyclic sulfone or a chain sulfone, but in the case of a cyclic sulfone, the number of carbon atoms is usually 3 to 6, preferably 3 to 5, and in the case of a chain sulfone. , Usually, a compound having 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms is preferable. The number of sulfonyl groups in one molecule of the sulfone compound is not particularly limited, but is usually 1 or 2.

Examples of the cyclic sulfone include trimethylene sulfones, tetramethylene sulfones and hexamethylene sulfones which are monosulfone compounds; trimethylene disulfones, tetramethylene disulfones and hexamethylene disulfones which are disulfone compounds. Among them, 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, sulfolanes and / or sulfolane derivatives (hereinafter, sulfolanes may be abbreviated as "sulfolanes") are preferable. The sulfolane derivative is preferably one in which one or more hydrogen atoms bonded on the carbon atom constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group.

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-difluoro Methyl 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 because they have high ionic conductivity and high input / output.

Examples of the chain sulfone include dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, and n-. Butylmethylsulfone, n-butylethylsulfone, t-butylmethylsulfone, t-butylethylsulfone, monofluoromethylmethylsulfone, difluoromethylmethylsulfone, trifluoromethylmethylsulfone, monofluoroethylmethylsulfone, difluoroethylmethylsulfone, Trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trifluoromethyl sulfone, perfluoroethyl methyl sulfone, ethyl trifluoroethyl sulfone, ethyl pentafluoroethyl sulfone, di (tri) Fluoroethyl) sulfone, perfluorodiethyl sulfone, fluoromethyl-n-propyl sulfone, difluoromethyl-n-propyl sulfone, trifluoromethyl-n-propyl sulfone, fluoromethyl isopropyl sulfone, difluoromethyl isopropyl sulfone, trifluoromethyl isopropyl sulfone , Trifluoroethyl-n-propyl sulfone, trifluoroethyl isopropyl sulfone, pentafluoroethyl-n-propyl sulfone, pentafluoroethyl isopropyl sulfone, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone, penta Fluoroethyl-n-butyl sulfone, pentafluoroethyl-t-butyl sulfone and the like can be mentioned.

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, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone, trifluoromethyl-n-butyl sulfone, trifluoromethyl-t -Butyl sulfone or the like is preferable because it has high ionic conductivity and high input / output.

The content of the sulfone compound is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.3% by volume or more, preferably 0.% by volume, based on the total amount of the solvent in the non-aqueous electrolyte solution. It is 5% by volume or more, more preferably 1% by volume or more, and usually 40% by volume or less, preferably 35% by volume or less, more preferably 30% by volume or less. When the content of the sulfone compound is within the above range, the viscosity of the non-aqueous electrolyte solution can be set within an appropriate range, and a decrease in electrical conductivity can be avoided.

<1-5. Auxiliary agent>
<1-5-1. Carbon containing at least one of carbon-carbon unsaturated bond and fluorine atom>
The non-aqueous electrolyte solution of the present invention further comprises at least a cyclic carbonate having a carbon-carbon unsaturated bond (hereinafter, may be abbreviated as “unsaturated cyclic carbonate”) and a cyclic carbonate containing a fluorine atom. One may be contained. Further, the non-aqueous electrolyte solution of the present invention contains a fluorinated unsaturated cyclic carbonate, a cyclic sulfonic acid ester compound, a compound having a cyano group, a diisocyanato compound, a carboxylic acid anhydride, an overcharge inhibitor, and other auxiliaries. It may be included.

The cyclic carbonate having a carbon-carbon unsaturated bond is not particularly limited as long as it is a cyclic carbonate having a carbon-carbon unsaturated bond, and a carbonate having an arbitrary carbon-carbon unsaturated bond can be used. The cyclic carbonate having a substituent having an aromatic ring is also included in the cyclic carbonate having a carbon-carbon unsaturated bond. The method for producing the unsaturated cyclic carbonate is not particularly limited, and a known method can be arbitrarily selected for production.

Examples of the unsaturated cyclic carbonate include vinylene carbonates, ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond, phenyl carbonates, vinyl carbonates, allyl carbonates and the like.

Examples of the vinylene carbonates include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethylvinylene carbonate, phenylvinylene carbonate, 4,5-diphenylvinylene carbonate, vinyl vinylene carbonate, allyl vinylene carbonate and the like.

Specific examples of ethylene carbonates substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond include vinyl ethylene carbonate, 4,5-divinylethylene carbonate, phenylethylene carbonate, 4,5-diphenylethylene carbonate, and the like. Examples thereof include ethynyl ethylene carbonate and 4,5-dietinyl ethylene carbonate.

Among them, vinylene carbonates, ethylene carbonate substituted with a substituent having an aromatic ring or a carbon-carbon unsaturated bond are preferable, and vinylene carbonate, 4,5-diphenylvinylene carbonate, 4,5-dimethylvinylene carbonate, and vinyl are particularly preferable. Ethylene carbonate and ethynyl ethylene carbonate are more preferably used because they form a stable interfacial protective film.

The molecular weight of the unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight of the unsaturated cyclic carbonate is usually 50 or more, preferably 80 or more, and usually 250 or less, preferably 150 or less. Within this range, the solubility of the unsaturated cyclic carbonate in the non-aqueous electrolyte solution can be easily ensured, and the effect of the present invention can be sufficiently exhibited.

As the unsaturated cyclic carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio. The content of the unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The content of the unsaturated cyclic carbonate is usually 0.001% by mass or more, preferably 0.01% by mass or more, and more preferably 0.1% by mass or more, based on the total amount of the non-aqueous electrolyte solution. It is more preferably 0.2% by mass or more, and usually 10% by mass or less, preferably 8% by mass or less, and more preferably 5% by mass or less. Within the above range, the non-aqueous electrolyte secondary battery tends to exhibit sufficient high-temperature storage characteristics and cycle characteristic improvement effects in addition to low-temperature storage characteristics.

In the present invention, it is known that the compound represented by the general formula (1) acts as a positive electrode film forming material, and the unsaturated cyclic carbonate acts as a negative electrode film forming material. Therefore, by using the compound represented by the general formula (1) in combination with the unsaturated cyclic carbonate, a film is formed on the positive electrode and the negative electrode, the decomposition of the chain ether and the carboxylic acid ester is suppressed, and the non-aqueous electrolyte solution is used. It is considered that the increase in resistance is suppressed.

The cyclic carbonate having a fluorine atom (hereinafter, may be abbreviated as "fluorinated cyclic carbonate") is not particularly limited as long as it is a cyclic carbonate having a fluorine atom.

Examples of the fluorinated cyclic carbonate include derivatives of cyclic carbonate having an alkylene group having 2 to 6 carbon atoms, and examples thereof are ethylene carbonate derivatives. Examples of the ethylene carbonate derivative include ethylene carbonate or a fluorinated product of ethylene carbonate substituted with an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms), and among them, those having 1 to 8 fluorine atoms. Is preferable.

Specifically, monofluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4,5-difluoro-4-methylethylene carbonate, 4- Fluoro-5-methylethylene carbonate, 4,4-difluoro-5-methylethylene carbonate, 4- (fluoromethyl) -ethylene carbonate, 4- (difluoromethyl) -ethylene carbonate, 4- (trifluoromethyl) -ethylene carbonate , 4- (Fluoromethyl) -4-fluoroethylene carbonate, 4- (Fluoromethyl) -5-fluoroethylene carbonate, 4-Fluoro-4,5-dimethylethylene carbonate, 4,5-difluoro-4,5-dimethyl Ethylene carbonate, 4,4-difluoro-5,5-dimethylethylene carbonate and the like can be mentioned.

Among them, at least one selected from the group consisting of monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate and 4,5-difluoro-4,5-dimethylethylene carbonate has high ionic conduction. It is more preferable in that it imparts properties and preferably forms a film on the negative electrode.

As the fluorinated cyclic carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio. The content of the fluorinated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired, but it is usually 0.001% by mass or more, preferably 0.001% by mass or more, based on the total amount of the non-aqueous electrolyte solution. It is 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 85% by mass or less, preferably 80% by mass or less, and more preferably 75% by mass or less.
The fluorinated cyclic carbonate may be used as a main solvent or a secondary solvent of the non-aqueous electrolyte solution. The content of the fluorinated cyclic carbonate when used as the main solvent is usually 8% by mass or more, preferably 10% by mass or more, and more preferably 12% by mass or more, based on the total amount of the non-aqueous electrolyte solution. Yes, it is usually 85% by mass or less, preferably 80% by mass or less, and more preferably 75% by mass or less. Within this range, the non-aqueous electrolyte secondary battery tends to exhibit a sufficient effect of improving cycle characteristics, and it is easy to avoid a decrease in the discharge capacity retention rate. The content of the fluorinated cyclic carbonate when used as a secondary solvent is usually 0.001% by mass or more, preferably 0.01% by mass or more, based on the total amount of the non-aqueous electrolyte solution. It is preferably 0.1% by mass or more, and usually 8% by mass or less, preferably 6% by mass or less, and more preferably 5% by mass or less. Within this range, the non-aqueous electrolyte secondary battery tends to exhibit sufficient cycle characteristics and high temperature storage characteristics in addition to the low temperature output characteristics.

<1-5-2. Fluorinated unsaturated cyclic carbonate>
As the fluorinated cyclic carbonate, a cyclic carbonate having an unsaturated bond and a fluorine atom (hereinafter, may be abbreviated as "fluorinated unsaturated cyclic carbonate") can be used. The fluorinated unsaturated cyclic carbonate is not particularly limited. Of these, those having one or two fluorine atoms are preferable. The method for producing the fluorinated unsaturated cyclic carbonate is not particularly limited, and a known method can be arbitrarily selected for production.

Examples of the fluorinated unsaturated cyclic carbonate include a vinylene carbonate derivative, an ethylene carbonate derivative substituted with an aromatic ring or a substituent having a carbon-carbon unsaturated bond, and the like.

Examples of the vinylene carbonate derivative include 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4,5-difluoroethylene carbonate and the like.

Examples of the ethylene carbonate derivative substituted with an aromatic ring or a substituent having a carbon-carbon unsaturated bond include 4-fluoro-4-vinylethylene carbonate, 4-fluoro-5-vinylethylene carbonate, and 4,4-difluoro-4. -Vinyl ethylene carbonate, 4,5-difluoro-4-vinylethylene carbonate, 4-fluoro-4,5-divinylethylene carbonate, 4,5-difluoro-4,5-divinylethylene carbonate, 4-fluoro-4-phenyl Examples thereof include ethylene carbonate, 4-fluoro-5-phenylethylene carbonate, 4,4-difluoro-5-phenylethylene carbonate, 4,5-difluoro-4-phenylethylene carbonate and the like.

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 of the fluorinated unsaturated cyclic carbonate is usually 50 or more, preferably 80 or more, and usually 250 or less, preferably 150 or less. Within this range, the solubility of the fluorinated cyclic carbonate in the non-aqueous electrolyte solution can be easily ensured, and the effect of the present invention can be easily exhibited.

As the fluorinated unsaturated cyclic carbonate, one type may be used alone, or two or more types may be used in combination in any combination and ratio. The amount 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 content of the fluorinated unsaturated cyclic carbonate is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, based on the total amount of the non-aqueous electrolyte solution. Further, it is usually 20% by mass or less, preferably 15% by mass or less, preferably 10% by mass or less, and more preferably 5% by mass or less. Within this range, the non-aqueous electrolyte secondary battery tends to exhibit the effect of improving the low temperature output characteristics.

<1-5-3. Cyclic sulfonic acid ester compound>
The type of the cyclic sulfonic acid ester compound that can be used in the non-aqueous electrolyte solution of the present invention is not particularly limited, but the compound represented by the following general formula (5) is preferable. The method for producing the cyclic sulfonic acid ester compound is not particularly limited, and a known method can be arbitrarily selected for production.

(In the general formula (5), R ⁵ and R ⁶ are each independently composed of an atom selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom and a halogen atom. Representing an organic group, R ⁵ and R ⁶ may contain unsaturated bonds together with -O-SO _2- .)
Here, R ⁵ and R ⁶ are preferably organic groups composed of atoms composed of carbon atoms, hydrogen atoms, oxygen atoms, and sulfur atoms, and among them, hydrocarbon groups having 1 to 3 carbon atoms, − It is preferably an organic group having O-SO _2- .

The molecular weight of the cyclic sulfonic acid ester compound is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight of the cyclic sulfonic acid ester compound is usually 100 or more, preferably 110 or more, and usually 250 or less, preferably 220 or less. Within this range, it is easy to secure the solubility of the cyclic sulfonic acid ester compound in the non-aqueous electrolyte solution, and the effect of the present invention is likely to be exhibited.

Specific examples of the compound represented by the general formula (5) include, for example.
1,3-Propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone , 2-Methyl-1,3-Propane Sultone, 3-Methyl-1,3-Propane Sultone, 1-Propen-1,3-Sultone, 2-Propen-1,3-Sultone, 1-Fluoro-1-Propen -1,3-sultone, 2-fluoro-1-propen-1,3-sultone, 3-fluoro-1-propen-1,3-sultone, 1-fluoro-2-propen-1,3-sultone, 2 -Fluoro-2-propen-1,3-sultone, 3-fluoro-2-propen-1,3-sultone, 1-methyl-1-propen-1,3-sultone, 2-methyl-1-propen-1 , 3-Sultone, 3-Methyl-1-propen-1,3-Sultone, 1-Methyl-2-Propen-1,3-Sultone, 2-Methyl-2-Propen-1,3-Sultone, 3-Methyl -2-Propen-1,3-sultone, 1,4-butane sultone, 1-fluoro-1,4-butane sultone, 2-fluoro-1,4-butane sultone, 3-fluoro-1,4-butane sultone, 4-fluoro -1,4-Butansultone, 1-Methyl-1,4-Butansultone, 2-Methyl-1,4-Butansultone, 3-Methyl-1,4-Butansultone, 4-Methyl-1,4-Butansultone, 1-Butene -1,4-sultone, 2-butene-1,4-sultone, 3-butene-1,4-sultone, 1-fluoro-1-butene-1,4-sultone, 2-fluoro-1-butene-1 , 4-sultone, 3-fluoro-1-butene-1,4-sultone, 4-fluoro-1-butene-1,4-sultone, 1-fluoro-2-butene-1,4-sultone, 2-fluoro -2-buten-1,4-sultone, 3-fluoro-2-butene-1,4-sultone, 4-fluoro-2-butene-1,4-sultone, 1-fluoro-3-butene-1,4 -Sultone, 2-fluoro-3-butene-1,4-sultone, 3-fluoro-3-butene-1,4-sultone, 4-fluoro-3-butene-1,4-sultone, 1-methyl-1 -Butene-1,4-sultone, 2-methyl-1-butene-1,4-sultone, 3-methyl-1-butene-1,4-sultone, 4-methyl-1-butene-1,4-sultone , 1-Methyl-2-butene-1,4 −Sulton, 2-methyl-2-butene-1,4-sulton, 3-methyl-2-butene-1,4-sulton, 4-methyl-2-butene-1,4-sulton, 1-methyl-3 − Butene-1,4-sulton, 2-methyl-3-butene-1,4-sulton, 3-methyl-3-butene-1,4-sulton, 4-methyl-3-butene-1,4-sulton , 1,5-Pentane Sulton, 1-Fluoro-1,5-Pentane Sulton, 2-Fluoro-1,5-Pentane Sulton, 3-Fluoro-1,5-Pentane Sulton, 4-Fluoro-1,5-Pentane Sulton, 5-fluoro-1,5-pentane sulton, 1-methyl-1,5-pentane sulton, 2-methyl-1,5-pentane sulton, 3-methyl-1,5-pentane sulton, 4-methyl- 1,5-Pentane Sulton, 5-Methyl-1,5-Pentane Sulton, 1-Pentane-1,5-Sulton, 2-Pentane-1,5-Sulton, 3-Penten-1,5-Sulton, 4- Pentane-1,5-sulton, 1-fluoro-1-pentene-1,5-sulton, 2-fluoro-1-pentane-1,5-sulton, 3-fluoro-1-pentene-1,5-sulton, 4-Fluoro-1-pentane-1,5-sulton, 5-fluoro-1-pentane-1,5-sulton, 1-fluoro-2-pentene-1,5-sulton, 2-fluoro-2-pentene- 1,5-Sulton, 3-Fluoro-2-pentene-1,5-Sulton, 4-Fluoro-2-Pentane-1,5-Sulton, 5-Fluoro-2-Pentane-1,5-Sulton, 1- Fluoro-3-pentane-1,5-sultone, 2-fluoro-3-pentane-1,5-sulton, 3-fluoro-3-pentane-1,5-sulton, 4-fluoro-3-penten-1, 5-Sulton, 5-Fluoro-3-pentane-1,5-Sulton, 1-Fluoro-4-Pentane-1,5-Sulton, 2-Fluoro-4-Pentane-1,5-Sulton, 3-Fluoro- 4-Pentane-1,5-sulton, 4-fluoro-4-pentene-1,5-sulton, 5-fluoro-4-pentane-1,5-sulton, 1-methyl-1-pentene-1,5- Sulton, 2-methyl-1-pentane-1,5-sulton, 3-methyl-1-pentane-1,5-sulton, 4-methyl-1-pentane-1,5-sulton, 5-methyl-1- Pentane-1,5-sulton, 1-methyl -2-Penten-1,5-sultone, 2-methyl-2-penten-1,5-sultone, 3-methyl-2-penten-1,5-sultone, 4-methyl-2-penten-1,5 -Sultone, 5-Methyl-2-pentene-1,5-sultone, 1-methyl-3-pentene-1,5-sultone, 2-methyl-3-pentene-1,5-sultone, 3-methyl-3 -Penten-1,5-sultone, 4-methyl-3-penten-1,5-sultone, 5-methyl-3-penten-1,5-sultone, 1-methyl-4-penten-1,5-sultone , 2-Methyl-4-pentene-1,5-sultone, 3-Methyl-4-pentene-1,5-sultone, 4-Methyl-4-pentene-1,5-sultone, 5-Methyl-4-pentene -1,5-sultone, 1,2-oxathiolane-2,2-dioxide-4-yl-acetate, 1,2-oxathiolan-2,2-dioxide-4-yl-propionate, 5-methyl-1,2 -Sultone compounds such as -oxathiolane-2,2-dioxide-4-one-2,2-dioxide, 5,5-dimethyl-1,2-oxathiolane-2,2-dioxide-4-one-2,2-dioxide ;

Sulfate compounds such as methylene sulphate, ethylene sulphate, propylene sulphate;

Disulfonate compounds such as methylene methane disulfonate and ethylene methane disulfonate;

1,2,3-oxathiazolidine-2,2-dioxide, 3-methyl-1,2,3-oxathiazolidine-2,2-dioxide, 3H-1,2,3-oxathiazole-2,2-dioxide , 5H-1,2,3-oxathiazole-2,2-dioxide, 1,2,4-oxathiazolidine-2,2-dioxide, 4-methyl-1,2,4-oxathiazolidine-2,2- Dioxide, 3H-1,2,4-oxathiazole-2,2-dioxide, 5H-1,2,4-oxathiazole-2,2-dioxide, 1,2,5-oxathiazolidine-2,2-dioxide , 5-Methyl-1,2,5-oxathiazolidine-2,2-dioxide, 3H-1,2,5-oxathiazole-2,2-dioxide, 5H-1,2,5-oxathiazole-2, 2-Dioxide, 1,2,3-oxathiadinane-2,2-dioxide, 3-methyl-1,2,3-oxathiadinane-2,2-dioxide, 5,6-dihydro-1,2,3-oxathiazine- 2,2-Dioxide, 1,2,4-oxathiadinane-2,2-dioxide, 4-methyl-1,2,4-oxathiadinane-2,2-dioxide, 5,6-dihydro-1,2,4- Oxathiazine-2,2-dioxide, 3,6-dihydro-1,2,4-oxathiazine-2,2-dioxide, 3,4-dihydro-1,2,4-oxathiazine-2,2-dioxide, 1, 2,5-oxathiadinane-2,2-dioxide, 5-methyl-1,2,5-oxathiadinane-2,2-dioxide, 5,6-dihydro-1,2,5-oxathiazine-2,2-dioxide, 3,6-dihydro-1,2,5-oxathiazine-2,2-dioxide, 3,4-dihydro-1,2,5-oxathiazine-2,2-dioxide, 1,2,6-oxathiadinane-2, 2
-Dioxide, 6-methyl-1,2,6-oxathiadinane-2,2-dioxide, 5,6-dihydro-1,2,6-oxathiazine-2,2-dioxide, 3,4-dihydro-1,2 , 6-Oxathiazine-2,2-dioxide, 5,6-dihydro-1,2,6-oxathiazine-2,2-dioxide and other nitrogen-containing compounds;

1,2,3-oxathiaphoslan-2,2-dioxide, 3-methyl-1,2,3-oxathiaphosrane-2,2-dioxide, 3-methyl-1,2,3-oxati Aphoslan-2,2,3-trioxide, 3-methoxy-1,2,3-oxathiaphosrane-2,2,3-trioxide, 1,2,4-oxathiaphosrane-2,2-dioxide , 4-Methyl-1,2,4-oxathiaphosrane-2,2-dioxide, 4-methyl-1,2,4-oxathiaphosrane-2,2,4-trioxide, 4-methoxy-1 , 2,4-oxathiaphoslan-2,2,4-trioxide, 1,2,5-oxathiaphosrane-2,2-dioxide, 5-methyl-1,2,5-oxathiaphosrane- 2,2-Dioxide, 5-Methyl-1,2,5-oxathiaphosrane-2,2,5-trioxide, 5-methoxy-1,2,5-oxathiaphosrane-2,2,5- Trioxide, 1,2,3-oxathiaphosphinan-2,2-dioxide, 3-methyl-1,2,3-oxathiaphosphinan-2,2-dioxide, 3-methyl-1,2,3- Oxatiaphosphinan-2,2,3-trioxide, 3-methoxy-1,2,3-oxathiaphosphinan-2,2,3-trioxide, 1,2,4-oxathiaphosphinan-2,2 -Dioxide, 4-methyl-1,2,4-oxathiaphosphinan-2,2-dioxide, 4-methyl-1,2,4-oxathiaphosphinan-2,2,3-trioxide, 4-methyl -1,5,2,4-dioxathiaphosphinan-2,4-dioxide, 4-methoxy-1,5,2,4-dioxathiaphosphinan-2,4-dioxide, 3-methoxy-1 , 2,4-oxathiaphosphinan-2,2,3-trioxide, 1,2,5-oxathiaphosphinan-2,2-dioxide, 5-methyl-1,2,5-oxathiaphosphinan- 2,2-Dioxide, 5-Methyl-1,2,5-oxathiaphosphinan-2,2,3-trioxide, 5-methoxy-1,2,5-oxathiaphosphinan-2,2,3- Trioxide, 1,2,6-oxathiaphosphinan-2,2-dioxide, 6-methyl-1,2,6-oxathiaphosphinan-2,2-dioxide, 6-methyl-1,2,6- Oxatiaphosphinan-2,2,3-trioxide, 6-methoxy-1,2,6-oxatiaphosphinan-2,2 , 3-Trioxide Phosphorus-containing compounds;
And so on.

Of these
1,3-Propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-propen-1,3-sultone, 1-Fluoro-1-propen-1,3-sultone, 2-fluoro-1-propen-1,3-sultone, 3-fluoro-1-propen-1,3-sultone, 1,4-butane sultone, methylenemethane Disulfonate and ethylenemethane disulfonate are preferable from the viewpoint of improving storage characteristics, 1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1. , 3-Propane sultone, 1-propen-1,3-sultone are more preferable.

As the cyclic sulfonic acid ester compound, one type may be used alone, or two or more types may be used in combination in any combination and ratio. The amount of the cyclic sulfonic acid ester compound to be blended with respect to the entire non-aqueous electrolyte solution of the present invention is not limited and is arbitrary as long as the effect of the present invention is not significantly impaired. 001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.3% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less. It is preferably contained at a concentration of 3% by mass or less. When the above range is satisfied, it is preferable from the viewpoint that the decomposition of the chain ether and the carboxylic acid ester at the positive electrode can be suppressed and the increase in resistance in the non-aqueous electrolyte solution can be suppressed.

<1-5-4. Compound with cyano group>
In the non-aqueous electrolyte solution of the present invention, the type of the compound having a cyano group that can be used is not particularly limited as long as it is a compound having a cyano group in the molecule, but the following general formula (6) can be used. The compound represented is more preferred. The method for producing the compound having a cyano group is not particularly limited, and a known method can be arbitrarily selected for production.

(In the general formula (6), T represents an organic group composed of an atom selected from the group consisting of carbon atom, hydrogen atom, nitrogen atom, oxygen atom, sulfur atom, phosphorus atom and halogen atom, and U is substituted. It is a V-valent organic group having 1 to 10 carbon atoms which may have a group. V is an integer of 1 or more, and when V is 2 or more, T may be the same as or different from each other. Good.)

The molecular weight of the compound having a cyano group is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight of the compound having a cyano group is usually 40 or more, preferably 45 or more, more preferably 50 or more, and usually 200 or less, preferably 180 or less, more preferably 170 or less. Within this range, it is easy to secure the solubility of the compound having a cyano group in a non-aqueous electrolyte solution, and the effect of the present invention is likely to be exhibited.

Specific examples of the compound represented by the general formula (6) include, for example.
Acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile 2-methylbutyronitrile, trimethylnitrile, hexanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, acrylonitrile, methacrylonitrile, Crotononitrile, 3-methylcrotononitrile, 2-methyl-2-butennitril, 2-pentenenitrile, 2-methyl-2-pentenenitrile, 3-methyl-2-pentenenitrile, 2-hexenenitrile, fluoro Acetonitrile, difluoronitrile, trifluoronitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2,2-difluoropropionitrile, 2,3-difluoropropionitrile, 3,3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3-trifluoropropionitrile, 3,3'-oxydipropionitrile, 3,3'-thiodipropionitrile, 1,2,3-propanetri Compounds having one cyano group such as carbonitrile, 1,3,5-pentanetricarbonitrile, pentafluoropropionitrile;

Marononitrile, succinonitrile, glutaronitrile, adiponitrile, pimeronitrile, suberonitrile, azelanitrile, sebaconitrile, undecandinitrile, dodecandinitrile, methylmalononitrile, ethylmalononitrile, isopropylmalononitrile, tert-butylmalononitrile, methylsuccinonitrile , 2,2-Dimethylsuccinonitrile, 2,3-dimethylsuccinonitrile, trimethylsuccinonitrile, tetramethylsuccinonitrile, 3,3'-(ethylenedioxy) dipropionitrile, 3,3'-( Ethylenedithio) A compound having two cyano groups such as dipropionitrile;

Compounds having three cyano groups such as 1,2,3-tris (2-cyanoethoxy) propane and tris (2-cyanoethyl) amine;

Cyanate compounds such as methyl cyanate, ethyl cyanate, propyl cyanate, butyl cyanate, pentyl cyanate, hexyl cyanate, heptyl cyanate;

Methyl thiocyanate, ethyl thiocyanate, propyl thiocyanate, butyl thiocyanate, pentyl thiocyanate, hexyl thiocyanate, heptyl thiocyanate, methanesulfonyl cyanate, ethanesulfonyl cyanate, propanesulfonyl cyanate, butane sulfonyl cyanate, pentansulfonyl cyanate, hexanesulfonyl cyanate , Heptane Sulfonyl Cyanide, Methyl Sulfronidate, Ethyl Sulfrusiocyanate, Procyl Sulfrusiocyanate, Butyl Sulfronidate, Pentilsulfrusiocyanate, Hexylsulfrusiocyanate, Heptylsul Sulfur-containing compounds such as frothiocyanate;

Cyanodimethylphosphine, cyanodimethylphosphine oxide, methyl cyanomethylphosphinate, methyl cyanomethyl phosphinate, dimethylphosphinic acid cyanide, dimethyl phosphite cyanide, dimethyl cyanophosphonate, dimethyl cyano phosphite, cyanomethyl methylphosphonate, methyl phosphon Phosphate-containing compounds such as cyanomethyl acid and cyanodimethyl phosphite;
And so on.

Of these
Acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, crotononitrile, 3-methylcrotononitrile, malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimeronitrile, suberonitrile, Azelanitrile, sebaconitrile, undecandinitrile, and dodecandinitrile are preferable from the viewpoint of improving storage characteristics, and cyano such as malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimeronitrile, suberonitrile, azellanitrile, sebaconitrile, undecandinitrile, and dodecanenitrile A compound having two groups is more preferable.

As the compound having a cyano group, one type may be used alone, or two or more types may be used in combination in any combination and ratio. The content of the compound having a cyano group in the entire non-aqueous electrolyte solution of the present invention is not limited and is arbitrary as long as the effect of the present invention is not significantly impaired. However, the content of the non-aqueous electrolyte solution of the present invention is usually 0. 001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.3% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less. It is preferably contained at a concentration of 3% by mass or less. When the above range is satisfied, the effects such as low temperature output characteristics, charge / discharge rate characteristics, cycle characteristics, and high temperature storage characteristics are further improved.

<1-5-5. Diisocianato compound>
The diisocyanate compound that can be used in the non-aqueous electrolyte solution of the present invention has a nitrogen atom only in the isocyanato group and two isocyanato groups in the molecule, and has the following general formula (7). The compound represented by is preferable.

In the above general formula (7), X is an organic group having a cyclic structure and having 1 or more and 15 or less carbon atoms. The carbon number of X is usually 2 or more, preferably 3 or more, more preferably 4 or more, and usually 14 or less, preferably 12 or less, more preferably 10 or less, still more preferably 8 or less.

In the above general formula (7), X is particularly preferably an organic group having 4 to 15 carbon atoms and having one or more cycloalkylene groups having 4 to 6 carbon atoms or aromatic hydrocarbon groups. At this time, the hydrogen atom on the cycloalkylene group may be substituted with a methyl group or an ethyl group. Since the diisocyanate compound having the cyclic structure is sterically bulky and therefore a molecule, side reactions on the positive electrode are unlikely to occur, and as a result, the cycle characteristics and the high temperature storage characteristics are improved. Here, the bonding site of the group bonded to the cycloalkylene group or the aromatic hydrocarbon group is not particularly limited and may be any of the meta position, the para position and the ortho position, but the meta position or the para position is the film. It is preferable that the cross-linking distance is appropriate because the lithium ion conductivity is advantageous and the resistance is easily lowered. Further, the cycloalkylene group is preferably a cyclopentylene group or a cyclohexylene group from the viewpoint that the diisocyanate compound itself is unlikely to cause a side reaction, and a cyclohexylene group is preferable because of the influence of molecular motility. It is more preferable because it is easily lowered.

Further, it is preferable to have an alkylene group having 1 to 3 carbon atoms between the cycloalkylene group or the aromatic hydrocarbon group and the isocyanate group. Since having an alkylene group makes it three-dimensionally bulky, side reactions on the positive electrode are less likely to occur. Further, if the alkylene group has 1 to 3 carbon atoms, the ratio of the isocyanate group to the total molecular weight does not change significantly, so that the effect of the present invention can be remarkably exhibited.

The molecular weight of the diisocyanate compound represented by the general formula (7) is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is usually 80 or more, preferably 115 or more, more preferably 170 or more, and usually 300 or less, preferably 230 or less. Within this range, it is easy to secure the solubility of the diisocyanate compound in the non-aqueous electrolyte solution, and the effect of the present invention is likely to be exhibited.

Specific examples of the diisocyanate compound include, for example.
1,2-Diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, 1,2 -Bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-2,4' Cycloalkane ring-containing diisocyanates such as −diisocyanate, dicyclohexylmethane-3,3′-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate;
1,2-phenylenediisocyanate, 1,3-phenylenediocyanate, 1,4-phenylenediocyanate, tolylen-2,3-diisocyanate, tolylen-2,4-diisocyanate, tolylen-2,5-diisocyanate, tolylen-2,6 -Diisocyanate, Trilen-3,4-Diisocyanate, Trilen-3,5-Diisocyanate, 1,2-bis (isocyanatomethyl) benzene, 1,3-bis (isocyanatomethyl) benzene, 1,4-bis (isocyanatomethyl) Natomethyl) benzene, 2,4-diisocyanatobiphenyl, 2,6-diisocyanatobiphenyl, 2,2'-diisocyanatobiphenyl, 3,3'-diisocyanatobiphenyl, 4,4'-diisocyanato- 2-Methylbiphenyl, 4,4'-diisocyanato-3-methylbiphenyl, 4,4'-diisocyanato-3,3'-dimethylbiphenyl, 4,4'-diisocyanato diphenylmethane, 4,4'-diisocyanato-2 -Methyldiphenylmethane, 4,4'-diisocyanato-3-methyldiphenylmethane, 4,4'-diisocyanato-3,3'-dimethyldiphenylmethane, 1,5-diisocyanatonaphthalene, 1,8-diisocyanatonaphthalene, 2 , 3-Diisocyanatonaphthalene, 1,5-bis (isocyanatomethyl) naphthalene, 1,8-bis (isocyanatomethyl) naphthalene, 2,3-bis (isocyanatomethyl) naphthalene and other aromatic ring-containing diisocyanates ;
And so on.

Among these,
1,2-Diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, 1,2 -Bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, 1,2-phenylenediocyanate, 1,3-phenylenediocyanate, 1,4 − Phenylene diisocyanate, 1,2-bis (isocyanatomethyl) benzene, 1,3-bis (isocyanatomethyl) benzene, 1,4-bis (isocyanatomethyl) benzene, 2,4-diisocyanatobiphenyl, 2, , 6-Diisocyanatobiphenyl is preferred because it forms a denser complex film on the negative electrode, resulting in improved battery durability.

Among these,
1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, 1,3-phenylenediocyanate, 1,4-phenylenediocyanate, 1,2-bis (isocyanatomethyl) benzene, Due to the symmetry of the molecules of 1,3-bis (isocyanatomethyl) benzene and 1,4-bis (isocyanatomethyl) benzene, a film advantageous for lithium ion conductivity is formed on the negative electrode, resulting in low temperature. It is more preferable because the battery characteristics such as output characteristics and cycle characteristics are further improved.

Further, the above-mentioned diisocyanate compound may be used alone or in combination of two or more in any combination and ratio.

The content of the diisocyanate compound that can be used in the non-aqueous electrolyte solution of the present invention is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. Usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.3% by mass or more, and usually 5% by mass or less, preferably 4% by mass. Hereinafter, it is more preferably 3% by mass or less, still more preferably 2% by mass or less. When the content is within the above range, battery characteristics such as low temperature output and cycle characteristics tend to be further improved.

The method for producing the diisocyanate compound is not particularly limited, and a known method can be arbitrarily selected for production. Moreover, you may use a commercially available product.

<1-5-6. Carboxylic acid anhydride>
As the carboxylic acid anhydride that can be used in the non-aqueous electrolyte solution of the present invention, a compound represented by the following general formula (8) is preferable. The method for producing the carboxylic acid anhydride is not particularly limited, and a known method can be arbitrarily selected for production.

(In the general formula (5), R ¹ and R ² each independently represent a hydrocarbon group having 1 to 15 carbon atoms which may have a substituent. R ¹ and R ² are bonded to each other. It may form an annular structure.)

The types of R ¹ and R ² are not particularly limited as long as they are monovalent hydrocarbon groups. For example, it may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, or may be a bond of an aliphatic hydrocarbon group and an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be a saturated hydrocarbon group or may contain an unsaturated bond (carbon-carbon double bond or carbon-carbon triple bond). The aliphatic hydrocarbon group may be chain-like or cyclic, and in the case of chain-like, it may be linear or branched-chain. Furthermore, it may be a combination of a chain and a ring. In addition, R ¹ and R ² may be the same as each other or may be different from each other.

Further, when R ¹ and R ² are bonded to each other to form a cyclic structure, the hydrocarbon group formed by bonding R ¹ and R ² to each other is divalent. The type of divalent hydrocarbon group is not particularly limited. That is, it may be an aliphatic group or an aromatic group, or may be a combination of an aliphatic group and an aromatic group. In the case of an aliphatic group, it may be a saturated group or an unsaturated group. Further, it may be a chain group or a cyclic group, and in the case of a chain group, it may be a linear group or a branched chain group. Further, a chain group and a cyclic group may be bonded.

When the hydrocarbon groups of R ¹ and R ² have a substituent, the type of the substituent is not particularly limited as long as it is not contrary to the gist of the present invention, and examples thereof include a fluorine atom, a chlorine atom and a bromine atom. , Halogen atom such as iodine atom, preferably fluorine atom. Further, examples of the substituent other than the halogen atom include a substituent having a functional group such as an ester group, a cyano group, a carbonyl group and an ether group, and a cyano group and a carbonyl group are preferable. The hydrocarbon groups of R ¹ and R ² may have only one of these substituents, or may have two or more of them. When having two or more substituents, the substituents may be the same or different from each other.

The carbon number of each hydrocarbon group of R ¹ and R ² is usually 1 or more, and is usually 15 or less, preferably 12 or less, more preferably 10 or less, and further preferably 9 or less. When R ¹ and R ² are bonded to each other to form a divalent hydrocarbon group, the number of carbon atoms of the divalent hydrocarbon group is usually 1 or more, and usually 15 or less, preferably 15 or less. It is 13 or less, more preferably 10 or less, still more preferably 8 or less. When the hydrocarbon groups of R ¹ and R ² have a substituent containing a carbon atom, it is preferable that the total number of carbon atoms of R ¹ and R ² including the substituent satisfies the above range.

Next, a specific example of the acid anhydride represented by the general formula (5) will be described. In the following examples, the term "related material" refers to an acid anhydride obtained by replacing a part of the structure of the exemplified acid anhydride with another structure within a range not contrary to the gist of the present invention. Dimers, trimers and tetramers composed of a plurality of acid anhydrides, or structurally heterogeneous ones having the same number of carbon atoms but having a branched chain, and the substituents are acids. Examples thereof include those having different sites that bind to the anhydride.

First, specific examples of acid anhydrides having the same R ¹ and R ² are given below.

Specific examples of acid anhydrides in which R ¹ and R ² are chain alkyl groups include acetic anhydride, propionic acid anhydride, butanoic anhydride, 2-methylpropionic acid anhydride, and 2,2-dimethylpropionic acid anhydride. , 2-Methylbutanoic anhydride, 3-Methylbutanoic anhydride, 2,2-dimethylbutanoic anhydride, 2,3-dimethylbutanoic anhydride, 3,3-dimethylbutanoic anhydride, 2,2 3-trimethylbutanoic anhydride, 2,3,3-trimethylbutanoic anhydride, 2,2,3,3-tetramethylbutanoic anhydride, 2-ethylbutanoic anhydride, etc., and their analogs, etc. Can be mentioned.

Specific examples of the acid anhydride in which R ¹ and R ² are cyclic alkyl groups include cyclopropanecarboxylic acid anhydride, cyclopentane carboxylic acid anhydride, cyclohexanecarboxylic acid anhydride and the like, and their analogs. ..

Specific examples of acid anhydrides in which R ¹ and R ² are alkenyl groups include acrylic anhydride, 2-methylacrylic anhydride, 3-methylacrylic anhydride, 2,3-dimethylacrylic anhydride, and the like. 3,3-Dimethylacrylic anhydride, 2,3,3-trimethylacrylic anhydride, 2-phenylacrylic anhydride, 3-phenylacrylic anhydride, 2,3-diphenylacrylic anhydride, 3, 3-Diphenylacrylic anhydride, 3-butenoic anhydride, 2-methyl-3-butenoic anhydride, 2,2-dimethyl-3-butenoic anhydride, 3-methyl-3-butenoic anhydride, 2-Methyl-3-methyl-3-butenoic anhydride, 2,2-dimethyl-3-methyl-3-butenoic acid anhydride, 3-pentenoic acid anhydride, 4-pentenoic acid anhydride, 2-cyclopentencarboxylic acid Examples thereof include acid anhydrides, 3-cyclopentenecarboxylic acid anhydrides, 4-cyclopentenecarboxylic acid anhydrides and the like, and their analogs.

Specific examples of acid anhydrides in which R ¹ and R ² are alkynyl groups include propic acid anhydride, 3-phenylpropic acid anhydride, 2-butynic anhydride, 2-pentyne anhydride, and 3-butynic acid. Examples thereof include anhydrides, 3-pentanoic anhydrides, 4-pentanoic anhydrides and the like, and their analogs.

Specific examples of acid anhydrides in which R ¹ and R ² are aryl groups include benzoic acid anhydride, 4-methylbenzoic acid anhydride, 4-ethyl benzoic acid anhydride, 4-tert-butyl benzoic acid anhydride, and the like. Examples thereof include 2-methylbenzoic acid anhydride, 2,4,6-trimethylbenzoic acid anhydride, 1-naphthalenecarboxylic acid anhydride, 2-naphthalenecarboxylic acid anhydride and the like, and analogs thereof.

Further, as an example of an acid anhydride in which R ¹ and R ² are substituted with a halogen atom, an example of an acid anhydride in which R ¹ and R ² are mainly substituted with a fluorine atom is given below, and some or all of these fluorine atoms are used. An acid anhydride obtained by substituting a chlorine atom, a bromine atom, or an iodine atom is also included in the exemplary compound.

Examples of acid anhydrides in which R ¹ and R ² are chain alkyl groups substituted with halogen atoms include fluoroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, 2-fluoropropionic anhydride, and so on. 2,2-Difluoropropionic acid anhydride, 2,3-difluoropropionic acid anhydride, 2,2,3-trifluoropropionic acid anhydride, 2,3,3-trifluoropropionic acid anhydride, 2,2 3,3-Tetrapropionic acid anhydride, 2,3,3,3-tetrapropionic acid anhydride, 3-fluoropropionic acid anhydride, 3,3-difluoropropionic acid anhydride, 3,3,3-trifluoro Examples thereof include propionic acid anhydride, perfluoropropionic acid anhydride and the like, and their analogs.

Examples of acid anhydrides in which R ¹ and R ² are cyclic alkyl groups substituted with halogen atoms include 2-fluorocyclopentanecarboxylic acid anhydride, 3-fluorocyclopentanecarboxylic acid anhydride, and 4-fluorocyclopentane. Examples thereof include carboxylic acid anhydrides and their analogs.

Examples of acid anhydrides in which R ¹ and R ² are alkenyl groups substituted with halogen atoms include 2-fluoroacrylic acid anhydride, 3-fluoroacrylic acid anhydride, 2,3-difluoroacrylic acid anhydride, and so on. 3,3-Difluoroacrylic anhydride, 2,3,3-trifluoroacrylic anhydride, 2- (trifluoromethyl) acrylic anhydride, 3- (trifluoromethyl) acrylic anhydride, 2,3 -Bis (trifluoromethyl) acrylate anhydride, 2,3,3-tris (trifluoromethyl) acrylate anhydride, 2- (4-fluorophenyl) acrylate anhydride, 3- (4-fluorophenyl) Acrylic anhydride, 2,3-bis (4-fluorophenyl) acrylate anhydride, 3,3-bis (4-fluorophenyl) acrylate anhydride, 2-fluoro-3-butenoic anhydride, 2, 2-Difluoro-3-butenoic anhydride, 3-fluoro-2-butenoic anhydride, 4-fluoro-3-butenoic anhydride, 3,4-difluoro-3-butenoic anhydride, 3,3 Examples thereof include 4-trifluoro-3-butenoic anhydride and the like, and their analogs.

As an example of an acid anhydride in which R ¹ and R ² are alkynyl groups substituted with halogen atoms,
3-Fluoro-2-propic anhydride, 3- (4-fluorophenyl) -2-propic anhydride, 3- (2,3,4,5,6-pentafluorophenyl) -2-propic anhydride , 4-Fluoro-2-butynic anhydride, 4,4-difluoro-2-butynic anhydride, 4,4,4-trifluoro-2-butynic anhydride, etc., and their analogs, etc. Can be mentioned.

Examples of acid anhydrides in which R ¹ and R ² are aryl groups substituted with halogen atoms include 4-fluorobenzoic acid anhydride, 2,3,4,5,6-pentafluorobenzoic acid anhydride, 4 -Trifluoromethylbenzoic anhydride and the like, and their analogs and the like.

Examples of acid anhydrides in which R ¹ and R ² have substituents having functional groups such as esters, nitriles, ketones, and ethers include methoxyhydrides, ethoxygeic anhydrides, and methyloxalate anhydrides. Ethyl oxalic anhydride, 2-cyanoacetate anhydride, 2-oxopropionic acid anhydride, 3-oxobutanoic acid anhydride, 4-acetylbenzoic acid anhydride, methoxyacetic anhydride, 4-methoxybenzoic acid anhydride, etc. And their relatives and the like.

Subsequently, specific examples of acid anhydrides in which R ¹ and R ² are different from each other are given below.

As R ¹ and R ² , the above-mentioned examples and all combinations of their analogs can be considered, and typical examples are given below.

Examples of combinations of chain alkyl groups include propionic acetate anhydride, butanoic anhydride, butane propionic anhydride, 2-methylpropionic anhydride,
And so on.

Examples of the combination of the chain alkyl group and the cyclic alkyl group include cyclopentanoic acid anhydride, cyclohexaneic acid acetate anhydride, propionic anhydride, and the like.

Examples of the combination of the chain alkyl group and the alkenyl group include acrylic anhydride, 3-methylacrylic acetate anhydride, 3-butenoic acid anhydride, propionic anhydride and the like.

Examples of combinations of chain alkyl groups and alkynyl groups include propic acid anhydride, 2-butynate acetate, 3-butynic acetate, 3-phenylpropic anhydride, propionic acid anhydride. Things, etc.

Examples of the combination of the chain alkyl group and the aryl group include benzoic acid anhydride, 4-methylbenzoic acid anhydride, 1-naphthalenecarboxylic acid anhydride, propionic anhydride and the like.

Examples of combinations of a chain alkyl group and a hydrocarbon group having a functional group include fluoroacetic acid anhydride, trifluoroacetic acid anhydride, 4-fluorobenzoic acid anhydride, fluoropropionic acid anhydride, and alkyl acetate. Examples thereof include oxalic acid anhydride, 2-cyanoacetic acid anhydride, 2-oxopropionic acid acetate anhydride, methoxyacetylacetic acid anhydride, and propionic acid methoxyacetate anhydride.

Examples of combinations of cyclic alkyl groups include cyclopentanoic acid cyclohexaneic anhydride.

Examples of combinations of cyclic alkyl groups and alkenyl groups include cyclopentanoic anhydride, 3-methylacrylate cyclopentanoic anhydride, 3-butenoic cyclopentanoic anhydride, cyclohexaneic anhydride, and the like. Can be mentioned.

Examples of the combination of the cyclic alkyl group and the alkynyl group include cyclopentanoic anhydride, 2-butynate cyclopentanoic anhydride, cyclohexaneic anhydride, and the like.

Examples of the combination of the cyclic alkyl group and the aryl group include cyclopentanoic anhydride of benzoate, cyclopentanoic anhydride of 4-methylbenzoate, cyclohexaneic anhydride of benzoate, and the like.

Examples of combinations of cyclic alkyl groups and hydrocarbon groups having functional groups include cyclopentanoic anhydride, cyclopentanoic acid trifluoroacetic anhydride, cyclopentanoic 2-cyanoacetate anhydride, and methoxyacetic acid cyclopentanoate. Anhydride, cyclohexanoic acid fluoroacetic anhydride, and the like can be mentioned.

Examples of combinations of alkenyl groups include 2-methylacrylic acid anhydride, 3-methylacrylic acid anhydride, 3-butenoic acid anhydride, and 3-methylacrylic acid anhydride, 2-methylacrylate. Things, etc.

Examples of the combination of the alkenyl group and the alkynyl group include acrylic acid propicic anhydride, acrylic acid 2-butynic anhydride, 2-methylacrylic acid propicic anhydride, and the like.

Examples of the combination of the alkenyl group and the aryl group include acrylate benzoic acid anhydride, 4-methylbenzoic acid anhydride, 2-methylacrylic acid benzoic acid anhydride and the like.

Examples of combinations of an alkenyl group and a hydrocarbon group having a functional group include fluoroacetic acid anhydride, trifluoroacetic acid anhydride, 2-cyanoacetic acid anhydride, methoxyacetic acid anhydride, 2-. Examples thereof include methyl acrylate fluoroacetic acid anhydride.

Examples of combinations of alkynyl groups include propanoic acid 2-butynic anhydride, propic acid 3-butynic anhydride, 2-butynic acid 3-butynic anhydride, and the like.

Examples of the combination of the alkynyl group and the aryl group include benzoic acid propicic anhydride, 4-methylbenzoic acid propicic anhydride, benzoic acid 2-butynic anhydride, and the like.

Examples of combinations of an alkynyl group and a hydrocarbon group having a functional group are fluoroacetic anhydride, trifluoroacetic anhydride, 2-cyanoacetic anhydride, 2-cyanoacetic anhydride, methoxyacetic anhydride, 2-. Fluoroacetic anhydride, butynate, and the like.

Examples of combinations of aryl groups include 4-methylbenzoic acid anhydride, 1-naphthalenecarboxylic acid anhydride, 4-methylbenzoic acid 1-naphthalenecarboxylic acid anhydride, and the like.

Examples of combinations of an aryl group and a hydrocarbon group having a functional group include fluoroacetic anhydride of benzoate, trifluoroacetic anhydride of benzoate, 2-cyanoacetate anhydride of benzoate, methoxyacetic anhydride of benzoate, 4- Fluoroacetic anhydride of methylbenzoate, and the like.

Examples of combinations of hydrocarbon groups having functional groups include trifluoroacetic acid anhydride, fluoroacetic acid 2-cyanoacetate anhydride, fluoroacetic acid methoxyacetic acid anhydride, trifluoroacetic acid 2-cyanoacetate anhydride, and the like. Can be mentioned.

Of the acid anhydrides forming the above chain structure, preferably
Acetic anhydride, propionic acid anhydride, 2-methylpropionic acid anhydride, cyclopentanecarboxylic acid anhydride, cyclohexanecarboxylic acid anhydride, etc., acrylic acid anhydride, 2-methylacrylic acid anhydride, 3-methylacrylic acid anhydride , 2,3-dimethylacrylic acid anhydride, 3,3-dimethylacrylic acid anhydride, 3-butenoic acid anhydride, 2-methyl-3-butenoic acid anhydride, propic acid anhydride, 2-butanoic acid anhydride , Anhydrous benzoate, 2-Methyl benzoate anhydride, 4-Methyl benzoate anhydride, 4-tert-butyl benzoic acid anhydride, trifluoroacetate anhydride, 3,3,3-trifluoropropionic acid anhydride , 2- (Trifluoromethyl) acrylate anhydride, 2- (4-fluorophenyl) acrylate anhydride, 4-fluorobenzoic acid anhydride, 2,3,4,5,6-pentafluorobenzoic acid anhydride , Cymoxyanhydride, ethoxygeic anhydride, more preferably.
Acrylic anhydride, 2-methylacrylic anhydride, 3-methylacrylic anhydride, benzoic acid anhydride, 2-methylbenzoic acid anhydride, 4-methylbenzoic acid anhydride, 4-tert-butyl benzoic acid anhydride Substances, 4-fluorobenzoic acid anhydride, 2,3,4,5,6-pentafluorobenzoic acid anhydride, methoxygic acid anhydride, ethoxygic acid anhydride.

These compounds can improve the charge / discharge rate characteristics, low temperature output characteristics, and impedance characteristics, especially after the durability test, by appropriately forming a bond with the lithium oxalate salt to form a film having excellent durability. It is preferable from the viewpoint of being able to do it.

Subsequently, specific examples of the acid anhydride in which R ¹ and R ² are bonded to each other to form a cyclic structure will be given below.

First, specific examples of acid anhydrides in which R ¹ and R ² are bonded to each other to form a 5-membered ring structure include succinic anhydride, 4-methylsuccinic anhydride, and 4,4-dimethylsuccinic anhydride. Thing, 4
, 5-Dimethylsuccinic anhydride, 4,4,5-trimethylsuccinic anhydride, 4,4,5,5-Tetramethylsuccinic anhydride, 4-Vinylsuccinic anhydride, 4,5-Divinylsuccinic acid Anhydride, 4-phenylsuccinic anhydride, 4,5-diphenylsuccinic anhydride, 4,4-diphenylsuccinic anhydride, citraconic acid anhydride, maleic anhydride, 4-methylmaleic anhydride, 4, 5-Dimethylmaleic anhydride, 4-phenylmaleic anhydride, 4,5-diphenylmaleic anhydride, itaconic acid anhydride, 5-methylitaconic acid anhydride, 5,5-dimethylitaconic acid anhydride, anhydrous Examples thereof include phthalic acid, 3,4,5,6-tetrahydrophthalic anhydride and the like, and their analogs.

Specific examples of the acid anhydride in which R ¹ and R ² are bonded to each other to form a 6-membered ring structure include cyclohexane-1,2-dicarboxylic acid anhydride and 4-cyclohexene-1,2-dicarboxylic acid. Examples thereof include anhydrides, glutaric anhydrides and the like, and their analogs.

Specific examples of the acid anhydride in which R ¹ and R ² are bonded to each other to form another cyclic structure include 5-norbornene-2,3-dicarboxylic acid anhydride and cyclopentanetetracarboxylic acid dianhydride. , Pyromellitic anhydride, diglycolic acid anhydride and the like, and their analogs and the like.

Specific examples of the acid anhydride in which R ¹ and R ² are bonded to each other to form a cyclic structure and substituted with a halogen atom include 4-fluorosuccinic anhydride and 4,4-difluorosuccinic anhydride. , 4,5-Difluorosuccinic anhydride, 4,4,5-trifluorosuccinate anhydride, 4,4,5,5-tetrafluorosuccinic anhydride, 4-fluoromaleic anhydride, 4,5 -Difluoromaleic anhydride, 5-fluoroitaconic anhydride, 5,5-difluoroitaconic anhydride and the like, and their analogs and the like can be mentioned.

Of the acid anhydrides in which R ¹ and R ² are bonded, preferably
Succinic anhydride, 4-methylsuccinic anhydride, 4-vinylsuccinic anhydride, 4-phenylsuccinic anhydride, citraconic acid anhydride, maleic anhydride, 4-methylmaleic anhydride, 4-phenylmaleic anhydride , Itaconic Acid Anhydride, 5-Methylitaconic Acid Anhydride, Gluteric Acid Anhydride, Phthalic Anhydride, Cyclohexane-1,2-Dicarboxylic Acid Anhydride, 5-Norbornen-2,3-dicarboxylic Acid Anhydride, Cyclopentanetetra Carboxydic dianhydride, pyromellitic anhydride, 4-fluorosuccinic anhydride, 4-fluoromaleic anhydride, 5-fluoroitaconic acid anhydride,
And more preferably
Succinic anhydride, 4-methylsuccinic anhydride, 4-vinylsuccinic anhydride, citraconic acid anhydride, cyclohexane-1,2-dicarboxylic acid anhydride, 5-norbornene-2,3-dicarboxylic acid anhydride, cyclopentanetetra It is a carboxylic acid dianhydride, a pyromellitic anhydride, and a 4-fluorosuccinic anhydride. These compounds are preferable because they appropriately form a bond with the lithium oxalate salt to form a film having excellent durability, and thus the capacity retention rate after the durability test is improved.

The molecular weight of the carboxylic acid anhydride is not limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but it is usually 90 or more, preferably 95 or more, while it is usually 300 or less, preferably 200 or less. .. When the molecular weight of the carboxylic acid anhydride is within the above range, the increase in the viscosity of the electrolytic solution can be suppressed, and the film density is optimized, so that the durability can be appropriately improved without lowering the low temperature output. it can.

Further, the method for producing the carboxylic acid anhydride is not particularly limited, and a known method can be arbitrarily selected for production. The carboxylic acid anhydride described above may be contained alone in the non-aqueous electrolyte solution of the present invention, or two or more thereof may be coexisted in any combination and ratio.

Further, the content of the carboxylic acid anhydride in the non-aqueous electrolyte solution of the present invention is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0 with respect to the non-aqueous electrolyte solution of the present invention. It is desirable to contain it in a concentration of 0.01% by mass or more, preferably 0.1% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less. When the content of the carboxylic acid anhydride is within the above range, the effect of improving the cycle characteristics is likely to be exhibited, and since the reactivity is preferable, the battery characteristics are likely to be improved.

<1-5-7. Overcharge inhibitor ＞
In the non-aqueous electrolyte solution of the present invention, an overcharge inhibitor can be used in order to effectively suppress the explosion and ignition of the non-aqueous electrolyte secondary battery when it is in a state of overcharging or the like. ..

Examples of the overcharge inhibitor include biphenyl, alkylbiphenyl, terphenyl, a partially hydride of terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, diphenylcyclohexane, 1,1,3-trimethyl. Aromatic compounds such as -3-phenylindan; partially fluorinated compounds of the above aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoro Fluoro-containing anisole compounds such as anisole, 2,6-difluoroanisole and 3,5-difluoroanisole; 3-propylphenylacetate, 2-ethylphenylacetate, benzylphenylacetate, methylphenylacetate, benzylacetate, phenethylphenylacetate and the like. Aromatic acetates; Examples thereof include aromatic carbonates such as diphenyl carbonate and methylphenyl carbonate. Among them, biphenyl, alkylbiphenyl, terphenyl, partially hydride of terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, diphenylcyclohexane, 1,1,3-trimethyl-3-phenylindan. , 3-propylphenylacetate, 2-ethylphenylacetate, benzylphenylacetate, methylphenylacetate, benzylacetate, phenethylphenylacetate, diphenylcarbonate, methylphenylcarbonate 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, a partially hydride of biphenyl, alkylbiphenyl, terphenyl, terphenyl, cyclohexylbenzene, t-butylbenzene, At least one selected from oxygen-free aromatic compounds such as t-amylbenzene and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether and dibenzofuran are used in combination for overcharge prevention characteristics and high-temperature storage. It is preferable from the viewpoint of the balance of characteristics.

The content 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 content of the overcharge inhibitor is usually 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more, still more preferably 0, based on the total amount of the non-aqueous electrolyte solution. It is 5.5% by mass or more, and usually 5% by mass or less, preferably 4.8% by mass or less, and more preferably 4.5% by mass or less. Within this range, the effect of the overcharge inhibitor can be sufficiently exhibited, and the characteristics of the battery such as high temperature storage characteristics are improved.

<1-5-8. Other auxiliaries>
Other known auxiliaries can be used for the non-aqueous electrolyte solution of the present invention. Other auxiliaries include
Carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate;
Methyl-2-propynyl oxalate, ethyl-2-propynyl oxalate, bis (2-propynyl) oxalate, 2-propynyl acetate, 2-propynylformate, 2-propynyl methacrylate, di (2-propynyl) glutarate, Methyl-2-propynyl carbonate, ethyl-2-propynyl carbonate, bis (2-propynyl) carbonate, 2-butin-1,4-diyl-dimethanesulfonate, 2-butin-1,4-diyl-diethanesulfonate, 2-Butin-1,4-diyl-diformate, 2-butin-1,4-diyl-diacetate, 2-butine-1,4-diyl-dipropionate, 4-hexadiin-1,6-diyl-dimethanesulfonate , 2-Propinyl-Methanesulfonate, 1-Methyl-2-Propinyl-Methanesulfonate, 1,1-dimethyl-2-Propinyl-Methanesulfonate, 2-Propinyl-ethanesulfonate, 2-Propinyl-Vinylsulfonate, 2-Propinyl- Triple bond-containing compounds such as 2- (diethoxyphosphoryl) acetate, 1-methyl-2-propynyl-2- (diethoxyphosphoryl) acetate, 1,1-dimethyl-2-propynyl-2- (diethoxyphosphoryl) acetate ;
Spiro compounds such as 2,4,8,10-tetraoxaspiro [5.5] undecane, 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane;
Ethylene sulfide, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methane sulfonate, ethyl methane sulfonate, busulfane, sulfolene, ethylene sulfate, vinylene sulfate, diphenyl sulfone, N, N-dimethylmethane sulfonamide, N, N- Sulfur-containing compounds such as diethylmethanesulfonamide, trimethylsilyl methylsulfate, trimethylsilyl ethylsulfate, 2-propynyl-trimethylsilylsulfate;
2-Isocyanatoethyl acrylate, 2-Isocyanatoethyl methacrylate, 2-Isocyanatoethyl crotonate, 2- (2-Isocyanatoethoxy) ethyl acrylate, 2- (2-Isocyanatoethoxy) ethyl methacrylate, 2- (2) − Isocyanatoethoxy) Isocyanate compounds such as ethyl crotonate;
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;
Fluorobenzene, difluorobenzene, hexafluorobenzene, benzotrifluoride, orthofluorotoluene, metafluorotoluene, parafluorotoluene, 1,2-bis (trifluoromethyl) benzene, 1-trifluoromethyl-2-difluoromethylbenzene, 1,3-bis (trifluoromethyl) benzene, 1-trifluoromethyl-3-difluoromethylbenzene, 1,4-bis (trifluoromethyl) benzene, 1-trifluoromethyl-4-difluoromethylbenzene, 1, Fluorine-containing aromatic compounds such as 3,5-tris (trifluoromethyl) benzene, pentafluorophenylmethane sulfonate, pentafluorophenyl trifluoromethanesulfonate, pentafluorophenyl acetate, trifluoroacetate pentafluorophenyl, methyl pentafluorophenyl carbonate;
Tris borate (trimethylsilyl), tris borate (trimethoxysilyl), tris phosphate (trimethylsilyl), tris phosphate (trimethoxysilyl), dimethoxyaluminoxytrimethoxysilane, diethoxyaluminoxytriethoxysilane, dipropoxyalumino Xitriethoxysilane, dibutoxyaluminoxytrimethoxysilane, dibutoxyaluminoxytriethoxysilane, titanium tetrakis (trimethylsiloxide), titanium tetrakis (triethylsiloxide),
Silane compounds such as;
2-Propinyl 2- (methanesulfonyloxy) propionic acid, 2-methyl 2- (methanesulfonyloxy) propionic acid, 2-ethyl 2- (methanesulfonyloxy) propionic acid, 2-propynyl methanesulfonyloxyacetic acid, methanesulfonyloxy Ester compounds such as 2-methyl acetate and 2-ethyl methanesulfonyloxy acetate;
Lithylethylmethyloxycarbonylphosphonate, lithium ethylethyloxycarbonylphosphonate, lithium ethyl-2-propynyloxycarbonylphosphonate, lithium ethyl-1-methyl-2-propynyloxycarbonylphosphonate, lithium ethyl-1,1-dimethyl-2-propynyl Lithyl salts such as oxycarbonylphosphonate;
And so on. These may be used alone or in combination of two or more. By adding these auxiliaries, capacity retention characteristics and cycle characteristics after high-temperature storage can be improved.

The content of other auxiliaries is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The content of the other auxiliary agent is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and more preferably 0.2% by mass or more, based on the total amount of the non-aqueous electrolyte solution. It is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less. Within this range, the effects of other auxiliaries are likely to be sufficiently exhibited, and battery characteristics such as low temperature output characteristics are improved.

<2. Non-aqueous electrolyte secondary battery ＞
The non-aqueous electrolyte secondary battery of the present invention has a positive electrode having a current collector and a positive electrode active material layer provided on the current collector, and a negative electrode active material provided on the current collector and the current collector. It includes a negative electrode having a layer and capable of occluding and releasing ions, and the above-mentioned non-aqueous electrolyte solution of the present invention.

<2-1. Battery configuration>
The non-aqueous electrolyte secondary battery of the present invention has the same configuration as the conventionally known non-aqueous electrolyte secondary battery except for the above-mentioned non-aqueous electrolyte secondary battery of the present invention. Usually, the positive electrode and the negative electrode are laminated via a porous membrane (separator) impregnated with the non-aqueous electrolyte solution of the present invention, and these are housed in a case (exterior body). Therefore, the shape of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and may be any of cylindrical type, square type, laminated type, coin type, large size and the like.

<2-2. Non-aqueous electrolyte>
As the non-aqueous electrolyte solution, the above-mentioned non-aqueous electrolyte solution of the present invention is used. It is also possible to mix and use other non-aqueous electrolyte solutions with the non-aqueous electrolyte solution of the present invention as long as the gist of the present invention is not deviated.

<2-3. Negative electrode ＞
The negative electrode has a negative electrode active material layer on the current collector, and the negative electrode active material layer contains a negative electrode active material. Hereinafter, the negative electrode active material will be described.
The negative electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions. Specific examples thereof include carbonaceous materials, metal alloy materials, lithium-containing metal composite oxide materials, and the like. One of these may be used alone, or two or more thereof may be arbitrarily combined and used in combination.

<2-3-1. Carbonaceous material>
As a carbonaceous material used as a negative electrode active material,
(1) Natural graphite,
(2) A carbonaceous material obtained by heat-treating an artificial carbonaceous substance and an artificial graphite substance at least once in the range of 400 to 3200 ° C.
(3) A carbonaceous material in which the negative electrode active material layer is composed of at least two or more kinds of carbonaceous materials having different crystallinities and / or has an interface in which the carbonaceous materials having different crystallinities are in contact with each other.
(4) A carbonaceous material in which the negative electrode active material layer is composed of at least two or more kinds of carbonaceous materials having different orientations and / or has an interface in which the carbonaceous materials having different orientations are in contact with each other.
The one selected from is preferable because it has a good balance between initial irreversible capacitance and high current density charge / discharge characteristics. Further, as the carbonaceous materials (1) to (4), one type may be used alone, or two or more types may be used in combination in any combination and ratio.

Specific examples of the artificial carbonaceous material and the artificial graphite material of the above (2) include natural graphite, coke-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, or those obtained by oxidizing these pitches. Needle coke, pitch coke and carbon materials obtained by partially graphitizing them, thermal decomposition products of organic substances such as furnace black, acetylene black, and pitch-based carbon fibers, carbonizable organic substances, and carbonized substances thereof, or carbonizable organic substances. Examples thereof include a solution dissolved in a low molecular weight organic solvent such as benzene, toluene, xylene, quinoline and n-hexane, and carbonized products thereof.

<2-3-2. Composition, physical properties, preparation method of carbonaceous negative electrode ＞
Regarding the properties of the carbonaceous material, the negative electrode containing the carbonaceous material, the electrode conversion method, the current collector, and the non-aqueous electrolyte secondary battery, any one of (1) to (13) shown below or It is desirable that multiple terms are satisfied at the same time.

(1) X-ray parameters The d value (interlayer distance) of the lattice planes (002 planes) obtained by X-ray diffraction of carbonaceous materials is usually 0.335 to 0.340 nm, and in particular 0.335. It is preferably about 0.338 nm, particularly 0.335 to 0.337 nm. The crystallite size (Lc) determined by X-ray diffraction by the Gakushin method is usually 1.0 nm or more, preferably 1.5 nm or more, and particularly preferably 2 nm or more.

(2) Volume-based average particle diameter The volume-based average particle diameter (median diameter) of the carbonaceous material determined by the laser diffraction / scattering method 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.

The volume-based average particle size is measured by dispersing carbon powder in a 0.2 mass% aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction / scattering particle size distribution. This is performed using a total (LA-700 manufactured by HORIBA, Ltd.). The median diameter obtained 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-price range The Raman R value of a carbonaceous material is usually 0.01 or more, preferably 0.03 or more, preferably 0.03 or more, as measured by an argon ion laser Raman spectroscopy method. 1 or more is more preferable, and usually 1.5 or less, 1.2 or less is preferable, 1 or less is further preferable, and 0.5 or less is particularly preferable.

If the Raman R value is less than the above range, the crystallinity of the particle surface becomes too high, and the number of sites where Li enters between layers may decrease due to charging and discharging. That is, the charge acceptability may decrease. Further, when the negative electrode is densified by pressing after being applied to the current collector, the crystals are likely to be oriented in the direction parallel to the electrode plate, which may lead to deterioration of the load characteristics. On the other hand, if it exceeds the above range, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte solution is increased, and the efficiency may be lowered and the gas generation may be increased.

The Raman half width around 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, 80 cm ^-1 or less. Preferably, 60 cm ^-1 or less is more preferable, and 40 cm ^-1 or less is particularly preferable.

If the Raman half width is less than the above range, the crystallinity of the particle surface becomes too high, and the number of sites where Li enters between layers may decrease due to charging and discharging. That is, the charge acceptability may decrease. Further, when the negative electrode is densified by pressing after being applied to the current collector, the crystals are likely to be oriented in the direction parallel to the electrode plate, which may lead to deterioration of the load characteristics. On the other hand, if it exceeds the above range, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte solution is increased, and the efficiency may be lowered and the gas generation may be increased.

The Raman spectrum is measured by using a Raman spectroscope (Raman spectroscope manufactured by JASCO Corporation) to fill the sample by naturally dropping it into the measurement cell, and 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 IA of a peak PA around 1580 cm ^-1, and measuring the intensity IB of the peak PB around 1360 cm ^-1, and calculates the intensity ratio R (R = IB / IA) . The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material in the present invention. Further, the half width of the peak PA near 1580 cm ^-1 of the obtained Raman spectrum is measured, and this is defined as the Raman half width of the carbonaceous material in the present invention.

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

(4) BET Specific Surface Area The BET specific surface area of carbonaceous materials is such that the value of the specific surface area measured by the BET method is usually 0.1 m ² · g ^-1 or more, and 0.7 m ² · g ^-1 or more. Is preferable, 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, 25 m ² · g ^-1 or less. Preferably, 15 m ² · g ^-1 or less is more preferable, and 10 m ² · g ^-1 or less is particularly preferable.

If the value of the BET specific surface area is less than this range, the acceptability of lithium tends to deteriorate during charging when used as a negative electrode material, and lithium tends to precipitate on the electrode surface, which may reduce stability. On the other hand, if it exceeds this range, the reactivity with the non-aqueous electrolyte solution increases when used as the negative electrode material, gas generation tends to increase, and it may be difficult to obtain a preferable battery.

To measure the specific surface area by the BET method, a surface area meter (fully automatic surface area measuring device manufactured by Okura Riken) is used to pre-dry the sample at 350 ° C for 15 minutes under nitrogen flow, and then the nitrogen to atmospheric pressure is measured. The nitrogen adsorption BET 1-point method by the gas flow method is performed using a nitrogen-helium mixed gas accurately adjusted so that the relative pressure value is 0.3. The specific surface area obtained by the measurement is defined as the BET specific surface area of the carbonaceous material in the present invention.

(5) Circularity When the circularity is measured as the degree of sphere of the carbonaceous material, it is preferably within the following range. The circularity is defined by "circularity = (peripheral length of a corresponding circle having the same area as the projected particle shape) / (actual peripheral length of the projected particle shape)", and is theoretical when the circularity is 1. Become a true sphere.

The circularity of the particles having a particle size in the range of 3 to 40 μm is preferably as close as 1, preferably 0.1 or more, more preferably 0.5 or more, still more preferably 0.8 or more. , 0.85 or more is particularly preferable, and 0.9 or more is most preferable.

The high current density charge / discharge characteristics 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 the particles is increased, and the high current density charge / discharge characteristics for a short time may be lowered.

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 mass% aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and ultrasonic waves of 28 kHz were irradiated at an output of 60 W for 1 minute. , The detection range is specified as 0.6 to 400 μm, and the measurement is performed on particles having a particle size in the range of 3 to 40 μm. The circularity obtained by the measurement is defined as the circularity of the carbonaceous material in the present invention.

The method for improving the circularity is not particularly limited, but a sphere-shaped one is preferable because the shape of the interparticle voids when the electrode body is formed is adjusted. Examples of spheroidizing treatment include a method of mechanically approaching a sphere by applying shearing force and compressive force, and a mechanical / physical treatment method of granulating a plurality of fine particles by the adhesive force of the binder or the particles themselves. Can be 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. cm ^-3 or more are particularly preferred, and is preferably 2 g · ^{cm -3} or less, 1.8 g · ^{cm -3} and more preferably less, 1.6 g · ^{cm -3} or less are particularly preferred.

If the tap density is lower than the above range, the filling density is difficult to increase when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, if it exceeds the above range, the voids between the particles in the electrode become too small, it becomes difficult to secure the conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.

To measure the tap density, pass through a sieve with a mesh size of 300 μm, drop the sample into a tapping cell of 20 cm ³ to fill the sample up to the upper end surface of the cell, and then use 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 in 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. If the orientation ratio is less than the above range, the high-density charge / discharge characteristics may deteriorate. The upper limit of the above range is the theoretical upper limit of the orientation ratio of the carbonaceous material.

The orientation ratio is measured by X-ray diffraction after pressure molding the sample. A molded product obtained by filling 0.47 g of a sample into a molding machine having a diameter of 17 mm and compressing it with 58.8 MN · m- ² was set using clay so as to be flush with the surface of the sample holder for measurement. Measure X-ray diffraction. From the peak intensities of (110) diffraction and (004) diffraction of the obtained carbon, the ratio expressed 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 in the present invention.

The X-ray diffraction measurement conditions are as follows. In addition, "2θ" indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator ・ Slit:
Divergence slit = 0.5 degrees Light receiving slit = 0.15 mm
Scattering slit = 0.5 degrees ・ Measurement range and step angle / measurement time:
(110) Surface: 75 degrees ≤ 2θ ≤ 80 degrees 1 degree / 60 seconds (004) Surface: 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, usually 10 or less, preferably 8 or less, and more preferably 5 or less. If the aspect ratio exceeds the above range, streaks or a uniform coated surface cannot be obtained at the time of electrode plate formation, and the high current density charge / discharge characteristics may deteriorate. The lower limit of the above range is the theoretical lower limit of the aspect ratio of the carbonaceous material.

The aspect ratio is measured by magnifying and observing the particles of the carbonaceous material with a scanning electron microscope. A carbonaceous material when arbitrarily 50 graphite particles fixed to the end face of a metal having a thickness of 50 microns or less are selected, and the stage on which the sample is fixed is rotated and tilted for three-dimensional observation. The longest diameter P of the particles and the shortest diameter Q orthogonal to it are measured, and the average value of P / Q is obtained. The aspect ratio (P / Q) obtained by the measurement is defined as the aspect ratio of the carbonaceous material in the present invention.

(9) Electrode production Any known method can be used for the production of the negative electrode as long as the effect of the present invention is not significantly limited. For example, a binder, a solvent, and if necessary, a thickener, a conductive material, a filler, etc. are added to a negative electrode active material to form a slurry, which is applied to a current collector, dried, and then pressed to form a slurry. Can be done.

The thickness of the negative electrode active material layer per side at the stage immediately before the non-aqueous electrolyte injection step of the battery is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and usually 150 μm or less. , 120 μm or less, more preferably 100 μm or less. This is because if the thickness of the negative electrode active material exceeds this range, the non-aqueous electrolyte solution does not easily penetrate to the vicinity of the current collector interface, so that the high current density charge / discharge characteristics may deteriorate. Further, if it falls below this range, the volume ratio of the current collector to the negative electrode active material may increase, and the capacity of the battery may decrease. Further, the negative electrode active material may be roll-molded to be a sheet electrode, or may be compression-molded to be a pellet electrode.

(10) Current collector A known current collector can be arbitrarily used as the current collector for holding the negative electrode active material. Examples of the current collector of the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel, but copper is particularly preferable from the viewpoint of ease of processing and cost.

When the current collector is made of a metal material, the shape of the current collector may be, for example, a metal foil, a metal column, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foamed metal, or the like. 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, both of which can be used as a current collector.

When the thickness of the copper foil is thinner than 25 μm, a copper alloy having higher strength than pure copper (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) can be used.

The thickness of the current collector is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, and more preferably 50 μm or less. If the thickness of the metal film is thinner than 1 μm, the strength is lowered and coating may be difficult. Further, if it is thicker than 1 mm, the shape of the electrode such as winding may be deformed. The current collector may be in the form of a mesh.

(11) Ratio of thickness between current collector and negative electrode active material layer The ratio of thickness between current collector and negative electrode active material layer is not particularly limited, but "(Negative electrode activity on one side immediately before injection of non-aqueous electrolyte solution) The value of "material layer thickness) / (thickness of current collector)" is usually preferably 150 or less, 20 or less, more preferably 10 or less, and usually 0.1 or more, 0.4 or more, 1 The above is more preferable.

If the ratio of the thickness of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charging / discharging. Further, if it falls below the above range, the volume ratio of the current collector to the negative electrode active material may increase, and the capacity of the battery may decrease.

(12) Electrode density The electrode structure when the negative electrode active material is converted into an electrode is not particularly limited, but the density of the negative electrode active material existing on the current collector is preferably 1 g · cm ^-3 or more. 2 g · cm ^-3 or more is more preferable, 1.3 g · cm ^-3 or more is further preferable, 2.2 g · cm ^-3 or less is preferable, 2.1 g · cm ^-3 or less is more preferable, and 2.0 g. -Cm- ³ or less is more preferable, and 1.9 g-cm- ³ or less is particularly preferable. If the density of the negative electrode active material existing on the current collector exceeds the above range, the negative electrode active material particles are destroyed, the initial irreversible capacity increases, and the non-aqueous system near the current collector / negative electrode active material interface High current density charge / discharge characteristics may deteriorate due to a decrease in the permeability of the electrolytic solution. Further, if it falls below the above range, the conductivity between the negative electrode active materials may decrease, the battery resistance may increase, and the capacity per unit volume may decrease.

(13) Binder The binder for binding the negative electrode active material is not particularly limited as long as it is a non-aqueous electrolytic solution or a material stable to the solvent used in electrode production.

Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, and NBR ( Acrylonitrile-butadiene rubber), rubber-like polymers such as ethylene-propylene rubber; styrene-butadiene-styrene block copolymer or hydrogen additive thereof; EPDM (ethylene-propylene-diene ternary copolymer), styrene-ethylene- Thermoplastic elastomeric polymers such as butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers or hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer Soft resinous polymers such as coalesced and propylene / α-olefin copolymers; fluoropolymers such as polyvinylidene polyvinylidene, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers; alkalis Examples thereof include a polymer composition having ionic conductivity of metal ions (particularly lithium ions). These may be used alone or in any combination and ratio of two or more.

The type of solvent for forming the slurry is 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 the conductive material used as required. However, either an aqueous solvent or an organic solvent may be used.

Examples of aqueous solvents include water, alcohol and the like, and examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N. , N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethylsulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like. ..

In particular, when an aqueous solvent is used, it is preferable to include a dispersant or the like in addition to the thickener and slurry using a latex such as SBR. As these solvents, one type may be used alone, or two or more types may be used in any combination and ratio.

The ratio of the binder to the negative electrode active material is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 0.6% by mass or more, and 20% by mass or less. It is preferably 15% by mass or less, more preferably 10% by mass or less, and particularly preferably 8% by mass or less. If the ratio of the binder to the negative electrode active material exceeds the above range, the ratio of the binder in which the amount of the binder does not contribute to the battery capacity increases, which may lead to a decrease in the battery capacity. Further, if it falls below the above range, the strength of the negative electrode may decrease.

In particular, when a rubber-like polymer typified by SBR is contained in the 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 is 0. .6% by mass or more is more preferable, and usually 5% by mass or less, 3% by mass or less is preferable, and 2% by mass or less is more preferable.

When a fluoropolymer represented by polyvinylidene fluoride is contained as a main component, 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. In addition, it is usually 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

Thickeners are commonly used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used alone or in any combination and ratio of two or more.

Further, when a thickener is used, the ratio of the thickener to the negative electrode active material is not particularly limited, but is usually 0.1% by mass or more, preferably 0.5% by mass or more, preferably 0.6% by mass. The above is more preferable, and it is usually 5% by mass or less, preferably 3% by mass or less, and further preferably 2% by mass or less. If the ratio of the thickener to the negative electrode active material is less than the above range, the coatability may be significantly lowered. On the other hand, if it exceeds the above range, the ratio of the negative electrode active material to the negative electrode active material layer decreases, which may cause a problem that the capacity of the battery decreases and an increase in resistance between the negative electrode active materials.

<2-3-3. Composition, physical properties, preparation method of metal compound material and negative electrode using metal compound material>
As the metal compound-based material used as the negative electrode active material, if lithium can be occluded and released, a single metal or alloy forming a lithium alloy, or their oxides, carbides, nitrides, silices, sulfides, etc. Any compound such as a phosphoride is not particularly limited. Examples of such metal compounds include compounds containing metals such as Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, and Zn. Among them, it is preferably a simple substance or alloy that forms a lithium alloy, more preferably a material containing a metal / semi-metal element of Group 13 or Group 14 (that is, excluding carbon), and further, silicon (Si). ), Tin (Sn) or lead (Pb) (hereinafter, these three elements may be referred to as "specific metal elements"), alloys containing these atoms, or their metals (specific metal elements). ) Is preferred, and silicon elemental metals, alloys and compounds, and tin elemental metals, alloys and compounds are particularly preferred. One of these may be used alone, or two or more thereof may be used in any combination and ratio.

Examples of a negative electrode active material having at least one atom selected from a specific metal element include a single metal of any one specific metal element, an alloy consisting of two or more specific metal elements, and one or two or more types. Specified metal element and other alloys consisting of one or more metal elements, compounds containing one or more specified metal elements, or oxides, carbides, and nitrides of the compounds. -Examples include composite compounds such as siliceous compounds, sulfides and phosphors. By using these metal simple substances, alloys or metal compounds as the negative electrode active material, it is possible to increase the capacity of the battery.

Further, a compound in which these composite compounds are complicatedly bonded to several kinds of elements such as a simple substance of a metal, an alloy, or a non-metal element can be mentioned as an example. More 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. Further, for example, in 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 act as a negative electrode, and a non-metal element can also be used. ..

Among these negative electrode active materials, since the capacity per unit mass is large when made into a battery, a single metal of any one specific metal element, an alloy of two or more specific metal elements, and oxidation of a specific metal element. Substances, carbides, nitrides and the like are preferable, and in particular, silicon and / or tin metal units, alloys, oxides, carbides, nitrides and the like are preferable from the viewpoint of capacity per unit mass and environmental load.

Further, although the capacity per unit mass is inferior to that of using a simple substance or an alloy, the following compounds containing silicon and / or tin are also preferable because they are excellent in cycle characteristics.
-The elemental ratio of silicon and / or tin to oxygen is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. “Silicon and / or tin oxide” of 3 or less, more preferably 1.1 or less.
-The element ratio of silicon and / or tin to nitrogen is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. "Silicon and / or tin nitride" of 3 or less, more preferably 1.1 or less.
-The element ratio of silicon and / or tin to carbon is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. "Carbides of silicon and / or tin" of 3 or less, more preferably 1.1 or less.

As the above-mentioned negative electrode active material, any one type may be used alone, or two or more types may be used in combination in any combination and ratio.

The negative electrode in the non-aqueous electrolyte secondary battery of the present invention can be produced by any known method. Specifically, as a method for manufacturing a negative electrode, for example, a method in which a binder, a conductive material, or the like is added to the above-mentioned negative electrode active material is directly rolled to form a sheet electrode, or compression molding is performed to form a pellet electrode. However, usually, the above-mentioned negative electrode is used by a coating method, a vapor deposition method, a sputtering method, a plating method, or the like on a current collector for a negative electrode (hereinafter, may be referred to as a “negative electrode current collector”). A method of forming a thin film layer (negative electrode active material layer) containing an active material is used. In this case, a binder, a thickener, a conductive material, a solvent, etc. are added to the above-mentioned negative electrode active material to form a slurry, which is applied to the negative electrode current collector, dried, and then pressed to increase the density. , A negative electrode active material layer is formed on the negative electrode current collector.

Examples of the material of the negative electrode current collector include steel, copper alloy, nickel, nickel alloy, stainless steel and the like. Of these, copper foil is preferable from the viewpoint of easy processing into a thin film and cost.

The thickness of the negative electrode current collector is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less. This is because if the thickness of the negative electrode current collector is too thick, the capacity of the entire battery may be reduced too much, and conversely, if it is too thin, handling may be difficult.

In addition, in order to improve the binding effect with the negative electrode active material layer formed on the surface, it is preferable that the surface of these negative electrode current collectors is roughened in advance. Surface roughening methods include blasting, rolling with a rough surface roll, polishing cloth with abrasive particles fixed, a grindstone, emeri buff, a wire brush equipped with a steel wire, etc. to polish the surface of the current collector. Specific polishing method, electrolytic polishing method, chemical polishing method and the like can be mentioned.

The slurry for forming the negative electrode active material layer is usually prepared by adding a binder, a thickener, or the like to the negative electrode material. The term "negative electrode material" as used herein refers to a material in which the negative electrode active material and the conductive material are combined.

The content of the negative electrode active material in the negative electrode material is usually 70% by mass or more, particularly preferably 75% by mass or more, and usually 97% by mass or less, particularly preferably 95% by mass or less. If the content of the negative electrode active material is too small, the capacity of the secondary battery using the obtained negative electrode tends to be insufficient, and if it is too large, the content of the binder or the like is relatively insufficient. This is because the strength of the negative electrode tends to be insufficient. When two or more negative electrode active materials are used in combination, the total amount of the negative electrode active materials may satisfy the above range.

Examples of the conductive material used for the negative electrode include metal materials such as copper and nickel; carbon materials such as graphite and carbon black. One of these may be used alone, or two or more thereof may be used in any combination and ratio. In particular, it is preferable to use a carbon material as the conductive material because the carbon material also acts as an active material. The content of the conductive material in the negative electrode material is usually preferably 3% by mass or more, particularly preferably 5% by mass or more, and usually 30% by mass or less, particularly preferably 25% by mass or less. This is because if the content of the conductive material is too small, the conductivity tends to be insufficient, and if it is too large, the content of the negative electrode active material or the like is relatively insufficient, and the battery capacity and strength tend to decrease. .. When two or more conductive materials are used in combination, the total amount of the conductive materials may satisfy the above range.

As the binder used for the negative electrode, any binder can be used as long as it is a material that is safe for the solvent and electrolytic solution used in the production of the electrode. Examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene / butadiene rubber / isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, ethylene / methacrylic acid copolymer and the like. One of these may be used alone, or two or more thereof may be used in any combination and ratio. The content of the binder is usually 0.5 parts by mass or more, particularly preferably 1 part by mass or more, and usually 10 parts by mass or less, particularly preferably 8 parts by mass or less, based on 100 parts by mass of the negative electrode material. If the content of the binder is too small, the strength of the obtained negative electrode tends to be insufficient, and if it is too large, the content of the negative electrode active material or the like is relatively insufficient, so that the battery capacity and conductivity tend to be insufficient. This is because. When two or more binders are used in combination, the total amount of the binders may satisfy the above range.

Examples of the thickener used for the negative electrode include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and the like. One of these may be used alone, or two or more thereof may be used in any combination and ratio. The thickener may be used as needed, but when used, the content of the thickener in the negative electrode active material layer is usually in the range of 0.5% by mass or more and 5% by mass or less. Is preferable.

The slurry for forming the negative electrode active material layer is prepared by mixing the negative electrode active material with a conductive material, a binder, and a thickener as necessary, and using an aqueous solvent or an organic solvent as a dispersion medium. .. Water is usually used as the aqueous solvent, but a solvent other than water such as alcohols such as ethanol and cyclic amides such as N-methylpyrrolidone is used in combination with water at a ratio of about 30% by mass or less. You can also do it. The organic solvent is usually cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic carbides such as anisole, toluene and xylene. Examples thereof include alcohols such as hydrogens, butanol and cyclohexanol, and among them, cyclic amides such as N-methylpyrrolidone and linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. .. Any one of these may be used alone, or two or more thereof may be used in any combination and ratio.

The viscosity of the slurry is not particularly limited as long as it can be applied onto the current collector. The amount of the solvent used may be changed at the time of preparing the slurry so that the viscosity can be applied, and the slurry may be appropriately prepared.

The obtained slurry is applied onto the above-mentioned negative electrode current collector, dried, and then pressed to form a negative electrode active material layer. The method of application is not particularly limited, and a method known per se can be used. The drying method is not particularly limited, and known methods such as natural drying, heat drying, and vacuum drying can be used.

The electrode structure when the negative electrode active material is made into an electrode by the above method is not particularly limited, but the density of the active material existing on the current collector is preferably 1 g · cm ^-3 or more, preferably 1.2 g · cm. ^-3 or more is more preferable, 1.3 g · cm ^-3 or more is particularly preferable, 2.2 g · cm ^-3 or less is preferable, 2.1 g · cm ^-3 or less is more preferable, and 2.0 g · cm ^{−. 3} or less is more preferable, and 1.9 g · cm ^-3 or less is particularly preferable.

If the density of the active material existing on the current collector exceeds the above range, the active material particles are destroyed, the initial irreversible capacity increases, and the non-aqueous electrolyte solution near the current collector / active material interface High current density charge / discharge characteristics may deteriorate due to reduced permeability. Further, if it falls below the above range, the conductivity between the active materials may decrease, the battery resistance may increase, and the capacity per unit volume may decrease.

<2-3-4. Composition, physical properties, preparation method of negative electrode using carbonaceous material and metal compound material>
As the negative electrode active material, a metal compound-based material and the carbonaceous material may be contained. Here, the negative electrode active material containing the metal compound-based material and the carbonaceous material is a single metal or alloy forming a lithium alloy, or a compound such as an oxide, a carbide, a nitride, a silice, or a sulfide thereof. Any of them may be a mixture in which carbonaceous materials are mixed in the state of particles independent of each other, a single metal or alloy forming a lithium alloy, or oxides, carbides, nitrides, silices, sulfides and the like thereof. The compound may be a composite in which the compound of the above is present on the surface or inside of a carbonaceous material. In the present specification, the composite is not particularly limited as long as it contains a metal compound-based material and a carbonaceous material, but preferably the metal compound-based material and the carbonaceous material are physical and / or chemical. It is united by a typical bond. In a more preferable form, the metal compound-based material and the carbonaceous material are in a state in which each solid component is dispersed and present to the extent that they are present at least on the surface of the composite and inside the bulk, and they are physically present. It is a form in which a carbonaceous material is present to integrate by target and / or chemical bond.

In such a form, the particle surface is observed with a scanning electron microscope, the particles are embedded in a resin to prepare a thin piece of the resin, and the particle cross section is cut out, or the coating film composed of the particles is prepared with a cross section polisher. After cutting out the particle cross section, observation is possible by an observation method such as particle cross section observation with a scanning electron microscope.

The content ratio of the metal compound-based material used for the negative electrode active material containing the metal compound-based material and the carbonaceous material is not particularly limited, but is usually 0.1% by mass or more, preferably 1% by mass or more, and more preferably 1. .5% by mass or more, more preferably 2% by mass or more, particularly preferably 3% by mass or more, and usually 99% by mass or less, preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably. It is 30% by mass or less, more preferably 25% by mass or less, particularly preferably 15% by mass or less, and most preferably 10% by mass or less. This range is preferable in that a sufficient capacity can be obtained.

It is preferable that the carbonaceous material used for the negative electrode active material containing the metal compound material and the carbonaceous material satisfies the requirements described in <2-3-2> above. Further, it is desirable that the following conditions are satisfied for the metal compound-based material.

As the elemental metal or alloy forming the lithium alloy, any conventionally known elemental metal can be used, but from the viewpoint of capacity and cycle life, the elemental metal forming the lithium alloy is, for example, Fe, Co, Sb, etc. A metal selected from the group consisting of Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, Nb, Mo, Cu, Zn, Ge, In, Ti and the like or a compound thereof. Is preferable. Further, as the alloy for forming the lithium alloy, a metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn and W or a compound thereof is preferable.

The single metals or alloys that form a lithium alloy, or compounds such as oxides, carbides, nitrides, silices, and sulfides thereof, are metal oxides, metal carbides, metal nitrides, metal silices, and metal sulfides. And so on. Further, an alloy composed of two or more kinds of metals may be used. Among these, Si or a Si compound is preferable in terms of increasing the capacity. In the present specification, Si or Si compounds are collectively referred to as Si compounds. Specific examples of the Si compound include SiOx, SiNx, SiCx, SiZxOy (Z is C or N), and the like, preferably SiOx. The value of x in the above general formula is not particularly limited, but usually 0 ≦ x <2. The general formula SiOx is obtained by using silicon dioxide (SiO ₂ ) and metal Si (Si) as raw materials. SiOx has a larger theoretical capacity than graphite, and amorphous Si or nano-sized Si crystals allow alkaline ions such as lithium ions to easily enter and exit, making it possible to obtain a high capacity.

The value of x in SiOx is not particularly limited, but usually x is 0 ≦ x <2, preferably 0.2 or more, more preferably 0.4 or more, still more preferably 0.6 or more, and also. It is preferably 1.8 or less, more preferably 1.6 or less, and even more preferably 1.4 or less. Within this range, it is possible to reduce the irreversible capacity due to the combination of Li and oxygen at the same time as having a high capacity.
As a method for confirming that the metal compound material is a metal material that can be alloyed with lithium, identification of the metal particle phase by X-ray diffraction, observation and elemental analysis of the particle structure by an electron microscope, and fluorescence Elemental analysis by X-ray and the like can be mentioned.

The average particle size (d50) of the metal compound-based material used for the negative electrode active material containing the metal compound-based material and the carbonaceous material is not particularly limited, but is usually 0.01 μm or more, preferably 0, from the viewpoint of cycle life. It is 0.05 μm or more, more preferably 0.1 μm or more, still more preferably 0.3 μm or more, and usually 10 μm or less, preferably 9 μm or less, more preferably 8 μm or less. When the average particle size (d50) is within the above range, the volume expansion due to charge / discharge is reduced, and good cycle characteristics can be obtained while maintaining the charge / discharge capacity.
The average particle size (d50) can be obtained by a laser diffraction / scattering particle size distribution measuring method or the like.

The specific surface area of the metal compound-based material used for the negative electrode active material containing the metal compound-based material and the carbonaceous material is not particularly limited by the BET method, but is usually 0.5 m ² / g or more, preferably 1 m ² / g or more. In addition, it is usually 60 m ² / g or less, preferably 40 m ² / g. When the specific surface area of the metal particles that can be alloyed with Li by the BET method is within the above range, the charge / discharge efficiency and discharge capacity of the battery are high, lithium is taken in and out quickly in high-speed charge / discharge, and the rate characteristics are excellent, which is preferable.

The amount of oxygen contained in the metal compound-based material used for the negative electrode active material containing the metal compound-based material and the carbonaceous material is not particularly limited, but is usually 0.01% by mass or more, preferably 0.05% by mass or more. Further, it is usually 8% by mass or less, preferably 5% by mass or less. The oxygen distribution state in the particle may be present near the surface, inside the particle, or uniformly in the particle, but it is particularly preferable that the oxygen is present near the surface. When the oxygen content of the metal compound-based material is within the above range, the volume expansion due to charging / discharging is suppressed due to the strong bond between Si and O, and the cycle characteristics are excellent, which is preferable.

Further, as for the negative electrode preparation of the metal compound-based material used for the negative electrode active material containing the metal compound-based material and the carbonaceous material, the one described in <2-3-1> carbonaceous material can be used.

<2-3-5. Composition, physical properties, and preparation method of lithium-containing metal composite oxide material and negative electrode using 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 lithium-containing composite metal oxide material containing titanium is preferable, and composite oxidation of lithium and titanium is preferable. A substance (hereinafter, abbreviated as "lithium-titanium composite oxide") is particularly preferable. That is, it is particularly preferable to use a lithium titanium composite oxide having a spinel structure contained in the negative electrode active material for a non-aqueous electrolyte secondary battery because the output resistance is greatly reduced.

Further, at least lithium or titanium of the lithium titanium composite oxide is 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 kind of element are also preferable.

The metal oxide is a lithium titanium composite oxide represented by the general formula (5), and in the general formula (5), 0.7 ≦ x ≦ 1.5, 1.5 ≦ y ≦ 2.3, It is preferable that 0 ≦ z ≦ 1.6 because the structure at the time of doping and dedoping of lithium ions is stable.

LixTiyMzO ₄ (5)
[In the general formula (5), 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 above general formula (5),
(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 it has a good balance of battery performance.

Particularly preferable typical 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). It is ₄ . As for the structure of Z ≠ 0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ is preferable.

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 shape shown in (1) to (13) below. It is particularly preferable that two or more kinds are satisfied at the same time.

(1) BET Specific Surface Area The BET specific surface area of the lithium titanium composite oxide used as the negative electrode active material preferably has a specific surface area value of 0.5 m ² · g ^-1 or more measured by the BET method. 7 m ² · g ^-1 or more is more preferable, 1.0 m ² · g ^-1 or more is further preferable, 1.5 m ² · g ^-1 or more is particularly preferable, and 200 m ² · g ^-1 or less is preferable, and 100 m. ² · g ^-1 or less is more preferable, 50 m ² · g ^-1 or less is further preferable, and 25 m ² · g ^-1 or less is particularly preferable.

When the BET specific surface area is less than the above range, the reaction area in contact with the non-aqueous electrolytic solution 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 and end face portions of the titanium-containing metal oxide crystal increase, and the crystal is distorted due to this, so that the irreversible capacitance cannot be ignored, which is preferable. It may be difficult to obtain batteries.

To measure the specific surface area by the BET method, a surface area meter (fully automatic surface area measuring device manufactured by Okura Riken) is used to pre-dry the sample at 350 ° C for 15 minutes under nitrogen flow, and then the nitrogen to atmospheric pressure is measured. The nitrogen adsorption BET 1-point method by the gas flow method is performed using a nitrogen-helium mixed gas accurately adjusted so that the relative pressure value is 0.3. The specific surface area obtained 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 size The volume-based average particle size of the lithium titanium composite oxide (secondary particle size when the primary particles are aggregated to form secondary particles) is determined by the laser diffraction / scattering method. It is defined by the obtained volume-based average particle size (median diameter).

The volume-based average particle size of the lithium titanium composite oxide is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 0.7 μm or more, and usually 50 μm or less, preferably 40 μm or less, preferably 30 μm. The following is more preferable, and 25 μm or less is further preferable.

The volume-based average particle size is measured by dispersing carbon powder in a 0.2 mass% aqueous solution (10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and using a laser diffraction / scattering particle size distribution meter. (LA-700 manufactured by HORIBA, Ltd.) is used. The median diameter obtained by the measurement is defined as the volume-based average particle diameter of the carbonaceous material in the present invention.

If the volume average particle size of the lithium titanium composite oxide is less than the above range, a large amount of binder is required at the time of electrode fabrication, and as a result, the battery capacity may decrease. On the other hand, if it exceeds the above range, a non-uniform coating surface is likely to occur at the time of forming an electrode electrode plate, which may be undesirable in the battery manufacturing process.

(3) Average primary particle size When the primary particles are aggregated to form secondary particles, the average primary particle size of the lithium titanium composite oxide is usually 0.01 μm or more, and 0.05 μm or more. Preferably, 0.1 μm or more is more preferable, 0.2 μm or more is further preferable, and usually 2 μm or less, 1.6 μm or less is preferable, 1.3 μm or less is more preferable, and 1 μm or less is further 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 filling property and greatly reduces the specific surface area. Therefore, the battery has output characteristics and the like. There is a high possibility that performance will deteriorate. Further, if it falls below the above range, the performance of the secondary battery may be deteriorated, for example, the reversibility of charge / discharge is inferior due to the underdeveloped crystals.

The primary particle size is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph having a magnification at which the particles can be confirmed, for example, a magnification of 1000 to 100,000, 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 set for any 50 primary particles. It is calculated by calculating and taking the average value.

(4) Shape The shape of the lithium titanium composite oxide particles is a mass, a polyhedron, a spherical shape, an elliptical spherical shape, a plate shape, a needle shape, a columnar shape, or the like as conventionally used. Therefore, it is preferable that the secondary particles are formed and the shape of the secondary particles is spherical or elliptical spherical.

Normally, in an electrochemical element, the active material in the electrode expands and contracts with charging and discharging, so that the stress tends to cause deterioration such as destruction of the active material and breakage of the conductive path. Therefore, it is because the stress of expansion and contraction is alleviated and the deterioration is prevented when the primary particles are aggregated to form the secondary particles rather than the active material of the single particles having only the primary particles.

Further, since the spherical or elliptical spherical particles have less orientation during molding of the electrode than the plate-shaped equiaxed particles, the expansion and contraction of the electrode during charging and discharging is also smaller, and the electrode is manufactured. It is also preferable to mix with the conductive material at the time of mixing because it is easy to be mixed uniformly.

(5) Tap Density Tap density lithium-titanium composite oxide is preferably from 0.05 g · ^{cm -3} or more, more preferably 0.1 g · ^{cm -3} or more, more preferably 0.2 g · ^{cm -3} or more, 0.4 g · cm ^-3 or more is particularly preferable, 2.8 g · cm ^-3 or less is more preferable, 2.4 g · cm ^-3 or less is further preferable, and 2 g · cm ^-3 or less is particularly preferable. When the tap density is lower than the above range, the filling density is difficult to increase when used as a negative electrode, and the contact area between particles is reduced, so that the resistance between particles may increase and the output resistance may increase. On the other hand, if it exceeds the above range, the voids between the particles in the electrode become too small, and the flow path of the non-aqueous electrolyte solution decreases, so that the output resistance may increase.

To measure the tap density, pass through a sieve with a mesh size of 300 μm, drop the sample into a tapping cell of 20 cm ³ to fill the sample up to the upper end surface of the cell, and then use 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 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 lithium titanium composite oxide in the present invention.

(6) Circularity The degree of sphere of the lithium titanium composite oxide is preferably within the following range when the circularity is measured. The circularity is defined by "circularity = (peripheral length of a corresponding circle having the same area as the projected particle shape) / (actual peripheral length of the projected particle shape)", and when the circularity is 1, a theoretical true sphere. It becomes.

The circularity of the lithium titanium composite oxide is preferably closer to 1, usually 0.10 or more, preferably 0.80 or more, more preferably 0.85 or more, still more preferably 0.90 or more. The high current density charge / discharge characteristics 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 the particles is increased, and the high current density charge / discharge characteristics for a short time may be lowered.

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 mass% aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and ultrasonic waves of 28 kHz were irradiated at an output of 60 W for 1 minute. , The detection range is specified as 0.6 to 400 μm, and the measurement is performed on particles having a particle size 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 usually 1 or more, usually 5 or less, preferably 4 or less, more preferably 3 or less, still more preferably 2 or less. If the aspect ratio exceeds the above range, streaks or a uniform coated surface cannot be obtained at the time of electrode plate formation, and the high current density charge / discharge characteristics may deteriorate for a short time. The lower limit of the above range is the theoretical lower limit of the aspect ratio of the lithium titanium composite oxide.

The aspect ratio is measured by magnifying and observing the particles of the lithium titanium composite oxide with a scanning electron microscope. Arbitrary 50 particles fixed to the end face of a metal with a thickness of 50 μm or less are selected, and the stage on which the sample is fixed is rotated and tilted for each, and the longest of the particles is obtained when observed three-dimensionally. The diameter P'and the shortest diameter Q'orthogonal to the diameter P'are measured, and the average value of P'/ Q'is obtained. The aspect ratio (P'/ Q') obtained by the measurement is defined as the aspect ratio of the lithium titanium composite oxide in the present invention.

(8) Method for Producing Negative Electrode Active Material The method for producing a lithium titanium composite oxide is not particularly limited as long as it does not exceed the gist of the present invention, but some methods can be mentioned and are generally used as a method for producing an inorganic compound. Method is used.

For example, a method in which a titanium raw material such as titanium oxide, a raw material of another element as required, and a Li source such as LiOH, Li ₂ CO ₃ , LiNO ₃ are uniformly mixed and fired at a high temperature to obtain an active material. Can be mentioned.

In particular, various methods can be considered for producing a spherical or elliptical spherical active material. As an 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, and the pH is adjusted while stirring to create a spherical precursor. Examples thereof include a method of recovering the substance, drying it as necessary, adding a Li source such as LiOH, Li ₂ CO ₃ and Li NO ₃ and firing at a high temperature to obtain an active substance.

Further, 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, and the material is dried and molded by a spray dryer or the like to form a spherical shape. Alternatively, a method of obtaining an active material by preparing an elliptical spherical precursor, adding a Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ to the precursor and firing 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 , LiNO ₃ and, if necessary, a raw material of another element are dissolved or pulverized in a solvent such as water. Examples thereof include a method in which the residue is dispersed and dried and molded with a spray dryer or the like to form a spherical or elliptical spherical precursor, which is then fired at a high temperature to obtain an active material.

In addition, 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 can also be present in the titanium-containing metal oxide structure and / or in contact with the titanium-containing oxide. By containing these elements, it is possible to control the operating voltage and capacity of the battery.

(9) Electrode production Any known method can be used for electrode production. For example, a binder, a solvent, and if necessary, a thickener, a conductive material, a filler, etc. are added to a negative electrode active material to form a slurry, which is applied to a current collector, dried, and then pressed to form a slurry. Can be done.

The thickness of the negative electrode active material layer per side at the stage immediately before the non-aqueous electrolyte injection step of the battery is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and the upper limit is 150 μm or less, preferably 120 μm. Below, more preferably 100 μm or less.

If it exceeds this range, the non-aqueous electrolyte solution does not easily permeate to the vicinity of the current collector interface, so that the high current density charge / discharge characteristics may deteriorate. If it falls below this range, the volume ratio of the current collector to the negative electrode active material may increase and the capacity of the battery may decrease. Further, the negative electrode active material may be roll-molded to be a sheet electrode, or may be compression-molded to be a pellet electrode.

(10) Current collector A known current collector can be arbitrarily used as the current collector for holding the negative electrode active material. Examples of the current collector of the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel, and copper is particularly preferable from the viewpoint of ease of processing and cost.

When the current collector is made of a metal material, the shape of the current collector may be, for example, a metal foil, a metal column, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foamed metal, or the like. Among them, a metal foil film containing copper (Cu) and / or aluminum (Al) is preferable, copper foil and aluminum foil are more preferable, and rolled copper foil by a rolling method and electrolytic copper by an electrolytic method are more preferable. There are foils, both of which can be used as current collectors.

When the thickness of the copper foil is thinner than 25 μm, a copper alloy having higher strength than pure copper (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) can be used. Further, since the aluminum foil has a light specific gravity, it is possible to reduce the mass of the battery when it is used as a current collector, and it can be preferably used.

The current collector made of copper foil produced by the rolling method is suitable for small cylindrical batteries because the copper crystals are lined up in the rolling direction and therefore it is hard to break even if the negative electrode is rounded tightly or sharply. be able to.

In the electrolytic copper foil, for example, a metal drum is immersed in a non-aqueous electrolytic solution in which copper ions are dissolved, and a current is passed while rotating the drum to deposit copper on the surface of the drum and peel it off. It is obtained by Copper may be deposited on the surface of the rolled copper foil by an electrolytic method. One side or both sides of the copper foil may be roughened or surface-treated (for example, chromate treatment having a thickness of several nm to 1 μm, base treatment such as Ti, etc.).

The thickness of the current collector is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, and more preferably 50 μm or less.

When the thickness of the current collector is within the above range, the strength is improved, the application is facilitated, and the shape of the electrode is stable, which is preferable.

(11) Ratio of thickness between current collector and active material layer The ratio of thickness between current collector and active material layer is not particularly limited, but "(one-sided active material layer immediately before injection of non-aqueous electrolyte solution) The value of "thickness) / (thickness of current collector)" is usually 150 or less, preferably 20 or less, more preferably 10 or less, and usually 0.1 or more, preferably 0.4 or more. 1 or more is more preferable.

If the ratio of the thickness of the current collector to the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during high current density charging / discharging. Further, if it falls below the above range, the volume ratio of the current collector to the negative electrode active material may increase, and the capacity of the battery may decrease.

(12) 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 active material existing on the current collector is preferably 1 g · cm ^-3 or more, preferably 1.2 g. · ^{cm -3} or more, and more preferably 1.3 g · ^{cm -3} or more, particularly preferably 1.5 g · ^{cm -3} or more, preferably 3 g · ^{cm -3} or less, 2.5 g · cm ^{- 3} or less is more preferable, 2.2 g · cm ^-3 or less is further preferable, and 2 g · cm ^-3 or less is particularly preferable.

If the density of the active material existing on the current collector exceeds the above range, the bond between the current collector and the negative electrode active material becomes weak, and the electrode and the active material may dissociate. Further, if it falls below the above range, the conductivity between the negative electrode active materials may decrease and the battery resistance may increase.

(13) Binder The binder for binding the negative electrode active material is not particularly limited as long as it is a non-aqueous electrolytic solution or a material stable to the solvent used in electrode production.

Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethylmethacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, and fluororubber. Rubber-like polymers such as NBR (acrylonitrile-butadiene rubber), ethylene-propylene rubber; styrene-butadiene-styrene block copolymer and its hydrogen additive; EPDM (ethylene-propylene-diene ternary copolymer), styrene- Thermoplastic elastomeric polymers such as ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers and their hydrogenated products; syndiotactics-1,2-
Soft resinous polymers such as polybutadiene, polyvinylacetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene Fluoropolymers such as ethylene copolymers; polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions) and the like can be mentioned. These may be used alone or in any combination and ratio of two or more.

The type of solvent for forming the slurry is particularly limited as long as it is a solvent capable of dissolving or dispersing a negative electrode active material, a binder, a thickener and a conductive material used as necessary. However, either an aqueous solvent or an organic solvent may be used.

Examples of aqueous solvents include water, alcohol and the like, and examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N. , N-Dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamerylphosphalamide, dimethylsulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like. In particular, when an aqueous solvent is used, a dispersant or the like is added in addition to the above-mentioned thickener, and a latex such as SBR is used to form a slurry. It should be noted that these may be used alone or in any combination and ratio of two or more.

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, more preferably 0.6% by mass or more, and usually 20% by mass or less, 15% by mass. % Or less is preferable, 10% by mass or less is more preferable, and 8% by mass or less is further preferable.

When the ratio of the binder to the negative electrode active material is within the above range, the ratio of the binder whose amount of binder does not contribute to the battery capacity decreases, the battery capacity increases, and the strength of the negative electrode electrode is maintained, which is preferable in the battery manufacturing process. ..

In particular, when a rubbery polymer typified by SBR is contained in the main component, the ratio of the binder to the 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 usually 5% by mass or less, 3% by mass or less is preferable, and 2% by mass or less is more preferable.

When a fluorine-based polymer typified by polyvinylidene fluoride is contained in the main component, the ratio to the active material is usually 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more. , Usually 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

Thickeners are commonly used to adjust the viscosity of the slurry. The thickener is not particularly limited, and specific examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, and salts thereof. These may be used alone or in any combination and ratio of two or more.

Further, when a thickener is used, 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. Further, it is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. When the ratio of the thickener to the negative electrode active material is within the above range, it is preferable in terms of the applicability of the pressure-sensitive adhesive.
Further, the ratio of the active material to the negative electrode active material layer is preferable, and it is preferable in terms of the capacity of the battery and the resistance between the negative electrode active materials.

<2-4. Positive electrode>
The positive electrode has a positive electrode active material layer on the current collector, and the positive electrode active material layer contains a positive electrode active material. Hereinafter, the positive electrode active material will be described.

<2-4-1. Positive electrode active material>
The positive electrode active material used for the positive electrode will be described below.

(1) Composition The positive electrode active material is not particularly limited as long as it can electrochemically occlude and release lithium ions, but for example, a substance containing lithium and at least one transition metal is preferable. Specific examples include a lithium transition metal composite oxide and a lithium-containing transition metal phosphoric acid compound.

The transition metal of the lithium transition metal composite oxide is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu or the like, and specific examples thereof include a lithium cobalt composite oxide such as LiCoO ₂ , LiMnO ₂ , LiMn. ₂ O _{4, Li} 2 lithium-manganese composite oxides such as MnO _4, LiNiO ₂ and lithium-nickel composite oxide, and the like. Further, some of the transition metal atoms that are the main constituents of these lithium transition metal composite oxides are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si. Examples thereof include those substituted with other metals such as lithium-cobalt-nickel composite oxide, lithium-cobalt-manganese composite oxide, lithium-nickel-manganese composite oxide, and lithium-nickel composite oxide. Examples include cobalt-manganese composite oxides.

Specific examples of the substituted ones include, for example, Li _{1 + a} Ni _0.5 Mn _0.5 O ₂ , Li _{1 + a} Ni _0.8 Co _0.2 O ₂ , Li _{1 + a} Ni _0.85 Co _0.10 Al _{0. 05} O ₂ , Li _{1 + a} Ni _0.33 Co _0.33 Mn _0.33 O ₂ , Li _{1 + a} Ni _0.45 Co _0.45 Mn _0.1 O ₂ , Li _{1 + a} Mn _1.8 Al _0.2 O ₄ , Li _{1 + a} Mn _1.5 Ni _0.5 O ₄ , xLi ₂ MnO ₃ , (1-x) Li _{1 + a} MO ₂ (M = transition metal) and the like (a = 0 <a ≦ 3.0).

The lithium-containing transition metal phosphate compound is LixMPO ₄ (M = a kind of element selected from the group consisting of transition metals of groups 4 to 11 of the 4th period of the periodic table, x is 0 <x <1.2). Can be expressed as the basic composition, and the transition metal (M) is selected from the group consisting of V, Ti, Cr, Mg, Zn, Ca, Cd, Sr, Ba, Co, Ni, Fe, Mn and Cu. It is preferably at least one element selected from the group consisting of Co, Ni, Fe, and Mn, and more preferably at least one element. For _{example, LiFePO 4, Li 3 Fe 2} (PO 4) 3, LiFeP 2 O 7 , etc. of phosphorus Santetsurui, cobalt phosphate such as LiCoPO _4, manganese phosphate such as LiMnPO _4, phosphoric acids such as LiNiPO ₄ Nickel, some of the transition metal atoms that are the main constituents of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Examples thereof include those substituted with other metals such as Nb and Si.
The above-mentioned "LixMPO ₄ " includes not only those having a composition represented by the composition formula but also those in which a part of the transition metal (M) site in the crystal structure is replaced with another element. means. Further, it means that not only the stoichiometric composition but also the non-stoichiometric composition in which some elements are deleted or the like is included. When the above-mentioned other element substitution is performed, it is usually 0.1 mol%, preferably 0.2 mol% or more. Further, it is usually 5 mol% or less, preferably 2.5 mol% or less.

The positive electrode active material may be used alone or in combination of two or more.

(2) Surface coating A substance having a composition different from that of the substance constituting the main positive electrode active material (hereinafter, appropriately referred to as “surface adhering substance”) may be used on the surface of the positive electrode active material. it can. Examples of surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide and other oxides, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, etc. Examples thereof include sulfates such as calcium sulfate and aluminum sulfate, and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.

These surface-adhering substances are, for example, dissolved or suspended in a solvent, impregnated and added to the positive electrode active material, and then dried, or the surface-adhering substance precursor is dissolved or suspended in the solvent and impregnated and added to the positive electrode active material. After that, it can be attached 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 at the same time, or the like.

The mass of the surface-adhering substance adhering to the surface of the positive electrode active material is usually 0.1 ppm or more, preferably 1 ppm or more, more preferably 10 ppm or more, and usually 20% with respect to the mass of the positive electrode active material. It is less than or equal to, preferably 10% or less, and more preferably 5% or less.

The surface-adhering substance can suppress the oxidation reaction of the non-aqueous electrolyte solution on the surface of the positive electrode active material, and can improve the battery life. However, if the amount of adhesion is less than the above range, the effect is not sufficiently exhibited, and if it exceeds the above range, resistance may increase due to inhibition of the inflow and outflow of lithium ions, so the above range is preferable.

(3) Shape The shape of the positive electrode active material particles may be agglomerates, polyhedrons, spheres, elliptical spheres, plates, needles, columns, etc. as conventionally used, but among them, the primary particles are aggregated and secondary. It is preferably formed by forming secondary particles, and the shape of the secondary particles is spherical or elliptical spherical.

Normally, in an electrochemical element, the active material in the electrode expands and contracts with charging and discharging, so that the stress tends to cause deterioration such as destruction of the active material and breakage of the conductive path. Therefore, it is because the stress of expansion and contraction is alleviated and the deterioration is prevented when the primary particles are aggregated to form the secondary particles rather than the single particle active material containing only the primary particles.

In addition, since spherical or elliptical spherical particles have less orientation during molding of the electrode than plate-shaped equiaxed particles, the expansion and contraction of the electrode during charging and discharging is also smaller, and when the electrode is prepared. It is also preferable to mix with the conductive material of the above because it is easy to mix uniformly.

(4) Tap density The tap density of the positive electrode active material is usually 0.4 g · cm ^-3 or more, preferably 0.6 g · cm ^-3 or more, and more preferably 0.8 g · cm ^-3 or more. 0 g · ^{cm -3} or more are particularly preferred, and generally not more than ^{4.0g · cm -3, 3.8g · cm} -3 or less.

By using the metal composite oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. Therefore, when the tap density of the positive electrode active material is lower than the above range, the amount of the dispersion medium required for forming the positive electrode active material layer increases, and the required amount of the conductive material and the binder increases, so that the positive electrode active material layer becomes available. The filling rate of the positive electrode active material is restricted, and the battery capacity may be restricted. Also,
Generally, the larger the tap density is, the more preferable it is, and there is no particular upper limit. However, if it is less than the above range, the diffusion of lithium ions through the non-aqueous electrolyte solution in the positive electrode active material layer becomes rate-determining, and the load characteristics may easily deteriorate. is there.

To measure the tap density, pass a sieve with a mesh size of 300 μm, drop the sample into a tapping cell of 20 cm ³ to fill the cell volume, and then use a powder density measuring device (for example, a tap density manufactured by Seishin Enterprise Co., Ltd.). Using this, 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 mass of the sample. The tap density calculated by the measurement is defined as the tap density of the positive electrode active material in the present invention.

(5) Median diameter d50
The median diameter d50 of the particles of the positive electrode active material (secondary particle diameter when the primary particles are aggregated to form secondary particles) shall also be measured using a laser diffraction / scattering particle size distribution measuring device. Can be done.

The median diameter d50 is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, further preferably 3 μm or more, and usually 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less. , 15 μm or less is more preferable. If the median diameter d50 is less than the above range, a high bulk density product may not be obtained, and if it exceeds the above range, it takes time to diffuse lithium in the particles, so that the battery characteristics are deteriorated and the positive electrode of the battery is prepared. That is, when the active material and the conductive material, the binder, or the like are slurried with a solvent and applied in the form of a thin film, streaks may occur.

By mixing two or more types of positive electrode active materials having different median diameters d50 at an arbitrary ratio, the filling property at the time of producing the positive electrode can be further improved.

The median diameter d50 was measured by using a 0.1 mass% sodium hexametaphosphate aqueous solution as a dispersion medium and using LA-920 manufactured by HORIBA, Ltd. as a particle size distribution meter to obtain a measured refractive index of 1.24 after ultrasonic dispersion for 5 minutes. Set and measure.

(6) Average primary particle size When the primary particles are aggregated to form secondary particles, the average primary particle size of the positive electrode active material is usually 0.03 μm or more, preferably 0.05 μm or more, and 0. 08 μm or more is more preferable, 0.1 μm or more is further preferable, and usually 5 μm or less, 4 μm or less is preferable, 3 μm or less is more preferable, and 2 μm or less is further preferable. If it exceeds the above range, it is difficult to form spherical secondary particles, which adversely affects powder filling properties and greatly reduces the specific surface area, so that there is a high possibility that battery performance such as output characteristics will deteriorate. is there. Further, if it is less than the above range, the performance of the secondary battery may be deteriorated, for example, the reversibility of charge / discharge is inferior because the crystals are underdeveloped.

The average primary particle size is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000, 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 the average value is taken. Be done.

(7) BET Specific Surface Area The BET specific surface area of the positive electrode active material is such that the value of the specific surface area measured by the BET method is usually 0.1 m ² · g ^-1 or more, and 0.2 m ² · g ^-1 or more. Is preferable, 0.3 m ² · g ^-1 or more is more preferable, and usually 50 m ² · g ^-1 or less, 40 m ² · g ^-1 or less is preferable, and 30 m ² · g ^-1 or less is more preferable. When the value of the BET specific surface area is less than the above range, the battery performance tends to deteriorate. On the other hand, if it exceeds the above range, the tap density is difficult to increase, and the coatability at the time of forming the positive electrode active material may decrease.

The BET specific surface area is measured using a surface area meter (fully automatic surface area measuring device manufactured by Okura RIKEN). The sample was pre-dried at 150 ° C. for 30 minutes under nitrogen flow, and then a gas was used using a nitrogen-helium mixed gas that was accurately adjusted so that the relative pressure value of nitrogen with respect to atmospheric pressure was 0.3. Nitrogen adsorption by the flow method Measured by the BET 1-point method. The specific surface area obtained by the measurement is defined as the BET specific surface area of the anode active material in the present invention.

(8) Method for Producing Positive Electrode Active Material The method for producing the positive electrode active material is not particularly limited as long as it does not exceed the gist of the present invention, but some methods are mentioned and are general as a method for producing an inorganic compound. The method is used.

In particular, various methods can be considered for producing spherical or elliptical spherical active materials. For example, one of them is a transition metal raw material such as transition metal nitrate or sulfate, and if necessary, a raw material of other elements. Is dissolved or pulverized and dispersed in a solvent such as water, the pH is adjusted while stirring to prepare and recover a spherical precursor, which is dried as necessary, and then LiOH, Li ₂ CO ₃ , Li NO. Examples thereof include a method of adding a Li source such as ₃ and firing at a high temperature to obtain an active material.

Further, as an example of another method, a transition metal raw material such as transition metal nitrate, sulfate, hydroxide, oxide and, if necessary, a raw material of another element are dissolved or pulverized and dispersed in a solvent such as water. Then, it is dried and molded with a spray dryer or the like to form a spherical or elliptical spherical precursor, to which Li sources such as LiOH, Li ₂ CO ₃ and Li NO ₃ are added and fired at a high temperature to obtain an active material. Can be mentioned.

As an example of yet another method, transition metal raw materials such as transition metal nitrates, sulfates, hydroxides, and oxides, Li sources such as LiOH, Li ₂ CO ₃ , and LiNO ₃ , and other elements as required. Is a method of dissolving or pulverizing and dispersing the raw material of the above in a solvent such as water, drying and molding it with a spray dryer or the like to obtain a spherical or elliptical spherical precursor, and firing this at a high temperature to obtain an active material. Can be mentioned.

<2-4-2. Electrode structure and manufacturing method>
The configuration of the positive electrode used in the present invention and the method for producing the same will be described below.

(1) Method for producing a positive electrode A positive electrode is produced by forming a positive electrode active material layer containing positive electrode active material particles and a binder on a current collector. The positive electrode using the positive electrode active material can be produced by any known method. That is, a positive electrode active material, a binder, and if necessary, a conductive material, a thickener, and the like are mixed in a dry manner to form a sheet, which is then pressure-bonded to the positive electrode current collector, or these materials are used as a liquid medium. A positive electrode can be obtained by forming a positive electrode active material layer on the current collector by applying the slurry as a slurry to the positive electrode current collector and drying it.

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 further preferably 84% by mass or more. The upper limit is preferably 99% by mass or less, more preferably 98% by mass or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the electric capacity may be insufficient. On the contrary, if the content is too high, the strength of the positive electrode may be insufficient. As the positive electrode active material powder in the present invention, one type may be used alone, or two or more types having different compositions or different powder physical properties may be used in combination in any combination and ratio.

(2) Conductive material As the conductive material, a known conductive material can be arbitrarily used. Specific examples include metal materials such as copper and nickel; graphite (graphite) such as natural graphite and artificial graphite; carbon black such as acetylene black; and carbonaceous materials such as amorphous carbon such as needle coke. It should be noted that one of these may be used alone, or two or more thereof may be used in any combination and 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, and usually 50% by mass or less, preferably 30% by mass or less in the positive electrode active material layer. , More preferably, it is used so as to contain 15% by mass or less. If the content is lower than the above range, the conductivity may be insufficient. If it exceeds the above range, the battery capacity may decrease.

(3) Binder The binder used for producing the positive electrode active material layer is not particularly limited as long as it is a material stable to the non-aqueous electrolytic solution and the solvent used for producing the electrode.

In the case of the coating method, any material may be used as long as it is a material that is dissolved or dispersed in the liquid medium used during electrode production. Specific examples thereof include polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and nitro. Resin-based polymer such as cellulose; rubber-like polymer such as SBR (styrene / butadiene rubber), NBR (acrylonitrile / butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, ethylene / propylene rubber; styrene / butadiene / styrene block Copolymers or hydrogenated products thereof, EPDM (ethylene / propylene / diene ternary copolymer), styrene / ethylene / butadiene / ethylene copolymers, styrene / isoprene / styrene block copolymers or hydrogenated products thereof, etc. Thermoplastic elastomeric polymer; soft resinous polymer such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride (PVdF) ), Polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymer and other fluoropolymers; polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions), etc. Be done. In addition, these substances may be used individually by 1 type, and may use 2 or more types together in arbitrary combinations and ratios.

The proportion 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 usually 50% by mass or less, 30% by mass. % Or less is preferable, 10% by mass or less is more preferable, and 8% by mass or less is further preferable. When the ratio of the binder is within the above range, the positively active substance can be sufficiently retained, the mechanical strength of the positive electrode is maintained, and it is preferable from the viewpoint of cycle characteristics, battery capacity and conductivity.

(4) Liquid medium The liquid medium for forming the slurry may be a solvent capable of dissolving or dispersing a positive electrode active material, a conductive material, a binder, and a thickener used as needed. For example, the type is not particularly limited, 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 organic media 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, methylethylketone and cyclohexanone. Classes; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine, N, N-dimethylaminopropylamine; ethers such as diethyl ether and tetrahydrofuran (THF); N-methylpyrrolidone (NMP), dimethylformamide , Amides such as dimethylacetamide; aprotonic polar solvents such as hexamethylphosphalamide and dimethylsulfoxide can be mentioned. It should be noted that one of these may be used alone, or two or more thereof may be used in any combination and ratio.

(5) Thickener When an aqueous medium is used as the liquid medium for forming the slurry, it is preferable to use a thickener and a latex such as styrene-butadiene rubber (SBR) to form a slurry. Thickeners are commonly used to adjust the viscosity of the slurry.

The thickener is not limited as long as the effect of the present invention is not significantly limited, but specifically, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. And so on. These may be used alone or in any combination and ratio of two or more.

Further, when a thickener is used, the ratio of the thickener to the 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, and more. Usually 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. If it is below the above range, the coatability may be significantly lowered, and if it exceeds the above range, the ratio of the active material in the positive electrode active material layer is lowered, which causes a problem that the battery capacity is lowered and resistance between the positive electrode active materials. May increase.

(6) Consolidation 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 g · cm ^-3 or more, more preferably 1.5 g · cm ^-3 or more, further preferably 2 g · cm ^-3 or more, and preferably 4 g · cm ^-3 or less. 3.8 g · ^{cm -3,} more preferably less, more preferably 3.7 g · ^{cm -3} or less.

If the density of the positive electrode active material layer exceeds the above range, the permeability of the non-aqueous electrolyte solution to the vicinity of the current collector / active material interface may decrease, and the charge / discharge characteristics may be particularly deteriorated at a high current density. If it falls below the above range, the conductivity between the active materials may decrease and the battery resistance may increase.

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

Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, foamed metal, etc. in the case of metal material, and carbon plate in the case of carbonaceous material. Examples include a carbon thin film and a carbon column. Of these, a metal thin film is preferable. The thin film may be formed in a mesh shape as appropriate.

The thickness of the current collector is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, and more preferably 50 μm or less. When the thin film is within the above range, the strength required as a current collector is maintained, and it is also preferable from the viewpoint of handleability.

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 the electrolytic solution injection) / (thickness of the current collector) is It is usually 20 or less, preferably 15 or less, more preferably 10 or less, and the lower limit is usually 0.5 or more, preferably 0.8 or more, and more preferably 1 or more. If it exceeds this range, the current collector may generate heat due to Joule heat during high current density charging / discharging. Below this range, the volume ratio of the current collector to the positive electrode active material may increase and the capacity of the battery may decrease.

<2-5. Separator>
A separator is usually interposed between the positive electrode and the negative electrode to prevent a short circuit. In this case, the non-aqueous electrolyte solution of the present invention is usually used by impregnating this separator.

The material and shape of the separator are not particularly limited, and any known separator can be used as long as the effects of the present invention are not significantly impaired. Among them, resins, glass fibers, inorganic substances and the like formed of a material stable to the non-aqueous electrolytic solution of the present invention are used, and a porous sheet or a non-woven fabric-like material having excellent liquid retention property is used. Is preferable.

As the material of the resin and the glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene, polyether sulfone, glass filter and the like can be used. Of these, glass filters and polyolefins are preferable, and polyolefins are more preferable. One of these materials may be used alone, or two or more of these materials may be used in any combination and ratio.

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, and more preferably 30 μm or less. If the separator is too thin than the above range, the insulating property and mechanical strength may decrease. Further, if it is too thick than the above range, not only the battery performance such as rate characteristics may be deteriorated, but also the energy density of the non-aqueous electrolyte secondary battery as a whole may be lowered.

Further, when a porous material such as a porous sheet or a non-woven 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. Further, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too small than the above range, the film resistance tends to increase and the rate characteristics tend to deteriorate. On the other hand, if it is larger than the above range, the mechanical strength of the separator tends to decrease and the insulating property tends to decrease.

The average pore size 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 is likely to occur. Further, if it falls below the above range, the film resistance may increase and the rate characteristics may deteriorate.

On the other hand, as the inorganic material, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used, and have a particle shape or a fiber shape. Things are used.

As the form, a thin film such as a non-woven fabric, a woven fabric, or a microporous film is used. As the thin film shape, a thin film having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm is preferably used. In addition to the independent thin film shape, a separator obtained 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, alumina particles having a 90% particle size of less than 1 μm are formed on both sides of the positive electrode by using a fluororesin as a binder to form a porous layer.

<2-6. Battery design>
[Electrode group]
The electrode group has a laminated structure in which the above-mentioned positive electrode plate and the negative electrode plate are formed by the above-mentioned separator, and a structure in which the above-mentioned positive electrode plate and the negative electrode plate are spirally wound through the above-mentioned separator. Either may be used. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy rate) is usually 40% or more, preferably 50% or more, and usually 90% or less, 80% or less. preferable. When the electrode group occupancy rate is less than the above range, the battery capacity becomes small. Further, if it exceeds the above range, the void space is small, and the internal pressure rises due to the expansion of the member due to the high temperature of the battery and the increase of the vapor pressure of the liquid component of the electrolyte, and the charge / discharge repetition performance as a battery. In some cases, various characteristics such as high temperature storage may be deteriorated, and a gas discharge valve that releases internal pressure to the outside may operate.

[Current collector structure]
The current collecting structure is not particularly limited, but in order to more effectively improve the discharge characteristics of the non-aqueous electrolyte solution of the present invention, it is necessary to use a structure that reduces the resistance of the wiring portion and the joint portion. preferable. When the internal resistance is reduced in this way, the effect of using the non-aqueous electrolyte solution of the present invention is particularly well exhibited.

When the electrode group has the above-mentioned laminated structure, a structure formed by bundling the metal core portions of each electrode layer and welding them to the terminals is preferably used. When the area of one electrode becomes large, the internal resistance becomes large. Therefore, it is also preferably used to reduce the resistance by providing a plurality of terminals in the electrode. When the electrode group has the above-mentioned wound structure, the internal resistance can be reduced by providing a plurality of lead structures on the positive electrode and the negative electrode and bundling them in the terminals.

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

In the outer case using the metals, the metals are welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed and sealed structure, or the metals are used to caulk the structure via a resin gasket. There are things to do. Examples of the outer case using the laminated film include a case in which resin layers are heat-sealed to form a sealed and sealed structure. In order to improve the sealing property, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when the resin layer is heat-sealed via the current collecting terminal to form a closed structure, the metal and the resin are bonded to each other. Therefore, a resin having a polar group or a modification in which a polar group is introduced as an intervening resin is introduced. Resin is preferably used.

[Protective element]
As the above-mentioned protection elements, PTC (Positive Temperature Coafficient) whose resistance increases when abnormal heat generation or excessive current flows, thermal fuse, thermistor, and current flowing in the circuit due to a sudden rise in battery internal pressure or internal temperature during abnormal heat generation. A valve that shuts off the current (current cutoff valve) and the like can be mentioned. It is preferable to select the protective element under conditions that do not operate under normal use of high current, and from the viewpoint of high output, it is more preferable to design the protective element 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 accommodating the above-mentioned non-aqueous electrolyte, negative electrode, positive electrode, separator and the like inside the exterior. There is no limitation on this exterior body, and a known one can be arbitrarily adopted as long as the effect of the present invention is not significantly impaired.

Specifically, the material of the exterior body is arbitrary, but usually, for example, nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium or the like is used.

Further, the shape of the exterior body is also arbitrary, and may be any of, for example, a cylindrical type, a square type, a laminated type, a coin type, and a large size.

Hereinafter, the present invention will be described in more detail with reference to Examples and Reference Examples, but the present invention is not limited to these Examples as long as the gist thereof is not exceeded.
<Raw materials>
Compound A: Tricredyl phosphate (manufactured by Daihachi Chemical Co., Ltd., para-positional substituent: meta-positional substituent: ortho-positional substituent 67:33: 0)

<Evaluation method>
[Evaluation of initial -30 ° C output characteristics]
The battery for which the evaluation of the initial discharge capacity was completed was charged at 25 ° C. with a constant current of 0.2 C so as to have a capacity half of the initial discharge capacity. This was discharged at 0.5C, 1.0C, 1.5C, 2C and 2.5C at −30 ° C., and the voltage at 10 seconds was measured. The current value at 2.8 V was obtained from the current-voltage straight line, and 3.0 × (current value at 3.0 V) was taken as the output (W).

(Example 1)
[Preparation of negative electrode]
98 parts by mass of carbonaceous material, 1 part by mass of aqueous dispersion of sodium carboxymethyl cellulose (concentration of sodium carboxymethyl cellulose 1% by mass) and aqueous dispersion of styrene-butadiene rubber (of styrene-butadiene rubber) as a thickener and binder. (Concentration 50% by mass) 1 part by mass was added and mixed with a disperser to form a slurry. The obtained slurry was applied to a copper foil having a thickness of 10 μm, dried, and rolled by a press. The size of the active material layer was 30 mm in width, 40 mm in length, and 5 mm in width and 9 mm in length. It was cut out into a shape having a portion and used as a negative electrode.

[Preparation of positive electrode]
90% by mass of Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ (LNMC) as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder. ) 5% by mass was mixed in an N-methylpyrrolidone solvent to form a slurry. The obtained slurry was applied to one side of a 15 μm-thick aluminum foil previously coated with a conductive auxiliary agent, dried, and rolled by a press machine. The size of the active material layer was 30 mm in width and 30 mm in length. It was cut into a shape having an uncoated portion of 40 mm, a width of 5 mm, and a length of 9 mm to obtain a positive electrode.

[Preparation of electrolyte]
Under a dry argon atmosphere, 1 mol / L of LiPF ₆ dried in a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and 1,2-dimethoxyethane (DME) (volume ratio 30:60:10) was added. The basic electrolyte was adjusted to a ratio. An electrolytic solution was prepared by mixing 0.5 parts by mass of vinylene carbonate (VC) and 3 parts by mass of compound A with this electrolytic solution.

[Manufacturing of lithium secondary batteries]
The above positive electrode, negative electrode, and polyethylene separator were laminated in this order of the negative electrode, the separator, and the positive electrode to prepare a battery element. After inserting this battery element into a bag made of a laminated film in which both sides of aluminum (thickness 40 μm) are coated with a resin layer while projecting the positive electrode and negative electrode terminals, the above electrolytic solution is injected into the bag to create a vacuum. A laminated battery was prepared which was sealed and fully charged at 4.2 V.

(Example 2)
Under a dry argon atmosphere, LiPF ₆ dried in a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and 1,2-dimethoxyethane (volume ratio 30:50:20) is added to a ratio of 1 mol / L. A laminated lithium secondary battery was produced and evaluated in the same manner as in Example 1 except that the basic electrolyte was adjusted as described above. The results are shown in Table 1.

(Example 3)
Under a dry argon atmosphere, LiPF ₆ dried in a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and methyl propionate (MP) (volume ratio 30:60:10) is at a ratio of 1 mol / L. A laminated lithium secondary battery was produced and evaluated in the same manner as in Example 1 except that the basic electrolyte was adjusted as described above. The results are shown in Table 1.

(Comparative Example 1)
Except that the basic electrolyte was adjusted so that the ratio of dried LiPF ₆ to a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio 30:70) was 1 mol / L under a dry argon atmosphere. , A laminated lithium secondary battery was produced in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

(Comparative Example 2)
Under a dry argon atmosphere, LiPF ₆ dried in a mixture (volume ratio 30:60:10) of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and 2-methyltetrahydrofuran (2MeTHF) was added at a ratio of 1 mol / L. A laminated lithium secondary battery was produced and evaluated in the same manner as in Example 1 except that the basic electrolyte was adjusted so as to be. The results are shown in Table 1.

(Comparative Example 3)
Under a dry argon atmosphere, LiPF ₆ dried in a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and 1,3-dioxolane (DOL) (volume ratio 30:60:10) at a ratio of 1 mol / L. A laminated lithium secondary battery was produced and evaluated in the same manner as in Example 1 except that the basic electrolyte was adjusted so as to be. The results are shown in Table 1.

(Comparative Example 4)
A laminated lithium secondary battery was produced and evaluated in the same manner as in Example 1 except that compound A was not added and 3 parts by mass of triallyl phosphate (TAP) was added. The results are shown in Table 1.

As is clear from Table 1, it can be seen that Examples 1 to 3 are superior in -30 ° C output (low temperature output) to Comparative Examples 1 to 4.
Further, from Examples 1 to 3 and Comparative Example 1, when a chain ether such as 1,2-dimethoxyethane or a chain carboxylic acid ester such as methyl propionate is used as a non-aqueous solvent, the output is −30 ° C. It can be seen that can be improved.
However, in Comparative Example 2 and Comparative Example 3 using a solvent other than the chain ether or the carboxylic acid ester (2-methyltetrahydrofuran, 1,3-dioxolane), the output at −30 ° C. was significantly reduced.
From Example 1 and Comparative Example 4, a phosphoric acid ester having no chain alkyl group in the aromatic ring, such as triallyl phosphate, does not have a sufficient low temperature output. Therefore, it can be seen that the output at −30 ° C. is improved only when the chain ether or carboxylic acid ester is combined with the compound represented by the general formula (1) having a chain alkyl group in the aromatic ring.
As described above, by using the compound of the general formula (1) and the chain ether and / or the chain carboxylic acid ester in the non-aqueous electrolyte solution, the non-aqueous electrolyte solution and the non-aqueous electrolyte solution have excellent low temperature output. A liquid secondary battery can be obtained.

According to the non-aqueous electrolyte solution of the present invention, the low temperature output characteristics of the non-aqueous electrolyte secondary battery can be improved, and it is useful as an in-vehicle power source for electric vehicles and the like.
Further, the non-aqueous electrolyte solution of the present invention and the non-aqueous electrolyte secondary battery using the same can be used for various known applications that may be used in a low temperature environment. Specific examples include, for example, laptop computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copies, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, mini discs. , Transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, bikes, motorized bicycles, bicycles, lighting equipment, toys, game equipment, watches, power tools, strobes, cameras, household backups Examples include a power source, a backup power source for business establishments, a power source for load leveling, a natural energy storage power source, and a lithium ion capacitor.

Claims (15)

A nonaqueous electrolytic solution containing an electrolyte and a non-aqueous solvent, looking containing compounds and at least one compound selected from the group consisting of linear ethers and carboxylic acid esters of the following general formula (1),
The compound represented by the general formula (1) is contained in two or more kinds , and the ratio of the substitution positions of R _{1 to} R ₃ is 50 for the total of the ortho-position, meta-position, and para-position. % Or more , non-aqueous electrolyte solution.

(In the formula (1), _R 1 ~R ₃ during their respective shows a chain hydrocarbon group having a carbon number of 1-10. Formula, a, b, c are an integer of 0 to 5, a + b + c is Indicates an integer from _{1 to} 9. R _{1 to} R ₃ may be the same or different.) Wherein, in the general formula (1), _R 1 to R ₃ is a methyltransferase group, a non-aqueous electrolyte solution of claim 1. The non-aqueous electrolyte solution according to claim 1 or 2, wherein R _{1 to} R ₃ are methyl groups in the general formula (1) and a = b = c = 1 or 2. The compound represented by the general formula (1) includes any of the following structural formulas (2) to (4).
The non-aqueous electrolyte solution according to any one of claims 1 to 3.

The non-aqueous electrolytic solution according to claim 4, wherein two or more of the structural formulas (2) to (4) are contained in the non-aqueous electrolytic solution. According to any one of claims 1 to 5 , the content of the compound represented by the general formula (1) is 0.001% by mass or more and 10% by mass or less with respect to the total amount of the non-aqueous electrolyte solution. The non-aqueous electrolyte solution described. It said chain ether, or at least one compound selected from the group consisting of carboxylic acid ester, contain 80% by volume or less than 0.5% by volume based on the solvent total non-aqueous electrolyte solution according to claim 1 to 6 The non-aqueous electrolyte solution according to any one of the above. The non-aqueous electrolyte solution according to any one of claims 1 to 7, wherein the chain ether is at least one of dimethoxyethane, ethoxymethoxyethane, and diethoxyethane. Any one of claims 1 to 8, wherein the carboxylic acid ester is at least one of methyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and gamma butyrolactone. The non-aqueous electrolyte solution described in 1. The non-aqueous electrolyte solution according to any one of claims 1 to 9, further containing a carbon-carbon unsaturated bond or a carbonate containing at least one of fluorine atoms. 10. The carbonate containing at least one of a carbon-carbon unsaturated bond or a fluorine atom is at least one selected from the group consisting of vinylene carbonate, vinylethylene carbonate, ethynylethylene carbonate, and fluoroethylene carbonate, according to claim 10 . The non-aqueous electrolyte solution described. A non-aqueous electrolyte secondary battery comprising a negative electrode and a positive electrode capable of storing and releasing lithium ions, and the non-aqueous electrolyte solution according to any one of claims 1 to 11 . The negative electrode has a negative electrode active material layer on a current collector, and the negative electrode active material layer is a simple substance metal of silicon, an alloy and a compound, a simple substance metal of tin, an alloy and a compound, a carbonaceous material, and a lithium titanium composite. The non-aqueous electrolyte secondary battery according to claim 12 , which contains at least one selected from the group consisting of oxides. The positive electrode has a positive electrode active material layer on a current collector, and the positive electrode active material layer is a lithium-cobalt composite oxide, a lithium-cobalt-nickel composite oxide, a lithium-manganese composite oxide, or a lithium-cobalt. 12. Claim 12 contains at least one selected from the group consisting of manganese composite oxides, lithium-nickel composite oxides, lithium-nickel-manganese composite oxides, and lithium-cobalt-nickel-manganese composite oxides. The non-aqueous electrolyte secondary battery described. The positive electrode includes a positive active material layer on the current collector, the positive electrode active material layer, LixMPO 4 _(M is selected from the group consisting of the fourth period of the Group 4 to 11 transition metal of the periodic table The non-aqueous electrolyte secondary battery according to claim 12 , wherein at least one element, x, contains 0 <x <1.2).