JP2023109905A - Nonaqueous electrolyte solution and nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide a nonaqueous electrolyte solution for realizing a nonaqueous electrolyte secondary battery superior in suppressing battery expansion when charge and discharge operations are repeated.SOLUTION: A nonaqueous electrolyte solution hereof satisfies the requirement (i) or (ii) below. Requirement (i): the topological polarity surface area (TPSA) value is larger than 0 and equal to or smaller than 45 square angstroms, and the nonaqueous electrolyte solution contains at least one of compounds given by the general formula (A) below. Requirement (ii): TPSA value is 0 square angstroms, and the nonaqueous electrolyte solution contains at least one of compounds given by the general formula (B) below. (R1-R6 independently represent a substituent group other than F, provided that any substituent group of R1-R4 may bond to form a ring. n is an integer of 1-10.)SELECTED DRAWING: Figure 1

Description

The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery, more specifically, a non-aqueous electrolyte containing a specific amount of a specific compound, and a non-aqueous electrolyte secondary battery using this non-aqueous electrolyte Regarding.

Non-aqueous electrolyte secondary batteries such as lithium secondary batteries for a wide range of applications such as power sources for small consumer devices such as mobile phones such as smartphones and notebook computers, and vehicle power sources for driving electric vehicles. has been put into practical use.
However, when a negative electrode containing a negative electrode active material containing a metal that can occlude and release metal ions and that can be alloyed with Li and graphite is used, the thickness of the negative electrode expands due to repeated charging and discharging, and the battery becomes weak. There was a problem that it swelled.

As means for improving the battery characteristics of non-aqueous electrolyte secondary batteries, many studies have been made in the field of active materials for positive and negative electrodes and additives for non-aqueous electrolytes.
For example, Patent Literature 1 and Patent Literature 6 disclose a study of reducing the internal resistance of a battery by including a specific silicon compound in a non-aqueous electrolytic solution.
Patent Literature 2 discloses a study of suppressing the amount of free acid in a non-aqueous electrolytic solution by including a specific silane compound in the non-aqueous electrolytic solution.

Patent Literature 3 discloses a study of improving the cycle capacity retention rate by including a specific silicon compound in a non-aqueous electrolytic solution.
Patent Document 4 discloses a study to improve the initial capacity and cycle characteristics by using lithium cobalt oxide for the positive electrode, a carbon active material for the negative electrode, and a non-aqueous electrolytic solution containing an alkyl(trimethylsilyl)acetate compound for the electrolytic solution. It is

Patent Document 5 discloses a study of trapping water and hydrogen halide in a non-aqueous electrolyte by adding an alkyl(trimethylsilyl)acetate compound to the non-aqueous electrolyte.

JP-A-3-236168 Japanese Patent Application Laid-Open No. 2001-307772 JP-A-62-211873 JP-A-2002-313416 Japanese Patent Application Laid-Open No. 2004-206907 JP-A-3-236169

In recent years, the increase in capacity of lithium secondary batteries has been accelerated for applications such as in-vehicle power sources for electric vehicles and power sources for mobile phones such as smartphones. The introduction of system active materials is being considered. When carbon and a silicon compound are used in combination for the negative electrode active material, there is a problem that the thickness of the negative electrode expands due to repeated charging and discharging, resulting in swelling of the battery. Therefore, it is important to suppress swelling of the negative electrode due to charging and discharging.

However, according to the studies of the present inventors, when the electrolyte solution containing the specific silicon compound containing at least two unsaturated bonds disclosed in Patent Document 1 is used, Li and Li, which can occlude and release metal ions, There has been a problem in suppressing the thickness of the battery during charging and discharging of the negative electrode containing the negative electrode active material containing an alloyable metal and graphite.
In the above Patent Documents 1 to 6, by adding a specific silicon compound represented by an alkyl (trimethylsilyl) acetate compound to a non-aqueous electrolytic solution, the cycle capacity retention rate is improved and the free acid content in the electrolytic solution is captured. Although some studies have been made, there is no disclosure regarding suppression of battery thickness during charging and discharging of a negative electrode containing a negative electrode active material containing graphite and a metal that can occlude and release metal ions and can be alloyed with Li. However, there was still an issue with electrode swelling.

As a result of intensive studies to solve the above problems, the present inventors have found that by using a non-aqueous electrolytic solution containing a specific silicon compound, a metal and graphite that can occlude and release metal ions and can be alloyed with Li. The inventors have found that electrode swelling during charging and discharging of a negative electrode containing a negative electrode active material containing and can be suppressed, and have arrived at the present invention.

That is, the present invention provides specific embodiments and the like shown in [1] to [14] below.
[1] a positive electrode capable of intercalating and deintercalating metal ions;
a negative electrode comprising a negative electrode active material containing a metallic material capable of intercalating and deintercalating metal ions and capable of being alloyed with Li, and graphite;
A non-aqueous electrolyte used in a non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent,
A non-aqueous electrolytic solution that satisfies the following conditions (i) or (ii).
Condition (i): The topological polar surface area (TPSA) value is greater than 0 square Angstroms and 45 square Angstroms or less, and contains at least one compound represented by the following general formula (A).

(In the compound having the structure represented by the general formula (A), R ¹ to R ⁴ are each independently a substituent other than F, provided that any substituent of R ¹ to R ⁴ is bonded may form a ring.)
Condition (ii): The TPSA value is 0 square angstroms, and at least one compound represented by the following general formula (B) is contained.

(In the compound having the structure represented by the general formula (B), R ⁵ to R ⁶ are each independently a substituent other than F, and n is an integer of 1 to 10.)

[2] The non-aqueous electrolytic solution according to [1], wherein the condition (i) is the condition (iii).
Condition (iii): The topological polar surface area (TPSA) value is 10 square angstroms or more and 40 square angstroms or less, and at least one compound represented by the following general formula (A) is contained.

(In the compound having the structure represented by the general formula (A), R ¹ to R ⁴ are each independently a substituent other than F, provided that any substituent of R ¹ to R ⁴ is bonded may form a ring.)

[3] The non-aqueous electrolytic solution according to [1] or [2], wherein the compound represented by the general formula (A) is a compound represented by the following general formula (a).

(In the general formula (a), R ⁷ to R ⁹ are each independently a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a halogen atom, and in the hydrocarbon, at least 1 one carbon atom may be substituted with an oxygen atom, a nitrogen atom, or a sulfur atom, X is an alkylene group having 1 to 10 carbon atoms, and in the alkylene group, at least one carbon atom is an oxygen atom or nitrogen atom, may be substituted with a sulfur atom, and Y represents a structure selected from the group consisting of a cyano group, a thiol group and a group represented by the following general formula (1).)

(In general formula (1) above, R ^a represents a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a halogen atom.)

[4] The above [1] to wherein the metallic material capable of being alloyed with Li is at least one metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn and W or a metal compound thereof. The non-aqueous electrolytic solution according to any one of [3].
[5] The non-aqueous electrolytic solution according to [4] above, wherein the metallic material that can be alloyed with Li is Si or a Si metal oxide.
[6] The above [1] to [5], wherein the negative electrode active material containing the metallic material that can be alloyed with Li and graphite is a composite and / or a mixture of the metallic material and graphite. Non-aqueous electrolytic solution according to any one.
[7] The content of the metallic material that can be alloyed with Li in the negative electrode active material is 0.1 to 25% by mass with respect to the total amount of the metallic material that can be alloyed with Li and graphite. , The non-aqueous electrolytic solution according to any one of [1] to [6].
[8] The total content of at least one compound selected from the group of compounds satisfying the conditions (i) and (ii) is 0.001 to 10% by mass with respect to the total amount of the non-aqueous electrolytic solution. , The non-aqueous electrolytic solution according to any one of [1] to [7].
[9] A non-aqueous electrolyte for a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte comprising an electrolyte and a non-aqueous solvent together with a cyclic carbonate having a carbon-carbon unsaturated bond and a halogenated cyclic carbonate. A non-aqueous electrolytic solution containing at least one compound selected from the above and satisfying the following condition (i) or (ii).
Condition (i): The topological polar surface area (TPSA) value is greater than 0 square Angstroms and 45 square Angstroms or less, and contains at least one compound represented by the following general formula (A).

(In the compound having the structure represented by the general formula (A), R ¹ to R ⁴ are each independently a substituent other than F, provided that any substituent of R ¹ to R ⁴ is bonded may form a ring.)
Condition (ii): The TPSA value is 0 square angstroms, and at least one compound represented by the following general formula (B) is contained.

(In the compound having the structure represented by the general formula (B), R ⁵ to R ⁶ are each independently a substituent other than F, and n is an integer of 1 to 10.)
[10] The non-aqueous electrolytic solution according to [9], wherein the condition (i) is the following condition (iii). Condition (iii): The topological polar surface area (TPSA) value is 10 square angstroms or more and 40 square angstroms or less, and at least one compound represented by the following general formula (A) is contained.

(In the compound having the structure represented by the general formula (A), R ¹ to R ⁴ are each independently a substituent other than F, provided that any substituent of R ¹ to R ⁴ is bonded may form a ring.)
[11] The nonaqueous electrolytic solution according to [10], wherein the compound represented by the general formula (A) is a compound represented by the following general formula (a).

(In the general formula (a), R ⁷ to R ⁹ are each independently a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a halogen atom, and in the hydrocarbon, at least 1 one carbon atom may be substituted with an oxygen atom, a nitrogen atom, or a sulfur atom, X is an alkylene group having 1 to 10 carbon atoms, and in the alkylene group, at least one carbon atom is an oxygen atom or nitrogen atom, may be substituted with a sulfur atom, and Y represents a structure selected from the group consisting of a cyano group, a thiol group and a group represented by the following general formula (1).)

(In general formula (1) above, R ^a represents a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a halogen atom.)
[12] The total content of the compound represented by the general formula (A) and the compound represented by (B) is 0.001 to 10% by mass with respect to the total amount of the non-aqueous electrolytic solution, [9] The non-aqueous electrolytic solution according to any one of [11].
[13] A non-aqueous electrolyte for a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte containing an electrolyte and a non-aqueous solvent together with a compound represented by the following general formula (c).

(In the general formula (c), R ¹ to R ³ are each independently a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a halogen atom, and in the hydrocarbon, at least 1 one carbon atom may be substituted with an oxygen atom, a nitrogen atom, or a sulfur atom, X is an alkylene group having 1 to 10 carbon atoms, and in the alkylene group, at least one carbon atom is an oxygen atom or nitrogen atom, may be substituted with a sulfur atom.)
[14] The non-aqueous electrolytic solution according to [13], wherein the content of the compound represented by the general formula (c) is 0.001 to 10% by mass with respect to the total amount of the non-aqueous electrolytic solution. .

According to the present invention, it is possible to obtain a non-aqueous electrolyte secondary battery that is excellent in suppressing swelling of the battery due to charging and discharging.
Among them, by combining a negative electrode containing a negative electrode active material containing a metal that can occlude and release metal ions and capable of being alloyed with Li and graphite, and a non-aqueous electrolytic solution containing a specific silicon compound, repeated charging and discharging can be performed. It is possible to obtain a non-aqueous electrolyte secondary battery that can suppress battery swelling in.

4 is a graph showing the relationship between battery swelling and TPSA in batteries manufactured in Examples of the present application.

BEST MODE FOR CARRYING OUT THE INVENTION 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 to these. In addition, the present invention can be arbitrarily changed and implemented without departing from the gist thereof.
In this specification, unless otherwise specified, the term "~" is used to include the numerical values before and after it as lower and upper limits.
In addition, the phrase "independently" used when describing two or more objects together means that the two or more objects may be the same or different.
<1. Non-aqueous electrolytic solution>
The non-aqueous electrolytic solution according to the embodiment of the present invention (hereinafter also referred to as "first embodiment") satisfies the following condition (i) or condition (ii), and in particular, the condition (i) is the following condition ( iii) is preferred. Further, when the following condition (i) and condition (ii) are compared, it is preferable that the compound satisfies the condition (i) from the viewpoint of high reaction activity with Si particles and suitable modification of the Si surface.
Condition (i): The topological polar surface area (TPSA) value is greater than 0 square Angstroms and 45 square Angstroms or less, and contains at least one compound represented by the following general formula (A).
Condition (ii): The TPSA value is 0 square angstroms, and at least one compound represented by the following general formula (B) is contained.
Condition (iii): The topological polar surface area (TPSA) value is 10 square angstroms or more and 40 square angstroms or less, and at least one compound represented by the following general formula (A) is contained.
From the above conditions (i) to (iii), the non-aqueous electrolytic solution contains at least a compound represented by the following general formula (A) or (B).

<1-1. Compound Represented by General Formula (A) or (B)>

In the compound having the structure represented by formula (A), R ¹ to R ⁴ are each independently a substituent other than F. However, optional substituents of R ¹ to R ⁴ may combine to form a ring.

In the compound having the structure represented by formula (B), R ⁵ to R ⁶ are each independently a substituent other than F. Also, n represents an integer value of 1-10.

The compound represented by the general formula (A) is preferably a compound having a structure represented by the following general formula (a).

In the general formula (a), R ⁷ to R ⁹ are each independently a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a halogen atom, and in the alkylene group, at least one A carbon atom may be substituted with an oxygen atom, a nitrogen atom, or a sulfur atom, X is an alkylene group having 1 to 10 carbon atoms, and in the alkylene group, at least one carbon atom is an oxygen atom or a nitrogen atom , may be substituted with a sulfur atom, and Y represents a structure selected from the group consisting of a cyano group, a thiol group and a group represented by the following general formula (1).

In general formula (1) above, R ^a represents a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a halogen atom.

Here, in the general formula (A), the substituents R ¹ to R ⁴ other than F are each independently a cyano group, an isocyanato group, a thiol group, an amino group (—N—(R ^m ) ₂ ), amide group (-N-(R ^m )-(C=O)-R ^m ), acyl group (-(C=O)-R ^m ), acyloxy group (-O(C=O)-R ^m ), alkoxycarbonyl group (-(C=O)O-R ^m ), sulfonyl group (-SO ₂ -R ^m ), sulfonyloxy group (-O(SO ₂ )-R ^m ), alkoxysulfonyl group (-( SO ₂ )-OR ^m ), alkoxycarbonyloxy group (-O-( ^{C=O)-OR m ), ether group (-OR m )} , acrylic group, methacrylic group, trifluoromethyl group etc. These functional groups are also referred to herein as “optional substituents of R ¹ to R ⁴ ”.
Among these substituents, cyano group, isocyanato group, thiol group, amino group (-N-(R ^m ) ₂ ), amide group (-N-(R ^m )-(C=O)-R ^m ), more preferably a cyano group, an isocyanato group, or a thiol group.
Further, these substituents may be bonded to silicon through a hydrocarbon group such as an alkylene group, and in the hydrocarbon, at least one carbon atom may be substituted with an oxygen atom, a nitrogen atom, or a sulfur atom. good. In particular, a nitrogen atom is preferred because the polarity of the compound is optimal and it reacts favorably with Si particles. Moreover, R ¹ to R ⁴ are preferably functional groups represented by R ⁷ to R ⁹ in the general formula (a) and functional groups satisfying (-XY).
R ^m represents an optionally fluorine-substituted alkyl group having 1 to 10 carbon atoms, alkenyl group having 2 to 10 carbon atoms, alkynyl group having 2 to 10 carbon atoms, or trimethylsilyl group.

Specific examples of hydrocarbon groups for R ⁷ to R ⁹ in general formula (a) and R ^a in general formula (1) include alkyl groups, alkenyl groups, alkynyl groups, and aryl groups.

Specific examples of the alkyl group for R ¹ to R ⁴ in general formula (A), R ⁷ to R ⁹ in general formula (a) and R ^a in (1) include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, tert-butyl group, n-pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group and the like. Among them, preferably methyl group, ethyl group, n-propyl group, n-butyl group, tert-butyl group, n-pentyl group and hexyl group, more preferably methyl group, ethyl group, n-propyl group and n-butyl group, tert-butyl group, n-pentyl group, particularly preferably methyl group, ethyl group, n-butyl group and tert-butyl group. A methyl group and an ethyl group are preferable because the concentration of the compound on the surface of the negative electrode active material is facilitated.

Specific examples of alkenyl groups for R ¹ to R ⁴ in general formula (A), R ⁷ to R ⁹ in general formula (a), and R ^a in (1) include vinyl group, allyl group, methallyl group, 2-butenyl group, 3-methyl-2-butenyl group, 3-butenyl group, 4-pentenyl group and the like. Among them, preferred are vinyl group, allyl group, methallyl group and 2-butenyl group, more preferred are vinyl group, allyl group and methallyl group, and particularly preferred is vinyl group. This is because when the hydrocarbon group is the above-mentioned alkenyl group, the negative electrode active material reforming reaction can be suitably controlled.

Specific examples of alkynyl groups for R ¹ to R ⁴ in general formula (A), R ⁷ to R ⁹ in general formula (a), and R ^a in (1) include ethynyl and 2-propynyl. group, 2-butynyl group, 3-butynyl group, 4-pentynyl group, 5-hexynyl group and the like. Among them, ethynyl group, 2-propynyl group, 2-butynyl group and 3-butynyl group are more preferred, 2-propynyl group and 3-butynyl group are more preferred, and 2-propynyl group is particularly preferred. This is because when the hydrocarbon group is the above-mentioned alkynyl group, the negative electrode active material reforming reaction can be suitably controlled.

Specific examples of the aryl group for R ⁷ to R ⁹ in general formula (a) and R ^a in (1) include phenyl, tolyl, benzyl and phenethyl groups. Among them, a phenyl group is preferable because concentration of the compound into the negative electrode active material is facilitated.

The conditions for R ⁵ and R ⁶ in the general formula (B) can similarly apply the conditions for R ¹ to R ⁴ in the general formula (A). In general formula (A), when any substituents of R ¹ to R ⁴ are combined to form a ring, the compound represented by general formula (A) and general formula (B) compound may have a similar structure.

Specific structures and TPSA values of the compounds represented by the general formula (A) or (B) are shown below.

The total content of the compounds represented by the general formulas (A) and (B) with respect to the total amount of the non-aqueous electrolyte is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and usually 10% by mass or less, preferably 4.5% by mass or less, and more preferably 4.0% by mass or less, It is more preferably 3.5% by mass or less, particularly preferably 3.0% by mass or less, and most preferably 2.0% by mass or less.
If the total content of the compounds represented by the general formulas (A) and (B) with respect to the total amount of the non-aqueous electrolyte is within the above range, the reforming reaction of the negative electrode active material proceeds favorably, and during charging and discharging The swelling of the negative electrode is suppressed, making it possible to manufacture a battery that is less likely to swell.

<1-2. Topological Polar Surface Area (TPSA)>
Topological polar surface area (TPSA) is the calculated surface area of the polar portion of a molecule and is described in J. Am. Med. Chem. 2000, 43, 3714. can be calculated by adding contributions from polar substructures by the method described in . In addition, the topological polar surface area (TPSA) in the present invention is defined in J. Am. Med. Chem. 2000, 43, 3714. It means the value calculated by the method described in .

The TPSA range of the compound represented by the general formula (A) is greater than 0 square Angstroms, preferably 5 square Angstroms or more, and more preferably 10 square Angstroms or more. Moreover, it is 45 square angstroms or less, preferably 40 square angstroms or less.
The TPSA range of the compound represented by the general formula (B) is 0 square angstroms.

In the non-aqueous electrolyte, in addition to the compound represented by the general formula (A) or (B), one or more selected from cyclic carbonates and halogenated cyclic carbonates having a carbon-carbon unsaturated bond described later. By using them together, swelling of the negative electrode due to charging and discharging is further suppressed, and a battery that is less likely to swell can be obtained.
By containing the compound of the general formula (A) or (B), the effect of suppressing the thickness change of the battery during charging and discharging of the negative electrode containing the negative electrode active material containing the metal that can be alloyed with Li and graphite. Although the obtained mechanism is not clear, it is speculated as follows.

The volume changes of the carbon active material and the Si-based active material (for example, Si) at full charge are 10% and 300%, respectively. When the negative electrode blended with carbon and Si is fully charged, the adjoining carbon is extruded due to the expansion of the Si negative electrode, and the expansion of the electrode is more pronounced than when carbon alone or Si alone is used as the active material. There is a problem that the thickness of the battery itself increases. Further, the particles of the Si-based active material are pulverized by repeated charging and discharging, thereby exposing new surfaces (dangling bonds) with high activity. There is also the problem that the surface of the active material deteriorates due to the reaction between the exposed surface and the electrolytic solution, and the active material swells more than before the repeated charging and discharging of the Si particles.

To solve this problem, in the present invention, compounds represented by general formulas (A) and (B) having specific TPSA values are contained in the electrolytic solution. TPSA represents the area of the polar portion of the molecular surface as described above. When the value of TPSA is high, the ratio of polar functional groups having a polarized structure in the molecule is high, so the reaction activity with Si particles is high, and the Si surface is modified. However, if the TPSA value is too high, the polarity of the reaction product of the Si particles and the compound is high, the insulation of the electrode surface becomes insufficient, and the decomposition reaction of the electrolytic solution cannot be suppressed. Therefore, it is considered necessary that the value of TPSA is within a specific range. In addition, the compound represented by the general formula (A) has, in its structure, a site such as Y, which has high reactivity with the Si-based active material. In addition, the compound represented by the general formula (B) has a TPSA value of 0, but the compound represented by the general formula (B) has a large strain in the ring structure, so it is suitable for the surface of the Si-based active material. It modifies the surface by reacting.

As described above, by including at least the compound represented by the general formula (A) or (B) having a specific TPSA value in the non-aqueous electrolytic solution, swelling of the negative electrode active material due to repeated charging and discharging is suppressed. Since it is suppressed, it is thought that it contributes to suppressing the thickness change of the battery.
The method of including the compound represented by general formula (A) or (B) in the electrolytic solution is not particularly limited. In addition to the method of adding the above compound directly to the electrolyte, there is a method of generating the above compound in the battery or in the electrolyte.

The content of the compound represented by the general formula (A) or (B) is at the time of manufacturing the non-aqueous electrolyte, at the time of pouring the non-aqueous electrolyte into the battery, or at the time of shipment as a battery. means the content in

The non-aqueous electrolytic solutions, which are the following two other embodiments, can be used by appropriately combining the aspects of the non-aqueous electrolytic solutions described above.
The non-aqueous electrolyte, which is another embodiment of the present invention, is a non-aqueous electrolyte for a non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte is combined with the electrolyte and the non-aqueous solvent to form a carbon-carbon unsaturated bond. and containing at least one compound selected from the group consisting of cyclic carbonates and halogenated cyclic carbonates, and the non-aqueous electrolyte satisfying the following condition (i) or (ii). Conditions (i) and (ii) below are the same as conditions (i) and (ii) above.
Condition (i): The topological polar surface area (TPSA) value is greater than 0 square Angstroms and 45 square Angstroms or less, and contains at least one compound represented by the following general formula (A).

In the compound having the structure represented by general formula (A), the conditions for R ¹ to R ⁴ can be applied independently in the same manner as the conditions for R ¹ to R ⁴ in general formula (A) described above. can.

Condition (ii): The TPSA value is 0 square angstroms, and at least one compound represented by the following general formula (B) is contained.

In the compound having the structure represented by general formula (B), the conditions for R ⁵ to R ⁶ can be applied independently in the same manner as the conditions for R ⁵ to R ⁶ in general formula (B) described above. can.

A non-aqueous electrolytic solution which is still another embodiment of the present invention is a non-aqueous electrolytic solution for a non-aqueous electrolytic solution secondary battery, wherein the non-aqueous electrolytic solution is an electrolyte and a non-aqueous solvent together with the following general formula (c) It is a non-aqueous electrolytic solution containing a compound represented by.

In the compound represented by the general formula (c), the conditions of R ¹ to R ³ can be independently applied in the same manner as the conditions of R ¹ to R ³ in the general formula (A) described above; As for the condition of X, the condition of X in the general formula (a) described above can be similarly applied.

The content of the compound represented by the general formula (C) with respect to the total amount of the non-aqueous electrolyte 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 0.2% by mass or more, and usually 10% by mass or less, preferably 4 0.5% by mass or less, more preferably 4.0% by mass or less, still more preferably 3.5% by mass or less, particularly preferably 3.0% by mass or less, and most preferably 2.0% by mass or less.
If the content of the compound represented by the general formula (C) with respect to the total amount of the non-aqueous electrolytic solution is within the above range, the reforming reaction of the negative electrode active material proceeds favorably, and swelling of the negative electrode during charging and discharging is suppressed. , it is possible to manufacture a battery that does not easily swell.

<1-3. Cyclic carbonate compound having a carbon-carbon unsaturated bond>
The cyclic carbonate having a carbon-carbon unsaturated bond (hereinafter sometimes referred to as "unsaturated cyclic carbonate") is a cyclic carbonate having a carbon-carbon double bond or a carbon-carbon triple bond, especially Any unsaturated carbonate can be used without limitation. A cyclic carbonate having an aromatic ring is also included in the unsaturated cyclic carbonate.

Examples of unsaturated cyclic carbonates include vinylene carbonates, ethylene carbonates substituted with substituents having aromatic rings or carbon-carbon double bonds or carbon-carbon triple bonds, phenyl carbonates, vinyl carbonates, allyl carbonates, catechol carbonates and the like.

Vinylene carbonates include vinylene carbonate, methylvinylene carbonate, 4,5-dimethylvinylene carbonate, phenylvinylene carbonate, 4,5-diphenylvinylene carbonate, vinylvinylene carbonate, 4,5-vinylvinylene carbonate, 4,5-divinyl vinylene carbonate, allylvinylene carbonate, 4,5-diallylvinylene carbonate, 4-fluorovinylene carbonate, 4-fluoro-5-methylvinylene carbonate, 4-fluoro-5-phenylvinylene carbonate, 4-fluoro-5-vinylvinylene carbonate , 4-allyl-5-fluorovinylene carbonate and the like.

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

Among them, preferred unsaturated cyclic carbonates include vinylene carbonate, methylvinylene carbonate, 4,5-dimethylvinylene carbonate, vinylvinylene carbonate, 4,5-vinylvinylene carbonate, allylvinylene carbonate, 4,5-diallylvinylene carbonate, vinyl Ethylene carbonate, 4,5-divinylethylene carbonate, 4-methyl-5-vinylethylene carbonate, 4-allyl-5-vinylethylene carbonate, ethynylethylene carbonate, 4,5-diethynylethylene carbonate, 4-methyl-5- Examples include ethynylethylene carbonate, 4-vinyl-5-ethynylethylene carbonate, allylethylene carbonate, 4,5-diallylethylene carbonate, and 4-methyl-5-allylethylene carbonate.

Vinylene carbonate, vinylethylene carbonate, and ethynylethylene carbonate are particularly preferred because they form a more stable interfacial protective film.
The molecular weight of the unsaturated cyclic carbonate is not particularly limited, and is arbitrary as long as it does not significantly impair the effects of the present invention. The molecular weight is preferably 80 or more and 250 or less. Within this range, it is easy to ensure the solubility of the unsaturated cyclic carbonate in the non-aqueous electrolytic solution, and the effects of the present invention are easily exhibited. The molecular weight of the unsaturated cyclic carbonate is more preferably 85 or more and more preferably 150 or less. The method for producing the unsaturated cyclic carbonate is not particularly limited, and any known method can be selected for production.

Unsaturated cyclic carbonates may be used singly or in combination of two or more in any desired ratio. In addition, the amount of the unsaturated cyclic carbonate is not particularly limited, and is arbitrary as long as it does not significantly impair the effects of the present invention. 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.5% by mass or more, particularly preferably 1% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less , more preferably 3% by mass or less, and particularly preferably 2% by mass or less. Within this range, the non-aqueous electrolyte secondary battery is likely to exhibit a sufficient effect of improving cycle characteristics, and high-temperature storage characteristics deteriorate, the amount of gas generated increases, and the discharge capacity retention rate decreases. It is easy to avoid situations.

<1-4. Cyclic carbonate having a halogen atom>
As examples of cyclic carbonate compounds having halogen atoms, examples of acid anhydrides mainly substituted with fluorine atoms are listed below. The acid anhydride obtained by the above is also included in the exemplified compounds.
Halogen-containing cyclic carbonate compounds include fluorinated cyclic carbonates having an alkylene group of 2 to 6 carbon atoms and derivatives thereof, such as fluorinated ethylene carbonate and derivatives thereof. Derivatives of fluorinated ethylene carbonate include, for example, fluorinated ethylene carbonate substituted with an alkyl group (eg, an alkyl group having 1 to 4 carbon atoms). Among them, ethylene carbonate having 1 to 8 fluorine atoms and derivatives thereof are preferred.

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

Among them, at least one selected from the group consisting of monofluoroethylene carbonate, 4,4-difluoroethylene carbonate and 4,5-difluoroethylene carbonate provides high ionic conductivity and preferably forms an interfacial protective film. is more preferable.
A cyclic carbonate compound having a halogen atom may be used alone, or two or more thereof may be used in any combination and ratio.

The amount of the cyclic carbonate having a halogen atom in the entire non-aqueous electrolytic solution is not limited, and is arbitrary as long as it does not significantly impair the effects of the present invention.
It 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 0.5% by mass or more, particularly preferably 1% by mass or more. It is 10% by mass or less, preferably 7% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. However, monofluoroethylene carbonate may be used as a solvent, and in that case, the content is not limited to the above.

<1-5. Electrolyte>
<Lithium salt>
The electrolyte in the non-aqueous electrolyte is not particularly limited, but lithium salt is usually used. 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. Specific examples include the following.

Examples of lithium salts include inorganic lithium salts such as LiBF ₄ , LiClO ₄ , LiAlF ₄ , LiSbF ₆ , LiTaF ₆ and LiWF ₇ ; lithium fluorophosphates such as LiPF ₆ ; lithium tungstate salts such as LiWOF ₅ ; _{2Li , CH3CO2Li , CH2FCO2Li , CHF2CO2Li , CF3CO2Li , CF3CH2CO2Li , CF3CF2CO2Li , CF3CF2CF2CO _ _ _ 2Li} , _{CF3CF2CF2CF2CO2Li} and other carboxylic acid lithium _{salts ; CH3SO3Li} and other sulfonic acid lithium salts; LiN( _FCO2 ) _{2 , LiN} (FCO ₎ ( _FSO2 ), 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, lithium imide salts such as LiN(CF ₃ SO ₂ )(C ₄ F ₉ SO ₂ ); LiC(FSO ₂ ) ₃ , LiC(CF ₃ SO ₂ ) ₃ Lithium _methide salts such as LiC( _{C2F5SO2 ) 3} ; _LiPF4 ( _{CF3 ) 2} , _LiPF4 ( _C2F5 ) ₂ , _LiPF4 ( _{CF3SO2 ) 2} , _LiPF4 (C _{2F5SO2 ) 2 , LiBF3CF3 , LiBF3C2F5 , LiBF3C3F7 , LiBF2} ( _CF3 ) _{2 , LiBF2} ( _{C2F5 ) 2 , LiBF2} ( _CF3 SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ and other fluorine-containing organic lithium salts;

In addition to the effect of suppressing swelling of the negative electrode due to repeated charge and discharge obtained by the present invention, from the viewpoint of further enhancing the effect of improving the charge / discharge rate charge / discharge characteristics and impedance characteristics, inorganic lithium salts, lithium fluorophosphate salts, lithium sulfonate salts , and lithium imide salts.
Among them, LiPF ₆ , LiBF ₄ , LiSbF 6 , LiTaF ₆ , 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 and the like are particularly preferable because they are effective in improving low-temperature output characteristics, high-rate charge/discharge characteristics, impedance characteristics, high-temperature storage characteristics, cycle characteristics, and the like. Moreover, the said electrolyte salt may be used independently, or may use 2 or more types together.

The total concentration of these electrolytes in the non-aqueous electrolyte is not particularly limited, but is usually 8% by mass or more, preferably 8.5% by mass or more, more preferably 9% by mass, relative to the total amount of the non-aqueous electrolyte. % or more, and usually 18% by mass or less, preferably 17% by mass or less, more preferably 16% by mass or less. When the total concentration of the electrolytes is within the above range, the electrical conductivity is appropriate for battery operation, so there is a tendency to obtain sufficient output characteristics.

<1-6. Non-aqueous solvent>
The non-aqueous electrolytic solution normally contains, as its main component, a non-aqueous solvent that dissolves the above-described electrolyte, like common non-aqueous electrolytic solutions. The non-aqueous solvent used here is not particularly limited, and known organic solvents can be used. Examples of organic solvents include saturated cyclic carbonates, chain carbonates, ether compounds, sulfones and the like, but are not particularly limited to these. These can be used individually by 1 type or in combination of 2 or more types.

<1-6-1. Saturated cyclic carbonate>
Examples of saturated cyclic carbonates include those having an alkylene group having 2 to 4 carbon atoms, and saturated cyclic carbonates having 2 to 3 carbon atoms are preferably used from the viewpoint of improving battery characteristics resulting from an improvement in the degree of dissociation of lithium ions. .
Examples of saturated cyclic carbonates include ethylene carbonate, propylene carbonate, and butylene carbonate. Among them, ethylene carbonate and propylene carbonate are preferable, and ethylene carbonate, which is difficult to be oxidized and reduced, is more preferable. Saturated cyclic carbonates may be used alone, or two or more of them may be used in any combination and ratio.

The content of the saturated cyclic carbonate is not particularly limited, and is arbitrary as long as it does not significantly impair the effects of the present invention. 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, and to improve the large current discharge characteristics of the non-aqueous electrolyte secondary battery, the stability to the negative electrode, and the cycle characteristics. It is usually 90% by volume or less, preferably 85% by volume or less, more preferably 80% by volume or less. Within this range, the oxidation/reduction resistance of the non-aqueous electrolytic solution tends to improve, and the stability during high-temperature storage tends to improve.
In addition, the volume % in the present invention means the volume at 25° C. and 1 atm.

<1-6-2. Chain carbonate>
As the chain carbonate, those having 3 to 7 carbon atoms are usually used, and chain carbonates having 3 to 5 carbon atoms are preferably used in order to adjust the viscosity of the electrolytic solution within an appropriate range.
Specifically, the chain carbonates include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate, isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, t-butyl ethyl carbonate and the like.

Among them, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate and methyl-n-propyl carbonate are preferred, and dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are particularly preferred. be.
Chain carbonates having a fluorine atom (hereinafter sometimes abbreviated as “fluorinated chain carbonate”) can also be preferably used. The number of fluorine atoms in the fluorinated linear carbonate is not particularly limited as long as it is 1 or more, but it is usually 6 or less, preferably 4 or less. When the fluorinated linear carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon or different carbons. Examples of fluorinated chain carbonates include fluorinated dimethyl carbonate derivatives, fluorinated ethylmethyl carbonate derivatives, fluorinated diethyl carbonate derivatives and the like.

Fluorinated dimethyl carbonate derivatives include fluoromethylmethyl carbonate, difluoromethylmethyl carbonate, trifluoromethylmethyl carbonate, bis(fluoromethyl) carbonate, bis(difluoro)methyl carbonate, bis(trifluoromethyl) carbonate and the like.
Fluorinated ethyl methyl carbonate derivatives include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2,2-tri fluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, ethyltrifluoromethyl carbonate and the like.

Fluorinated diethyl carbonate derivatives include ethyl-(2-fluoroethyl) carbonate, ethyl-(2,2-difluoroethyl) carbonate, bis(2-fluoroethyl) carbonate, 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, 2-trifluoroethyl-2',2'-difluoroethyl carbonate, bis(2,2,2-trifluoroethyl) carbonate and the like.

A chain carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.
The content of the chain carbonate is not particularly limited, but is usually 15% by volume or more, preferably 20% by volume or more, more preferably 25% by volume or more, relative to the total amount of the solvent in the non-aqueous electrolytic solution, and It is usually 90% by volume or less, preferably 85% by volume or less, 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 is set in an appropriate range, the decrease in ionic conductivity is suppressed, and the output characteristics of the non-aqueous electrolyte secondary battery are kept in a good range. It becomes easier to

Furthermore, by combining a specific linear carbonate with a specific content of ethylene carbonate, the battery performance can be remarkably improved.
For example, when diethyl carbonate and ethyl methyl carbonate are selected as specific chain carbonates, the content of ethylene carbonate is not particularly limited and is arbitrary as long as it does not significantly impair the effects of the present invention. It is usually 15% by volume or more, preferably 20% by volume or more, and usually 45% by volume or less, preferably 40% by volume or less, based on the total amount of the solvent, and the content of diethyl carbonate is the total amount of the solvent in the non-aqueous electrolytic solution. 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 ethyl methyl carbonate is usually 20% by volume or more, preferably 30% by volume. % by volume or more, and usually 50% by volume or less, preferably 45% by volume or less. By setting the content within the above range, there is a tendency that high-temperature stability is excellent and gas generation is suppressed.

<1-6-3. Ether-based compound>
Preferred ether compounds are chain ethers having 3 to 10 carbon atoms and cyclic ethers having 3 to 6 carbon atoms.
Chain ethers having 3 to 10 carbon atoms include diethyl ether, di(2-fluoroethyl) ether, di(2,2-difluoroethyl) ether, di(2,2,2-trifluoroethyl) ether, ethyl (2-fluoroethyl) ether, ethyl (2,2,2-trifluoroethyl) ether, ethyl (1,1,2,2-tetrafluoroethyl) ether, (2-fluoroethyl) (2,2,2 -trifluoroethyl)ether, (2-fluoroethyl)(1,1,2,2-tetrafluoroethyl)ether, (2,2,2-trifluoroethyl)(1,1,2,2-tetrafluoro ethyl) 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-trifluoro-n -propyl)(2,2,3,3-tetrafluoro-n-propyl) ether, (3,3,3-trifluoro-n-propyl)(2,2,3,3,3-pentafluoro-n -propyl) ether, di(2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,3,3-tetrafluoro-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)methane, methoxy(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)methane di(2,2,2-trifluoroethoxy)methane, (2,2,2-trifluoroethoxy)(1, 1,2,2-tetrafluoroethoxy)methane, di(1,1,2,2-tetrafluoroethoxy)methane, dimethoxyethane, methoxyethoxyethane, methoxy(2-fluoroethoxy)ethane, methoxy(2,2, 2-trifluoroethoxy)ethane, methoxy(1,1,2,2-tetrafluoroethoxy)ethane, diethoxyethane, ethoxy(2-fluoroethoxy)ethane, ethoxy(2,2,2-trifluoroethoxy)ethane , ethoxy(1,1,2,2-tetrafluoroethoxy)ethane, di(2-fluoroethoxy)ethane, (2-fluoroethoxy)(2,2,2-trifluoroethoxy)ethane, (2-fluoroethoxy ) (1,1,2,2-tetrafluoroethoxy)ethane, di(2,2,2-trifluoroethoxy)ethane, (2,2,2-trifluoroethoxy)(1,1,2,2- tetrafluoroethoxy)ethane, di(1,1,2,2-tetrafluoroethoxy)ethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether and the like.

Among these, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have high solvating ability to lithium ions and ion dissociation. It is preferable in terms of improvement. Particularly preferred are dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, since they have low viscosity and give high ionic conductivity.

Cyclic ethers having 3 to 6 carbon atoms include tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1 , 4-dioxane, etc., and fluorinated compounds thereof.
The content of the ether compound is not particularly limited, and is arbitrary as long as it does not significantly impair the effects of the present invention. is 3% by volume or more, and usually 30% by volume or less, preferably 25% by volume or less, more preferably 20% by volume or less. If the content of the ether-based compound is within the above preferable range, it is easy to secure the effect of improving the degree of lithium ion dissociation of the ether and improving the ionic conductivity derived from the viscosity reduction. In addition, when the negative electrode active material is a carbonaceous material, the phenomenon of co-insertion of the chain ether together with the lithium ions can be suppressed, so that the input/output characteristics and charge/discharge rate characteristics can be set within appropriate ranges.

<1-6-4. Sulfone compound>
The sulfone-based compound is not particularly limited, even if it is a cyclic sulfone or a chain sulfone. , compounds having usually 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms, are preferred. Although the number of sulfonyl groups in one molecule of the sulfone compound is not particularly limited, it is usually one or two.

Cyclic sulfones include trimethylene sulfones, tetramethylene sulfones and hexamethylene sulfones which are monosulfone compounds; and trimethylene disulfones, tetramethylene disulfones and hexamethylene disulfones which are disulfone compounds. Among them, tetramethylenesulfones, tetramethylenedisulfones, hexamethylenesulfones, and hexamethylenedisulfones are more preferable, and tetramethylenesulfones (sulfolanes) are particularly preferable from the viewpoint of dielectric constant and viscosity.

As sulfolanes, sulfolane and/or sulfolane derivatives (hereinafter sometimes abbreviated as “sulfolane” including sulfolane) are preferable. As the sulfolane derivative, one in which one or more hydrogen atoms bonded to carbon atoms constituting a sulfolane ring is substituted with a fluorine atom or an alkyl group is preferable.
Among others, 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-methylsulfolane, 5-fluoro-3-methylsulfolane, 5-fluoro-2-methylsulfolane, 2-fluoromethylsulfolane, 3-fluoromethylsulfolane, 2-difluoromethylsulfolane, 3-difluoro methylsulfolane, 2-trifluoromethylsulfolane, 3-trifluoromethylsulfolane, 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 of their high ionic conductivity and high input/output.

Examples of chain sulfone include dimethylsulfone, ethylmethylsulfone, diethylsulfone, n-propylmethylsulfone, n-propylethylsulfone, di-n-propylsulfone, isopropylmethylsulfone, isopropylethylsulfone, diisopropylsulfone, n- butylmethylsulfone, n-butylethylsulfone, t-butylmethylsulfone, t-butylethylsulfone, monofluoromethylmethylsulfone, difluoromethylmethylsulfone, trifluoromethylmethylsulfone, monofluoroethylmethylsulfone, difluoroethylmethylsulfone, trifluoroethylmethylsulfone, pentafluoroethylmethylsulfone, ethylmonofluoromethylsulfone, ethyldifluoromethylsulfone, ethyltrifluoromethylsulfone, perfluoroethylmethylsulfone, ethyltrifluoroethylsulfone, ethylpentafluoroethylsulfone, di(tri fluoroethyl)sulfone, perfluorodiethylsulfone, fluoromethyl-n-propylsulfone, difluoromethyl-n-propylsulfone, trifluoromethyl-n-propylsulfone, fluoromethylisopropylsulfone, difluoromethylisopropylsulfone, trifluoromethylisopropylsulfone , trifluoroethyl-n-propylsulfone, trifluoroethylisopropylsulfone, pentafluoroethyl-n-propylsulfone, pentafluoroethylisopropylsulfone, trifluoroethyl-n-butylsulfone, trifluoroethyl-t-butylsulfone, penta fluoroethyl-n-butylsulfone, pentafluoroethyl-t-butylsulfone and the like.

Among others, dimethylsulfone, ethylmethylsulfone, diethylsulfone, n-propylmethylsulfone, isopropylmethylsulfone, n-butylmethylsulfone, t-butylmethylsulfone, monofluoromethylmethylsulfone, difluoromethylmethylsulfone, trifluoromethylmethylsulfone , monofluoroethylmethylsulfone, difluoroethylmethylsulfone, trifluoroethylmethylsulfone, pentafluoroethylmethylsulfone, ethylmonofluoromethylsulfone, ethyldifluoromethylsulfone, ethyltrifluoromethylsulfone, ethyltrifluoroethylsulfone, ethylpentafluoro ethylsulfone, trifluoromethyl-n-propylsulfone, trifluoromethylisopropylsulfone, trifluoroethyl-n-butylsulfone, trifluoroethyl-t-butylsulfone, trifluoromethyl-n-butylsulfone, trifluoromethyl-t -Butyl sulfone and the like are preferable in terms of improving the high-temperature storage stability of the electrolytic solution.

The content of the sulfone-based compound is not particularly limited, and is arbitrary as long as it does not significantly impair the effects of the present invention. 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. If the content of the sulfone-based compound is within the above range, there is a tendency to obtain an electrolytic solution having excellent high-temperature storage stability.

<2. Non-aqueous electrolyte secondary battery>
A non-aqueous electrolyte secondary battery using the non-aqueous electrolyte described above includes a positive electrode that can occlude and release metal ions, a metallic material that can occlude and release metal ions and can be alloyed with Li, and graphite. and a negative electrode containing a negative electrode active material containing and the non-aqueous electrolytic solution described above.

<2-1. Battery configuration>
The non-aqueous electrolyte secondary battery is the same as conventionally known non-aqueous electrolyte secondary batteries except for the non-aqueous electrolyte described above. Usually, a positive electrode and a negative electrode are laminated via a porous film (separator) impregnated with a non-aqueous electrolytic solution, and these are housed in a case (exterior body). Therefore, the shape of the non-aqueous electrolyte secondary battery is not particularly limited, and may be cylindrical, rectangular, laminated, coin-shaped, large-sized, or the like.

<2-2. Non-aqueous electrolytic solution>
As the non-aqueous electrolytic solution, the non-aqueous electrolytic solution described above is used. It should be noted that other non-aqueous electrolytic solutions may be blended with the non-aqueous electrolytic solution without departing from the gist of the present invention.
<2-3. negative electrode>
The negative electrode may have a negative electrode active material layer on a current collector, and the negative electrode active material layer contains the negative electrode active material. The negative electrode active material will be described below.

The negative electrode active material is not particularly limited as long as it can electrochemically intercalate and deintercalate lithium ions. Specific examples thereof include carbonaceous materials, metal alloy materials, lithium-containing metal composite oxide materials, and the like, and graphite is preferably included as the carbonaceous material. These may be used individually by 1 type, and may be used together, combining 2 or more types arbitrarily.
<2-3-1. Carbonaceous Material>
As a carbonaceous material used as a negative electrode active material,
(1) natural graphite,
(2) carbonaceous materials obtained by heat-treating artificial carbonaceous substances and artificial graphite substances at a temperature in the range of 400 to 3200° C. one or more times;
(3) a carbonaceous material in which the negative electrode active material layer is composed of at least two types of carbonaceous materials with different crystallinities and/or has an interface where the carbonaceous materials with different crystallinities are in contact;
(4) a carbonaceous material in which the negative electrode active material layer is composed of at least two types of carbonaceous matter with different orientations and/or has an interface where the carbonaceous matter with different orientations are in contact;
Those selected from are preferable because they have a good balance between initial irreversible capacity and high current density charge/discharge characteristics. In addition, the carbonaceous materials of (1) to (4) may be used singly, or two or more of them may be used in any combination and ratio. Specific examples of graphite substances include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, or oxidized products of these pitches, needle coke, pitch coke, and partial graphite of these. Carbonized carbon materials, furnace black, acetylene black, thermal decomposition products of organic substances such as pitch-based carbon fibers, carbonizable organic substances, and carbonized products thereof or carbonizable organic substances are converted to benzene, toluene, xylene, quinoline, n- A solution dissolved in a low-molecular-weight organic solvent such as xane, and a carbonized product thereof may be mentioned.

<2-3-2. Structure, physical properties, and preparation method of carbonaceous negative electrode>
Regarding the properties of carbonaceous materials, negative electrodes and electrode preparation methods containing carbonaceous materials, current collectors, and non-aqueous electrolyte secondary batteries, any one of the following (1) to (13) or It is desirable to satisfy multiple terms at the same time.

(1) X-ray parameters The d value (interlayer distance) of the lattice plane (002 plane) determined by X-ray diffraction of the carbonaceous material according to the Gakushin method is usually 0.335 to 0.340 nm, preferably 0.340 nm. 335 to 0.338 nm, particularly preferably 0.335 to 0.337 nm.
Also, the crystallite size (Lc) determined by X-ray diffraction according to 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 size The volume-based average particle size (median diameter d50) of the carbonaceous material is not particularly limited, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and particularly 7 μm or more. It is preferably 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, even more preferably 30 μm or less, and particularly preferably 25 μm or less.

The average particle size (d50) can be obtained by laser diffraction/scattering particle size distribution measuring method or the like.
The volume-based average particle size is measured by dispersing carbon powder in a 0.2% by mass aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, a surfactant, and measuring the particle size distribution by laser diffraction/scattering. (eg, LA-700 manufactured by Horiba, Ltd.). The median diameter d50 obtained by the measurement is defined as the volume-based average particle diameter of the carbonaceous material.

(3) Raman R value and Raman half-value width The Raman R value of the carbonaceous material measured using an argon ion laser Raman spectroscopy is usually 0.01 or more, preferably 0.03 or more, and 0.03 or more. It is more preferably 1 or more, and usually 1.5 or less, preferably 1.2 or less, further preferably 1 or less, and particularly preferably 0.5 or less.

When the Raman R value is below the above range, the crystallinity of the particle surface becomes too high, and the number of sites where Li intercalates between layers may decrease during charging and discharging. That is, the charge acceptability may deteriorate. Moreover, when the density of the negative electrode is increased by pressing after coating the current collector, crystals tend to be oriented in the direction parallel to the electrode plate, which may lead to deterioration in load characteristics. On the other hand, when the above range is exceeded, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolytic solution increases, and this may lead to a decrease in efficiency and an increase in gas generation.

In addition, although the Raman half width of the carbonaceous material near 1580 cm ⁻¹ is not particularly limited, it is usually 10 cm ⁻¹ or more, preferably 15 cm ⁻¹ or more, and usually 100 cm ⁻¹ or less, and 80 cm ⁻¹ or less. It is preferably 60 cm ^-1 or less, more preferably 40 cm ^-1 or less.
When the Raman half-value width is below the above range, the crystallinity of the particle surface becomes too high, and the number of sites where Li intercalates between layers may decrease during charging and discharging. That is, the charge acceptability may deteriorate. Moreover, when the density of the negative electrode is increased by pressing after coating the current collector, crystals tend to be oriented in the direction parallel to the electrode plate, which may lead to deterioration in load characteristics. On the other hand, when the above range is exceeded, the crystallinity of the particle surface decreases, the reactivity with the non-aqueous electrolytic solution increases, and this may lead to a decrease in efficiency and an increase in gas generation.

The Raman spectrum was measured using a Raman spectrometer (for example, a Raman spectrometer manufactured by JASCO Corporation). while rotating the cell in a plane perpendicular to the laser beam. For the obtained Raman spectrum, the intensity IA of the peak PA near 1580 cm ⁻¹ and the intensity IB of the peak PB near 1360 cm ⁻¹ are measured to calculate 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. Also, the half width of the peak PA near 1580 cm ⁻¹ of the obtained Raman spectrum is measured and defined as the Raman half width of the carbonaceous material in the present invention.

Moreover, the above Raman measurement conditions are as follows.
・Argon ion laser wavelength: 514.5 nm
・Laser power on the sample: 15 to 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 the carbonaceous material is usually 0.1 m ² ·g ⁻¹ or more, and 0.7 m ² ·g ⁻¹ or more, as measured using the BET method. is preferred, more preferably 1.0 m ² ·g ⁻¹ or more, particularly preferably 1.5 m ² ·g ⁻¹ or more, and usually 100 m ² ·g ⁻¹ or less, and 25 m ² ·g ⁻¹ or less. It is preferably 15 m ² ·g ⁻¹ or less, and particularly preferably 10 m ² ·g ⁻¹ or less.

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

Measurement of the specific surface area by the BET method uses a surface area meter (for example, fully automatic surface area measuring device manufactured by Okura Riken) to pre-dry the sample at 350 ° C. for 15 minutes under nitrogen flow. Using a nitrogen-helium mixed gas accurately adjusted so that the value of the relative pressure of nitrogen is 0.3, the nitrogen adsorption BET single-point method is performed by the gas flow method. The specific surface area determined by the measurement is defined as the BET specific surface area of the carbonaceous material in the present invention.

(5) Circularity When the degree of circularity of the carbonaceous material is measured, it preferably falls within the following range. The degree of circularity is defined as "degree of circularity = (perimeter of an equivalent circle having the same area as the projected particle shape)/(actual perimeter of the projected shape of the particle)". Become a true sphere.
The circularity of the carbonaceous material having a particle diameter in the range of 3 to 40 μm is preferably as close to 1 as possible, and is preferably 0.1 or more, more preferably 0.5 or more, and further preferably 0.8 or more. , 0.85 or more is particularly preferred, and 0.9 or more is most preferred.

High-current-density charge-discharge characteristics are improved as the degree of circularity increases. Therefore, when the circularity is below the above range, the filling property of the negative electrode active material is lowered, the resistance between particles is increased, and the short-time high-current-density charge-discharge characteristics may be deteriorated.
Circularity is measured using a flow-type particle image analyzer (for example, FPIA manufactured by Sysmex Corporation). About 0.2 g of the sample is dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. , the detection range is specified to be 0.6 to 400 μm, and the particle size is measured 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 it is preferable to subject the particles to spheroidization treatment so that the shape of the inter-particle voids is uniform when the electrode body is formed. Examples of spheroidizing treatment include a method of mechanically approximating a spherical shape by applying a shearing force or a compressive force, a mechanical/physical treatment method of granulating a plurality of fine particles using a binder or the adhesive force of the particles themselves. is mentioned.

(6) Tap density The tap density of the carbonaceous material is usually 0.1 g cm ^-3 or more, preferably 0.5 g cm ^-3 or more, more preferably 0.7 g cm ^-3 or more, and 1 g cm -3 or more. cm ⁻³ or more is particularly preferable, and usually 2 g·cm ⁻³ or less is preferable, 1.8 g·cm ⁻³ or less is more preferable, and 1.6 g·cm ⁻³ or less is particularly preferable.

If the tap density is less than the above range, it is difficult to increase the packing density when used as a negative electrode,
It may not be possible to obtain a high-capacity battery. On the other hand, when the above range is exceeded, the voids between the particles in the electrode become too small, it becomes difficult to ensure the conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.
The tap density is measured by passing the sample through a sieve with an opening of 300 μm, dropping the sample into a tapping cell of 20 cm ³ and filling the sample to the upper end surface of the cell, and then using a powder density measuring instrument (for example, manufactured by Seishin Enterprise Co., Ltd. Using a tap densityr, tapping is performed 1000 times with a stroke length of 10 mm, 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 below 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. 0.47 g of the sample is filled in a molding machine with a diameter of 17 mm and compressed at 58.8 MN m ⁻² , and the molded body obtained is set on the same plane as the surface of the sample holder for measurement using clay. X-ray diffraction is measured. From the obtained peak intensities of (110) diffraction and (004) diffraction of carbon, a ratio represented by (110) diffraction peak intensity/(004) diffraction peak intensity is calculated. The orientation ratio calculated by the measurement is defined as the orientation ratio of the carbonaceous material in the present invention.

The X-ray diffraction measurement conditions are as follows. Note that "2θ" indicates a diffraction angle.
・Target: Cu (Kα ray) graphite monochromator ・Slit:
Divergence slit = 0.5 degrees Receiving slit = 0.15 mm
Scattering slit = 0.5 degrees Measurement range and step angle/measurement time:
(110) face: 75 degrees ≤ 2θ ≤ 80 degrees 1 degree / 60 seconds (004) face: 52 degrees ≤ 2θ ≤ 57 degrees 1 degree / 60 seconds

(8) Aspect ratio (powder)
The aspect ratio of the carbonaceous material is usually 1 or more and usually 10 or less, preferably 8 or less, more preferably 5 or less. If the aspect ratio exceeds the above range, streaks may occur during the production of an electrode plate, and a uniform coating surface may not be obtained, resulting in deterioration in high-current-density charge-discharge characteristics. 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 carbonaceous material particles with a scanning electron microscope. Select any 50 graphite particles fixed to the end face of metal with a thickness of 50 microns or less, rotate and tilt the stage on which the sample is fixed for each, and observe the carbonaceous material three-dimensionally. The longest diameter P of the particles and the shortest diameter Q orthogonal thereto are measured, and the average value of P/Q is obtained. The aspect ratio (P/Q) determined 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 to produce the negative electrode as long as it does not significantly limit the effects of the present invention. For example, a negative electrode active material may be formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc., to form a slurry, applying the slurry to a current collector, drying the slurry, and pressing the 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. , is preferably 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 electrolytic solution is less likely to permeate to the vicinity of the current collector interface, which may deteriorate the high current density charge/discharge characteristics. Also, if the ratio falls below this range, the volume ratio of the current collector to the negative electrode active material increases, and the capacity of the battery may decrease. Further, the negative electrode active material may be roll-molded to form a sheet electrode, or compression-molded to form a pellet electrode.

(10) Current collector Any known current collector can be used as the current collector for holding the negative electrode active material. Examples of the current collector for the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Copper is particularly preferable in terms of ease of processing and cost.
When the current collector is made of a metal material, examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punched metal, and foamed metal. Among them, metal thin films are preferred, copper foils are more preferred, and rolled copper foils produced by a rolling method and electrolytic copper foils produced by an electrolysis method are more preferred, both of which can be used as current collectors.

If the thickness of the copper foil is less than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu--Cr--Zr alloy, etc.) having higher strength than pure copper can be used.
Although the thickness of the current collector is arbitrary, it 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 less than 1 μm, the strength may be lowered, which may make coating difficult. Moreover, if the thickness is more than 1 mm, the shape of the electrode may be deformed due to winding or the like. Note that the current collector may be mesh-like.

(11) Thickness Ratio of Current Collector and Negative Electrode Active Material Layer The thickness ratio of the current collector and the negative electrode active material layer is not particularly limited, The value of "substance layer thickness)/(current collector thickness)" 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, and 1 The above is more preferable.

When the thickness ratio of the current collector and the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during charging and discharging at a high current density. On the other hand, below the above range, the volume ratio of the current collector to the negative electrode active material increases, and the capacity of the battery may decrease.

(12) Electrode Density The electrode structure when the negative electrode active material is formed into an electrode is not particularly ^limited . 2 g·cm ⁻³ or more is more preferable, 1.3 g·cm ⁻³ or more is more preferable, and usually 2.2 g·cm ⁻³ or less is preferable, and 2.1 g·cm ⁻³ or less is more preferable. 0 g·cm ⁻³ or less is more preferable, and 1.9 g·cm ⁻³ or less is particularly preferable. When the density of the negative electrode active material present 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 A deterioration in high-current-density charge-discharge characteristics may be caused due to a decrease in permeability of the electrolytic solution. On the other hand, 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 that binds the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolytic solution and the solvent used in electrode production.
Specific examples include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, NBR ( Acrylonitrile-butadiene rubber), rubbery polymers such as ethylene-propylene rubber; styrene-butadiene-styrene block copolymers or hydrogenated products thereof; EPDM (ethylene-propylene-diene terpolymer), 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 copolymers Coalescence, soft resinous polymers such as propylene/α-olefin copolymers; fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene/ethylene copolymers; alkalis Examples thereof include polymer compositions having ion conductivity of metal ions (especially lithium ions). These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

As the solvent for forming the slurry, there is no particular limitation on the type of solvent as long as it is capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive material used as necessary. Either an aqueous solvent or an organic solvent may be used.
Examples of aqueous solvents include water and alcohols, and examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, 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 using an aqueous solvent, it is preferable to add a dispersant and the like together with the thickener and make a slurry using a latex such as SBR. In addition, these solvent may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.
The ratio of the binder to the negative electrode active material is 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 usually 20% by mass or less. is preferred, 15% by mass or less is more preferred, 10% by mass or less is even more preferred, and 8% by mass or less is particularly preferred. If the ratio of the binder to the negative electrode active material exceeds the above range, the ratio of the binder that does not contribute to the battery capacity increases, which may lead to a decrease in the battery capacity. On the other hand, when it is less than the above range, the strength of the negative electrode may be lowered.

In particular, when a rubber-like polymer represented by SBR is contained as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and 0.5% by mass or more. .6% by mass or more is more preferable, and it is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less.
Further, when a fluorine-based polymer 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. Also, 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 slurries. The thickener is not particularly limited, but specific examples include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

Furthermore, 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, and 0.6% by mass. % or more is more preferable, and it is usually 5% by mass or less, preferably 3% by mass or less, and more 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 remarkably deteriorated. On the other hand, when the above range is exceeded, the proportion of the negative electrode active material in the negative electrode active material layer decreases, which may lead to a problem of a decrease in battery capacity and an increase in resistance between the negative electrode active materials.

<2-3-3. Structure, Physical Properties, and Preparation Method of Metallic Compound-Based Material and Negative Electrode Using Metallic Compound-Based Material>
Metal compound-based materials used as the negative electrode active material include elemental metals or alloys that form lithium alloys, or oxides, carbides, nitrides, silicides, sulfides thereof, as long as they can absorb and release lithium. Any compound such as a phosphide is not particularly limited. Examples of such metal compounds include compounds containing metals such as Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, Pb, Sb, Si, Sn, Sr, and Zn. Among them, it is preferably a single metal or alloy that forms a lithium alloy, more preferably a material containing a Group 13 or Group 14 metal/metalloid element (that is, excluding carbon), and furthermore, silicon (Si ), tin (Sn), or lead (Pb) (hereinafter, these three elements may be referred to as "specified metal elements") single metals or alloys containing these atoms, or those metals (specified metal elements ), and particularly preferred are elemental metals, alloys and compounds of silicon, and elemental metals, alloys and compounds of tin. One of these may be used alone, or two or more thereof may be used in any combination and ratio.

Examples of the negative electrode active material having at least one atom selected from the specific metal elements include a single metal of any one specific metal element, an alloy composed of two or more specific metal elements, one or more alloys consisting of the specified metal element and one or more other metal elements, compounds containing one or more specified metal elements, or oxides, carbides, and nitrides of these compounds・Composite compounds such as silicides, sulfides and phosphides are included. By using these simple metals, alloys, or metal compounds as the negative electrode active material, it is possible to increase the capacity of the battery.

Compounds in which these complex compounds are intricately combined with several kinds of elements such as elemental metals, alloys, or non-metallic elements can also be cited as examples. More specifically, for silicon and tin, for example, an alloy of these elements and a metal that does not act as a negative electrode can be used. In addition, for example, in the case of tin, a complex compound containing 5 to 6 elements can be used in combination with a metal other than tin and silicon that acts as a negative electrode, a metal that does not act as a negative electrode, and a non-metallic element. .

Among these negative electrode active materials, since the capacity per unit mass is large when made into a battery, any single metal of one specific metal element, an alloy of two or more specific metal elements, and an oxidation of a specific metal element metals, carbides, nitrides and the like are preferred, and silicon and/or tin metal simple substances, alloys, oxides, carbides, nitrides and the like are particularly preferred from the viewpoint of capacity per unit mass and environmental load.
In addition, the following compounds containing silicon and/or tin are also preferable because they are excellent in cycle characteristics, although they are inferior in capacity per unit mass to the use of simple metals or alloys.
- The element 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 1.5. 3 or less, more preferably 1.1 or less "oxides of silicon and/or tin".
・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 1.3 or less, more preferably 1.1 or less "nitrides of silicon and/or tin".
- 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 1.5. 3 or less, more preferably 1.1 or less "carbides of silicon and/or tin".

Any one of the negative electrode active materials described above may be used alone, or two or more thereof may be used in any combination and ratio.
The negative electrode in the non-aqueous electrolyte secondary battery can be manufactured using any known method. Specifically, as a method for manufacturing the negative electrode, for example, a method in which a binder, a conductive material, or the like is added to the negative electrode active material described above is directly roll-molded into a sheet electrode, or a pellet electrode is formed by compression molding. Usually, the above-mentioned negative electrode is coated on a current collector for a negative electrode (hereinafter sometimes referred to as a "negative electrode current collector") by a method such as a coating method, a vapor deposition method, a sputtering method, or a plating method. 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, and the like are added to the negative electrode active material described above to form a slurry, which is applied to the negative electrode current collector, dried, and then pressed to increase the density. forming a negative electrode active material layer on the negative electrode current collector;

Examples of materials for the negative electrode current collector include steel, copper alloys, nickel, nickel alloys, stainless steel, and the like. Among these, copper foil is preferable from the point of view of ease of processing into a thin film and the point of 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 too low, and if it is too thin, handling may become difficult.

In addition, in order to improve the binding effect with the negative electrode active material layer formed on the surface, the surfaces of these negative electrode current collectors are preferably roughened in advance. Surface roughening methods include blasting, rolling with rough surface rolls, abrasive coated paper to which abrasive particles are fixed, grindstones, emery buffs, and machines that polish the current collector surface with wire brushes equipped with steel wires, etc. Examples include a mechanical polishing method, an electrolytic polishing method, a chemical polishing method, and the like.

A slurry for forming the negative electrode active material layer is usually prepared by adding a binder, a thickener, and the like to the negative electrode material. In this specification, the term “negative electrode material” refers to a material obtained by combining a negative electrode active material and a conductive material.
The content of the negative electrode active material in the negative electrode material is usually 70% by mass or more, preferably 75% by mass or more, and is 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 resulting secondary battery using the negative electrode tends to be insufficient. This is because the strength of the negative electrode tends to be insufficient. When two or more negative electrode active materials are used together, the total amount of the negative electrode active materials should 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. These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios. 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 3% by mass or more, preferably 5% by mass or more, and is usually 30% by mass or less, particularly preferably 25% by mass or less. 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, etc. will be relatively insufficient, resulting in a tendency for the battery capacity and strength to decrease. . When two or more conductive materials are used together, the total amount of the conductive materials should satisfy the above range.

As the binder used for the negative electrode, any material can be used as long as it is a material that is safe with respect to the solvent and electrolytic solution used during electrode production. Examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene/butadiene rubber/isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, and ethylene/methacrylic acid copolymer. These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios. The content of the binder is usually 0.5 parts by mass or more, preferably 1 part by mass or more, and usually 10 parts by mass or less, particularly preferably 8 parts by mass or less, relative to 100 parts by mass of the negative electrode material. If the content of the binder is too small, the strength of the resulting negative electrode tends to be insufficient. This is because When two or more binders are used together, the total amount of the binders should satisfy the above range.

Examples of the thickening agent used for the negative electrode include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and the like. These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios. A thickening agent may be used as necessary, but when it is used, the content of the thickening agent 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 preferred.

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 thickening agent, if necessary, and using an aqueous solvent or an organic solvent as a dispersion medium. . As the aqueous solvent, water is usually used, but solvents other than water, such as alcohols such as ethanol and cyclic amides such as N-methylpyrrolidone, are used in combination at a ratio of about 30% by mass or less with respect to water. can also As the organic solvent, cyclic amides such as N-methylpyrrolidone, linear amides such as N,N-dimethylformamide and N,N-dimethylacetamide, and aromatic hydrocarbons such as anisole, toluene, and xylene are generally used. Hydrogens, alcohols such as butanol and cyclohexanol, among others, cyclic amides such as N-methylpyrrolidone and linear amides such as N,N-dimethylformamide and N,N-dimethylacetamide are preferred. . 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 to be used, etc. may be changed when the slurry is prepared so that the slurry has a viscosity that allows application.
The negative electrode active material layer is formed by applying the obtained slurry onto the above negative electrode current collector, drying it, and then pressing it. The method of application is not particularly limited, and a method known per se can be used. The method of drying is also not particularly limited, and known methods such as natural drying, heat drying, and reduced pressure drying can be used.

The electrode structure when the negative electrode active material is formed into an electrode by the above method is not particularly limited, but the density of the active material present on the current collector is preferably 1 g cm ⁻³ or more, and 1.2 g cm ⁻³ or more is more preferable, 1.3 g·cm ⁻³ or more is particularly preferable, and usually 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 electrolytic solution near the interface between the current collector and the active material. A deterioration in high-current-density charge-discharge characteristics may be caused due to a decrease in permeability. On the other hand, 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. Configuration, physical properties, and preparation method of negative electrode using carbonaceous material and metal-based material>
The negative electrode active material may contain a metal-based material and the carbonaceous material. Here, the negative electrode active material containing a metal-based material and a carbonaceous material is a single metal or alloy that can be alloyed with lithium, or a compound such as an oxide, carbide, nitride, silicide, or sulfide thereof. Either of them and a carbonaceous material may be mixed in a state of independent particles, or a single metal or alloy that can be alloyed with lithium, or oxides, carbides, nitrides, silicides, and sulfides thereof It may be a composite in which a compound such as a substance exists on the surface or inside the carbonaceous material, and is particularly preferably a composite and/or mixture of a metal-based material and a carbonaceous material (especially graphite). In the present specification, the term "composite" is not particularly limited as long as it contains a metallic material and a carbonaceous material, but preferably the metallic material and the carbonaceous material are physically and/or chemically united by bonding. In a more preferred form, the metallic material and the carbonaceous material are in a state in which each solid component is dispersed to the extent that they are present at least both on the surface of the composite and inside the bulk, and they are physically separated. and/or in which carbonaceous material is present for integration by chemical bonding.

Such a form includes observation of the particle surface with a scanning electron microscope, embedding of particles in resin to prepare a thin piece of resin and cutting out the particle cross section, or preparation of a coating film cross section of a coating film made of particles with a cross section polisher. After cutting out the cross section of the particle, it can be observed by an observation method such as observation of the cross section of the particle using a scanning electron microscope.
The content of the metal-based material with respect to the total of the negative electrode active material (especially graphite) containing the metal-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, 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 , more preferably 30% by mass or less, particularly preferably 25% by mass or less, and most preferably 15% by mass or less. This range is preferable in that a sufficient capacity can be obtained.

The carbonaceous material used for the negative electrode active material containing the metal-based material and the carbonaceous material preferably satisfies the requirements described in <2-3-2> above. In addition, it is desirable that the metal-based material satisfy the following.
Any conventionally known metallic material that can be alloyed with lithium can be used. From the viewpoint of capacity and cycle life, metallic materials that can be alloyed with lithium include, for example, Fe, Co , Sb, Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, V, Mn, Nb, Mo, Cu, Zn, Ge, In, Ti and the like. or metal compounds thereof are preferred. Moreover, as the alloy that can be alloyed with lithium, at least one metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn and W or a metal compound thereof is preferable.

Single metals or alloys that can be alloyed with lithium, or compounds such as oxides, carbides, nitrides, silicides, and sulfides thereof include metal oxides, metal carbides, metal nitrides, metal silicides, and metal sulfides. things, etc. Also, an alloy composed of two or more metals may be used. Among these, Si or a Si compound (particularly Si metal oxide) is preferable from the viewpoint of increasing the capacity. In this specification, Si or Si compounds are collectively referred to as Si compounds. Specific examples of the Si compound include SiO _x , SiN _x , SiC _x , SiZ _x O _y (where Z is C or N), etc., and SiO x is preferred. . Although the value of x in the above general formula is not particularly limited, it usually satisfies 0≦x<2. The SiO _x is obtained using silicon dioxide (SiO ₂ ) and metal silicon (Si) as raw materials. SiO _x has a larger theoretical capacity than graphite, and amorphous Si or nano-sized Si crystals facilitate the entry and exit of alkali ions such as lithium ions, making it possible to obtain a high capacity.

The value of x in SiO _x is not particularly limited, but usually x is 0≦x<2, preferably 0.2 or more, more preferably 0.4 or more, and still more preferably 0.6 or more, Also, it is preferably 1.8 or less, more preferably 1.6 or less, and still 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 while achieving a high capacity.

In addition, as a method for confirming that the metallic material is a metallic material that can be alloyed with lithium, identification of the metallic particle phase by X-ray diffraction, observation and elemental analysis of the particle structure by an electron microscope, fluorescence Elemental analysis using X-rays and the like can be mentioned.
The volume-based average particle diameter (median diameter d50) of the metallic material is not particularly limited, but from the viewpoint of cycle life, it is usually 0.01 μm or more, preferably 0.05 μm or more, more preferably 0.1 μm or more, and more preferably 0.1 μm or more. is 0.3 μm or more, and is 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 laser diffraction/scattering particle size distribution measuring method or the like.
Although the specific surface area of the metal-based material used for the negative electrode active material containing the metal-based material and the carbonaceous material is not particularly limited by the BET method, it is usually 0.5 m ² /g or more, preferably 1 m ² /g or more. , usually 60 m ² /g or less, preferably 40 m ² /g or less. When the specific surface area of the metal particles that can be alloyed with Li as determined by the BET method is within the above range, the charge/discharge efficiency and discharge capacity of the battery are high, lithium is quickly taken in and out during high-speed charge/discharge, and the rate characteristics are excellent.

The amount of oxygen contained in the metal-based material used for the negative electrode active material containing the metal-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, and It is usually 8% by mass or less, preferably 5% by mass or less. Oxygen may be distributed in the particle in the vicinity of the surface, in the interior of the particle, or evenly distributed in the particle, but preferably in the vicinity of the surface. When the amount of oxygen contained in the metal-based material is within the above range, the strong bond between Si and O suppresses volume expansion accompanying charging and discharging, and the cycle characteristics are excellent, which is preferable.

In addition, for manufacturing a negative electrode from a metal-based material used for a negative electrode active material containing a metal-based material and a carbonaceous material, the materials described in <2-3-1> Carbonaceous material can be used.

<2-3-5. Lithium-Containing Metal Composite Oxide Material, and Configuration, Physical Properties, and Preparation Method of 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 a composite oxide of lithium and titanium (hereinafter abbreviated as "lithium-titanium composite oxide") is particularly preferred. That is, it is particularly preferable to include a lithium-titanium composite oxide having a spinel structure in a negative electrode active material for a non-aqueous electrolyte secondary battery because the output resistance is greatly reduced.

In addition, at least lithium and titanium in the lithium-titanium composite oxide are selected from the group consisting of other metal elements such as Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb. Those substituted with one element are also preferred.
The metal oxide is a lithium-titanium composite oxide represented by the composition formula (4), wherein 0.7 ≤ x ≤ 1.5, 1.5 ≤ y ≤ 2.3, It is preferable that 0≦z≦1.6 because the structure is stable during doping and dedoping of lithium ions.

_{LixTiyMzO4 ( 4 )}
In the above compositional formula (4), 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 compositional formula (4),
(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
is particularly preferred because it has a good balance of battery performance.

Particularly preferred representative compositions of the above compounds are Li _4/3 Ti _5/3 O ₄ in (a), Li ₁ Ti ₂ O ₄ in (b), and Li _4/5 Ti _11/5 O in (c). ₄ . Moreover, 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 further satisfies at least one of the following characteristics such as physical properties and shape shown in (1) to (13). are preferred, and it is particularly preferred to satisfy two or more 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 is preferably 0.5 m ² ·g ⁻¹ or more, and 0.5 m 2 ·g −1 or more, as measured using the BET method. 7 m ² ·g ^-1 or more is more 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 200 m ² ·g ^-1 or less is preferable, It is more preferably 100 m ² ·g ⁻¹ or less, further preferably 50 m ² ·g ⁻¹ or less, and particularly preferably 25 m ² ·g ⁻¹ or less.

If the BET specific surface area is below the above range, the reaction area in contact with the non-aqueous electrolytic solution when used as a negative electrode material may decrease, resulting in an increase in output resistance. On the other hand, when the above range is exceeded, the surface and end face portions of the metal oxide containing titanium increase, and due to this, crystal strain also occurs, so the irreversible capacity cannot be ignored, which is preferable. Batteries may be difficult to obtain.

Measurement of the specific surface area by the BET method uses a surface area meter (for example, fully automatic surface area measuring device manufactured by Okura Riken) to pre-dry the sample at 350 ° C. for 15 minutes under nitrogen flow. Using a nitrogen-helium mixed gas accurately adjusted so that the value of the relative pressure of nitrogen is 0.3, the nitrogen adsorption BET single-point method is performed by the gas flow method. The specific surface area determined by the measurement is defined as the BET specific surface area of the lithium-titanium composite oxide in the present invention.

(2) Volume-based average particle size The volume-based average particle size of lithium-titanium composite oxide (secondary particle size when primary particles aggregate to form secondary particles) can be determined by a laser diffraction/scattering method. It is defined by the obtained volume-based average particle diameter (median diameter d50).
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, and 30 μm. The following is more preferable, and 25 μm or less is even more preferable.

The volume-based average particle size is measured by dispersing carbon powder in a 0.2% by mass aqueous solution (10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and using a laser diffraction/scattering particle size distribution meter. (eg, LA-700 manufactured by Horiba, Ltd.). The median diameter d50 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 during electrode production, which may result in a decrease in battery capacity. On the other hand, if the thickness exceeds the above range, the coated surface tends to be non-uniform when forming an electrode plate, which may not be desirable in terms of 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. It is preferably 0.1 µm or more, more preferably 0.2 µm or more, and is usually 2 µm or less, preferably 1.6 µm or less, more preferably 1.3 µm or less, and even more preferably 1 µm or less. If the volume-based average primary particle size exceeds the above range, it is difficult to form spherical secondary particles, which adversely affects the powder filling property and significantly reduces the specific surface area. Possibility of degraded performance may increase. On the other hand, if it is less than the above range, the performance of the secondary battery may be deteriorated, for example, the reversibility of charging/discharging is generally inferior due to underdeveloped crystals.

The primary particle size is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of, for example, 10,000 to 100,000 times that the particles can be confirmed, the maximum value of the intercept of the left and right boundary lines of the primary particles with respect to the horizontal straight line is measured for any 50 primary particles. obtained by taking the average value.

(4) Shape The shape of the particles of the lithium-titanium composite oxide is conventionally used, such as massive, polyhedral, spherical, oval, plate-like, needle-like, and columnar. Preferably, secondary particles are formed, and the shape of the secondary particles is spherical or ellipsoidal.

Generally, the active material in the electrode of an electrochemical element expands and contracts as it is charged and discharged, and the stress tends to cause deterioration such as breakage of the active material and disconnection of conductive paths. Therefore, the primary particles aggregate to form secondary particles, rather than a single particle active material consisting of only primary particles, to alleviate the stress of expansion and contraction and prevent deterioration.
In addition, since spherical or ellipsoidal particles have less orientation during electrode molding than plate-like equiaxially oriented particles, the electrode expands and shrinks less during charging and discharging, and the electrode is produced. Also in mixing with the conductive material at the time of mixing, it is preferable because it is easily mixed uniformly.

(5) Tap density The tap density of the lithium-titanium composite oxide is preferably 0.05 g cm ^-3 or more, more preferably 0.1 g cm ^-3 or more, and still more preferably 0.2 g cm ^-3 or more. It is particularly preferably 0.4 g·cm ⁻³ or more, more preferably 2.8 g·cm ⁻³ or less, still more preferably 2.4 g·cm ⁻³ or less, and particularly preferably 2 g·cm ⁻³ or less. If the tap density is less than the above range, it is difficult to increase the packing density when used as a negative electrode, and the contact area between particles decreases, so the resistance between particles increases and the output resistance may increase. On the other hand, when the above range is exceeded, the voids between the particles in the electrode become too small, and the flow paths for the non-aqueous electrolytic solution are reduced, which may increase the output resistance.

The tap density is measured by passing the sample through a sieve with an opening of 300 μm, dropping the sample into a tapping cell of 20 cm ³ and filling the sample to the upper end surface of the cell, and then using a powder density measuring instrument (for example, manufactured by Seishin Enterprise Co., Ltd. Using a tap densityr, tapping is performed 1000 times with a stroke length of 10 mm, and the density is calculated from the volume and mass of the sample at that time. The tap density calculated by the measurement is defined as the tap density of the lithium-titanium composite oxide in the present invention.

(6) Circularity When the degree of circularity is measured as the degree of sphericalness of the lithium-titanium composite oxide, it preferably falls within the following range. Circularity is defined as "circularity = (perimeter of equivalent circle having the same area as particle projection shape) / (actual perimeter of particle projection shape)". becomes.

The circularity of the lithium-titanium composite oxide is preferably as close to 1 as possible, usually 0.10 or more, preferably 0.80 or more, more preferably 0.85 or more, and even more preferably 0.90 or more. High-current-density charge-discharge characteristics are improved as the degree of circularity increases. Therefore, when the circularity is below the above range, the filling property of the negative electrode active material is lowered, the resistance between particles is increased, and the short-time high-current-density charge-discharge characteristics may be deteriorated.

Circularity is measured using a flow particle image analyzer (for example, Sysmex FPIA). About 0.2 g of the sample is dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and irradiated with ultrasonic waves of 28 kHz at an output of 60 W for 1 minute. , the detection range is specified to be 0.6 to 400 μm, and the particle size is measured 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 and usually 5 or less, preferably 4 or less, more preferably 3 or less, and even more preferably 2 or less. If the aspect ratio exceeds the above range, streaks may occur during the production of an electrode plate, and a uniform coated surface may not be obtained, resulting in deterioration in short-time high-current-density charge-discharge characteristics. 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 particles of the lithium-titanium composite oxide with a scanning electron microscope. Select any 50 particles fixed to the end face of metal with a thickness of 50 μm or less, rotate and tilt the stage on which the sample is fixed for each, and observe the longest particle when observed three-dimensionally. The diameter P' and the shortest diameter Q' perpendicular thereto are measured, and the average value of P'/Q' is obtained. The aspect ratio (P'/Q') determined 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 the lithium-titanium composite oxide is not particularly limited as long as it does not exceed the gist of the present invention. method is used.
For example, a method of uniformly mixing a titanium raw material such as titanium oxide, optionally a raw material of another element, and a Li source such as LiOH, Li ₂ CO ₃ or LiNO ₃ , and firing the mixture at a high temperature to obtain an active material. are mentioned.

In particular, various methods are conceivable for producing a spherical or ellipsoidal 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 prepare a spherical precursor. After recovering and drying this if necessary, a method of adding a Li source such as LiOH, Li ₂ CO ₃ or LiNO ₃ and sintering at a high temperature to obtain an active material is exemplified.

As another example, titanium raw materials such as titanium oxide and, if necessary, raw materials of other elements are dissolved or pulverized and dispersed in a solvent such as water, and then dried and molded using a spray dryer or the like to form spherical particles. Alternatively, an elliptical spherical precursor is added to a Li source such as LiOH, Li ₂ CO ₃ or LiNO ₃ and sintered at a high temperature to obtain an active material.
As another method, a titanium raw material such as titanium oxide, a Li source such as LiOH, Li ₂ CO ₃ or LiNO ₃ , and, if necessary, raw materials of other elements are dissolved or pulverized in a solvent such as water. It is dispersed, dried and molded with a spray dryer or the like to form a spherical or ellipsoidal precursor, which is fired at a high temperature to obtain an active material.

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

(9) Electrode production Any known method can be used to produce the electrode. For example, a negative electrode active material may be formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to form a slurry, applying the slurry to a current collector, drying the slurry, and then pressing the 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, preferably 150 μm or less. 120 μm or less, more preferably 100 μm or less is desirable.

If this range is exceeded, the non-aqueous electrolytic solution is less likely to permeate to the vicinity of the interface of the current collector, which may deteriorate the high current density charge/discharge characteristics. Further, when the content is below this range, the volume ratio of the current collector to the negative electrode active material increases, and the capacity of the battery may decrease. Further, the negative electrode active material may be roll-molded to form a sheet electrode, or compression-molded to form a pellet electrode.

(10) Current collector Any known current collector can be used as the current collector for holding the negative electrode active material. Examples of the current collector for the negative electrode include metallic materials such as copper, nickel, stainless steel, and nickel-plated steel. Among them, 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 includes, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punched metal, and a foamed metal. Among them, a metal foil film containing copper (Cu) and/or aluminum (Al) is preferable, more preferably a copper foil or an aluminum foil, and still more preferably a rolled copper foil by a rolling method or an electrolytic copper by an electrolysis method. There are foils, both of which can be used as current collectors.

If the thickness of the copper foil is less than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu--Cr--Zr alloy, etc.) having higher strength than pure copper can be used. In addition, since aluminum foil has a low specific gravity, it is possible to reduce the mass of the battery when it is used as a current collector, so that it can be preferably used.
A current collector made of a copper foil produced by a rolling method has copper crystals aligned in the rolling direction, so it is difficult to crack even if the negative electrode is rolled tightly or rolled at an acute angle, and is suitable for small cylindrical batteries. be able to.

For electrodeposited copper foil, for example, a metal drum is immersed in a non-aqueous electrolytic solution in which copper ions are dissolved, and an electric current is applied while rotating it 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 to a thickness of several nanometers to 1 μm, Ti or other underlayer treatment, etc.).

Although the thickness of the current collector is arbitrary, it 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, it is preferable in that the strength is improved, application is facilitated, and the shape of the electrode is stabilized.

(11) Thickness ratio of current collector and active material layer The ratio of the thickness of the current collector and the active material layer is not particularly limited, but "(the thickness of the active material layer on one side immediately before the injection of the 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 preferred.

When the thickness ratio of the current collector and the negative electrode active material layer exceeds the above range, the current collector may generate heat due to Joule heat during charging and discharging at high current density. On the other hand, below the above range, the volume ratio of the current collector to the negative electrode active material increases, and the capacity of the battery may decrease.

(12) Electrode density The electrode structure when the negative electrode active material is formed into an electrode is not particularly limited, but the density of the active material present on the current collector is preferably 1 g cm ^-3 or more, and 1.2 g · cm ⁻³ or more is more preferable, 1.3 g·cm ⁻³ or more is still more preferable, 1.5 g·cm ⁻³ or more is particularly preferable, and 3 g·cm ⁻³ or less is preferable, and 2.5 g·cm −3 or more is preferable ^{. 3} or less is more preferable, 2.2 g·cm ⁻³ or less is even more preferable, and 2 g·cm ⁻³ or less is particularly preferable.

When the density of the active material present on the current collector exceeds the above range, the binding between the current collector and the negative electrode active material is weakened, and the electrode and the active material may separate from each other. On the other hand, if it is less than the above range, the conductivity between the negative electrode active materials may decrease and the battery resistance may increase.

(13) Binder The binder that binds the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolytic solution and the solvent used in electrode production.

Specific examples include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluororubber, Rubber-like polymers such as NBR (acrylonitrile-butadiene rubber) and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers and hydrogenated products thereof; EPDM (ethylene-propylene-diene terpolymer), Thermoplastic elastomeric polymers such as ethylene/butadiene/styrene copolymers, styrene/isoprene/styrene block copolymers and hydrogenated products thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene/vinyl acetate Soft resinous polymers such as copolymers and propylene/α-olefin copolymers; fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene/ethylene copolymers a polymer composition having ion conductivity of alkali metal ions (especially lithium ions); These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

As the solvent for forming the slurry, there is no particular limitation on the type of the solvent as long as it is capable of dissolving or dispersing the negative electrode active material, binder, thickener and conductive material used as necessary. Either an aqueous solvent or an organic solvent may be used.
Examples of aqueous solvents include water and alcohols, and examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, 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 using an aqueous solvent, a dispersant or the like is added together with the above-described thickener, and the mixture is slurried using a latex such as SBR. In addition, these may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

The ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and is usually 20% by mass or less and 15% by mass. % or less is preferable, 10 mass % or less is more preferable, and 8 mass % or less is even more preferable.
When the ratio of the binder to the negative electrode active material is within the above range, the ratio of the binder that does not contribute to the battery capacity decreases, the battery capacity increases, and the strength of the negative electrode is maintained. .

In particular, when a rubber-like polymer represented by SBR is contained as a 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 0.5% by mass or more. It is more preferably 6% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less.
Further, when a fluorine-based polymer represented by polyvinylidene fluoride is contained as a 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. Also, 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 slurries. The thickener is not particularly limited, but specific examples include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

Furthermore, 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, and more preferably 0.6% by mass or more. Also, it is usually 5% by mass or less, preferably 3% by mass or less, 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 coating properties of the adhesive, and the ratio of the active material in the negative electrode active material layer is preferable, and the capacity of the battery and the negative electrode are improved. This is preferable in terms of resistance between active substances.

<2-4. Positive electrode>
The positive electrode used in the non-aqueous electrolyte secondary battery will be described below.

<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 a transition metal oxide that contains at least Ni and Co, and 50 mol % or more of the transition metals are Ni and Co, and is capable of electrochemically intercalating and deintercalating metal ions. Although there is no particular limitation as long as it is a material, for example, one that can electrochemically absorb and release lithium ions is preferable, and contains lithium, at least Ni, and Co, and 50 mol% or more of the transition metals are Ni. A transition metal oxide of Co is preferred. This is because Ni and Co are suitable for use as positive electrode materials for secondary batteries due to their oxidation-reduction potentials, and are suitable for high-capacity applications.

The transition metal component of the lithium transition metal oxide includes Ni and Co as essential elements, and other metals such as Mn, V, Ti, Cr, Fe, Cu, Al, Mg, Zr, and Er. Mn, Ti, Fe, Al, Mg, Zr and the like are preferred. Specific examples _{of lithium transition} metal oxides _{include LiNi0.85Co0.10Al0.05O2 , LiNi0.80Co0.15Al0.05O2 , LiNi0.33Co0 . 33Mn0.33O2 , Li1.05Ni0.33Mn0.33Co0.33O2 , LiNi0.5Co0.2Mn0.3O2 , Li1.05Ni0.50 _ _ _ _ _ _ _} Mn _0.29 Co _0.21 O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and the like.

Among them, transition metal oxides represented by the following compositional formula (5) are preferable.
Li _a1 Ni _b1 Co _c1 M _d1 O ₂ (5)
In the above composition formula (5), the numerical values of 0.9 ≤ a1 ≤ 1.1, 0.3 ≤ b1 ≤ 0.9, 0.1 ≤ c1 ≤ 0.5, 0.0 ≤ d1 ≤ 0.5 and satisfies 0.5≦b1+c1 and b1+c1+d1=1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti and Er.
In the above compositional formula (5), it is preferable to show a numerical value of 0.1≦d1≦0.5.

When the composition ratio of Ni and Co and the composition ratio of other metal species are as specified, the transition metal is less likely to be eluted from the positive electrode, and even if Ni and Co are eluted, Ni and Co are not contained in the non-aqueous secondary battery. This is because the adverse effect of
Among them, transition metal oxides represented by the following compositional formula (6) are more preferable.
Li _a2 Ni _b2 Co _c2 Md ₂ O ₂ (6)
In the above composition formula (6), the numerical values of 0.9 ≤ a2 ≤ 1.1, 0.3 ≤ b2 ≤ 0.9, 0.1 ≤ c2 ≤ 0.5, 0.0 ≤ d2 ≤ 0.5 and satisfy c2≤b2 and 0.6≤b2+c2 and b2+c2+d2=1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti and Er.
In the above compositional formula (6), it is preferable to show a numerical value of 0.1≦d2≦0.5.

Ni and Co are the main components, and the composition ratio of Ni is the same as or greater than the composition ratio of Co, so that when used as a positive electrode for a non-aqueous secondary battery, it is stable and produces a high capacity. This is because it becomes possible.
Among them, transition metal oxides represented by the following compositional formula (7) are more preferable.
Li _a3 Ni _b3 Co _c3 M _d3 O ₂ (7)
(In the composition formula (7), the numerical values of 0.9 ≤ a3 ≤ 1.1, 0.35 ≤ b3 ≤ 0.9, 0.1 ≤ c3 ≤ 0.5, 0.0 ≤ d3 ≤ 0.5 and satisfies c3<b3, 0.6≤b3+c3 and b3+c3+d3=1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti and Er.)
In the composition formula (7), it is preferable to show a numerical value of 0.1≤d3≤0.5.

Among them, transition metal oxides represented by the following compositional formula (8) are particularly preferable.
Li _a4 Ni _b4 Co _c4 M _d4 O ₂ (8)
(In the composition formula (8), the numerical values of 0.9 ≤ a4 ≤ 1.1, 0.5 ≤ b4 ≤ 0.9, 0.1 ≤ c4 ≤ 0.2, 0.0 ≤ d4 ≤ 0.3 and satisfies c4<b4, 0.7≤b4+c4 and b4+c4+d4=1. M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti and Er.)
In the composition formula (8), it is preferable to show a numerical value of 0.1≤d4≤0.3.

This is because the composition described above makes it possible to obtain a particularly high capacity when used as a positive electrode for a non-aqueous secondary battery.
Also, two or more of the above positive electrode active materials may be mixed and used. Similarly, at least one or more of the positive electrode active materials described above may be used in combination with other positive electrode active materials. Examples of other positive electrode active materials include transition metal oxides, transition metal phosphate compounds, transition metal silicate compounds, and transition metal borate compounds not listed above.

Among them, a lithium-manganese composite oxide having a spinel structure and a lithium-containing transition metal phosphate compound having an olivine structure are preferable. Specifically, LiMn ₂ O ₄ , LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O ₄ and the like are listed as lithium-manganese composite oxides having a spinel structure. This is because it has the most stable structure among them, and it is difficult to release oxygen even when the non-aqueous electrolyte secondary battery malfunctions, and is excellent in safety.

The transition metal of the lithium-containing transition metal phosphate compound is preferably V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. Specific examples include LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ , iron phosphates such as LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , manganese phosphates such as LiMnPO ₄ , and some of the transition metal atoms that are the main component of these lithium transition metal phosphate compounds are Al, Ti , V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W and the like substituted with other metals.

Among them, a lithium iron phosphate compound is preferable because iron is an abundant resource, an extremely inexpensive metal, and is less harmful. That is, among the above specific examples, LiFePO ₄ can be mentioned as a more preferable specific example.

(2) Surface coating It is also possible to use a material having a composition different from the material constituting the main positive electrode active material (hereinafter referred to as "surface-attached material") adhered to the surface of the above positive electrode active material. . Examples of surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, oxides such as bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, Examples include sulfates such as calcium sulfate and aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate, and carbon.

These surface-adhering substances are, for example, dissolved or suspended in a solvent and impregnated into the positive electrode active material and then dried, or dissolved or suspended in a solvent and impregnated into the positive electrode active material. 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 baking it at the same time, or the like. When carbon is deposited, a method of mechanically depositing carbonaceous matter in the form of activated carbon or the like later can also be used.

The mass of the surface-attached substance adhering to the surface of the positive electrode active material is preferably 0.1 ppm or more, more preferably 1 ppm or more, and even more preferably 10 ppm or more, relative to the mass of the positive electrode active material. Moreover, it is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less.
The surface-adhering substance can suppress the oxidation reaction of the non-aqueous electrolytic solution on the surface of the positive electrode active material, thereby improving the battery life. In addition, when the amount of adhesion is within the above range, the effect can be sufficiently exhibited, and the resistance does not easily increase without impeding the entry and exit of lithium ions.

(3) Shape As for the shape of the positive electrode active material particles, conventionally used lumps, polyhedrons, spheres, ellipsoids, plates, needles, columns, and the like are used. Further, the primary particles may aggregate to form secondary particles, and the secondary particles may have a spherical or ellipsoidal shape.

(4) Tap Density The tap density of the positive electrode active material is preferably 0.5 g·cm ⁻³ or more, more preferably 1.0 g·cm ⁻³ or more, and even more preferably 1.5 g·cm ^{−3 or} more. Further, it is preferably 4.0 g·cm ⁻³ or less, more preferably 3.7 g·cm ⁻³ or less.

By using a metal composite oxide powder with a high tap density, a high-density positive electrode active material layer can be formed. When the tap density of the positive electrode active material is within the above range, the amount of the dispersion medium required for forming the positive electrode active material layer is appropriate, and the amount of the conductive material and the binder is also appropriate. There is no restriction on the filling rate of the positive electrode active material, and the effect on the battery capacity is reduced.

The tap density of the positive electrode active material is measured by passing it through a sieve with an opening of 300 μm, dropping the sample into a tapping cell of 20 cm ³ to fill the cell volume, and then using a powder density measuring instrument (for example, manufactured by Seishin Enterprise Co., Ltd. Using a tap densityr, tapping is performed 1000 times with a stroke length of 10 mm, and the density is calculated from the volume and mass of the sample at that time. 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 (the secondary particle diameter when the primary particles aggregate to form secondary particles) can be measured using a laser diffraction/scattering particle size distribution analyzer. can.
The median diameter d50 is preferably 0.1 μm or more, more preferably 0.5 μm or more, still more preferably 1 μm or more, particularly preferably 3 μm or more, and preferably 30 μm or less, more preferably 20 μm or less, and 16 μm. The following are more preferable, and 15 μm or less is particularly preferable. When the median diameter d50 is within the above range, it becomes easy to obtain a high bulk density product, and furthermore, diffusion of lithium in the particles does not take much time, so the battery characteristics are less likely to deteriorate. In addition, streaks and the like are less likely to occur when the positive electrode of a battery is prepared, that is, when an active material, a conductive material, a binder, and the like are slurried with a solvent and applied in the form of a thin film.

By mixing two or more kinds of positive electrode active materials having different median diameters d50 at an arbitrary ratio, the filling property during manufacturing of the positive electrode can be further improved.
The median diameter d50 of the positive electrode active material is measured using a 0.1% by mass sodium hexametaphosphate aqueous solution as a dispersion medium and a particle size distribution meter (eg, LA-920 manufactured by Horiba, Ltd.) to measure the dispersion of the positive electrode active material. Measured after 5 minutes of ultrasonic dispersion against , setting the refractive index to 1.24.

(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 preferably 0.01 μm or more, more preferably 0.05 μm or more, It is more preferably 0.08 µm or more, particularly preferably 0.1 µm or more, and preferably 3 µm or less, more preferably 2 µm or less, even more preferably 1 µm or less, and particularly preferably 0.6 µm or less. Within the above range, it becomes easier to form spherical secondary particles, the powder filling property becomes moderate, and a sufficient specific surface area can be secured, so deterioration of battery performance such as output characteristics can be suppressed. .

The average primary particle size of the positive electrode active material is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10,000 times, the maximum value of the intercept of the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for arbitrary 50 primary particles, and the average value is obtained. be done.

(7) BET specific surface area The BET specific surface area of the positive electrode active material is preferably 0.2 m ² ·g ⁻¹ or more, and preferably 0.3 m ² ·g ⁻¹ as measured using the BET method. more preferably 0.4 m ² ·g ⁻¹ or more, more preferably 4.0 m ² ·g ⁻¹ or less, more preferably 2.5 m ² ·g ⁻¹ or less, and 1.5 m ² ·g ⁻¹ or less is more preferable. When the value of the BET specific surface area is within the above range, deterioration of battery performance can be easily prevented. Furthermore, a sufficient tap density can be ensured, and the coatability at the time of forming the positive electrode active material is improved.

The BET specific surface area of the positive electrode active material is measured using a surface area meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken). Specifically, the sample was pre-dried at 150° C. for 30 minutes under flowing nitrogen, and then a nitrogen-helium mixed gas accurately adjusted so that the relative pressure of nitrogen to atmospheric pressure was 0.3. is measured by the nitrogen adsorption BET one-point method by the gas flow method. The specific surface area determined by the measurement is defined as the BET specific surface area of the positive electrode 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. method is used.
In particular, various methods are conceivable for producing spherical or ellipsoidal active materials. One example is transition metal raw materials such as transition metal nitrates and sulfates, and, if necessary, raw materials of other elements. is dissolved or pulverized and dispersed in a solvent such as water, and the _pH is adjusted while stirring to prepare and recover spherical precursors _{. 3} or the like is added, followed by firing at a high temperature to obtain an active material.

As an example of another method, transition metal raw materials such as transition metal nitrates, sulfates, hydroxides and oxides and, if necessary, raw materials of other elements 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 obtain a spherical or elliptical precursor, and a Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ is added to the precursor and fired at a high temperature to obtain an active material. are mentioned.

As yet another example of a method, transition metal source materials such as transition metal nitrates, sulfates, hydroxides and oxides, Li sources such as LiOH, Li ₂ CO ₃ and LiNO ₃ and optionally other elements is dissolved or pulverized and dispersed in a solvent such as water, dried and molded with a spray dryer or the like to form a spherical or ellipsoidal precursor, which is fired at a high temperature to obtain an active material. mentioned.

<2-4-2. Positive electrode structure and manufacturing method>
The configuration of the positive electrode and the manufacturing method thereof will be described below.
(Manufacturing method of positive electrode)
The 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. A positive electrode using a positive electrode active material can be produced by any known method. For example, a positive electrode active material, a binder, and, if necessary, a conductive material, a thickener, etc., are mixed in a dry process to form a sheet, which is crimped to a positive electrode current collector, or these materials are dissolved in a liquid medium. Alternatively, a positive electrode can be obtained by forming a positive electrode active material layer on the current collector by dispersing and forming a slurry, applying the slurry to a positive electrode current collector, and drying the slurry.

The content of the positive electrode active material in the positive electrode active material layer is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and preferably 99.9% by mass or less. There is, and 99 mass % or less is more preferable. When the content of the positive electrode active material is within the above range, sufficient electrical capacity can be ensured. Furthermore, the strength of the positive electrode becomes sufficient. One kind of positive electrode active material powder may be used alone, or two or more kinds having different compositions or different powder physical properties may be used together in an arbitrary combination and ratio. When two or more active materials are used in combination, it is preferable to use the composite oxide containing lithium and manganese as a powder component. Cobalt and nickel are expensive metals with few resources, and large batteries that require high capacity such as for automobiles require a large amount of active material, which is not preferable in terms of cost. This is because it is desirable to use manganese as a main component as a transition metal.

(Conductive material)
Any known conductive material can be used as the conductive material. Specific examples include metal materials such as copper and nickel; 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. In addition, these may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

The content of the conductive material in the positive electrode active material layer is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 1% by mass or more, and preferably 50% by mass or less. is more preferably 30% by mass or less, and even more preferably 15% by mass or less. If the content is within the above range, sufficient electrical conductivity can be ensured. Furthermore, it is easy to prevent a decrease in battery capacity.

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

In the case of the coating method, the material is not particularly limited as long as it can be dissolved or dispersed in the liquid medium used during electrode production. Specific examples include polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, and cellulose. , resin-based polymers such as nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber; Styrene block copolymer or hydrogenated product thereof, EPDM (ethylene-propylene-diene terpolymer), styrene-ethylene-butadiene-ethylene copolymer, styrene-isoprene-styrene block copolymer or hydrogenated product thereof Thermoplastic elastomeric polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene/vinyl acetate copolymers, propylene/α-olefin copolymers and other soft resinous polymers; polyvinylidene fluoride Fluorinated polymers such as (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene/ethylene copolymer; polymer compositions having ion conductivity for alkali metal ions (especially lithium ions), etc. is mentioned. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

The content of the binder in the positive electrode active material layer is preferably 0.1% by mass or more, more preferably 1% by mass or more, still more preferably 3% by mass or more, and preferably 80% by mass or less, 60% by mass or less is more preferable, 40% by mass or less is even more preferable, and 10% by mass or less is particularly preferable. When the ratio of the binder is within the above range, the positive electrode active material can be sufficiently retained and the mechanical strength of the positive electrode can be ensured, resulting in good battery performance such as cycle characteristics. Furthermore, it leads to avoiding deterioration of battery capacity and conductivity.

(liquid medium)
The liquid medium used for preparing the slurry for forming the positive electrode active material layer is a solvent capable of dissolving or dispersing the positive electrode active material, the conductive material, the binder, and the thickening agent used as necessary. If so, the type thereof is not particularly limited, and either an aqueous solvent or an organic solvent may be used.

Examples of aqueous media include water, mixed media 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, methyl ethyl ketone and cyclohexanone. esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) and dimethylformamide , dimethylacetamide, and other amides; hexamethylphosphaamide, dimethylsulfoxide, and other aprotic polar solvents; In addition, these may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

(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 the slurry. Thickeners are commonly used to adjust the viscosity of slurries.
The thickening agent is not particularly limited as long as it does not significantly limit the effects of the present invention. Specific examples include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof. etc. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

When a thickener is used, the ratio of the thickener to the positive electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further 0.6% by mass or more. It is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less. When the ratio of the thickening agent is within the above range, the coatability becomes good, and further, the ratio of the active material in the positive electrode active material layer becomes sufficient, so the problem of the battery capacity decreasing and the positive electrode active material It becomes easier to avoid the problem of increased resistance between substances.

(consolidation)
The positive electrode active material layer obtained by applying the slurry to the current collector and drying it is preferably compacted by hand pressing, roller pressing, 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, particularly preferably 2 g·cm ⁻³ or more, and preferably 4 g·cm ⁻³ or less, 3.5 g·cm ⁻³ or less is more preferable, and 3 g·cm ⁻³ or less is particularly preferable. When the density of the positive electrode active material layer is within the above range, the permeability of the non-aqueous electrolytic solution to the vicinity of the current collector/active material interface does not decrease, and the charge/discharge characteristics are particularly good at high current densities. Become. Furthermore, the conductivity between the active materials is less likely to decrease, and the battery resistance is less likely to increase.

(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; and carbonaceous materials such as carbon cloth and carbon paper. Among them, metal materials, particularly aluminum, are preferred.

Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, foam metal, etc., in the case of metal materials, and carbon plate, A carbon thin film, a carbon cylinder, etc. are mentioned. Among these, metal thin films are preferred. Incidentally, the thin film may be appropriately formed in a mesh shape.
Although the thickness of the current collector is arbitrary, it is preferably 1 μm or more, more preferably 3 μm or more, still more preferably 5 μm or more, more preferably 1 mm or less, more preferably 100 μm or less, and further preferably 50 μm or less. preferable. When the thickness of the current collector is within the above range, the strength necessary for the current collector can be sufficiently secured. Furthermore, the handleability is also improved.

The thickness ratio of the current collector and the positive electrode active material layer is not particularly limited, but (thickness of active material layer on one side immediately before non-aqueous electrolyte injection) / (thickness of current collector) is preferably It is 150 or less, more preferably 20 or less, particularly preferably 10 or less, preferably 0.1 or more, more preferably 0.4 or more, and particularly preferably 1 or more. When the thickness ratio between the current collector and the positive electrode active material layer is within the above range, the current collector is less likely to generate heat due to Joule heat during charging and discharging at a high current density. Furthermore, it becomes difficult to increase the volume ratio of the current collector to the positive electrode active material, and a decrease in battery capacity can be prevented.

(electrode area)
From the viewpoint of high output and high temperature stability, the area of the positive electrode active material layer is preferably larger than the outer surface area of the battery outer case. Specifically, the total electrode area of the positive electrode is preferably 20 times or more, and more preferably 40 times or more, with respect to the surface area of the exterior of the non-aqueous electrolyte secondary battery. The outer surface area of the exterior case is the total area calculated from the length, width, and thickness of the case filled with the power generation element, excluding the protrusions of the terminals, in the case of a rectangular shape with a bottom. . In the case of a cylindrical shape with a bottom, it is the geometric surface area that approximates the case portion filled with the power generating element, excluding the projecting portion of the terminal, as a cylinder. The total electrode area of the positive electrode is the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material. , the sum of the areas calculated separately for each surface.

(discharge capacity)
When a non-aqueous electrolyte is used, the electrical capacity of the battery element contained in one battery exterior of the non-aqueous electrolyte secondary battery (the electrical capacity when the battery is discharged from a fully charged state to a discharged state) is When it is 1 ampere-hour (Ah) or more, the effect of improving low-temperature discharge characteristics is increased, which is preferable. Therefore, the positive electrode plate has a fully charged discharge capacity of preferably 3 Ah or more, more preferably 4 Ah or more, and preferably 100 Ah or less, more preferably 70 Ah or less, and particularly preferably 50 Ah or less. designed to When the electrical capacity of the battery element housed in one battery casing of the non-aqueous electrolyte secondary battery is within the above range, the voltage drop due to the electrode reaction resistance does not become too large when extracting a large current, and the electric power A deterioration in efficiency can be prevented. In addition, the temperature distribution due to the heat generated inside the battery during pulse charge/discharge does not become too large, and the durability of repeated charge/discharge is poor. phenomenon can be avoided.

(Thickness of positive electrode plate)
The thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity, high output, and high rate characteristics, the thickness of the positive electrode active material layer after subtracting the thickness of the current collector is is preferably 10 μm or more, more preferably 20 μm or more, and preferably 200 μm or less, more preferably 100 μm or less.

<2-5. Separator>
A separator is usually interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the separator is usually impregnated with the non-aqueous electrolytic solution.
There are no particular restrictions on the material and shape of the separator, and known materials can be arbitrarily adopted as long as they do not significantly impair the effects of the present invention. Among them, resins, glass fibers, inorganic substances, etc., which are made of materials that are stable with respect to non-aqueous electrolytes, are used, and it is preferable to use porous sheets or non-woven fabrics having excellent liquid retention properties.

As materials for the resin and glass fiber separators, for example, polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene, polyethersulfone, glass filters, and the like can be used. Among them, glass filters and polyolefins are preferred, and polyolefins are more preferred. One of these materials may be used alone, or two or more of them may be used in any combination and ratio.

Although the thickness of the separator is arbitrary, it 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 thinner than the above range, the insulating properties and mechanical strength may deteriorate. On the other hand, if the thickness is more than the above range, not only the battery performance such as rate characteristics may deteriorate, but also the energy density of the non-aqueous electrolyte secondary battery as a whole may deteriorate.

When a porous material such as a porous sheet or 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, and It is usually 90% or less, preferably 85% or less, more preferably 75% or less. If the porosity is too smaller than the above range, the film resistance tends to increase and the rate characteristics tend to deteriorate. On the other hand, when the thickness is too much larger than the above range, the mechanical strength of the separator tends to decrease and the insulation tends to decrease.

Although the average pore size of the separator is also arbitrary, it 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, short circuits tend to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.
On the other hand, as inorganic materials, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. things are used.

As for the form, thin films such as non-woven fabrics, woven fabrics and microporous films are used. In the form of a thin film, one having a pore size 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 can be used in which a composite porous layer containing the inorganic particles is formed on the surface of the positive electrode and/or the negative electrode using a resin binder. For example, a composite porous layer containing alumina particles with a 90% particle size of less than 1 μm is formed on both surfaces of the positive electrode using a fluororesin as a binder.

<2-6. Battery design>
[Electrode group]
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are sandwiched between the separators, and a structure in which the positive electrode plate and the negative electrode plate are spirally wound with the separator interposed therebetween. Anything is fine. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupancy) is usually 40% or more, preferably 50% or more, and usually 90% or less, and 80% or less. preferable. If the electrode group occupancy is below the above range, the battery capacity will be small. If the above range is exceeded, the void space is small, and the internal pressure rises due to the swelling of the members due to the high temperature of the battery and the increase in the vapor pressure of the liquid component of the electrolyte, and the repeated charging and discharging performance as a battery. In addition, the gas release valve that releases the internal pressure to the outside may operate.

[Current collection structure]
The current collection structure is not particularly limited, but in order to more effectively improve the discharge characteristics of the non-aqueous electrolytic solution, it is preferable to adopt a structure that reduces the resistance of the wiring portions and joint portions. When the internal resistance is reduced in this way, the effect of using the non-aqueous electrolytic solution is exhibited particularly well.

When the electrode group has the above-described laminated structure, a structure in which the metal core portions of the electrode layers are bundled and welded to a terminal is preferably used. When the area of one electrode increases, the internal resistance increases. Therefore, it is preferable to reduce the resistance by providing a plurality of terminals within the electrode. When the electrode group has the wound structure described above, the internal resistance can be reduced by providing a plurality of lead structures for each of the positive electrode and the negative electrode and bundling them around the terminal.

[Outer case]
The material of the exterior case is not particularly limited as long as it is stable with respect to the non-aqueous electrolytic solution used. Specifically, metals such as nickel-plated steel sheets, stainless steel, aluminum or aluminum alloys, and magnesium alloys, or laminate films of resin and aluminum foil are used. From the viewpoint of weight reduction, aluminum or aluminum alloy metals and laminate films are preferably used.

In the exterior case using the metals, the metals are welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed structure, or the metals are crimped through a resin gasket. There are things to do. Examples of the exterior case using the laminate film include those having a sealing and airtight structure by heat-sealing the resin layers to each other. A resin different from the resin used for the laminate film may be interposed between the resin layers in order to improve the sealing property. In particular, when the resin layer is heat-sealed through the current collector terminal to form a sealed structure, the metal and the resin are joined together. A resin is preferably used.

[Protection element]
As the protective element mentioned above, PTC (Positive Temperature Coefficient), which increases resistance when abnormal heat or excessive current flows, thermal fuse, thermistor, current flowing in the circuit due to sudden rise in battery internal pressure or internal temperature at abnormal heat and a valve (current cut-off valve) that cuts off the It is preferable to select the protective element under conditions that do not operate under normal high-current use, and from the viewpoint of high output, it is more preferable to design the protective element so that abnormal heat generation and thermal runaway do not occur even without the protective element.

[Exterior body]
A non-aqueous electrolyte secondary battery is generally configured by housing the above non-aqueous electrolyte, a negative electrode, a positive electrode, a separator, and the like in an exterior body. There is no restriction on this exterior body, and any known one can be employed as long as it does not significantly impair the effects of the present invention.
Specifically, although any material can be used for the exterior body, nickel-plated iron, stainless steel, aluminum or alloys thereof, nickel, titanium, or the like is usually used.

The shape of the exterior body is also arbitrary, and may be, for example, cylindrical, square, laminated, coin-shaped, large-sized, or the like.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded.
The compounds used in Examples and Comparative Examples are shown below. Table 2 shows the TPSA value of each compound.

<Examples 1-1 to 1-13, Comparative Examples 1-1 to 1-7>
[Preparation of positive electrode]
85% by mass of lithium-nickel-manganese-cobalt composite oxide (NMC) as a positive electrode active material, 10% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVDF) as a binder. Slurried in methylpyrrolidone solvent with disperser mixing. This was uniformly coated on both sides of an aluminum foil having a thickness of 21 μm, dried, and then pressed to form a positive electrode.

[Preparation of negative electrode]
50 g of Si fine particles with an average particle size of 0.2 μm are added to 2000 of scale-like graphite with an average particle size of 35 μm.
g, placed in a hybridization system (manufactured by Nara Machinery Co., Ltd.), and treated by circulating or staying in the apparatus at a rotor speed of 7000 rpm for 180 seconds to obtain a composite of Si and graphite particles. The obtained composite was mixed with coal tar pitch as an organic compound to be a carbonaceous material so that the coverage after firing was 7.5%, and kneaded and dispersed by a twin-screw kneader. The obtained dispersion was introduced into a firing furnace and fired at 1000° C. for 3 hours in a nitrogen atmosphere. The obtained baked product was further pulverized with a hammer mill and sieved (45 μm) to prepare a negative electrode active material. The content of elemental silicon, the average particle diameter d50, the tap density, and the specific surface area measured by the above measurement methods were 2.0% by mass, 20 μm, 1.0 g/cm ³ , and 7.2 m ² /g, respectively. .

An aqueous dispersion of sodium carboxymethylcellulose (concentration of sodium carboxymethylcellulose: 1% by mass) and an aqueous dispersion of styrene-butadiene rubber (concentration of styrene-butadiene rubber) were added to the negative electrode active material as thickeners and binders, respectively. 50% by mass) was added and mixed with a disperser to form a slurry. This slurry was uniformly coated on one side of a copper foil having a thickness of 10 μm, dried, and then pressed to form a negative electrode. The negative electrode after drying was prepared so that the mass ratio of negative electrode active material:sodium carboxymethylcellulose:styrene-butadiene rubber=97.5:1.5:1.

[Preparation of non-aqueous electrolytic solution]
In a dry argon atmosphere, a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (volumetric ratio 3:7) was added with 1.2 mol/L of sufficiently dried LiPF ₆ ( 2.0% by mass of vinylene carbonate (VC) was further added to the dissolved solution (in terms of concentration) (this is referred to as reference electrolyte solution 1). In Examples 1-1 to 1-13 and Comparative Examples 1-2 to 1-7, each compound 1 to 16 was added to the reference electrolytic solution 1 so that the content after adjustment was shown in Table 2 below. was added to prepare a non-aqueous electrolytic solution. However, Comparative Example 1-1 is the reference electrolytic solution 1 itself. In addition, the "content (% by mass)" in Table 2 is the concentration in 100% by mass of the non-aqueous electrolytic solution.

[Manufacture of non-aqueous electrolyte secondary battery]
A battery element was produced by stacking the positive electrode, the negative electrode, and the separator made of polyethylene in the order of the negative electrode, the separator, and the positive electrode. 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 and negative terminals, the electrolytic solution was injected into the bag and vacuumed. Sealing was performed, and a non-aqueous electrolyte secondary battery of a laminate type cell was produced.

<Evaluation of non-aqueous electrolyte secondary battery>
[High temperature cycle test]
In a constant temperature bath at 25° C., a laminated non-aqueous electrolyte secondary battery was charged to 4.0 V at a current corresponding to 0.05 C by constant current-constant voltage (CC-CV) charging. After that, it was discharged to 2.5V at 0.05C. Subsequently, after CC-CV charging to 4.0V at 0.2C, discharging to 2.5V at 0.2C, CC-CV charging to 4.2V at 0.2C, and then 2.5V at 0.2C. was discharged to stabilize the non-aqueous electrolyte secondary battery. After that, after CC-CV charging to 4.3 V at 0.2 C, initial conditioning was performed by discharging to 2.5 V at 0.2 C.

After the initial conditioning was completed, the thickness of the battery was measured using a micrometer (manufactured by Mitutoyo, model number: ID-C112XB), and then the cell was CC-CV charged to 4.2 V at 0.5 C in a constant temperature bath at 45 ° C. After that, 100 cycles were carried out, with the process of discharging to 2.5 V at a constant current of 0.5 C as one cycle. After that, the thickness of the battery was measured in the same manner as after the completion of the initial conditioning, and the change in the thickness of the battery due to the cycle charging and discharging was obtained. note that,
Table 2 below shows the rate of change in thickness of the battery in each example as "battery swelling" when the change in thickness of the battery in Comparative Example 1-1 is taken as 100. That is, when the "battery swelling" is less than 100, it indicates that the thickness change of the battery is small compared to Comparative Example 1-1, and when it exceeds 100, it indicates that the thickness change of the battery is large compared to Comparative Example 1-1. indicates FIG. 1 shows a graph plotting the experimental results in Table 2, with battery swelling on the vertical axis and TPSA on the horizontal axis.

As is clear from Table 2, the batteries manufactured in Examples 1-1 to 1-13 are more preferably prevented from swelling than the battery manufactured in Comparative Example 1-1. Recognize. In addition, when the TPSA value of the compound corresponding to the general formula (A) or (B) is not within the specific range (Comparative Examples 1-2 to 1-7), the effect of suppressing the swelling of the battery is ineffective. It turns out to be enough. From this, a negative electrode active material containing a compound represented by general formula (A) or (B) having a specific TPSA value, metal particles that can be alloyed with Li, and graphite particles can be combined. Therefore, swelling of the battery due to charging and discharging can be suitably suppressed.

According to the non-aqueous electrolyte solution according to the embodiment of the present invention, it is possible to improve the swelling of the battery due to repeated charging and discharging of the non-aqueous electrolyte secondary battery, and it is useful as a non-aqueous electrolyte solution for non-aqueous electrolyte secondary batteries. is.
Moreover, the non-aqueous electrolytic solution according to the embodiment of the present invention and the non-aqueous electrolytic solution secondary battery using the same can be used for various known applications using non-aqueous electrolytic solution secondary batteries. Specific examples include notebook computers, pen-input computers, mobile computers, e-book players, mobile phones, mobile faxes, mobile copiers, mobile printers, headphone stereos, video movies, liquid crystal televisions, handy cleaners, portable CDs, and minidiscs. , walkie-talkies, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game devices, clocks, power tools, strobes, cameras, household backups Power sources, business backup power sources, load leveling power sources, natural energy storage power sources, lithium ion capacitors, and the like.

Claims (7)

A non-aqueous electrolyte for a non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte is selected from the group consisting of a cyclic carbonate and a halogenated cyclic carbonate having a carbon-carbon unsaturated bond together with an electrolyte and a non-aqueous solvent. A non-aqueous electrolytic solution containing at least one compound and satisfying the following condition (i) or (ii).
Condition (i): The topological polar surface area (TPSA) value is greater than 0 square Angstroms and 45 square Angstroms or less, and contains at least one compound represented by the following general formula (A).

(In the compound having the structure represented by the general formula (A), R ¹ to R ⁴ are each independently a substituent other than F, provided that any substituent of R ¹ to R ⁴ is bonded may form a ring.)
Condition (ii): The TPSA value is 0 square angstroms, and at least one compound represented by the following general formula (B) is contained.

(In the compound having the structure represented by the general formula (B), R ⁵ to R ⁶ are each independently a substituent other than F, and n is an integer of 1 to 10.) The non-aqueous electrolytic solution according to claim 1, wherein the condition (i) is the following condition (iii).
Condition (iii): The topological polar surface area (TPSA) value is 10 square angstroms or more and 40 square angstroms or less, and at least one compound represented by the following general formula (A) is contained.

(In the compound having the structure represented by the general formula (A), R ¹ to R ⁴ are substituents other than F. However, optional substituents of R ¹ to R ⁴ are bonded to form a ring. may be formed). The non-aqueous electrolytic solution according to claim 2, wherein the compound represented by the general formula (A) is a compound represented by the following general formula (a).

(In the general formula (a), R ⁷ to R ⁹ are each independently a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a halogen atom, and in the hydrocarbon group, at least one carbon atom may be substituted with an oxygen atom, a nitrogen atom, or a sulfur atom, X is an alkylene group having 1 to 10 carbon atoms, and in the alkylene group, at least one carbon atom is an oxygen atom; It may be substituted with a nitrogen atom or a sulfur atom, and Y represents a structure selected from the group consisting of a cyano group, a thiol group and a group represented by the following general formula (1).)

(In general formula (1) above, R ^a represents a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a halogen atom.) The total content of the compound represented by the general formula (A) and the compound represented by (B) is 0.001 to 10% by mass with respect to the total amount of the non-aqueous electrolyte solution, claims 1 to 4. The non-aqueous electrolytic solution according to any one of 3. A non-aqueous electrolyte for a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte containing an electrolyte and a non-aqueous solvent together with a compound represented by the following general formula (c).

(In the general formula (c), R ¹ to R ³ are each independently a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a halogen atom, and in the hydrocarbon group, at least one carbon atom may be substituted with an oxygen atom, a nitrogen atom, or a sulfur atom, X is an alkylene group having 1 to 10 carbon atoms, and in the alkylene group, at least one carbon atom is an oxygen atom; It may be substituted with a nitrogen atom or a sulfur atom.) The non-aqueous electrolytic solution according to claim 5, wherein the content of the compound represented by the general formula (c) is 0.001 to 10% by mass with respect to the total amount of the non-aqueous electrolytic solution. A non-aqueous electrolyte secondary battery using the non-aqueous electrolyte according to any one of claims 1 to 6.

Images