JP2019040676A - Nonaqueous electrolytic solution and nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide a nonaqueous electrolytic solution which can largely improve a capacity retention rate and an input/output retention rate, and the swelling of a battery during endurance in comparison to those in the conventional art.SOLUTION: A nonaqueous electrolytic solution comprises: an electrolyte; and a nonaqueous solvent in which the electrolyte is dissolved. The nonaqueous electrolytic solution contains, as the electrolyte, lithium hexafluorophosphate and one or more second electrolytes selected from a group consisting of a lithium oxophosphate salt, a lithium salt containing a FSOgroup, and a lithium salt containing an oxalate complex. The nonaqueous electrolytic solution further contains a compound represented by the general formula (1) below. (In the general formula, each Rrepresents a saturated aliphatic hydrocarbon group coupled with an aromatic ring, of which the number of carbon atoms is one or more and six or less and in which at least one hydrogen atom is substituted with a fluorine atom. q represents the number of hydrocarbon groups coupled with the aromatic ring, which is an integer of 2 or more and 4 or less. R's may be identical to or different from each other in structure.)SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery. Specifically, lithium hexafluorophosphate (LiPF ₆ ), lithium oxophosphate, an FSO _2- group-containing lithium salt, and an oxalate complex-containing electrolyte are used as an electrolyte. The present invention relates to an electrolyte selected from the group consisting of lithium salts, a non-aqueous electrolyte containing an aromatic compound having a specific fluorinated alkyl group, and a non-aqueous electrolyte secondary battery using this non-aqueous electrolyte.

  Non-aqueous electrolyte secondary batteries, such as lithium secondary batteries, have been put to practical use in a wide range of applications, from consumer power sources such as mobile phones and laptop computers to in-vehicle power sources for automobiles and large power sources for stationary applications. ing. However, the demand for higher performance for non-aqueous electrolyte secondary batteries in recent years is increasing, and battery characteristics such as input / output characteristics, cycle characteristics, storage characteristics, continuous charge characteristics, safety, etc. It is required to achieve at a high level.

  Until now, as a means to improve the cycle characteristics of non-aqueous electrolyte secondary batteries, battery swelling during storage and continuous charging, and safety, various materials including positive and negative electrode active materials and non-aqueous electrolytes Numerous technologies have been studied for the components of such batteries.

  For example, in Patent Document 1 and Patent Document 2, in an organic electrolyte secondary battery having a positive electrode, a negative electrode, and an organic electrolyte as main components, the organic electrolyte contains a fluorine-containing aromatic compound. A technique capable of preventing a decrease in load characteristics accompanying an increase in discharge cycle is disclosed.

  Patent Document 3 discloses that a non-aqueous electrolyte secondary battery includes a positive electrode containing a nickel-containing lithium composite oxide and a non-aqueous electrolyte containing a fluorine atom-containing aromatic compound, thereby forming a nickel-containing lithium composite battery. In the case of using an oxide, a technique for giving good charge / discharge cycle characteristics even in a high temperature environment is disclosed.

  Patent Document 4 discloses that the non-aqueous solvent contains a cyclic carbonate having a carbon-carbon unsaturated bond in the molecule and a fluorine-containing aromatic compound having 9 or less carbon atoms, whereby discharge characteristics after continuous charging, A technique that can provide a non-aqueous electrolyte secondary battery that is excellent in load characteristics and cycle characteristics and generates a small amount of gas is disclosed.

Patent Document 5 discloses that the thickness of the battery is reduced by gas generation inside the battery by including LiPF ₆ and LiBF ₄ , a high-boiling organic solvent, vinylene carbonate, and an aromatic compound in the non-aqueous electrolyte solution. A technique capable of suppressing an increasing phenomenon is disclosed.

  Further, Patent Document 6 is one of the causes for increasing the heat generation rate by using a nonaqueous electrolytic solution comprising a nonaqueous solvent containing a specific fluorine-containing aromatic compound and an electrolyte. There has been disclosed a technique for obtaining an electrolyte solution that has a low reaction rate between the positive electrode and the electrolyte solution and is unlikely to cause thermal runaway.

  Patent Document 7 also discloses that the content of aminated benzenes contained as impurities in the non-aqueous solvent is less than 100 ppm when the non-aqueous solvent contains halogenated benzenes, so that A technique is disclosed that has a low rate of abnormal heat generation and that can provide high safety.

JP-A-10-112335 JP 2003-132950 A JP 2006-236981 A JP 2004-139963 A JP-A-2005-056841 JP 2000-106209 A JP 2005-243490 A

  As demands for higher performance of secondary batteries in recent years have increased, as described above, further improvements in lithium secondary battery performance, that is, capacity retention ratio and input / output maintenance ratio during durability such as during cycling and storage There is a demand for improvement of the battery and reduction of battery swelling.

  However, in the non-aqueous electrolyte battery using the electrolyte solution described in Patent Documents 1 to 7, it was difficult to say that the capacity retention rate, input / output maintenance rate, and battery swelling during durability were still sufficient.

  The reason for this is not fully understood at present, but is presumed as follows. That is, a fluorine-containing aromatic compound selected as a low-polarity and low-viscosity solvent is decomposed by a side reaction on the electrode surface during charge and discharge, and the side reaction product is deposited on the electrode surface to form a lithium ion electrode. It is assumed that the insertion / extraction reaction to the active material is inhibited. In addition, the side reaction product causes a new side reaction such as further decomposition of the electrolyte salt and the solvent, thereby reducing the charge / discharge capacity and input / output maintenance ratio during the cycle and after storage, and battery swelling. There is also a possibility that battery deterioration at the time of durability is accelerated.

  In addition, when there are many side reactions as described above, if the charge / discharge current value in the charge / discharge process after battery assembly is too large, the reduction reaction of the electrolyte solution on the negative electrode surface becomes non-uniform and is formed on the negative electrode surface. Variations in the amount of coating occur, so that a portion with a large amount of coating and a portion with a small amount of coating coexist on the negative electrode surface. Under such circumstances, the battery output is reduced due to the large resistance at locations where the coating amount is large. Further, since the deterioration is likely to occur from a place where the film is not properly formed, the deterioration is accelerated as compared with the case where the film is uniformly formed, and the durability may be lowered.

  In addition, the non-uniformity of the reduction reaction of the electrolyte solution on the negative electrode surface can also cause local gas generation and retention. When local gas stagnation occurs in this way, lithium ion insertion / desorption reaction cannot be performed between the electrolytic solution and the electrode at the location where the gas is accumulated, resulting in an increase in battery resistance. In addition, since a load is applied to a portion where gas is not accumulated, battery deterioration may be accelerated.

  The problems as described above are also strongly dependent on the battery design. Particularly in recent years, there is a strong demand for higher capacity of non-aqueous electrolyte batteries, and it has been studied to add as many active materials as possible in a limited battery volume. However, in a battery designed to increase the density by pressurizing the active material layer of the electrode, for example, the internal voids of the battery are reduced, and thus the problem caused by the nonuniformity of the film formation due to the shortening of the battery running-in process time Tend to be particularly evident.

  The present invention has been made in view of the background art, and its problem is that the capacity maintenance rate, input / output maintenance rate, and battery swelling during durability such as during cycle operation and storage at high temperatures are greatly increased compared to the prior art. An object of the present invention is to provide a non-aqueous electrolyte that can be improved.

As a result of intensive studies to solve the above problems, the present inventor has obtained a non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent for dissolving the electrolyte, lithium hexafluorophosphate and lithium oxophosphate as the electrolyte. Including at least one second electrolyte selected from the group consisting of a salt, an FSO ₂ group-containing lithium salt, and an oxalate complex-containing lithium salt, and further a compound of the following general formula (1) (hereinafter referred to as “compound of formula (1)”) , Which may be described as “compound (1)”), greatly improves the capacity, input / output characteristics and battery swelling during cycle operation and storage at high temperatures compared to the prior art. The headline and the present invention have been completed.


(However, R _f represents a saturated aliphatic hydrocarbon group having 1 to 6 carbon atoms bonded to an aromatic ring, and at least one hydrogen atom is substituted with a fluorine atom. Q is bonded to an aromatic ring. And represents an integer of 2 or more and 4. The structures of R _f may be the same or different.)

That is, the present invention provides specific embodiments shown in [1] to [8] below.
[1]
A non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent for dissolving the electrolyte, comprising lithium hexafluorophosphate, lithium oxophosphate, lithium salt containing FSO ₂ and lithium salt containing oxalate complex as the electrolyte A nonaqueous electrolytic solution comprising a second electrolyte selected from the group and further containing a compound of the following general formula (1).


(However, R _f represents a saturated aliphatic hydrocarbon group having 1 to 6 carbon atoms bonded to an aromatic ring, and at least one hydrogen atom is substituted with a fluorine atom. Q is bonded to an aromatic ring. The number of saturated aliphatic hydrocarbon groups is an integer of 2 or more and 4 or less, and the structures of R _f may be the same or different.
[2]
The non-aqueous electrolyte solution according to [1], wherein the second electrolyte contains lithium oxophosphate.
[3]
The non-aqueous electrolyte solution according to [1] or [2], wherein the second electrolyte contains a sulfonic acid lithium salt.
[4]
The non-aqueous electrolyte solution according to any one of [1] to [3], wherein the second electrolyte includes an oxalate complex-containing lithium salt.
[5]
The content of the compound of the general formula (1) is 0.01% by mass or more and 5% by mass or less with respect to the whole non-aqueous electrolyte solution. The non-aqueous electrolyte described.
[6]
In the compound of the general formula (1), R _f has 1 to 4 carbon atoms, and q is 2 to 3 in any one of [1] to [5] Non-aqueous electrolyte.
[7]
The non-aqueous electrolyte solution according to any one of [1] to [6], wherein the compound of the general formula (1) is 1,3-bis (trifluoromethyl) benzene.
[8]
The non-aqueous electrolyte solution according to any one of [1] to [6], wherein the compound of the general formula (1) is 1,4-bis (trifluoromethyl) benzene.
[9]
The nonaqueous electrolytic solution according to any one of [1] to [8], further comprising a carbonate having at least one of a carbon-carbon unsaturated bond and a fluorine atom.
[10]
The carbonate having at least one of the carbon-carbon unsaturated bond and the fluorine atom is at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, ethynyl ethylene carbonate, and fluoroethylene carbonate, [9] The nonaqueous electrolytic solution according to [9].
[11]
The non-aqueous electrolyte solution according to any one of [1] to [10], wherein the non-aqueous electrolyte solution contains at least one member selected from the group consisting of a cyclic carbonate, a chain carbonate, and a chain ester.
[12]
A non-aqueous electrolyte secondary battery comprising: a negative electrode and a positive electrode capable of inserting and extracting lithium ions; and the non-aqueous electrolyte solution according to any one of [1] to [11].
[13]
The negative electrode has a current collector and a negative electrode active material layer on the current collector, and the negative electrode active material layer includes a silicon simple metal, an alloy and a compound, a tin simple metal, an alloy and a compound, and a carbonaceous material. The nonaqueous electrolyte secondary battery according to [12], further comprising at least one selected from the group consisting of lithium titanium composite oxides.
[14]
The positive electrode has a current collector and a positive electrode active material layer on the current collector. The positive electrode active material layer includes a lithium / cobalt composite oxide, a lithium / cobalt / nickel composite oxide, and a lithium / manganese composite oxide. A lithium-cobalt-manganese composite oxide, a lithium-nickel composite oxide, a lithium-nickel-manganese composite oxide, and at least one selected from the group consisting of lithium-cobalt-nickel-manganese composite oxides The non-aqueous electrolyte secondary battery according to [12] or [13].
[15]
The positive electrode has a current collector and a positive electrode active material layer on the current collector, and the positive electrode active material layer is made of LixMPO ₄ (M is a transition metal of group 4 to group 11 of the fourth period of the periodic table). The non-aqueous electrolyte secondary battery according to [12] or [13], comprising at least one element selected from the group consisting of x and 0 <x <1.2).

The inventor of the present invention has developed a non-aqueous electrolyte secondary battery in order to develop a new non-aqueous electrolyte that significantly improves the capacity and input / output characteristics and battery swelling during cycle operation and storage compared to the prior art. Focusing on the formation mechanism and elementary reaction rate of the negative electrode film, various studies were conducted on the effects of various compounds and their combinations.

As a result, the present inventor comprises, in addition to lithium hexafluorophosphate, as a second electrolyte, a lithium oxophosphate, a FSO ₂ group-containing lithium salt, and an oxalate complex-containing lithium salt in a non-aqueous electrolyte solution. One or more selected from the group, and a compound of the general formula (1);


(However, R _f represents a saturated aliphatic hydrocarbon group having 1 to 6 carbon atoms bonded to an aromatic ring, which contains a fluorine atom and may contain a hydrogen atom. Two hydrogen atoms are substituted with fluorine atoms, q represents the number of substituents bonded to the aromatic ring, and is an integer of 2 or more and 4 or less, and the structures of R _f may be the same or different. Good.)
By incorporating one or more types, a technology has been established that significantly improves the capacity, input / output characteristics, and battery swelling during cycle operation and storage at high temperatures compared to the prior art.

  Regarding the effect of the fluorine atom-containing aromatic compound including the compound of the formula (1), for example, in Patent Document 3, the positive electrode active material is a basic metal oxide, but the fluorine atom-containing content in the non-aqueous electrolyte solution Since the aromatic ring of the aromatic compound has a low electron density on the aromatic ring due to the strong electron attractive force of fluorine, it is attracted to the oxygen atom of the metal oxide and adsorbs on the surface of the positive electrode active material to form a film. There is a description that a side reaction between the non-aqueous electrolyte and the positive electrode active material is suppressed.

  However, in addition to the oxidation-reactive positive electrode, a reduction-reactive negative electrode coexists in the battery, and it is necessary to control the reduction reactivity on the negative electrode in order to obtain high battery characteristics. Fluorine atom-containing aromatic compound is a non-aqueous electrolyte and a positive electrode active material by desorbing fluorine atoms under a negative potential to form lithium fluoride (LiF) with lithium ions in the electrolyte and fixing it on the negative electrode surface. It is estimated that the side reaction with is suppressed.

However, when the number of fluorine atoms contained in one compound molecule is large, the production efficiency of LiF becomes too high. LiF essentially has very low lithium ion conductivity, and may also inhibit the lithium ion insertion / extraction reaction between the negative electrode and the non-aqueous electrolyte. Therefore, the inventor verified the inhibitory factor by changing the functional group structure in various ways, and the compound of general formula (1) and lithium oxophosphate, FSO ₂ group-containing lithium salt as an electrolyte other than lithium hexafluorophosphate And a film formed by the second electrolyte other than lithium hexafluorophosphate is stabilized by the interaction between ions by containing at least one second electrolyte selected from the group consisting of lithium salts containing oxalate complexes. As a result, a technology was developed to improve the lithium ion conductivity of the coating and to improve the stability of the coating against thermal elution and decomposition. At the same time, this technique contributes to uniformizing the film formation reaction over the entire electrode. As a result, a side reaction between the negative electrode and the nonaqueous electrolytic solution can be suppressed, and the inhibition of the lithium ion insertion / extraction reaction can be minimized, and the present invention has been completed. Due to this effect, it is presumed that the durability of the battery is dramatically improved and the process time dependence of the battery running-in operation is lowered as compared with the conventional battery in which the film is not uniformly formed.

  According to the present invention, there is provided a non-aqueous electrolyte solution capable of realizing a non-aqueous electrolyte secondary battery with greatly improved capacity retention rate, input / output maintenance rate, and battery swelling during durability such as cycle operation and high-temperature storage. be able to. Further, according to a preferred embodiment of the present invention, not only the input / output characteristics, but also the impedance characteristics and charge / discharge rate characteristics, etc., and further, the non-aqueous system is excellent in cycle characteristics, high-temperature storage characteristics, continuous charge characteristics, safety, etc. It is possible to provide a non-aqueous electrolyte that can realize an electrolyte secondary battery. Moreover, the non-aqueous electrolyte secondary battery using this non-aqueous electrolyte can be provided.

  Hereinafter, embodiments of the present invention will be described in detail. The following embodiments are examples (representative examples) of the embodiments of the present invention, and the present invention is not limited to these. In addition, the present invention can be implemented with any modifications without departing from the scope of the invention.

<1. Non-aqueous electrolyte>
<1-1. Specific electrolyte>
The non-aqueous electrolyte solution according to one embodiment of the present invention is other than lithium hexafluorophosphate (hereinafter sometimes referred to as “LiPF ₆ ”, “lithium hexafluorophosphate”, etc.) and lithium hexafluorophosphate. 1 or more selected from the group consisting of the following electrolytes (hereinafter sometimes referred to as “second electrolyte”).

<1-1-1. LiPF ₆ >
In the non-aqueous electrolyte solution according to one embodiment of the present invention, LiPF ₆ is used. The content of LiPF ₆ in the nonaqueous electrolytic solution is not particularly limited as long as the effects of the present invention are not significantly impaired. Specifically, the lower limit of the molar content of LiPF ₆ is preferably 0.5 mol / L or more, more preferably 0.6 mol / L or more, and 0.7 mol / L or more. More preferably. Moreover, as an upper limit, it is preferable that it is 3.0 mol / L or less, It is more preferable that it is 2.0 mol / L or less, It is especially preferable that it is 1.5 mol / L or less. The concentration range of LiPF ₆ is preferably 0.5 mol / L or more and 3.0 mol / L or less, more preferably 0.5 mol / L or more and 2.0 mol / L or less, and 0.5 mol / L or less. More preferably, it is L or more and 1.5 mol / L or less.

If the concentration of LiPF ₆ is within the above preferred range, the total ion content in the non-aqueous electrolyte and the viscosity of the electrolyte are in an appropriate balance. It becomes low and the improvement effect of the cycle characteristic and input-output characteristic by the mixing | blending of LiPF ₆ becomes still easier to be expressed.

<1-1-2. Second electrolyte>
In the non-aqueous electrolyte solution according to one embodiment of the present invention, one or more selected from the group consisting of lithium oxophosphate, FSO ₂ group-containing lithium salt, and oxalate complex-containing lithium salt is used as the second electrolyte.
Examples of the lithium oxophosphate include LiPO _a F _4-a (a is 2 or 3).
Examples of the FSO ₂ group-containing lithium salt include FSO ₃ Li, (FSO ₂ ) ₂ NLi, (FSO ₂ ) (C _b F _{2b + 1} SO ₂ ) NLi (b is an integer of 1 to 3), and the like.
Examples of the oxalate complex-containing lithium salt include LiBF _4-2c (C ₂ O ₄ ) _c (c is an integer from 0 to 2), LiPF _6-2d (C ₂ O ₄ ) _d (d is an integer from 1 to 3), etc. Is mentioned.
A 2nd electrolyte can be used individually by 1 type or in combination of 2 or more types.

As a specific example of the second electrolyte,
Examples of the lithium oxophosphate include LiPO ₂ F ₂ and LiPO ₃ F;
As the FSO ₂ group-containing lithium salt, FSO ₃ Li, (FSO ₂ ) ₂ NLi, LiN (FCO ₂ ) (SO ₂ F), (FSO ₂ ) (CF ₃ SO ₂ ) NLi, (FSO ₂ ) (C _{2 F 5 SO 2) NLi, (} FSO 2) (C 4 F 9 SO 2) NLi;
Examples of oxalate complex-containing lithium salts include boron-containing oxalate salts such as lithium difluorobis (oxalate) borate and lithium bis (oxalate) borate; lithium tetrafluorooxalate phosphate, lithium difluorobis (oxalate) phosphate, lithium tris (oxalate) ) Phosphorus-containing oxalate salts such as phosphate.

When lithium oxophosphate is used as the second electrolyte, the interaction between ions in the film is relatively strong, so the lithium ion conductivity of the film is slightly improved while greatly improving the stability of the film against thermal elution and decomposition. Can be improved.
When the FSO _2- group-containing lithium salt is used as the second electrolyte, the ion-ion interaction in the coating works weakly, so that the lithium ion conductivity of the coating is greatly improved and the stability against thermal elution and decomposition of the coating is improved. It can be slightly improved.
When a lithium salt containing an oxalate complex is used as the second electrolyte, the ion-to-ion interaction in the coating works very strongly, so the stability of the coating against thermal elution and decomposition is not significantly impaired without impairing the lithium ion conductivity of the coating. Can be improved.

Among these, LiPO ₂ F ₂ , FSO ₃ Li, lithium difluoro (oxalate) borate, lithium bis (oxalate) borate _, lithium tetrafluorooxalate phosphate, lithium difluorobis (oxalate) phosphate, lithium tris (oxalate) phosphate By using Fate and LiN (SO ₂ F) ₂ , the effects of improving the initial input / output, the high rate charge / discharge characteristics, the output after storage at high temperature and after the cycle are further easily expressed.

Among these, LiPO ₂ F ₂ , FSO ₃ Li, lithium difluoro (oxalate) borate, lithium bis (oxalate) borate _, lithium difluorobis (oxalate) phosphate, and LiN (SO ₂ F) ₂ are represented by the general formula (1) The effect of alleviating the non-uniformity of the negative electrode coating film of the non-aqueous electrolyte solution using the compound (1) is particularly preferable.

Here, the preparation of the electrolytic solution when LiPO ₂ F ₂ or LiPO ₃ F is contained in the electrolytic solution may be performed by a known method, and is not particularly limited. For example, LiPO ₂ F ₂ or LiPO ₃ F synthesized separately by a known method is added to an electrolytic solution containing LiPF ₆ or water is allowed to coexist in battery components such as an active material and an electrode plate described later. In addition, there is a method of generating LiPO ₂ F ₂ or LiPO ₃ F in the system when assembling a battery using an electrolytic solution containing LiPF ₆ . Any method may be used in the present invention.
The method for measuring the content of the oxofluorophosphate in the non-aqueous electrolyte solution and the non-aqueous electrolyte battery is not particularly limited, and any known method can be used. Specific examples include ion chromatography and ¹⁹ F nuclear magnetic resonance spectroscopy (hereinafter sometimes referred to as “NMR”).

  When the concentration of the second electrolyte is within the above-mentioned preferable range, the effect of improving the initial input / output characteristics, the capacity and output after storage at high temperature and after cycling is further easily exhibited.

In addition to lithium hexafluorophosphate and the second electrolyte, other electrolytes can be added to the nonaqueous electrolytic solution as long as the effects of the present invention are not impaired. Examples of other electrolytes include the following.
For example, inorganic salts such as LiBF ₄ , LiClO ₄ , LiAlF ₄ , LiSbF ₆ , LiTaF ₆ , LiWOF ₅ , LiWF ₇ ;
HCO ₂ Li, CH ₃ CO ₂ Li, CH ₂ FCO ₂ Li, CHF ₂ CO ₂ Li, CF ₃ CO ₂ Li, CF ₃ CH ₂ CO ₂ Li, CF ₃ CF ₂ CO ₂ Li, CF ₃ CF ₂ CF ₂ Carboxylates such as CO ₂ Li, CF ₃ CF ₂ CF ₂ CF ₂ CO ₂ Li;
_{FSO 3 Na, FSO 3 K,} FSO 3 (n-C 2 H 5) 4 N, FSO 3 (n-C 4 H 9) 4 N, CH 3 SO 3 Li, CH 3 OSO 3 Li, CH 2 FSO 3 Sulfonates such as Li, CHF ₂ SO ₃ Li, CH ₃ SO ₃ Na, CH ₃ SO ₃ K, CH ₃ H ₂ SO ₃ Li, CH ₃ H ₂ OSO ₃ Li;
Lithium methyl sulfate, lithium ethyl sulfate, 2-propynyl lithium, 1-methyl-2-propynyl sulfate, 1,1-dimethyl-2-propynyl sulfate, 2,2,2-trifluoroethyl lithium sulfate, dilithium Sulfates such as ethylene disulfate;
NaN (FCO ₂ ) ₂ , KN (FCO ₂ ) ₂ , LiN (CF ₃ CO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiN Imide salts such as (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ ;
A methide salt such as LiC (SO ₂ F) ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ ;
LiBF ₃ CF ₃ , LiBF ₃ C ₂ F ₅ , LiBF ₃ C ₃ F ₇ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ ( Organoborates such as C ₂ F ₅ SO ₂ ) ₂ ;
However, it is not particularly limited to these, and one kind can be used alone or two or more kinds can be used in combination.

Among _{these, LiBF 4, LiSbF 6, LiTaF} 6, LiWOF 5, LiWF 7, FSO 3 Na, FSO 3 K, FSO 3 (n-C 2 H 5) 4 N, FSO 3 (n-C 4 H 9) ₄ N, lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonylimide, LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) _{2 and the} like However, it is preferable from the viewpoint of the effect of improving input / output characteristics, high-rate charge / discharge characteristics, high-temperature storage characteristics, cycle characteristics, and the like.

The total concentration of all the electrolytes described above, that is, LiPF ₆ , the second electrolyte, and other electrolytes in the nonaqueous electrolytic solution is not particularly limited, but is usually 8% by mass or more, preferably 8.5% by mass. As mentioned above, More preferably, it is 9 mass% or more. Moreover, the upper limit is 18 mass% or less normally, Preferably it is 17 mass% or less, More preferably, it is 16 mass% or less. It is preferable for the total concentration of the electrolyte to be within the above range because the electric conductivity is appropriate for battery operation.

  The content of the second electrolyte is not particularly limited as long as the effects of the present invention are not significantly impaired. Specifically, the lower limit of the content of the second electrolyte is preferably 0.01% by mass or more and 0.05% by mass or more based on the total amount of the non-aqueous electrolyte solution. Is more preferable, and it is further more preferable that it is 0.1 mass% or more. Further, the upper limit is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2.5% by mass or less, based on the total amount of the non-aqueous electrolyte solution. 2% by mass or less is particularly preferable.

The content of other electrolytes is not particularly limited as long as the effects of the present invention are not significantly impaired. Specifically, the lower limit of the other electrolyte content is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, based on the total amount of the non-aqueous electrolyte solution. More preferably, the content is 0.1% by mass or more. Further, the upper limit is preferably 3% by mass or less, more preferably 2.5% by mass or less, still more preferably 2% by mass or less, based on the total amount of the nonaqueous electrolyte solution. It is particularly preferably 1.5% by mass or less.

<2. Compound of general formula (1)>
The non-aqueous electrolyte solution of the present invention contains one or more selected from the group consisting of the compound of general formula (1).

(However, R _f represents a saturated aliphatic hydrocarbon group having 1 to 6 carbon atoms bonded to an aromatic ring, and at least one hydrogen atom is substituted with a fluorine atom. Q is bonded to an aromatic ring. The number of saturated aliphatic hydrocarbon groups is an integer of 2 or more and 4 or less, and the structures of R _f may be the same or different.

  In the general formula (1), q is an integer of 2 or more, 4 or less, more preferably 2 or more and 3 or less, and even more preferably 2. By setting it as this range, the solubility to electrolyte solution improves and a film can be uniformly formed in the electrode surface.

Specific examples of preferred fluorine-containing saturated aliphatic hydrocarbon groups as R _f include —CH ₂ F, —CHF ₂ , —CF ₃ , —CH ₂ CF ₃ , —CF ₂ CF ₃ , —CH _{2. CF 2 CF 3, -CF 2 CF} 2 CF 3, -CH (CF 3) 2, -CF 2 CF 3 CF 2 CF 2, - (CF 3) 3 C, -CH 2 CF 2 CF 2 CF 3, - _{C (CF 3) 2 (CH} 3), - CF 2 CF 2 CF 2 CF 2 CF 3, etc. _{-CF 2 CF 2 CF 2 CF 2} CF 2 CF 3 and the like.

  Further, the molecular weight of the compound of the general formula (1) is preferably 170 or more, more preferably 190 or more, still more preferably 210 or more, and preferably 1000 or less, more preferably 500 or less. Yes, more preferably 400 or less. If it is this range, the solubility to electrolyte solution will improve and a film can be uniformly formed in the electrode surface.

Specific examples of the compound of the general formula (1) include the following.
1,2-bis (trifluoromethyl) benzene, 1-trifluoromethyl-2-difluoromethylbenzene, 1-trifluoromethyl-2-fluoromethylbenzene, 1,2-bis (difluoromethyl) benzene, 1-difluoro Methyl-2-fluoromethylbenzene, 1,2-bis (fluoromethyl) benzene,
1,3-bis (trifluoromethyl) benzene, 1-trifluoromethyl-3-difluoromethylbenzene, 1-trifluoromethyl-3-fluoromethylbenzene, 1,3-bis (difluoromethyl) benzene, 1-difluoro Methyl-3-fluoromethylbenzene, 1,3-bis (fluoromethyl) benzene,
1,4-bis (trifluoromethyl) benzene, 1-trifluoromethyl-4-difluoromethylbenzene, 1-trifluoromethyl-4-fluoromethylbenzene, 1,4-bis (difluoromethyl) benzene, 1-difluoro Methyl-4-fluoromethylbenzene, 1,4-bis (fluoromethyl) benzene,
1,4-bis (trifluoromethyl) benzene, 1-trifluoromethyl-4-difluoromethylbenzene, 1-trifluoromethyl-4-fluoromethylbenzene, 1,4-bis (difluoromethyl) benzene, 1-difluoro Methyl-4-fluoromethylbenzene, 1,4-bis (fluoromethyl) benzene,
1,3,5-tris (trifluoromethyl) benzene, 1,3,5-tris (difluoromethyl) benzene, 1,3,5-tris (fluoromethyl) benzene, 1,2,4,5-tetrakis ( Trifluoromethyl) benzene, 1,2,4,5-tetrakis (difluoromethyl) benzene, 1,2,4,5-tetrakis (fluoromethyl) benzene,
1,2-bis (pentafluoroethyl) benzene, 1,2-bis (trifluoroethyl) benzene, 1,3-bis (pentafluoroethyl) benzene, 1,3-bis (trifluoroethyl) benzene, 1, 4-bis (pentafluoroethyl) benzene, 1,4-bis (trifluoroethyl) benzene, 1,3,5-tris (pentafluoroethyl) benzene, 1,3,5-tris (trifluoroethyl) benzene, 1,2,4,5-tetrakis (pentafluoroethyl) benzene, 1,2,4,5-tetrakis (trifluoroethyl) benzene,
1,2-bis (octafluorofluoro-n-propyl) benzene, 1,2-bis (hexafluoroisopropyl) benzene, 1,3-bis (octafluoro-n-propyl) benzene, 1,3-bis (hexa) Fluoroisopropyl) benzene, 1,4-bis (octafluorofluoro-n-propyl) benzene, 1,4-bis (hexafluoroisopropyl) benzene, 1,3,5-tris (octafluorofluoro-n-propyl) benzene 1,3,5-tris (hexafluoroisopropyl) benzene, 1,2,4,5-tetrakis (octafluorofluoro-n-propyl) benzene,
1,2-bis (nonafluoro-n-butyl) benzene, 1,2-bis (nonafluoro-tert-butyl) benzene, 1,3-bis (nonafluoro-n-butyl) benzene, 1,3-bis (nonafluoro- tert-butyl) benzene, 1,4-bis (nonafluoro-n-butyl) benzene, 1,4-bis (nonafluoro-tert-butyl) benzene, 1,3,5-tris (nonafluoro-n-butyl) benzene, 1,2,4,5-tetrakis (nonafluoro-n-butyl) benzene,
1,2-bis (undecafluoro-n-pentyl) benzene, 1,3-bis (undecafluoro-n-pentyl) benzene, 1,4-bis (undecafluoro-n-pentyl) benzene, 1, 3,5-tris (undecafluoro-n-pentyl) benzene, 1,2,4,5-tetrakis (undecafluoro-n-pentyl) benzene,
1,2-bis (tridecafluoro-n-hexyl) benzene, 1,3-bis (tridecafluoro-n-hexyl) benzene, 1,4-bis (tridecafluoro-n-hexyl) benzene, 1, 3,5-tris (tridecafluoro-n-hexyl) benzene, 1,2,4,5-tetrakis (tridecafluoro-n-hexyl) benzene.

Among these,
1,2-bis (trifluoromethyl) benzene, 1-trifluoromethyl-2-difluoromethylbenzene, 1-trifluoromethyl-2-fluoromethylbenzene, 1,2-bis (difluoromethyl) benzene, 1-difluoro Methyl-2-fluoromethylbenzene, 1,2-bis (fluoromethyl) benzene,
1,3-bis (trifluoromethyl) benzene, 1-trifluoromethyl-3-difluoromethylbenzene, 1-trifluoromethyl-3-fluoromethylbenzene, 1,3-bis (difluoromethyl) benzene, 1-difluoro Methyl-3-fluoromethylbenzene, 1,3-bis (fluoromethyl) benzene,
1,4-bis (trifluoromethyl) benzene, 1-trifluoromethyl-4-difluoromethylbenzene, 1-trifluoromethyl-4-fluoromethylbenzene, 1,4-bis (difluoromethyl) benzene, 1-difluoro Methyl-4-fluoromethylbenzene, 1,4-bis (fluoromethyl) benzene,
1,4-bis (trifluoromethyl) benzene, 1-trifluoromethyl-4-difluoromethylbenzene, 1-trifluoromethyl-4-fluoromethylbenzene, 1,4-bis (difluoromethyl) benzene, 1-difluoro Methyl-4-fluoromethylbenzene, 1,4-bis (fluoromethyl) benzene,
1,3,5-tris (trifluoromethyl) benzene, 1,3,5-tris (difluoromethyl) benzene, 1,3,5-tris (fluoromethyl) benzene, 1,2,4,5-tetrakis ( Trifluoromethyl) benzene, 1,2,4,5-tetrakis (difluoromethyl) benzene, 1,2,4,5-tetrakis (fluoromethyl) benzene,
1,2-bis (pentafluoroethyl) benzene, 1,3-bis (pentafluoroethyl) benzene, 1,4-bis (pentafluoroethyl) benzene, 1,3,5-tris (pentafluoroethyl) benzene,
1,2-bis (octafluorofluoro-n-propyl) benzene, 1,3-bis (octafluoro-n-propyl) benzene, 1,4-bis (octafluorofluoro-n-propyl) benzene, 1,3 , 5-tris (octafluorofluoro-n-propyl) benzene,
1,2-bis (nonafluoro-n-butyl) benzene, 1,3-bis (nonafluoro-n-butyl) benzene, 1,4-bis (nonafluoro-n-butyl) benzene, 1,3,5-tris ( Nonafluoro-n-butyl) benzene,
1,2-bis (undecafluoro-n-pentyl) benzene, 1,3-bis (undecafluoro-n-pentyl) benzene, 1,4-bis (undecafluoro-n-pentyl) benzene,
1,2-bis (tridecafluoro-n-hexyl) benzene, 1,3-bis (tridecafluoro-n-hexyl) benzene, 1,4-bis (tridecafluoro-n-hexyl) benzene and the like are electrolyzed. It is preferable from the viewpoint of ensuring solubility in the liquid.

Among these,
1,2-bis (trifluoromethyl) benzene, 1-trifluoromethyl-2-difluoromethylbenzene, 1,3-bis (trifluoromethyl) benzene, 1-trifluoromethyl-3-difluoromethylbenzene, 1, 4-bis (trifluoromethyl) benzene, 1-trifluoromethyl-4-difluoromethylbenzene, 1,3,5-tris (trifluoromethyl) benzene, 1,2-bis (pentafluoroethyl) benzene, 1, 3-bis (pentafluoroethyl) benzene, 1,4-bis (pentafluoroethyl) benzene, 1,2-bis (octafluorofluoro-n-propyl) benzene, 1,3-bis (octafluoro-n-propyl) ) Benzene, 1,4-bis (octafluorofluoro-n-propyl) benzene, 1,2 Bis (nonafluoro-n-butyl) benzene, 1,3-bis (nonafluoro-n-butyl) benzene, 1,4-bis (nonafluoro-n-butyl) benzene, 1,2-bis (undecafluoro-n- Pentyl) benzene, 1,3-bis (undecafluoro-n-pentyl) benzene, 1,4-bis (undecafluoro-n-pentyl) benzene, 1,2-bis (tridecafluoro-n-hexyl) Benzene, 1,3-bis (tridecafluoro-n-hexyl) benzene, 1,4-bis (tridecafluoro-n-hexyl) benzene, etc. improve the permeability of the electrolyte solution to the electrode to form a coating. From the viewpoint of uniform formation, it is more preferable.

Among these,
1,2-bis (trifluoromethyl) benzene, 1-trifluoromethyl-2-difluoromethylbenzene, 1,3-bis (trifluoromethyl) benzene, 1-trifluoromethyl-3-difluoromethylbenzene, 1, 4-bis (trifluoromethyl) benzene, 1-trifluoromethyl-4-difluoromethylbenzene, 1,3,5-tris (trifluoromethyl) benzene, etc. It is more preferable because durability such as input / output characteristics can be further improved and battery swelling can be further reduced.

  The compound of General formula (1) may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. Moreover, content in particular of the compound of General formula (1) is not restrict | limited, As long as the effect of this invention is not impaired remarkably, it is arbitrary. The content of the compound of the general formula (1) is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more in 100% by mass of the non-aqueous electrolyte solution. More preferably 0.3% by mass or more, and usually 5% by mass or less, preferably 4% by mass or less, more preferably 3% by mass or less, and further preferably 2% by mass or less. . Within the above range, durability such as cycle capacity, storage capacity and input / output characteristics can be further improved, and battery swelling can be further reduced, which is preferable.

<1-3. Nonaqueous solvent>
The non-aqueous electrolyte solution according to one embodiment of the present invention usually contains a non-aqueous solvent that dissolves the above-described electrolyte as a main component, like a general non-aqueous electrolyte solution. There is no restriction | limiting in particular about the nonaqueous solvent used here, A well-known organic solvent can be used. Examples of the organic solvent include saturated cyclic carbonates, chain carbonates, chain carboxylic acid esters, cyclic carboxylic acid esters, ether compounds, and sulfone compounds, but are not particularly limited thereto. These can be used alone or in combination of two or more.
Moreover, in one Embodiment of this invention, it is preferable that a non-aqueous electrolyte solution contains 1 or more types from the group which consists of cyclic carbonate, chain carbonate, and chain ester.

<1-3-1. Saturated cyclic carbonate>
Examples of the saturated cyclic carbonate include those having an alkylene group having 2 to 4 carbon atoms.

  Specifically, examples of the saturated cyclic carbonate having 2 to 4 carbon atoms include ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate and propylene carbonate are preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation. A saturated cyclic carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The content of the saturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. However, the lower limit of the content when used alone is usually 100% by volume of the non-aqueous solvent. It is 3% by volume or more, preferably 5% by volume or more. By setting this range, the decrease in electrical conductivity resulting from the decrease in the dielectric constant of the non-aqueous electrolyte is avoided, and the large current discharge characteristics, negative electrode stability, and cycle characteristics of the non-aqueous electrolyte secondary battery are good. It becomes easy to be in a range. Moreover, an upper limit is 90 volume% or less normally, Preferably it is 85 volume% or less, More preferably, it is 80 volume% or less. By setting this range, the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, the decrease in ionic conductivity is suppressed, and the input / output characteristics of the non-aqueous electrolyte secondary battery are further improved. Durability such as characteristics can be further improved, which is preferable.

Moreover, a saturated cyclic carbonate can also be used in arbitrary combinations of 2 or more types. One preferred combination is a combination of ethylene carbonate and propylene carbonate. In this case, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99: 1 to 40:60, and more preferably 95: 5 to 50:50. Furthermore, the lower limit of the amount of propylene carbonate in the entire non-aqueous solvent is usually 1% by volume or more, preferably 2% by volume or more, more preferably 3% by volume or more. Moreover, the upper limit is 30 volume% or less normally, Preferably it is 25 volume% or less, More preferably, it is 20 volume% or less. When propylene carbonate is contained within this range, the low temperature characteristics are further excellent, which is preferable.

<1-3-2. Chain carbonate>
As a chain carbonate, a C3-C7 thing is preferable.

  Specifically, as the chain carbonate having 3 to 7 carbon atoms, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, Examples include 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.

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

  Further, chain carbonates having a fluorine atom (hereinafter sometimes abbreviated as “fluorinated chain carbonate”) can also be suitably used. The number of fluorine atoms contained in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon or may be bonded to different carbons. Examples of the fluorinated chain carbonate include a fluorinated dimethyl carbonate derivative, a fluorinated ethyl methyl carbonate derivative, and a fluorinated diethyl carbonate derivative.

  Examples of the fluorinated dimethyl carbonate derivative include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl 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-trimethyl Examples include fluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, and ethyl trifluoromethyl carbonate.

  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, Examples include 2-trifluoroethyl-2 ′, 2′-difluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, and the like.

  A chain carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The 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 in 100% by volume of the nonaqueous solvent. Moreover, it is 90 volume% or less normally, Preferably it is 85 volume% or less, More preferably, it is 80 volume% or less. By setting the content of the chain carbonate within the above range, the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, and the decrease in ionic conductivity is suppressed. As a result, the input / output characteristics and charge / discharge of the non-aqueous electrolyte secondary battery are reduced. It becomes easy to make rate characteristics into a favorable range. In addition, a decrease in electrical conductivity due to a decrease in dielectric constant of the non-aqueous electrolyte solution can be avoided, and the input / output characteristics and charge / discharge rate characteristics of the non-aqueous electrolyte secondary battery can be easily set in a favorable range.

  Furthermore, battery performance can be remarkably improved by combining ethylene carbonate with a specific content with respect to a specific chain carbonate.

  For example, when dimethyl 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 the effects of the present invention are not significantly impaired. , Preferably 20% by volume, usually 45% by volume or less, preferably 40% by volume or less, and the content of dimethyl carbonate is usually 20% by volume or more, preferably 30% by volume or more, and usually 50% by volume or less, Preferably it is 45 volume% or less, and the content of ethyl methyl carbonate is usually 20 volume% or more, preferably 30 volume% or more, and usually 50 volume% or less, preferably 45 volume% or less. By setting the content within the above range, the viscosity of the nonaqueous electrolytic solution is lowered while the low-temperature deposition temperature of the electrolyte is lowered, and the ionic conductivity is improved, and high input / output can be obtained even at a low temperature.

<1-3-3. Chain carboxylic acid ester>
Examples of the chain carboxylic acid ester include those having 3 to 7 carbon atoms in the structural formula.

  Specifically, methyl acetate, ethyl acetate, acetic acid-n-propyl, isopropyl acetate, acetic acid-n-butyl, isobutyl acetate, acetic acid-t-butyl, methyl propionate, ethyl propionate, propionate-n-propyl, Isopropyl propionate, n-butyl propionate, isobutyl propionate, t-butyl propionate, methyl butyrate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, methyl isobutyrate, ethyl isobutyrate, isobutyric acid-n- Examples include propyl and isopropyl isobutyrate.

  Among them, methyl acetate, ethyl acetate, acetate-n-propyl acetate-n-butyl acetate, methyl propionate, ethyl propionate, propionate-n-propyl, isopropyl propionate, methyl butyrate, ethyl butyrate, etc. It is preferable from the viewpoint of improving ion conductivity and suppressing battery swelling during durability such as cycling and storage.

  The content of the chain carboxylic acid ester is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. However, in 100% by volume of the non-aqueous solvent, usually 5% by volume or more, preferably 8% by volume or more. In addition, it is usually 80% by volume or less, preferably 70% by volume or less. When the content of the chain carboxylic acid ester is within the above range, the electric conductivity of the non-aqueous electrolyte solution is improved, and the input / output characteristics and charge / discharge rate characteristics of the non-aqueous electrolyte secondary battery are easily improved. Moreover, increase in negative electrode resistance is suppressed, and the input / output characteristics and charge / discharge rate characteristics of the non-aqueous electrolyte secondary battery are easily set in a favorable range.

  In addition, when using chain | strand-shaped carboxylic acid ester, Preferably it is combined use with a cyclic carbonate, More preferably, it is combined use of a cyclic carbonate and a chain carbonate.

  For example, when a cyclic carbonate and a chain carboxylic acid ester are used in combination, the content of the cyclic carbonate is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 15% by volume or more, preferably 20 The content of the chain carboxylic acid ester is usually 20% by volume or more, preferably 30% by volume or more, and usually 55% by volume or less, preferably 40% by volume or less. Is 50% by volume or less. Further, when a cyclic carbonate, a chain carbonate, and a chain carboxylate are used in combination, the content of the cyclic carbonate is not particularly limited and is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 15% by volume or more. , Preferably 20% by volume, usually 45% by volume or less, preferably 40% by volume or less, and the content of the chain carbonate is usually 25% by volume or more, preferably 30% by volume or more, and usually 84% by volume or less. , Preferably it is 80 volume% or less. By making the content within the above range, while lowering the low temperature deposition temperature of the electrolyte, the viscosity of the nonaqueous electrolytic solution is also lowered to improve the ionic conductivity, and even higher input / output can be obtained even at a low temperature, Further, it is preferable from the viewpoint of further reducing battery swelling.

<1-3-4. Cyclic carboxylic acid ester>
Examples of the cyclic carboxylic acid ester include those having 3 to 12 total carbon atoms in the structural formula.

  Specific examples include gamma butyrolactone, gamma valerolactone, gamma caprolactone, epsilon caprolactone, and the like. Among these, gamma butyrolactone is particularly preferable from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation.

  The content of the cyclic carboxylic acid ester is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. However, in 100% by volume of the nonaqueous solvent, it is usually 3% by volume or more, preferably 5% by volume or more. Moreover, it is 60 volume% or less normally, Preferably it is 50 volume% or less. When the content of the cyclic carboxylic acid ester is within the above range, the electric conductivity of the non-aqueous electrolyte solution is improved, and the input / output characteristics and charge / discharge rate characteristics of the non-aqueous electrolyte secondary battery are easily improved. In addition, the viscosity of the non-aqueous electrolyte solution is set to an appropriate range, a decrease in electrical conductivity is avoided, the increase in negative electrode resistance is suppressed, and the input / output characteristics and charge / discharge rate characteristics of the non-aqueous electrolyte secondary battery are in a favorable range. And it will be easier.

<1-3-5. Ether compounds>
As the ether compound, a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms are preferable.

Examples of the chain ether 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 Olo-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-triflu (Ro-n-propyl) (2,2,3,3-tetrafluoro-n-propyl) ether, (3,3,3-trifluoro-n-propyl) (2,2,3,3,3-penta Fluoro-n-propyl) ether, di (2,2,3,3-tetrafluoro-n-propyl) ether, (2,2,3,3-tetrafluoro-n-propyl) (2,2,3 3,3-pentafluoro-n-propyl) ether, di (2,2,3,3,3-pentafluoro-n-propyl) ether, di-n-butyl ether, dimethoxymethane, methoxyethoxymethane, methoxy (2 -Fluoroethoxy) methane, methoxy (2,2,2-trifluoroethoxy) methanemethoxy (1,1,2,2-tetrafluoroethoxy) methane, diethoxymethane, ethoxy (2-fur Roethoxy) methane, ethoxy (2,2,2-trifluoroethoxy) methane, ethoxy (1,1,2,2-tetrafluoroethoxy) methane, di (2-fluoroethoxy) methane, (2-fluoroethoxy) ( 2,2,2-trifluoroethoxy) methane, (2-fluoroethoxy) (1,1,2,2-tetrafluoroethoxy) methanedi (2,2,2-trifluoroethoxy) methane, (2,2, 2-trifluoroethoxy) (1,1,2,2-tetrafluoroethoxy) methane, di (1,1,2,2-tetrafluoroethoxy) methane, dimethoxyethane, methoxyethoxyethane, methoxy (2-fluoroethoxy) ) Ethane, methoxy (2,2,2-trifluoroethoxy) ethane, methoxy (1,1,2,2-tetrafluoroeth) Xyl) ethane, diethoxyethane, ethoxy (2-fluoroethoxy) ethane, ethoxy (2,2,2-trifluoroethoxy) ethane, ethoxy (1,1,2,2-tetrafluoroethoxy) ethane, di (2 -Fluoroethoxy) ethane, (2-fluoroethoxy) (2,2,2-trifluoroethoxy) ethane, (2-fluoroethoxy) (1,1,2,2-tetrafluoroethoxy) ethane, di (2, 2,2-trifluoroethoxy) ethane, (2,2,2-trifluoroethoxy) (1,1,2,2-tetrafluoroethoxy) ethane, di (1,1,2,2-tetrafluoroethoxy) Ethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, etc. And the like.

Examples of the cyclic ether having 3 to 6 carbon atoms include tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1 , 4-dioxane and the like, and fluorinated compounds thereof.
Among 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 have ion dissociation properties. It is preferable in terms of improvement. Particularly preferred are dimethoxymethane, diethoxymethane, and ethoxymethoxymethane because they have low viscosity and give high ionic conductivity.

  The content of the ether compound is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. In 100% by volume of the nonaqueous solvent, usually 1% by volume or more, preferably 2% by volume or more, more preferably. 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 compound is within the above preferred range, it is easy to ensure the effect of improving the ionic conductivity resulting from the improvement of the lithium ion dissociation degree and the viscosity reduction of the chain ether. In addition, when the negative electrode active material is a carbonaceous material, the phenomenon that the chain ether is co-inserted with the lithium ions can be suppressed, so that the input / output characteristics and the charge / discharge rate characteristics can be within an appropriate range.

<1-3-6. Sulfone compounds>
As the sulfone compound, a cyclic sulfone having 3 to 6 carbon atoms and a chain sulfone having 2 to 6 carbon atoms are preferable. The number of sulfonyl groups in one molecule is preferably 1 or 2.

  Examples of the cyclic sulfone include trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones that are monosulfone compounds; trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones that are disulfone compounds. Among these, from the viewpoint of dielectric constant and viscosity, tetramethylene sulfones, tetramethylene disulfones, hexamethylene sulfones, and hexamethylene disulfones are more preferable, and tetramethylene sulfones (sulfolanes) are particularly preferable.

  The sulfolane is preferably sulfolane and / or a sulfolane derivative (hereinafter sometimes abbreviated as “sulfolane” including sulfolane). As the sulfolane derivative, one in which one or more hydrogen atoms bonded to the carbon atom constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group is preferable.

  Among them, 2-methylsulfolane, 3-methylsulfolane, 2-fluorosulfolane, 3-fluorosulfolane, 2,2-difluorosulfolane, 2,3-difluorosulfolane, 2,4-difluorosulfolane, 2,5-difluorosulfolane, 3,4-difluorosulfolane, 2-fluoro-3-methylsulfolane, 2-fluoro-2-methylsulfolane, 3-fluoro-3-methylsulfolane, 3-fluoro-2-methylsulfolane, 4-fluoro-3-methyl Sulfolane, 4-fluoro-2-methylsulfolane, 5-fluoro-3-methylsulfolane, 5-fluoro-2-methylsulfolane, 2-fluoromethylsulfolane, 3-fluoromethylsulfolane, 2-difluoromethylsulfolane, 3-difluoro Methyl sulfolane, 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 in terms of high ionic conductivity and high input / output.

As the chain sulfone, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, n- Butyl methyl sulfone, n-butyl ethyl sulfone, t-butyl methyl sulfone, t-butyl ethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone, Trifluoroethyl methyl sulfone, pentafluoroethyl methyl sulfone, ethyl monofluoromethyl sulfone, ethyl difluoromethyl sulfone, ethyl trif Oromethylsulfone, perfluoroethylmethylsulfone, ethyltrifluoroethylsulfone, ethylpentafluoroethylsulfone, di (trifluoroethyl) sulfone, perfluorodiethylsulfone, fluoromethyl-n-propylsulfone, difluoromethyl-n-propylsulfone Trifluoromethyl-n-propylsulfone, fluoromethylisopropylsulfone, difluoromethylisopropylsulfone, trifluoromethylisopropylsulfone, trifluoroethyl-n-propylsulfone, trifluoroethylisopropylsulfone, pentafluoroethyl-n-propylsulfone, Pentafluoroethyl isopropyl sulfone, trifluoroethyl-n-butyl sulfone, trifluoroethyl-t-butyl sulfone Emissions, pentafluoroethyl -n- butyl sulfone, pentafluoroethyl -t- butyl sulfone, and the like.

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

  The content of the sulfone compound is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. However, in 100% by volume of the nonaqueous solvent, usually 0.3% by volume or more, preferably 0.5% by volume. Above, 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 compound is within the above range, durability improvement effects such as cycle characteristics and storage characteristics can be easily obtained, and the viscosity of the non-aqueous electrolyte solution is within an appropriate range, resulting in a decrease in electrical conductivity. Can be avoided, and the input / output characteristics and charge / discharge rate characteristics of the non-aqueous electrolyte secondary battery can be within an appropriate range.

<1-4. Auxiliary>
<1-4-1. Carbonate having at least one of carbon-carbon unsaturated bond and fluorine atom>
The nonaqueous electrolytic solution according to one embodiment of the present invention may further contain at least one of a carbonate having a carbon-carbon unsaturated bond and a carbonate having a fluorine atom.
The carbonate having a carbon-carbon unsaturated bond is preferably a cyclic carbonate having a carbon-carbon unsaturated bond (hereinafter sometimes abbreviated as “unsaturated cyclic carbonate”), and a carbonate having a fluorine atom. As for, Preferably the cyclic carbonate which has a fluorine atom is mentioned. In addition, the non-aqueous electrolyte solution of the present invention contains a fluorinated unsaturated cyclic carbonate, a cyclic sulfonic acid ester compound, a compound having a cyano group, a diisocyanate compound, a carboxylic acid anhydride, an overcharge inhibitor, and other auxiliary agents. May be included.

  The cyclic carbonate having a carbon-carbon unsaturated bond is not particularly limited as long as it is a cyclic carbonate having a carbon-carbon unsaturated bond, and a carbonate having an arbitrary carbon-carbon unsaturated bond can be used. In addition, the cyclic carbonate which has a substituent which has an aromatic ring shall also be included by the cyclic carbonate which has a carbon-carbon unsaturated bond. The production method of the unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method.

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

  Examples of vinylene carbonates include vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, allyl vinylene carbonate, and the like.

  Specific examples of ethylene carbonates substituted with an aromatic ring or a substituent having a carbon-carbon unsaturated bond include vinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, phenyl ethylene carbonate, 4,5-diphenyl ethylene carbonate, Examples include ethynyl ethylene carbonate and 4,5-diethynyl ethylene carbonate.

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

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

  An unsaturated cyclic carbonate may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. Further, the content of the unsaturated cyclic carbonate is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The content of the unsaturated cyclic carbonate is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, in 100% by mass of the non-aqueous electrolyte. Preferably it is 0.2 mass% or more, and is 10 mass% or less normally, Preferably it is 8 mass% or less, More preferably, it is 5 mass% or less. If it is in the said range, a non-aqueous electrolyte secondary battery will be easy to express sufficient high temperature storage characteristics and cycling characteristics improvement effect.

  The cyclic carbonate having a fluorine atom (hereinafter sometimes abbreviated as “fluorinated cyclic carbonate”) is not particularly limited as long as it is a cyclic carbonate having a fluorine atom.

Examples of the fluorinated cyclic carbonate include derivatives of cyclic carbonates having an alkylene group having 2 to 6 carbon atoms, such as ethylene carbonate derivatives. Examples of the ethylene carbonate derivative include fluorinated products of ethylene carbonate or ethylene carbonate substituted with an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms), and particularly those having 1 to 8 fluorine atoms. Is 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 Le ethylene carbonate, 4,4-difluoro-5,5-dimethylethylene carbonate.

  Among them, at least one selected from the group consisting of monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, and 4,5-difluoro-4,5-dimethylethylene carbonate has high ionic conductivity. It is more preferable in terms of imparting properties and suitably forming an interface protective film.

A fluorinated cyclic carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. The content of the fluorinated cyclic carbonate is not particularly limited and may be arbitrary as long as the effects of the present invention are not significantly impaired. 0.01% by mass or more, more preferably 0.1% by mass or more, and usually 8% by mass or less, preferably 6% by mass or less, more preferably 5% by mass or less. Within this range, the nonaqueous electrolyte secondary battery tends to exhibit sufficient cycle characteristics and high temperature storage characteristics. Within this range, the nonaqueous electrolyte secondary battery tends to exhibit sufficient cycle characteristics and high temperature storage characteristics.
In addition, the fluorinated cyclic carbonate may be used as an auxiliary for the non-aqueous electrolyte solution or as a solvent. When used as a solvent, the content of the fluorinated cyclic carbonate is usually 8% by mass or more, preferably 10% by mass or more, more preferably 12% by mass or more, in 100% by mass of the non-aqueous electrolyte. Moreover, it is 85 mass% or less normally, Preferably it is 80 mass% or less, More preferably, it is 75 mass% or less. If it is this range, a non-aqueous electrolyte secondary battery will be easy to express sufficient cycling characteristics improvement effect, and it will be easy to avoid that a discharge capacity maintenance factor falls.
In the non-aqueous electrolyte solution according to one embodiment of the present invention, the carbonate having at least one of the carbon-carbon unsaturated bond and the fluorine atom is selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, ethynyl ethylene carbonate, and fluoroethylene carbonate. It is preferable that it is at least one selected.

<1-4-2. Fluorinated unsaturated cyclic carbonate>
As the fluorinated cyclic carbonate, a cyclic carbonate having an unsaturated bond and a fluorine atom (hereinafter sometimes abbreviated as “fluorinated unsaturated cyclic carbonate”) can be used. The fluorinated unsaturated cyclic carbonate is not particularly limited. Of these, those having 1 or 2 fluorine atoms are preferred. The production method of the fluorinated unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method.

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

  Examples of the vinylene carbonate derivative include 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4,5-difluoroethylene carbonate, and the like.

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

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

  A fluorinated unsaturated cyclic carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. Moreover, the compounding quantity of a fluorinated unsaturated cyclic carbonate is not restrict | limited in particular, As long as the effect of this invention is not impaired remarkably, it is arbitrary. The content of the fluorinated unsaturated cyclic carbonate is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, in 100% by mass of the non-aqueous electrolyte. The amount is usually 5% by mass or less, preferably 4% by mass or less, more preferably 3% by mass or less. If it is this range, a non-aqueous electrolyte secondary battery will be easy to express sufficient cycle characteristic improvement effect.

<1-4-3. Cyclic sulfonic acid ester compound>
The cyclic sulfonic acid ester compound that can be used in the nonaqueous electrolytic solution of the present invention is not particularly limited, but a compound represented by the following general formula (2) is preferable. The production method of the cyclic sulfonate compound is not particularly limited, and can be produced by arbitrarily selecting a known method.

In general formula (2), R ⁵ and R ⁶ are each independently an organic compound composed of an atom selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom and a halogen atom. Represents a group, and R ⁵ and R ⁶ may contain an unsaturated bond together with —O—SO ₂ —.
Here, R ⁵ and R ⁶ are preferably organic groups composed of atoms composed of carbon atoms, hydrogen atoms, oxygen atoms, and sulfur atoms, and among them, hydrocarbon groups having 1 to 3 carbon atoms, — An organic group having O—SO ₂ — is preferable.

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

Specific examples of the compound represented by the general formula (2) include, for example,
1,3-propane sultone, 1-fluoro-1,3-propane sultone, 2-fluoro-1,3-propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone 2-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone, 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro-1-propene -1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1-fluoro-2-propene-1,3-sultone, 2 -Fluoro-2-propene-1,3-sultone, 3-fluoro-2-propene-1,3-sultone, 1-methyl-1-propene-1,3-sultone, 2-methyl-1-propene -1,3-sultone, 3-methyl-1-propene-1,3-sultone, 1-methyl-2-propene-1,3-sultone, 2-methyl-2-propene-1,3-sultone, 3 -Methyl-2-propene-1,3-sultone, 1,4-butane sultone, 1-fluoro-1,4-butane sultone, 2-fluoro-1,4-butane sultone, 3-fluoro-1,4-butane sultone, 4 -Fluoro-1,4-butane sultone, 1-methyl-1,4-butane sultone, 2-methyl-1,4-butane sultone, 3-methyl-1,4-butane sultone, 4-methyl-1,4-butane sultone, 1 -Butene-1,4-sultone, 2-butene-1,4-sultone, 3-butene-1,4-sultone, 1-fluoro-1-butene-1,4-sultone, 2-fluoro- -Butene-1,4-sultone, 3-fluoro-1-butene-1,4-sultone, 4-fluoro-1-butene-1,4-sultone, 1-fluoro-2-butene-1,4-sultone 2-fluoro-2-butene-1,4-sultone, 3-fluoro-2-butene-1,4-sultone, 4-fluoro-2-butene-1,4-sultone, 1-fluoro-3-butene -1,4-sultone, 2-fluoro-3-butene-1,4-sultone, 3-fluoro-3-butene-1,4-sultone, 4-fluoro-3-butene-1,4-sultone, 1 -Methyl-1-butene-1,4-sultone, 2-methyl-1-butene-1,4-sultone, 3-methyl-1-butene-1,4-sultone, 4-methyl-1-butene-1 , 4-sultone, 1-methyl-2-butene-1,4 -Sultone, 2-methyl-2-butene-1,4-sultone, 3-methyl-2-butene-1,4-sultone, 4-methyl-2-butene-1,4-sultone, 1-methyl-3 -Butene-1,4-sultone, 2-methyl-3-butene-1,4-sultone, 3-methyl-3-butene-1,4-sultone, 4-methyl-3-butene-1,4-sultone 1,5-pentane sultone, 1-fluoro-1,5-pentane sultone, 2-fluoro-1,5-pentane sultone, 3-fluoro-1,5-pentane sultone, 4-fluoro-1,5-pentane Sultone, 5-fluoro-1,5-pentanthruton, 1-methyl-1,5-pentanthruton, 2-methyl-1,5-pentanthruton, 3-methyl-1,5-pentanthruton, 4-methyl- 1,5- N-pentene sultone, 5-methyl-1,5-pentanthrutone, 1-pentene-1,5-sultone, 2-pentene-1,5-sultone, 3-pentene-1,5-sultone, 4-pentene-1,5 -Sultone, 1-fluoro-1-pentene-1,5-sultone, 2-fluoro-1-pentene-1,5-sultone, 3-fluoro-1
-Pentene-1,5-sultone, 4-fluoro-1-pentene-1,5-sultone, 5-fluoro-1-pentene-1,5-sultone, 1-fluoro-2-pentene-1,5-sultone 2-fluoro-2-pentene-1,5-sultone, 3-fluoro-2-pentene-1,5-sultone, 4-fluoro-2-pentene-1,5-sultone, 5-fluoro-2-pentene -1,5-sultone, 1-fluoro-3-pentene-1,5-sultone, 2-fluoro-3-pentene-1,5-sultone, 3-fluoro-3-pentene-1,5-sultone, 4 -Fluoro-3-pentene-1,5-sultone, 5-fluoro-3-pentene-1,5-sultone, 1-fluoro-4-pentene-1,5-sultone, 2-fluoro-4-pentene-1 , 5-s , 3-fluoro-4-pentene-1,5-sultone, 4-fluoro-4-pentene-1,5-sultone, 5-fluoro-4-pentene-1,5-sultone, 1-methyl-1- Pentene-1,5-sultone, 2-methyl-1-pentene-1,5-sultone, 3-methyl-1-pentene-1,5-sultone, 4-methyl-1-pentene-1,5-sultone, 5-methyl-1-pentene-1,5-sultone, 1-methyl-2-pentene-1,5-sultone, 2-methyl-2-pentene-1,5-sultone, 3-methyl-2-pentene- 1,5-sultone, 4-methyl-2-pentene-1,5-sultone, 5-methyl-2-pentene-1,5-sultone, 1-methyl-3-pentene-1,5-sultone, 2- Methyl-3-pentene-1,5-s , 3-methyl-3-pentene-1,5-sultone, 4-methyl-3-pentene-1,5-sultone, 5-methyl-3-pentene-1,5-sultone, 1-methyl-4- Pentene-1,5-sultone, 2-methyl-4-pentene-1,5-sultone, 3-methyl-4-pentene-1,5-sultone, 4-methyl-4-pentene-1,5-sultone, 5-methyl-4-pentene-1,5-sultone, 1,2-oxathiolane-2,2-dioxide-4-yl-acetate, 1,2-oxathiolane-2,2-dioxide-4-yl-propionate, 5-methyl-1,2-oxathiolane-2,2-dioxide-4-one-2,2-dioxide, 5,5-dimethyl-1,2-oxathiolane-2,2-dioxide-4-one-2, 2-Doki Sultone compounds such as sid;

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

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

1,2,3-oxathiazolidine-2,2-dioxide, 3-methyl-1,2,3-oxathiazolidine-2,2-dioxide, 3H-1,2,3-oxathiazol-2,2-dioxide 5H-1,2,3-oxathiazol-2,2-dioxide, 1,2,4-oxathiazolidine-2,2-dioxide, 4-methyl-1,2,4-oxathiazolidine-2,2- Dioxide, 3H-1,2,4-oxathiazole-2,2-dioxide, 5H-1,2,4-oxathiazole-2,2-dioxide, 1,2,5-oxathiazolidine-2,2-dioxide 5-methyl-1,2,5-oxathiazolidine-2,2-dioxide, 3H-1,2,5-oxathiazole-2,2-dioxide, 5H-1,2,5-oxathiazole-2 2-dioxide, 1,2,3-oxathiazinane-2,2-dioxide, 3-methyl-1,2,3-oxathiazinane-2,2-dioxide, 5,6-dihydro-1,2,3-oxathiazine- 2,2-dioxide, 1,2,4-oxathiazinane-2,2-dioxide, 4-methyl-1,2,4-oxathiazinane-2,2-dioxide, 5,6-dihydro-1,2,4- Oxathiazine-2,2-dioxide, 3,6-dihydro-1,2,4-oxathiazine-2,2-dioxide, 3,4-dihydro-1,2,4-oxathiazine-2,2-dioxide, 1, 2,5-oxathiazinane-2,2-dioxide, 5-methyl-1,2,5-oxathiazinane-2,2-dioxide, 5,6-dihydro-1,2,5-oxathiazine-2 2-dioxide, 3,6
Dihydro-1,2,5-oxathiazine-2,2-dioxide, 3,4-dihydro-1,2,5-oxathiazine-2,2-dioxide, 1,2,6-oxathiazinane-2,2-dioxide, 6-methyl-1,2,6-oxathiazinane-2,2-dioxide, 5,6-dihydro-1,2,6-oxathiazine-2,2-dioxide, 3,4-dihydro-1,2,6- Nitrogen-containing compounds such as oxathiazine-2,2-dioxide, 5,6-dihydro-1,2,6-oxathiazine-2,2-dioxide;

1,2,3-oxathiaphoslane-2,2-dioxide, 3-methyl-1,2,3-oxathiaphoslane-2,2-dioxide, 3-methyl-1,2,3-oxathi Aphoslane-2,2,3-trioxide, 3-methoxy-1,2,3-oxathiaphoslane-2,2,3-trioxide, 1,2,4-oxathiaphoslane-2,2-dioxide 4-methyl-1,2,4-oxathiaphoslane-2,2-dioxide, 4-methyl-1,2,4-oxathiaphoslane-2,2,4-trioxide, 4-methoxy-1 , 2,4-Oxathiaphoslane-2,2,4-trioxide, 1,2,5-oxathiaphoslane-2,2-dioxide, 5-methyl-1,2,5-oxathiaphoslane- 2,2-dioxide, 5-methyl-1,2,5-oxathia Suranium-2,2,5-trioxide, 5-methoxy-1,2,5-oxathiaphoslane-2,2,5-trioxide, 1,2,3-oxathiaphosphinan-2,2-dioxide, 3-methyl-1,2,3-oxathiaphosphinan-2,2-dioxide, 3-methyl-1,2,3-oxathiaphosphinan-2,2,3-trioxide, 3-methoxy-1, 2,3-oxathiaphosphinan-2,2,3-trioxide, 1,2,4-oxathiaphosphinan-2,2-dioxide, 4-methyl-1,2,4-oxathiaphosphinan-2 , 2-dioxide, 4-methyl-1,2,4-oxathiaphosphinan-2,2,3-trioxide, 4-methyl-1,5,2,4-dioxathiaphosphinan-2,4- Dioxide, 4-methoxy 1,5,2,4-dioxathiaphosphinan-2,4-dioxide, 3-methoxy-1,2,4-oxathiaphosphinan-2,2,3-trioxide, 1,2,5-oxa Thiaphosphinan-2,2-dioxide, 5-methyl-1,2,5-oxathiaphosphinan-2,2-dioxide, 5-methyl-1,2,5-oxathiaphosphinan-2,2, 3-trioxide, 5-methoxy-1,2,5-oxathiaphosphinan-2,2,3-trioxide, 1,2,6-oxathiaphosphinan-2,2-dioxide, 6-methyl-1, 2,6-oxathiaphosphinan-2,2-dioxide, 6-methyl-1,2,6-oxathiaphosphinan-2,2,3-trioxide, 6-methoxy-1,2,6-oxathia Phosphinan-2,2 Phosphorus-containing compounds such as 1,3-trioxide;
Etc.

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

A cyclic sulfonic acid ester compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. There is no restriction | limiting in the compounding quantity of the cyclic sulfonate ester compound with respect to the whole non-aqueous electrolyte solution of this invention, Although it is arbitrary unless the effect of this invention is impaired remarkably, Usually, it is 0.8 with respect to the non-aqueous electrolyte solution of this invention. 001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 0.3% by mass or more,
Usually, it is contained at a concentration of 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less. When the said range is satisfy | filled, a cycling characteristic, a high temperature storage characteristic, etc. improve, and it is preferable from a viewpoint that a battery swelling falls.

<1-4-4. Compound having cyano group>
The compound having a cyano group that can be used in the nonaqueous electrolytic solution of the present invention is not particularly limited as long as it is a compound having a cyano group in the molecule, but is represented by the following general formula (3). The compounds represented are more preferred. The production method of the compound having a cyano group is not particularly limited, and can be produced by arbitrarily selecting a known method.

  In general formula (3), T represents an organic group composed of an atom selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom and a halogen atom, and U represents a substituent. And a V-valent organic group having 1 to 10 carbon atoms. V is an integer of 1 or more, and when V is 2 or more, T may be the same or different.

  The molecular weight of the compound having a cyano group is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight of the compound having a cyano group is usually 40 or more, preferably 45 or more, more preferably 50 or more, and usually 200 or less, preferably 180 or less, more preferably 170 or less. If it is this range, it will be easy to ensure the solubility of the compound which has a cyano group with respect to nonaqueous electrolyte solution, and the effect of this invention will be easy to be expressed.

Specific examples of the compound represented by the general formula (2) include, for example,
Acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile 2-methylbutyronitrile, trimethylacetonitrile, hexanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, acrylonitrile, methacrylonitrile, Crotononitrile, 3-methylcrotononitrile, 2-methyl-2-butenenitryl, 2-pentenenitrile, 2-methyl-2-pentenenitrile, 3-methyl-2-pentenenitrile, 2-hexenenitrile, fluoro Acetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3-fluoropropionitrile, 2,2-difluoropropionitrile, 2,3-diflu Lopropionitrile, 3,3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3-trifluoropropionitrile, 3,3'-oxydipropionitrile, 3,3'- Compounds having one cyano group such as thiodipropionitrile, 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, pentafluoropropionitrile;

Malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimonitrile, suberonitrile, azeronitrile, sebacononitrile, undecandinitrile, dodecandinitrile, methylmalononitrile, ethylmalononitrile, isopropylmalononitrile, tert-butylmalononitrile, methylsuccinonitrile 2,2-dimethylsuccinonitrile, 2,3-dimethylsuccinonitrile, trimethylsuccinonitrile, tetramethylsuccinonitrile, 3,3 ′-(ethylenedioxy) dipropionitrile,
Compounds having two cyano groups such as 3,3 ′-(ethylenedithio) dipropionitrile;

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

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

  Methyl thiocyanate, ethyl thiocyanate, propyl thiocyanate, butyl thiocyanate, pentyl thiocyanate, hexyl thiocyanate, heptyl thiocyanate, methanesulfonyl cyanide, ethanesulfonyl cyanide, propanesulfonyl cyanide, butanesulfonyl cyanide, pentanesulfonyl cyanide, hexanesulfonyl cyanide , Heptanesulfonyl cyanide, methylsulfurocyanidate, ethylsulfurocyanidate, propylsulfurocyanidate, butylsulfurocyanidate, pentylsulfurocyanidate, hexylsulfurocyanidate, heptylsulfur Sulfur-containing compounds such as frocyanidates;

Cyanodimethylphosphine, cyanodimethylphosphine oxide, methyl cyanomethylphosphinate, methyl cyanomethylphosphinate, dimethylphosphinic acid cyanide, dimethylphosphinic acid cyanide, dimethylphosphonic acid dimethyl, cyanophosphonic acid dimethyl, methylphosphonic acid cyanomethyl, methylphosphonic acid Phosphorus-containing compounds such as cyanomethyl acid, cyanodimethyl phosphate, and cyanodimethyl phosphite;
Etc.

Of these,
Acetonitrile, propionitrile, butyronitrile, isobutyronitrile, valeronitrile, isovaleronitrile, lauronitrile, crotononitrile, 3-methylcrotononitrile, malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimonitrile, suberonitrile, Azeronitrile, sebaconitrile, undecandinitrile, and dodecanedinitrile are preferable from the viewpoint of improving the storage characteristics, and cyano such as malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azeronitrile, sebacononitrile, undecandinitrile, dodecanedinitrile, etc. A compound having two groups is more preferred.

  The compound which has a cyano group may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. There is no restriction | limiting in content of the compound which has a cyano group with respect to the whole nonaqueous electrolyte solution of this invention, Although it is arbitrary unless the effect of this invention is impaired remarkably, Usually, it is 0.8 with respect to the nonaqueous electrolyte solution of this invention. 001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 0.3% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more Preferably, it is contained at a concentration of 3% by mass or less. When the above range is satisfied, effects such as input / output characteristics, charge / discharge rate characteristics, cycle characteristics, and high-temperature storage characteristics are further improved.

<1-4-5. Diisocyanate Compound>
The diisocyanate compound that can be used in the non-aqueous electrolyte of the present invention has a nitrogen atom only in the isocyanate group and two isocyanate groups in the molecule, and the following general formula (4) The compound represented by these is preferable.

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

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

  Moreover, it is preferable to have a C1-C3 alkylene group between a cycloalkylene group or an aromatic hydrocarbon group, and an isocyanate group. By having an alkylene group, it becomes sterically bulky, so that side reactions on the positive electrode are less likely to occur. Furthermore, if the alkylene group has 1 to 3 carbon atoms, the ratio of the isocyanate group to the total molecular weight does not change greatly, and thus the effect of the present invention is remarkably easily exhibited.

  The molecular weight of the diisocyanate compound represented by the general formula (4) is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The molecular weight is usually 80 or more, preferably 115 or more, more preferably 170 or more, and usually 300 or less, preferably 230 or less. If it is this range, it will be easy to ensure the solubility of the diisocyanate compound with respect to a non-aqueous electrolyte solution, and the effect of this invention will be easy to be expressed.

Specific examples of the diisocyanate compound include, for example,
1,2-diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, 1,2 -Bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-2,4 ' -Cycloalkane ring-containing diisocyanates such as diisocyanate, dicyclohexylmethane-3,3'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate;
1,2-phenylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene-2,3-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,5-diisocyanate, tolylene-2,6 -Diisocyanate, tolylene-3,4-diisocyanate, tolylene-3,5-diisocyanate, 1,2-bis (isocyanatomethyl) benzene, 1,3-bis (isocyanatomethyl) benzene, 1,4-bis (isocyanate) Natomethyl) benzene, 2,4-diisocyanatobiphenyl, 2,6-diisocyanatobiphenyl, 2,2'-diisocyanatobiphenyl, 3,3'-diisocyanatobiphenyl, 4,4'-diisocyanato- 2-methylbiphenyl, 4,4'-diisocyana -3-methylbiphenyl, 4,4'-diisocyanato-3,3'-dimethylbiphenyl, 4,4'-diisocyanatodiphenylmethane, 4,4'-diisocyanato-2-methyldiphenylmethane, 4,4'-diisocyanato- 3-methyldiphenylmethane, 4,4'-diisocyanato-3,3'-dimethyldiphenylmethane, 1,5-diisocyanatonaphthalene, 1,8-diisocyanatonaphthalene, 2,3-diisocyanatonaphthalene, 1,5 Aromatic ring-containing diisocyanates such as -bis (isocyanatomethyl) naphthalene, 1,8-bis (isocyanatomethyl) naphthalene, 2,3-bis (isocyanatomethyl) naphthalene;
Etc.

Among these,
1,2-diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, 1,2 -Bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, 1,2-phenylene diisocyanate, 1,3-phenylene diisocyanate, 1,4 -Phenylene diisocyanate, 1,2-bis (isocyanatomethyl) benzene, 1,3-bis (isocyanatomethyl) benzene, 1,4-bis (isocyanatomethyl) benzene, 2,4-diisocyanatobiphenyl, 2 , 6-Diisocyanatobiphenyl is more dense on the negative electrode Composite film is formed, as a result, since the battery durability is improved, which is preferable.

Among these,
1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 1,2-bis (isocyanatomethyl) benzene, 1,3-bis (isocyanatomethyl) benzene and 1,4-bis (isocyanatomethyl) benzene form a film advantageous for lithium ion conductivity on the negative electrode due to the symmetry of the molecule. It is more preferable because the characteristics are further improved.

  Moreover, the diisocyanate compound mentioned above may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  In the non-aqueous electrolyte solution of the present invention, the content of the diisocyanate compound that can be used is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired, but with respect to the non-aqueous electrolyte solution of the present invention, Usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% by mass or more, further preferably 0.3% by mass or more, and usually 5% by mass or less, preferably 4% by mass. Hereinafter, it is more preferably 3% by mass or less, and further preferably 2% by mass or less. When the content is within the above range, durability such as cycle and storage can be improved, and the effects of the present invention can be sufficiently exhibited.

  In addition, the manufacturing method in particular of a diisocyanate compound is not restrict | limited, A well-known method can be selected arbitrarily and can be manufactured. Moreover, you may use a commercial item.

<1-4-6. Carboxylic anhydride>
In the non-aqueous electrolyte solution of the present invention, the carboxylic acid anhydride that can be used is preferably a compound represented by the following general formula (5). The method for producing the carboxylic acid anhydride is not particularly limited, and any known method can be selected and produced.

(In General Formula (5), R ¹ and R ² each independently represents a hydrocarbon group having 1 to 15 carbon atoms which may have a substituent. R ¹ and R ² are bonded to each other. And a ring structure may be formed.)

The type of R ¹ and R ² is not particularly limited as long as it is a monovalent hydrocarbon group. For example, it may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, or a combination of an aliphatic hydrocarbon group and an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be a saturated hydrocarbon group and may contain an unsaturated bond (carbon-carbon double bond or carbon-carbon triple bond). Further, the aliphatic hydrocarbon group may be a chain or a ring, and in the case of a chain, it may be a straight chain or a branched chain. Further, a chain and a ring may be combined. R ¹ and R ² may be the same as or different from each other.

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

In addition, when the hydrocarbon group of R ¹ and R ² has a substituent, the type of the substituent is not particularly limited unless it is contrary to the gist of the present invention, but examples include a fluorine atom, a chlorine atom, and a bromine atom. And a halogen atom such as an iodine atom, preferably a fluorine atom. In addition, examples of the substituent other than the halogen atom include a substituent having a functional group such as an ester group, a cyano group, a carbonyl group, and an ether group, and a cyano group and a carbonyl group are preferable. The hydrocarbon group for R ¹ and R ² may have only one of these substituents, or may have two or more. In the case of having two or more substituents, these substituents may be the same or different from each other.

The carbon number of each hydrocarbon group of R ¹ and R ² is usually 1 or more, and usually 15 or less, preferably 12 or less, more preferably 10 or less, and further preferably 9 or less. When R ¹ and R ² are bonded to each other to form a divalent hydrocarbon group, the carbon number of the divalent hydrocarbon group is usually 1 or more, and usually 15 or less, preferably It is 13 or less, more preferably 10 or less, and still more preferably 8 or less. In addition, when the hydrocarbon group of R < ¹ >, R < ² > has a substituent containing a carbon atom, it is preferable that carbon number of R < ¹ >, R < ² > whole also including the substituent satisfy | fills the said range.

Next, specific examples of the acid anhydride represented by the general formula (5) will be described. In the following examples, “analogue” refers to an acid anhydride obtained by substituting a part of the structure of the illustrated acid anhydride with another structure without departing from the spirit of the present invention. For example, dimers, trimers and tetramers composed of a plurality of acid anhydrides, or structural isomers such as those having the same carbon number as the substituent but having a branched chain, and the substituent is an acid. Examples include those having different sites for binding to anhydrides.

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

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

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

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

Specific examples of acid anhydrides in which R ¹ and R ² are alkynyl groups include propionic acid anhydride, 3-phenylpropionic acid anhydride, 2-butyric acid anhydride, 2-pentynic acid anhydride, and 3-butyric acid. Anhydrides, 3-pentynoic acid anhydrides, 4-pentynic acid anhydrides, and the like, and analogs thereof are exemplified.

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

Examples of acid anhydrides in which R ¹ and R ² are substituted with halogen atoms include examples of acid anhydrides mainly substituted with fluorine atoms, but some or all of these fluorine atoms are Acid anhydrides obtained by substitution with chlorine atoms, bromine atoms, and iodine atoms are also included in the exemplified compounds.

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

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

Examples of acid anhydrides in which R ¹ and R ² are alkenyl groups substituted with a halogen atom include 2-fluoroacrylic anhydride, 3-fluoroacrylic anhydride, 2,3-difluoroacrylic anhydride, 3,3-difluoroacrylic anhydride, 2,3,3-trifluoroacrylic anhydride, 2- (trifluoromethyl) acrylic anhydride, 3- (trifluoromethyl) acrylic anhydride, 2,3 -Bis (trifluoromethyl) acrylic anhydride, 2,3,3-tris (trifluoromethyl) acrylic anhydride, 2- (4-fluorophenyl) acrylic anhydride, 3- (4-fluorophenyl) Acrylic anhydride, 2,3-bis (4-fluorophenyl) acrylic anhydride, 3,3-bis (4-fluorophenyl) acrylic anhydride, 2-fluoro-3 -Butenoic anhydride, 2,2-difluoro-3-butenoic anhydride, 3-fluoro-2-butenoic anhydride, 4-fluoro-3-butenoic anhydride, 3,4-difluoro-3-butene Examples thereof include acid anhydrides, 3,3,4-trifluoro-3-butenoic acid anhydrides, and analogs thereof.

Examples of acid anhydrides in which R ¹ and R ² are alkynyl groups substituted with halogen atoms include
3-fluoro-2-propionic anhydride, 3- (4-fluorophenyl) -2-propionic anhydride, 3- (2,3,4,5,6-pentafluorophenyl) -2-propionic anhydride 4-fluoro-2-butynoic acid anhydride, 4,4-difluoro-2-butyric acid anhydride, 4,4,4-trifluoro-2-butyric acid anhydride, and the like, and the like Can be mentioned.

Examples of acid anhydrides in which R ¹ and R ² are aryl groups substituted with halogen atoms include 4-fluorobenzoic anhydride, 2,3,4,5,6-pentafluorobenzoic anhydride, 4 -A trifluoromethyl benzoic anhydride etc., those analogs, etc. are mentioned.

Examples of acid anhydrides in which R ¹ and R ² have a substituent having a functional group such as ester, nitrile, ketone, and ether include methoxyformic anhydride, ethoxyformic anhydride, methyl oxalic anhydride, Ethyl oxalic anhydride, 2-cyanoacetic anhydride, 2-oxopropionic anhydride, 3-oxobutanoic anhydride, 4-acetylbenzoic anhydride, methoxyacetic anhydride, 4-methoxybenzoic anhydride, etc. And analogs thereof.

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

Examples of R ¹ and R ² include the above-mentioned examples and all combinations of analogs thereof. Typical examples are given below.

Examples of combinations of chain alkyl groups include propionic acid anhydride, acetic acid butanoic acid anhydride, butanoic acid propionic acid anhydride, acetic acid 2-methylpropionic acid anhydride,
Etc.

Examples of combinations of chain alkyl groups and cyclic alkyl groups include acetic acid cyclopentanoic acid anhydride, acetic acid cyclohexane acid anhydride, cyclopentanoic acid propionic acid anhydride, and the like.

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

  Examples of combinations of chain alkyl groups and alkynyl groups include propionic acid anhydride, acetic acid 2-butynoic acid anhydride, acetic acid 3-butynic acid anhydride, acetic acid 3-phenylpropionic acid anhydride, propionic acid propionic acid anhydride Thing, etc.

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

  Examples of combinations of linear alkyl groups and functional hydrocarbon groups include: acetic acid fluoroacetic anhydride, acetic acid trifluoroacetic acid anhydride, acetic acid 4-fluorobenzoic acid anhydride, fluoroacetic acid propionic acid anhydride, alkyl acetate Examples thereof include oxalic acid anhydride, acetic acid 2-cyanoacetic acid anhydride, acetic acid 2-oxopropionic acid anhydride, acetic acid methoxyacetic acid anhydride, methoxyacetic acid propionic acid anhydride, and the like.

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

  Examples of combinations of cyclic alkyl groups and alkenyl groups include acrylic acid cyclopentanoic acid anhydride, 3-methylacrylic acid cyclopentanoic acid anhydride, 3-butenoic acid cyclopentanoic acid anhydride, acrylic acid cyclohexane acid anhydride, etc. Is mentioned.

  Examples of the combination of a cyclic alkyl group and an alkynyl group include propionic acid cyclopentanoic acid anhydride, 2-butyric acid cyclopentanoic acid anhydride, propionic acid cyclohexane acid anhydride, and the like.

  Examples of the combination of a cyclic alkyl group and an aryl group include benzoic acid cyclopentanoic acid anhydride, 4-methylbenzoic acid cyclopentanoic acid anhydride, benzoic acid cyclohexane acid anhydride, and the like.

  Examples of combinations of cyclic alkyl groups and functional hydrocarbon groups include: cycloacetic acid cyclopentanoic acid anhydride, cyclopentanoic acid trifluoroacetic acid anhydride, cyclopentanoic acid 2-cyanoacetic acid anhydride, cyclopentanoic acid methoxyacetic acid An anhydride, cyclohexane acid fluoroacetic anhydride, etc. are mentioned.

  Examples of combinations of alkenyl groups include acrylic acid 2-methylacrylic anhydride, acrylic acid 3-methylacrylic anhydride, acrylic acid 3-butenoic anhydride, 2-methylacrylic acid 3-methylacrylic anhydride Thing, etc.

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

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

  Examples of combinations of alkenyl groups and functional hydrocarbon groups include acrylic acid fluoroacetic anhydride, acrylic acid trifluoroacetic acid anhydride, acrylic acid 2-cyanoacetic acid anhydride, acrylic acid methoxyacetic acid anhydride, 2- And methyl acrylic acid fluoroacetic anhydride.

  Examples of combinations of alkynyl groups include propionic acid 2-butynoic acid anhydride, propionic acid 3-butynoic acid anhydride, 2-butyric acid 3-butynoic acid anhydride, and the like.

  Examples of the combination of an alkynyl group and an aryl group include propionic anhydride of benzoic acid, propionic anhydride of 4-methylbenzoic acid, and 2-butynoic anhydride of benzoic acid.

  Examples of combinations of alkynyl groups and functional hydrocarbon groups include propionic acid fluoroacetic anhydride, propionic acid trifluoroacetic acid anhydride, propionic acid 2-cyanoacetic acid anhydride, propionic acid methoxyacetic acid anhydride, 2- And butyric acid fluoroacetic anhydride.

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

  Examples of combinations of aryl groups and functional hydrocarbon groups include benzoic acid fluoroacetic anhydride, benzoic acid trifluoroacetic acid anhydride, benzoic acid 2-cyanoacetic acid anhydride, benzoic acid methoxyacetic acid anhydride, 4- And methylbenzoic acid fluoroacetic anhydride.

  Examples of combinations of hydrocarbon groups having functional groups include fluoroacetic acid trifluoroacetic anhydride, fluoroacetic acid 2-cyanoacetic acid anhydride, fluoroacetic acid methoxyacetic acid anhydride, trifluoroacetic acid 2-cyanoacetic acid anhydride, etc. Is mentioned.

Of the acid anhydrides forming the chain structure, preferably,
Acetic anhydride, propionic anhydride, 2-methylpropionic anhydride, cyclopentanecarboxylic anhydride, cyclohexanecarboxylic anhydride, etc., acrylic anhydride, 2-methylacrylic anhydride, 3-methylacrylic anhydride 2,3-dimethylacrylic anhydride, 3,3-dimethylacrylic anhydride, 3-butenoic anhydride, 2-methyl-3-butenoic anhydride, propionic anhydride, 2-butynoic anhydride Benzoic anhydride, 2-methylbenzoic anhydride, 4-methylbenzoic anhydride, 4-tert-butylbenzoic anhydride, trifluoroacetic anhydride, 3,3,3-trifluoropropionic anhydride 2- (trifluoromethyl) acrylic anhydride, 2- (4-fluorophenyl) acrylic anhydride, 4-fluorobenzoic anhydride, 2,3,4,5,6 Pentafluorobenzoic acid anhydride, Metokishigi anhydride, Etokishigi anhydride,
And more preferably
Acrylic anhydride, 2-methylacrylic anhydride, 3-methylacrylic anhydride, benzoic anhydride, 2-methylbenzoic anhydride, 4-methylbenzoic anhydride, 4-tert-butylbenzoic anhydride 4-fluorobenzoic anhydride, 2,3,4,5,6-pentafluorobenzoic anhydride, methoxyformic anhydride, and ethoxyformic anhydride.

  These compounds can improve the charge / discharge rate characteristics, input / output characteristics, and impedance characteristics, especially after endurance testing, by appropriately forming a bond with lithium oxalate salt to form a film with excellent durability. It is preferable from a viewpoint that can be made.

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

First, specific examples of acid anhydrides in which R ¹ and R ² are bonded to each other to form a 5-membered ring structure include succinic anhydride, 4-methyl succinic anhydride, and 4,4-dimethyl succinic anhydride. 4,5-dimethyl succinic anhydride, 4,4,5-trimethyl succinic anhydride, 4,4,5,5-tetramethyl succinic anhydride, 4-vinyl succinic anhydride, 4,5- Divinyl succinic anhydride, 4-phenyl succinic anhydride, 4,5-diphenyl succinic anhydride, 4,4-diphenyl succinic anhydride, citraconic anhydride, maleic anhydride, 4-methyl maleic anhydride 4,5-dimethylmaleic anhydride, 4-phenylmaleic anhydride, 4,5-diphenylmaleic anhydride, itaconic anhydride, 5-methylitaconic anhydride, 5,5-dimethylitaconic anhydride , Phthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride and the like, and the like their analogs thereof.

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

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

Specific examples of acid anhydrides in which R ¹ and R ² are bonded to each other to form a cyclic structure and are substituted with a halogen atom include 4-fluorosuccinic anhydride, 4,4-difluorosuccinic anhydride 4,4-difluorosuccinic anhydride, 4,4,5-trifluorosuccinic anhydride, 4,4,5,5-tetrafluorosuccinic anhydride, 4-fluoromaleic anhydride, 4,5 -Difluoromaleic anhydride, 5-fluoroitaconic anhydride, 5,5-difluoroitaconic anhydride, etc., and analogs thereof.

Of the acid anhydrides in which R ¹ and R ² are bonded,
Succinic anhydride, 4-methyl succinic anhydride, 4-vinyl succinic anhydride, 4-phenyl succinic anhydride, citraconic anhydride, maleic anhydride, 4-methyl maleic anhydride, 4-phenyl maleic anhydride , Itaconic anhydride, 5-methylitaconic anhydride, glutaric anhydride, phthalic anhydride, cyclohexane-1,2-dicarboxylic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, cyclopentanetetra Carboxylic dianhydride, pyromellitic anhydride, 4-fluorosuccinic anhydride, 4-fluoromaleic anhydride, 5-fluoroitaconic anhydride,
And more preferably
Succinic anhydride, 4-methyl succinic anhydride, 4-vinyl succinic anhydride, citraconic anhydride, cyclohexane-1,2-dicarboxylic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, cyclopentanetetra They are carboxylic dianhydride, pyromellitic anhydride, and 4-fluorosuccinic anhydride. These compounds are preferable because a bond with a lithium oxalate salt is appropriately formed to form a film having excellent durability, and the capacity retention rate after the durability test is improved.

The molecular weight of the carboxylic acid anhydride is not limited and is arbitrary as long as the effects of the present invention are not significantly impaired. Usually, it is 90 or more, preferably 95 or more, and is usually 300 or less, preferably 200 or less. . When the molecular weight of the carboxylic acid anhydride is within the above range, an increase in the viscosity of the electrolytic solution can be suppressed and the film density is optimized, so that the durability can be appropriately improved.

  Moreover, there is no restriction | limiting in particular in the manufacturing method of the said carboxylic acid anhydride, It is possible to select and manufacture a well-known method arbitrarily. Any one of the carboxylic acid anhydrides described above may be contained alone in the nonaqueous electrolytic solution of the present invention, or two or more may be used in any combination and ratio.

  Moreover, there is no restriction | limiting in particular in content of the carboxylic acid anhydride with respect to the non-aqueous electrolyte solution of this invention, Although it is arbitrary unless the effect of this invention is impaired remarkably, it is 0 normally with respect to the non-aqueous electrolyte solution of this invention. It is desirable to contain it at a concentration of 0.01% by mass or more, preferably 0.1% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less. When the content of the carboxylic acid anhydride is within the above range, the effect of improving the cycle characteristics is easily exhibited, and the battery characteristics are easily improved because the reactivity is suitable.

<1-4-7. Overcharge prevention agent>
In the non-aqueous electrolyte solution of the present invention, an overcharge inhibitor can be used in order to effectively suppress battery explosion / ignition when the non-aqueous electrolyte secondary battery is in an overcharged state or the like. .

  As overcharge inhibitors, biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, diphenylcyclohexane, 1,1,3-trimethyl Aromatic compounds such as -3-phenylindane; partially fluorinated products of the above aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoro Fluorinated anisole compounds such as anisole, 2,6-difluoroanisole and 3,5-difluoroanisole; 3-propylphenyl acetate, 2-ethylphenyl acetate, benzylphenyl acetate, methylphenol Le acetate, benzyl acetate, aromatic acetates such as phenethyl phenylacetate; diphenyl carbonate, and aromatic carbonates such as methyl phenyl carbonate. Among them, biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, diphenylcyclohexane, 1,1,3-trimethyl-3-phenylindane 3-propylphenyl acetate, 2-ethylphenyl acetate, benzylphenyl acetate, methylphenyl acetate, benzyl acetate, phenethylphenyl acetate, diphenyl carbonate and methylphenyl carbonate are preferred. These may be used alone or in combination of two or more. When two or more kinds are used in combination, in particular, a combination of cyclohexylbenzene and t-butylbenzene or t-amylbenzene, biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, The combination of at least one selected from aromatic compounds not containing oxygen such as t-amylbenzene and at least one selected from oxygen-containing aromatic compounds such as diphenyl ether and dibenzofuran is used to prevent overcharge and preserve at high temperature. It is preferable from the viewpoint of balance of characteristics.

  The content of the overcharge inhibitor is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired. The content of the overcharge inhibitor is usually 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and still more preferably 0.1% by mass or more in 100% by mass of the non-aqueous electrolyte. It is 5 mass% or more, and is 5 mass% or less normally, Preferably it is 4.8 mass% or less, More preferably, it is 4.5 mass% or less. If it is this range, the effect of an overcharge inhibiting agent will be fully revealed, and battery characteristics, such as a high temperature storage characteristic, will improve.

<1-4-8. Other auxiliaries>
Other known auxiliary agents can be used in the non-aqueous electrolyte solution of the present invention. As other auxiliaries,
Carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate;
Methyl-2-propynyl oxalate, ethyl-2-propynyl oxalate, bis (2-propynyl) oxalate, 2-propynyl acetate, 2-propynyl formate, 2-propynyl methacrylate, di (2-propynyl) glutarate, Methyl-2-propynyl carbonate, ethyl-2-propynyl carbonate, bis (2-propynyl) carbonate, 2-butyne-1,4-diyl-dimethanesulfonate, 2-butyne-1,4-diyl-diethanesulfonate, 2-butyne-1,4-diyl-diformate, 2-butyne-1,4-diyl-diacetate, 2-butyne-1,4-diyl-dipropionate, 4-hexadiyne-1,6-diyl-dimethanesulfonate 2-propynyl-methanesulfonate, 1-methyl- -Propynyl-methanesulfonate, 1,1-dimethyl-2-propynyl-methanesulfonate, 2-propynyl-ethanesulfonate, 2-propynyl-vinylsulfonate, 2-propynyl-2- (diethoxyphosphoryl) acetate, 1-methyl- Triple bond-containing compounds such as 2-propynyl-2- (diethoxyphosphoryl) acetate and 1,1-dimethyl-2-propynyl-2- (diethoxyphosphoryl) acetate;
Spiro compounds such as 2,4,8,10-tetraoxaspiro [5.5] undecane and 3,9-divinyl-2,4,8,10-tetraoxaspiro [5.5] undecane;
Ethylene sulfite, methyl fluorosulfonate, ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, busulfan, sulfolene, ethylene sulfate, vinylene sulfate, diphenylsulfone, N, N-dimethylmethanesulfonamide, N, N- Sulfur-containing compounds such as diethyl methanesulfonamide, trimethylsilyl methyl sulfate, trimethylsilyl ethyl sulfate, 2-propynyl-trimethylsilyl sulfate;
2-isocyanatoethyl acrylate, 2-isocyanatoethyl methacrylate, 2-isocyanatoethyl crotonate, 2- (2-isocyanatoethoxy) ethyl acrylate, 2- (2-isocyanatoethoxy) ethyl methacrylate, 2- (2 -Isocyanatoethoxy) isocyanate compounds such as ethyl crotonate;
Nitrogen-containing compounds such as 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide;
Hydrocarbon compounds such as heptane, octane, nonane, decane, cycloheptane;
Fluorine-containing aromatics such as fluorobenzene, difluorobenzene, hexafluorobenzene, benzotrifluoride, pentafluorophenyl methanesulfonate, pentafluorophenyl trifluoromethanesulfonate, pentafluorophenyl acetate, pentafluorophenyl trifluoroacetate, and methylpentafluorophenyl carbonate Compound;
Boric acid tris (trimethylsilyl), boric acid tris (trimethoxysilyl), phosphoric acid tris (trimethylsilyl), phosphoric acid tris (trimethoxysilyl), dimethoxyaluminoxytrimethoxysilane, diethoxyaluminoxytriethoxysilane, dipropoxyalumino Xytriethoxysilane, dibutoxyaluminoxytrimethoxysilane, dibutoxyaluminoxytriethoxysilane, titanium tetrakis (trimethylsiloxide), titanium tetrakis (triethylsiloxide),
Silane compounds such as;
2-propynyl 2- (methanesulfonyloxy) propionate, 2-methyl 2- (methanesulfonyloxy) propionate, 2-ethyl 2- (methanesulfonyloxy) propionate, 2-propynyl methanesulfonyloxyacetate, methanesulfonyloxy Ester compounds such as 2-methyl acetate and 2-ethyl methanesulfonyloxyacetate;
Lithium ethylmethyloxycarbonylphosphonate, lithium ethylethyloxycarbonylphosphonate, lithium ethyl-2-propynyloxycarbonylphosphonate, lithium ethyl-1-methyl-2-propynyloxycarbonylphosphonate, lithium ethyl-1,1-dimethyl-2-propynyl Lithium salts such as oxycarbonylphosphonate;
Etc. These may be used alone or in combination of two or more. By adding these auxiliaries, capacity maintenance characteristics and cycle characteristics after high temperature storage can be improved.

  The content of other auxiliaries is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. The content of other auxiliaries is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more in 100% by mass of the non-aqueous electrolyte solution. 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less. If it is this range, the effect of other adjuvants will be sufficiently exhibited, and battery characteristics such as high-load discharge characteristics will be improved.

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

<2. Non-aqueous electrolyte secondary battery>
A non-aqueous electrolyte secondary battery according to one embodiment of the present invention is provided with a positive electrode having a current collector and a positive electrode active material layer provided over the current collector, and the current collector and the current collector. A negative electrode having a negative electrode active material layer and capable of occluding and releasing ions, and the non-aqueous electrolyte solution according to one embodiment of the present invention described above. In addition, the non-aqueous electrolyte secondary battery according to one embodiment of the present invention preferably includes a negative electrode and a positive electrode capable of inserting and extracting lithium ions, and the non-aqueous electrolyte solution according to one embodiment of the present invention described above.

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

<2-2. Non-aqueous electrolyte>
As the non-aqueous electrolyte, the above-described non-aqueous electrolyte of the present invention is used. In addition, in the range which does not deviate from the meaning of this invention, it is also possible to mix | blend and use other nonaqueous electrolyte solutions with respect to the nonaqueous electrolyte solution of this invention.

<2-3. Negative electrode>
The negative electrode has a negative electrode active material layer on a current collector, and the negative electrode active material layer contains a negative electrode active material. Hereinafter, the negative electrode active material will be described.
As the negative electrode active material, any material capable of electrochemically occluding and releasing lithium ions,
There is no particular limitation. Specific examples thereof include carbonaceous materials, metal alloy materials, lithium-containing metal composite oxide materials, and the like. These may be used individually by 1 type, and may be used together combining 2 or more types arbitrarily.
The negative electrode has a current collector and a negative electrode active material layer on the current collector, and the negative electrode active material layer is composed of a silicon simple metal, an alloy and a compound, a tin simple metal, an alloy and a compound, and a carbonaceous material. It is preferable to contain at least one selected from the group consisting of a material and a lithium titanium composite oxide.

<2-3-1. Carbonaceous material>
As a carbonaceous material used as a negative electrode active material,
(1) natural graphite,
(2) a carbonaceous material obtained by heat-treating an artificial carbonaceous material and an artificial graphite material at least once in the range of 400 to 3200 ° C .;
(3) a carbonaceous material in which the negative electrode active material layer is composed of at least two types of carbonaceous materials having different crystallinity and / or has an interface in contact with the different crystalline carbonaceous materials,
(4) a carbonaceous material in which the negative electrode active material layer is composed of carbonaceous materials having at least two or more different orientations and / or has an interface in contact with the carbonaceous materials having different orientations;
Is preferably a good balance between initial irreversible capacity and high current density charge / discharge characteristics. In addition, the carbonaceous materials (1) to (4) may be used alone or in combination of two or more in any combination and ratio.

  Specific examples of the artificial carbonaceous material and the artificial graphite material of (2) above include natural graphite, coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, or those obtained by oxidizing these pitches, Needle coke, pitch coke and carbon materials partially graphitized thereof, furnace black, acetylene black, organic pyrolysis products such as pitch-based carbon fibers, carbonizable organic materials, and these carbides or carbonizable organic materials Examples thereof include solutions dissolved in low-molecular organic solvents such as benzene, toluene, xylene, quinoline, and n-hexane, and carbides thereof.

<2-3-2. Configuration, physical properties, preparation method of carbonaceous negative electrode>
About the property about carbonaceous material, the negative electrode containing carbonaceous material, the electrode-izing method, the current collector, and the non-aqueous electrolyte secondary battery, the physical properties and shapes shown in the following (1) to (13) Of these characteristics, at least one kind is preferably satisfied, and two or more kinds are more preferably satisfied at the same time.

(1) X-ray parameters The d-value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method of carbonaceous materials is usually 0.335 to 0.340 nm, particularly 0.335. Those having a thickness of ˜0.338 nm, particularly 0.335 to 0.337 nm are preferred. The crystallite size (Lc) determined by X-ray diffraction by the Gakushin method is usually 1.0 nm or more, preferably 1.5 nm or more, and particularly preferably 2 nm or more.

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

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

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

  When the Raman R value is below the above range, the crystallinity of the particle surface becomes too high, and there are cases where the number of sites where Li enters between layers decreases with charge / discharge. That is, charge acceptance may be reduced. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, if it exceeds the above range, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte is increased, and the efficiency may be lowered and the gas generation may be increased.

Further, the Raman half-width in the vicinity of 1580 cm ^{−1 of the} carbonaceous material is not particularly limited, but is usually 10 cm ⁻¹ or more, preferably 15 cm ⁻¹ or more, and usually 100 cm ⁻¹ or less, and 80 cm ⁻¹ or less. Preferably, 60 cm ⁻¹ or less is more preferable, and 40 cm ⁻¹ or less is particularly preferable.

  If the Raman half width is less than the above range, the crystallinity of the particle surface becomes too high, and there are cases where the number of sites where Li enters between layers decreases with charge and discharge. That is, charge acceptance may be reduced. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, if it exceeds the above range, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte is increased, and the efficiency may be lowered and the gas generation may be increased.

The Raman spectrum is measured by using a Raman spectrometer (for example, a Raman spectrometer manufactured by JASCO Corporation) to drop the sample naturally into the measurement cell, filling it, and irradiating the sample surface in the cell with argon ion laser light. However, the cell is rotated in a plane perpendicular to the laser beam. The resulting Raman spectrum, the intensity IA of a peak PA around 1580 cm ^-1, and measuring the intensity IB of the peak PB around 1360 cm ^-1, and calculates the intensity ratio R (R = IB / IA) . The Raman R value calculated by the measurement is defined as the Raman R value of the carbonaceous material in the present invention. Further, the half width of the peak PA near 1580 cm ⁻¹ of the obtained Raman spectrum is measured, and this is defined as the Raman half width of the carbonaceous material in the present invention.

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

(4) BET specific surface area The BET specific surface area of the carbonaceous material has a specific surface area value measured by the BET method of usually 0.1 m ² · g ⁻¹ or more and 0.7 m ² · g ⁻¹ or more. , more preferably from 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, preferably ^{25 m} 2 · ^{g -1} or less, more preferably ^{15 m} 2 · ^{g -1} or less, ^{10 m} 2 · ^{g -1} or less are especially preferred.

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

  The specific surface area was measured by the BET method using a surface area meter (a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 350 ° C. for 15 minutes under nitrogen flow, Using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure becomes 0.3, the nitrogen adsorption BET one-point method by the gas flow method is used. The specific surface area determined by the measurement is defined as the BET specific surface area of the carbonaceous material in the present invention.

(5) Circularity When the circularity is measured as a spherical degree of the carbonaceous material, it is preferably within the following range. The circularity is defined as “circularity = (peripheral length of an equivalent circle having the same area as the particle projection shape) / (actual perimeter of the particle projection shape)”, and is theoretical when the circularity is 1. Become a true sphere.

  The degree of circularity of particles having a carbonaceous material particle size in the range of 3 to 40 μm is preferably closer to 1, more preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 0.8 or more. 0.85 or more is particularly preferable, and 0.9 or more is most preferable.

  High current density charge / discharge characteristics improve as the degree of circularity increases. Therefore, when the circularity is less than the above range, the filling property of the negative electrode active material is lowered, the resistance between particles is increased, and the high current density charge / discharge characteristics may be lowered for a short time.

  The circularity is measured using a flow type particle image analyzer (FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample was dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. The detection range is specified as 0.6 to 400 μm, and the particle size is measured in the range of 3 to 40 μm. The circularity obtained by the measurement is defined as the circularity of the carbonaceous material in the present invention.

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

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

When the tap density is below the above range, the packing density is difficult to increase when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, when the above range is exceeded, there are too few voids between particles in the electrode, it is difficult to ensure conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.

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

The orientation ratio is measured by X-ray diffraction after pressure-molding the sample. Set the molding obtained by filling 0.47 g of the sample into a molding machine with a diameter of 17 mm and compressing it with 58.8 MN · m ^{-2 so} that it is flush with the surface of the sample holder for measurement. X-ray diffraction is measured. From the (110) diffraction and (004) diffraction peak intensities of the obtained carbon, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated. The orientation ratio calculated by the measurement is defined as the orientation ratio of the carbonaceous material in the present invention.

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

(8) Aspect ratio (powder)
The aspect ratio of the carbonaceous material is usually 1 or more and usually 10 or less, preferably 8 or less, more preferably 5 or less. If the aspect ratio exceeds the above range, streaking or a uniform coated surface cannot be obtained when forming an electrode plate, and the high current density charge / discharge characteristics may deteriorate. The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the carbonaceous material.

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

(9) Electrode preparation For production of the negative electrode, any known method can be used as long as the effects of the present invention are not significantly limited. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to the negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can do.

  The thickness of the negative electrode active material layer per side in the stage immediately before the non-aqueous electrolyte injection process of the battery is usually 15 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and usually 150 μm or less. 120 μm or less is preferable, and 100 μm or less is more preferable. This is because if the thickness of the negative electrode active material exceeds this range, the non-aqueous electrolyte solution hardly penetrates to the vicinity of the current collector interface, and thus the high current density charge / discharge characteristics may be deteriorated. Further, if the ratio is below this range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease. Further, the negative electrode active material may be roll-formed to form a sheet electrode, or may be formed into a pellet electrode by compression molding.

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

  In addition, the shape of the current collector may be, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal, or the like when the current collector is a metal material. Among them, a metal thin film is preferable, a copper foil is more preferable, and a rolled copper foil by a rolling method and an electrolytic copper foil by an electrolytic method are more preferable, and both can be used as a current collector.

  In addition, when 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.

  The thickness of the current collector is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. If the thickness of the metal film is less than 1 μm, the strength may be reduced, making application difficult. Moreover, when it becomes thicker than 1 mm, the shape of electrodes, such as winding, may be deformed. The current collector may be mesh.

(11) Ratio of thickness of current collector and negative electrode active material layer The ratio of the thickness of current collector and negative electrode active material layer is not particularly limited. The value of “material 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 and 0.4 or more is preferable. The above is more preferable.

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

(12) Electrode density The electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g · cm ⁻³ or more. 2 g · cm ⁻³ or more is more preferable, 1.3 g · cm ⁻³ or more is more preferable, 2.2 g · cm ⁻³ or less is preferable, 2.1 g · cm ⁻³ or less is more preferable, and 2.0 g · ^{cm -3} and more preferably less, 1.9 g · ^{cm -3} or less are particularly preferred. When the density of the negative electrode active material existing on the current collector exceeds the above range, the negative electrode active material particles are destroyed, and the initial irreversible capacity increases or non-aqueous system near the current collector / negative electrode active material interface. There is a case where high current density charge / discharge characteristics are deteriorated due to a decrease in permeability of the electrolytic solution. On the other hand, if the amount is less than the above range, the conductivity between the negative electrode active materials decreases, the battery resistance increases, and the capacity per unit volume may decrease.

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

  Specific examples include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, 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 polymer such as butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene Soft resinous polymers such as vinyl acetate copolymer and propylene / α-olefin copolymer; Fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene / ethylene copolymer Polymers: Polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions), and the like. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.

  The solvent for forming the slurry is not particularly limited as long as it is a solvent capable of dissolving or dispersing the negative electrode active material, the binder, and the thickener and conductive material used as necessary. Alternatively, either an aqueous solvent or an organic solvent may be used.

  Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent 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, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. .

  In particular, when an aqueous solvent is used, it is preferable to add a dispersant or the like in addition to the thickener and slurry it using a latex such as SBR. In addition, these solvents may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

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

  In particular, when a rubbery polymer typified by SBR is contained as a main component, the ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, and 0 .6% by mass or more is more preferable, and is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less.

Further, when a fluorine-based polymer typified 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.
More preferably, it is 15% by mass or less, preferably 10% by mass or less, and more preferably 8% by mass or less.

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

  Further, when 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. The above is more preferable, and is usually 5% by mass or less, preferably 3% by mass or less, and more preferably 2% by mass or less. When the ratio of the thickener to the negative electrode active material is less than the above range, applicability may be significantly reduced. Moreover, when it exceeds the said range, the ratio of the negative electrode active material which occupies for a negative electrode active material layer will fall, and the problem that the capacity | capacitance of a battery falls and the resistance between negative electrode active materials may increase.

<2-3-3. Structure, physical properties, preparation method of negative electrode using metal compound material and metal compound material>
As the metal compound material used as the negative electrode active material, if lithium can be occluded / released, a single metal or alloy that forms a lithium alloy, or oxides, carbides, nitrides, silicides, sulfides thereof, Any compound such as 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, P, Pb, Sb, Si, Sn, Sr, and Zn. Among these, a single metal or an alloy that forms a lithium alloy is preferable, and a material containing a group 13 or group 14 metal / metalloid element (that is, excluding carbon) is more preferable. Furthermore, silicon (Si ), Tin (Sn) or lead (Pb) (hereinafter, these three elements may be referred to as “specific metal elements”), single metals or alloys containing these atoms, or their metals (specific metal elements) ), And silicon simple metals, alloys and compounds, and tin simple metals, alloys and compounds are particularly preferred. These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  Examples of the negative electrode active material having at least one kind of atom selected from the specific metal element include a single metal of any one specific metal element, an alloy composed of two or more specific metal elements, one type, or two or more types Alloys composed of the specified metal element and one or more other metal elements, and compounds containing one or more specified metal elements, or oxides, carbides and nitrides of the compounds -Complex compounds such as silicides, sulfides, and phosphides are listed. By using these simple metals, alloys or metal compounds as the negative electrode active material, the capacity of the battery can be increased.

  Moreover, the compound which these complex compounds combined with several elements, such as a metal simple substance, an alloy, or a nonmetallic element, can also be mentioned as an example. More specifically, for example, in silicon and tin, an alloy of these elements and a metal that does not operate as a negative electrode can be used. In addition, for example, in the case of tin, a complex compound containing 5 to 6 kinds of elements in combination with a metal that acts as a negative electrode other than tin and silicon, a metal that does not operate as a negative electrode, and a nonmetallic element can also be used. .

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

In addition, although the capacity per unit mass is inferior to that of using a single metal or an alloy, the following compounds containing silicon and / or tin are also preferred because of excellent cycle characteristics.
-The element ratio of silicon and / or tin and oxygen is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. “Silicon and / or tin oxide” of 3 or less, more preferably 1.1 or less.
-Element ratio of silicon and / or tin and nitrogen is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. “Silicon and / or tin nitride” of 3 or less, more preferably 1.1 or less.
The element ratio of silicon and / or tin to carbon is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and usually 1.5 or less, preferably 1. “Carbide of silicon and / or tin” of 3 or less, more preferably 1.1 or less.

  In addition, any one of the above-described negative electrode active materials 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 according to one embodiment of the present invention can be manufactured using any known method. Specifically, as a manufacturing method of the negative electrode, for example, a method in which a negative electrode active material added with a binder or a conductive material is roll-formed as it is to form a sheet electrode, or a compression-molded pellet electrode and The above negative electrode is usually applied to a negative electrode current collector (hereinafter also referred to as “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, by adding a binder, a thickener, a conductive material, a solvent, etc. to the above-mentioned negative electrode active material to form a slurry, applying this to the negative electrode current collector, drying, and pressing to increase the density A negative electrode active material layer is formed on the negative electrode current collector.

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

  The thickness of the negative electrode current collector is usually 1 μm or more, preferably 5 μm or more, and is 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 conversely if it is too thin, handling may be difficult.

  In addition, in order to improve the binding effect with the negative electrode active material layer formed on the surface, the surface of these negative electrode current collectors is preferably subjected to a roughening treatment in advance. Surface roughening methods include blasting, rolling with a rough surface roll, abrasive cloth paper with abrasive particles fixed, grinding wheel, emery buff, machine that polishes the current collector surface with a wire brush equipped with steel wire, etc. Examples thereof include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method.

  The 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 addition, the “negative electrode material” in this specification refers to a material in which a negative electrode active material and a conductive material are combined.

The content of the negative electrode active material in the negative electrode material is usually 70% by mass or more, particularly preferably 75% by mass or more, and usually 97% by mass or less, particularly preferably 95% by mass or less. When the content of the negative electrode active material is too small, the capacity of the secondary battery using the obtained negative electrode tends to be insufficient, and when the content is too large, the content of the binder or the like is relatively insufficient. This is because the strength of the negative electrode tends to be insufficient. When two or more negative electrode active materials are used in combination, the total amount of the negative electrode active materials may be set to 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 a ratio. In particular, it is preferable to use a carbon material as the conductive material because the carbon material acts as an active material. The content of the conductive material in the negative electrode material is usually 3% by mass or more, particularly preferably 5% by mass or more, and usually 30% by mass or less, particularly preferably 25% by mass or less. When the content of the conductive material is too small, the conductivity tends to be insufficient. When the content is too large, the content of the negative electrode active material or the like is relatively insufficient, which tends to decrease the battery capacity and strength. . Note that when two or more conductive materials are used in combination, the total amount of the conductive materials may satisfy the above range.

  As the binder used for the negative electrode, any material can be used as long as it is a material safe with respect to the solvent and the electrolytic solution used at the time of producing the electrode. 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 a ratio. The content of the binder is usually 0.5 parts by mass or more, particularly preferably 1 part by mass or more, and usually 10 parts by mass or less, particularly preferably 8 parts by mass or less, with respect to 100 parts by mass of the negative electrode material. When the content of the binder is too small, the strength of the obtained negative electrode tends to be insufficient. When the content is too large, the content of the negative electrode active material and the like is relatively insufficient, and thus the battery capacity and conductivity tend to be insufficient. It is because it becomes. In addition, when using two or more binders together, what is necessary is just to make it the total amount of a binder satisfy | fill the said range.

  Examples of the thickener used for the negative electrode include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. The thickener may be used as necessary, but when used, the thickener content 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, or a thickener as necessary, and using an aqueous solvent or an organic solvent as a dispersion medium. . As the aqueous solvent, water is usually used, but a solvent other than water such as alcohols such as ethanol or cyclic amides such as N-methylpyrrolidone is used in combination at a ratio of about 30% by mass or less with respect to water. You can also. As the organic solvent, usually, cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic carbonization such as anisole, toluene and xylene Examples thereof include alcohols such as hydrogens, butanol and cyclohexanol, among which cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. . Any one of these may be used alone, or two or more may be used in any combination and ratio.

  The viscosity of the slurry is not particularly limited as long as it is a viscosity that can be applied onto the current collector. What is necessary is just to prepare suitably by changing the usage-amount of a solvent etc. at the time of preparation of a slurry so that it may become the viscosity which can be apply | coated.

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

The electrode structure when the negative electrode active material is made into an electrode by the above method is not particularly limited, but the density of the active material 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, 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.

  When the density of the active material existing on the current collector exceeds the above range, the active material particles are destroyed, the initial irreversible capacity increases, and the non-aqueous electrolyte solution near the current collector / active material interface There is a case where high current density charge / discharge characteristics are deteriorated due to a decrease in permeability. On the other hand, below the above range, the conductivity between the active materials may be reduced, the battery resistance may be increased, and the capacity per unit volume may be reduced.

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

  In such a form, the surface of the particle is observed with a scanning electron microscope, the particle is embedded in a resin to produce a thin piece of resin, and the cross section of the particle is cut out, or the coating film made of particles is formed with a cross section polisher. After cutting out the particle cross-section, it can be observed by an observation method such as particle cross-sectional observation with a scanning electron microscope.

  The content ratio of the metal compound material used in the negative electrode active material containing the metal compound 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 0.5% by mass or more, more preferably 2% by mass or more, particularly preferably 3% by mass or more, and usually 99% by mass or less, preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably. It is 30% by mass or less, more preferably 25% by mass or less, particularly preferably 15% by mass or less, and most preferably 10% by mass or less. This range is preferable in that a sufficient capacity can be obtained.

  About the carbonaceous material used for the negative electrode active material containing a metal compound type material and a carbonaceous material, it is preferable to satisfy the requirements described in <2-3-2>. Moreover, it is desirable that the metal compound material satisfy the following.

As the single metal or alloy forming the lithium alloy, any conventionally known one can be used. From the viewpoint of capacity and cycle life, the single metal forming the lithium alloy is, for example, Fe, Co, Sb, Metal selected from the group consisting of Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, Nb, Mo, Cu, Zn, Ge, In, Ti, etc., or a compound thereof Is preferred. Moreover, as an alloy which forms a lithium alloy, the metal chosen from the group which consists of Si, Sn, As, Sb, Al, Zn, and W, or its compound is preferable.

A single metal or alloy forming a lithium alloy, or a compound thereof such as an oxide, carbide, nitride, silicide, or sulfide is a metal oxide, metal carbide, metal nitride, metal silicide, or metal sulfide. Etc. Moreover, you may use the alloy which consists of 2 or more types of metals. Among these, Si or Si compound is preferable in terms of increasing capacity. In this specification, Si or Si compounds are collectively referred to as Si compounds. Specific examples of the Si compound include SiOx, SiNx, SiCx, SiZxOy (Z is C or N), and SiOx is preferable. The value of x in the above general formula is not particularly limited, but usually 0 ≦ x <2. The general formula SiOx is obtained using Si dioxide (SiO ₂ ) and metal Si (Si) as raw materials. SiOx has a larger theoretical capacity than graphite, and amorphous Si or nano-sized Si crystals easily allow alkali ions such as lithium ions to enter and exit, so that a high capacity can be obtained.

The value of x in SiOx is not particularly limited, but usually x is 0 ≦ x <2, preferably 0.2 or more, more preferably 0.4 or more, and further preferably 0.6 or more. Preferably it is 1.8 or less, More preferably, it is 1.6 or less, More preferably, it is 1.4 or less. If it is this range, it becomes high capacity | capacitance and it becomes possible to reduce the irreversible capacity | capacitance by the coupling | bonding of Li and oxygen.
As a method for confirming that the metal compound material is a metal material that can be alloyed with lithium, identification of the metal particle phase by X-ray diffraction, observation of particle structure by electron microscope, elemental analysis, fluorescence Elemental analysis by X-rays can be mentioned.

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

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

  The oxygen content of the metal compound material used in the negative electrode active material containing the metal compound 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, Moreover, it is 8 mass% or less normally, Preferably it is 5 mass% or less. The oxygen distribution state in the particle may exist near the surface, may exist inside the particle, or may exist uniformly within the particle, but is preferably present near the surface. It is preferable for the oxygen content of the metal compound-based material to be in the above-mentioned range because the volume expansion associated with charge / discharge is suppressed due to strong bonding between Si and O and the cycle characteristics are excellent.

  Moreover, about the negative electrode preparation of the metal compound type material used for the negative electrode active material containing a metal compound type material and a carbonaceous material, the thing as described in said <2-3-1> carbonaceous material can be used.

<2-3-5. Lithium-containing metal composite oxide material, and negative electrode configuration, physical properties, and preparation method 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 lithium-containing composite metal oxide materials containing titanium are preferable, and lithium and titanium composite oxidation (Hereinafter abbreviated as “lithium titanium composite oxide”) is particularly preferable. That is, it is particularly preferable to use a lithium titanium composite oxide having a spinel structure in a negative electrode active material for a non-aqueous electrolyte secondary battery because the output resistance is greatly reduced.

  In addition, lithium or titanium of the lithium titanium composite oxide is at least selected from the group consisting of other metal elements such as Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. Those substituted with one element are also preferred.

  The metal oxide is a lithium titanium composite oxide represented by the general formula (6). In the general formula (6), 0.7 ≦ x ≦ 1.5, 1.5 ≦ y ≦ 2.3, It is preferable that 0 ≦ z ≦ 1.6 because the structure upon doping and dedoping of lithium ions is stable.

LixTiyMzO ₄ (6)
[In General Formula (6), M represents at least one element selected from the group consisting of Na, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn, and Nb. ]

Among the compositions represented by the general formula (6),
(A) 1.2 ≦ x ≦ 1.4, 1.5 ≦ y ≦ 1.7, z = 0
(B) 0.9 ≦ x ≦ 1.1, 1.9 ≦ y ≦ 2.1, z = 0
(C) 0.7 ≦ x ≦ 0.9, 2.1 ≦ y ≦ 2.3, z = 0
This structure is particularly preferable because of a good balance of battery performance.

Particularly preferred representative compositions of the above compounds are Li _4/3 Ti _5/3 O ₄ in (a), Li ₁ Ti ₂ O ₄ in (b), and Li _4/5 Ti _11/5 O in (c). ₄ . As for the structure of Z ≠ 0, for example, Li _4/3 Ti _4/3 Al _1/3 O ₄ is preferable.

  In addition to the above requirements, the lithium titanium composite oxide as the negative electrode active material in the present invention further satisfies at least one of the characteristics such as physical properties and shapes shown in the following (1) to (13). It is preferable to satisfy two or more at the same time.

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

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

  The specific surface area was measured by the BET method using a surface area meter (a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 350 ° C. for 15 minutes under nitrogen flow, Using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure becomes 0.3, the nitrogen adsorption BET one-point method by the gas flow method is used. The specific surface area determined by the measurement is defined as the BET specific surface area of the lithium titanium composite oxide in the present invention.

(2) Volume-based average particle diameter The volume-based average particle diameter of lithium-titanium composite oxide (secondary particle diameter when primary particles are aggregated to form secondary particles) is determined by laser diffraction / scattering method. It is defined by the obtained volume-based average particle diameter (median diameter).

  The volume-based average particle size of the lithium titanium composite oxide is 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, 30 μm. The following is more preferable, and 25 μm or less is further preferable.

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

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

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

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

(4) Shape As the shape of the lithium titanium composite oxide particles, a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, a column shape, etc., which are conventionally used, are used. Thus, it is preferable to form secondary particles, and the shape of the secondary particles is spherical or elliptical.

In general, an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken. Therefore, the primary particles are aggregated to form secondary particles rather than a single particle active material composed of only primary particles, so that the expansion and contraction stress is relieved and deterioration is prevented.

  In addition, spherical or oval spherical particles are less oriented during molding of the electrode than plate-like equiaxed particles, so there is less expansion and contraction of the electrode during charge and discharge, and an electrode is produced. The mixing with the conductive material is also preferable because it can be easily mixed uniformly.

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

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

(6) Circularity When the circularity is measured as the spherical degree of the lithium titanium composite oxide, it is preferably within the following range. The circularity is defined as “circularity = (peripheral length of an equivalent circle having the same area as the particle projection shape) / (actual perimeter of the particle projection shape)”. It becomes.

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

  The circularity is measured using a flow type particle image analyzer (FPIA manufactured by Sysmex Corporation). About 0.2 g of a sample was dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. The detection range is specified as 0.6 to 400 μm, and the particle size is measured in the range of 3 to 40 μm. The circularity 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 still more preferably 2 or less. If the aspect ratio exceeds the above range, streaking or a uniform coated surface cannot be obtained when forming an electrode plate, and high current density charge / discharge characteristics may be deteriorated for a short time. The lower limit of the above range is the theoretical lower limit value of the aspect ratio of the lithium titanium composite oxide.

The aspect ratio is measured by magnifying and observing lithium titanium composite oxide particles with a scanning electron microscope. Arbitrary 50 particles fixed on the end face of a metal having a thickness of 50 μm or less are selected, and the stage on which the sample is fixed is rotated and tilted for each, and the maximum particle size is obtained when three-dimensionally observed. The diameter P ′ 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 lithium titanium composite oxide in the present invention.

(8) Method for producing negative electrode active material The method for producing lithium-titanium composite oxide is not particularly limited as long as it does not exceed the gist of the present invention. The method is used.

For example, a method of obtaining an active material by uniformly mixing a titanium source material such as titanium oxide and a source material of another element and a Li source such as LiOH, Li ₂ CO ₃ , or LiNO ₃ as necessary, and firing at a high temperature. Is mentioned.

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

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

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

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

(9) Electrode preparation As long as the effect of the present invention is not significantly limited, any known method can be used for manufacturing the electrode. For example, it is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to the negative electrode active material to form a slurry, which is applied to a current collector, dried and then pressed. Can do.

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

If it exceeds this range, the non-aqueous electrolyte solution hardly penetrates to the vicinity of the current collector interface, and thus the high current density charge / discharge characteristics may deteriorate. On the other hand, below this range, the volume ratio of the current collector to the negative electrode active material increases, and the battery capacity may decrease. Further, the negative electrode active material may be roll-formed to form a sheet electrode, or may be formed into a pellet electrode by compression molding.

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

  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 punch metal, and a foam metal when the current collector is a metal material. Among them, a metal foil film containing copper (Cu) and / or aluminum (Al) is preferable, copper foil and aluminum foil are more preferable, and rolled copper foil by a rolling method and electrolytic copper by an electrolytic method are more preferable. There are foils, both of which can be used as current collectors.

  In addition, when 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. Moreover, since the specific gravity of aluminum foil is light, when it is used as a current collector, the mass of the battery can be reduced and can be preferably used.

  A current collector made of a copper foil produced by a rolling method is suitable for use in a small cylindrical battery because the copper crystals are arranged in the rolling direction so that the negative electrode is hard to crack even if it is rounded sharply or rounded at an acute angle. be able to.

  Electrolytic copper foil, for example, immerses a metal drum in a non-aqueous electrolyte solution in which copper ions are dissolved, and causes the copper to precipitate on the surface of the drum by flowing current while rotating it. Is obtained. 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 subjected to a roughening treatment or a surface treatment (for example, a chromate treatment having a thickness of about several nm to 1 μm, a base treatment such as Ti).

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

  When the thickness of the current collector is within the above range, it is preferable from the viewpoint of improving the strength and facilitating application and stabilizing the shape of the electrode.

(11) Thickness ratio between current collector and active material layer The thickness ratio between the current collector and active material layer is not particularly limited, but “(the active material layer on one side immediately before non-aqueous electrolyte injection) The value of “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. 1 or more is more preferable.

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

(12) Electrode density The electrode structure when the negative electrode active material is converted into an electrode is not particularly limited, but the density of the active material present on the current collector is preferably 1 g · cm ⁻³ or more, and 1.2 g More preferably, cm ⁻³ or more, 1.3 g · cm ⁻³ or more is more preferable, 1.5 g · cm ⁻³ or more is particularly preferable, 3 g · cm ⁻³ or less is preferable, and 2.5 g · cm ^{−. 3} or less is more preferable, and 2
. 2 g · cm ⁻³ or less is 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 becomes weak, and the electrode and the active material may be separated. On the other hand, below the above range, the conductivity between the negative electrode active materials may decrease, and the battery resistance may increase.

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

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

  The solvent for forming the slurry is not particularly limited as long as it is a solvent that can dissolve or disperse the negative electrode active material, binder, thickener and conductive material used as necessary. Alternatively, either an aqueous solvent or an organic solvent may be used.

  Examples of the aqueous solvent include water, alcohol and the like, and examples of the organic solvent 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, hexameryl phosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like. In particular, when an aqueous solvent is used, a dispersant or the like is added in addition to the above-described thickener, and a slurry is formed 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 a ratio.

  The ratio of the binder to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and usually 20% by mass or less, 15% by mass. % Or less is preferable, 10 mass% or less is more preferable, and 8 mass% or less is more preferable.

  When the ratio of the binder to the negative electrode active material is within the above range, the binder ratio in which the binder amount 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 rubbery polymer typified 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%
. 6 mass% or more is more preferable, and is 5 mass% or less normally, 3 mass% or less is preferable, and 2 mass% or less is more preferable.

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

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

  Furthermore, when using a thickener, the ratio of the thickener to the negative electrode active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, Moreover, it is 5 mass% or less normally, 3 mass% or less is preferable and 2 mass% or less is more preferable. When the ratio of the thickener to the negative electrode active material is within the above range, it is preferable from the viewpoint of applicability of the pressure-sensitive adhesive, and the ratio of the active material in the negative electrode active material layer is preferable. This is preferable in terms of resistance between active substances.

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

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

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

V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable as the transition metal of the lithium transition metal composite oxide. Specific examples include lithium-cobalt composite oxides such as LiCoO ₂ , LiMnO ₂ , LiMn. Examples thereof include lithium / manganese composite oxides such as ₂ O ₄ and Li ₂ MnO ₄ , lithium / nickel composite oxides such as LiNiO ₂ , and the like. Further, some of the transition metal atoms that are the main components of these lithium transition metal composite oxides are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, and Si. Specific examples include lithium / cobalt / nickel composite oxides, lithium / cobalt / manganese composite oxides, lithium / nickel / manganese composite oxides, lithium / nickel / Cobalt / manganese composite oxides are listed.

Specific examples of the substituted ones include, for example, Li _{1 + a} Ni _0.5 Mn _0.5 O ₂ , Li _{1 + a} Ni _0.8 Co _0.2 O ₂ , Li _{1 + a} Ni _0.85 Co _0.10 Al _{0. 05} O ₂ , Li _{1 + a} Ni _0.33 Co _0.33 Mn _0.33 O ₂ , Li _{1 + a} Ni _0.45 Co _0.45 Mn _0.1 O ₂ , Li _{1 + a} Mn _1.8 Al _0.2 O ₄ , Li _{1 + a} Mn _1.5 Ni _0.5 O ₄ , xLi ₂ MnO _3. (1-x) Li _{1 + a} MO ₂ (M = transition metal) and the like (a = 0 <a ≦ 3.0).

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

The said positive electrode active material may be used independently and may use 2 or more types together.
The positive electrode active material layer includes lithium / cobalt composite oxide, lithium / cobalt / nickel composite oxide, lithium / manganese composite oxide, lithium / cobalt / manganese composite oxide, lithium / nickel composite oxide, lithium / nickel / An embodiment containing at least one selected from the group consisting of a manganese composite oxide and a lithium / cobalt / nickel / manganese composite oxide is preferable. The positive electrode active material layer may be LixMPO ₄ (M is the fourth in the periodic table). Also preferred is an embodiment containing at least one element selected from the group consisting of transition metals of Group 4 to Group 11 of the period, and x is 0 <x <1.2).

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

  These surface adhering substances are, for example, a method in which they are dissolved or suspended in a solvent and impregnated and added to the positive electrode active material and then dried, or a surface adhering substance precursor is dissolved or suspended in a solvent and impregnated and added to the positive electrode active material. Then, it can be made to adhere to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing simultaneously.

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

The surface adhering substance can suppress the oxidation reaction of the non-aqueous electrolyte on the surface of the positive electrode active material, and can improve the battery life. However, when the adhesion amount is less than the above range, the effect is not sufficiently exhibited. When the adhesion amount is more than the above range, the resistance may increase in order to inhibit the entry / exit of lithium ions, so the above range is preferable.

(3) Shape As the shape of the positive electrode active material particles, a lump shape, a polyhedron shape, a sphere shape, an oval sphere shape, a plate shape, a needle shape, a column shape, etc., which are conventionally used, are used. It is preferable to form secondary particles, and the shape of the secondary particles is spherical or elliptical.

  In general, an electrochemical element expands and contracts as the active material in the electrode expands and contracts as it is charged and discharged. Therefore, the active material is easily damaged due to the stress or the conductive path is broken. Therefore, the primary particles are aggregated to form secondary particles rather than a single particle active material having only primary particles, so that the stress of expansion and contraction is relieved and deterioration is prevented.

  In addition, spherical or oval spherical particles are less oriented at the time of forming the electrode than the plate-like equiaxially oriented particles, so there is less expansion and contraction of the electrode during charge and discharge, and when creating the electrode Also in the mixing with the conductive material, it is preferable because it is easily mixed uniformly.

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

  By using a metal composite oxide powder having a high tap density, a high-density positive electrode active material layer can be formed. Therefore, when the tap density of the positive electrode active material is lower than the above range, the amount of the dispersion medium necessary for forming the positive electrode active material layer increases, and the necessary amount of the conductive material and the binder increases. The filling rate of the positive electrode active material is limited, and the battery capacity may be limited. In general, the tap density is preferably as large as possible, but there is no particular upper limit. However, if the tap density is less than the above range, diffusion of lithium ions in the positive electrode active material layer using the non-aqueous electrolyte solution as a medium becomes rate-determining, and load characteristics are likely to deteriorate. There is a case.

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

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

  The median diameter d50 is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, further preferably 3 μm or more, and usually 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less. More preferably, it is 15 μm or less. If the median diameter d50 is below the above range, a high bulk density product may not be obtained. If the median diameter d50 is above the above range, it takes time to diffuse lithium in the particles. That is, when an active material, a conductive material, a binder, or the like is slurried with a solvent and applied in a thin film shape, streaks may occur.

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

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

(6) Average primary particle diameter When primary particles aggregate to form secondary particles, the average primary particle diameter of the positive electrode active material is usually 0.03 μm or more, preferably 0.05 μm or more, and More preferably, it is 08 μm or more, more preferably 0.1 μm or more, and usually 5 μm or less, preferably 4 μm or less, more preferably 3 μm or less, and further preferably 2 μm or less. If the above range is exceeded, it may be difficult to form spherical secondary particles, which may adversely affect the powder filling property, or the specific surface area will be greatly reduced, which may increase the possibility that the battery performance such as output characteristics will deteriorate. is there. On the other hand, below the above range, the performance of the secondary battery may be lowered, for example, the reversibility of charge / discharge is inferior because the crystals are not developed.

  The average primary particle diameter is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles and obtained by taking the average value. It is done.

(7) BET specific surface area As for the BET specific surface area of the positive electrode active material, the value of the specific surface area measured using the BET method is usually 0.1 m ² · g ⁻¹ or more, and 0.2 m ² · g ⁻¹ or more. more preferably from 0.3 m ² · ^{g -1} or more, and is generally ^{50 m} 2 · ^{g -1} or less, preferably ^{40 m} 2 · ^{g -1} or less, more preferably ^{30 m} 2 · ^{g -1} or less. When the value of the BET specific surface area is below the above range, the battery performance tends to be lowered. Moreover, when it exceeds the said range, a tap density becomes difficult to raise and the applicability | paintability at the time of positive electrode active material formation may fall.

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

(8) Method for Producing Positive Electrode Active Material The method for producing the positive electrode active material is not particularly limited as long as it does not exceed the gist of the present invention, but there are several methods, which are common as methods for producing inorganic compounds. The method is used.

In particular, various methods are conceivable for producing a spherical or elliptical active material. For example, transition metal source materials such as transition metal nitrates and sulfates, and other element source materials as required. Is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring to produce and recover a spherical precursor, which is dried as necessary, and then LiOH, Li ₂ CO ₃ , LiNO There is a method in which an active material is obtained by adding a Li source such as ₃ and baking at a high temperature.

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

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

<2-4-2. Electrode structure and fabrication method>
Below, the structure of the positive electrode used for this invention and its preparation method are demonstrated.

(1) Method for Producing 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. The production of the positive electrode using the positive electrode active material can be produced by any known method. That is, a positive electrode active material and a binder, and if necessary, a conductive material and a thickener mixed in a dry form are pressure-bonded to a positive electrode current collector, or these materials are liquid media A positive electrode can be obtained by forming a positive electrode active material layer on the current collector by applying it to a positive electrode current collector and drying it as a slurry by dissolving or dispersing in a slurry.

  The content of the positive electrode active material in the positive electrode active material layer is preferably 80% by mass or more, more preferably 82% by mass or more, and still more preferably 84% by mass or more. Moreover, an upper limit becomes like this. Preferably it is 99 mass% or less, More preferably, it is 98 mass% or less. If the content of the positive electrode active material in the positive electrode active material layer is low, the electric capacity may be insufficient. Conversely, if the content is too high, the strength of the positive electrode may be insufficient. In addition, the positive electrode active material powder in this invention may be used individually by 1 type, and may use together 2 or more types of a different composition or different powder physical properties by arbitrary combinations and ratios.

(2) Conductive material As the conductive material, a known conductive material can be arbitrarily used. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (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 a ratio.

  The conductive material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 1% by mass or more, and usually 50% by mass or less, preferably 30% by mass or less in the positive electrode active material layer. More preferably, it is used so as to contain 15% by mass or less. If the content is lower than the above range, the conductivity may be insufficient. Moreover, when it exceeds the said range, battery capacity may fall.

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

In the case of the coating method, any material can be used as long as it is dissolved or dispersed in the liquid medium used during electrode production. Specific examples include polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitro Resin polymers such as cellulose; Rubber polymers such as SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluoro rubber, isoprene rubber, butadiene rubber, ethylene propylene rubber; styrene butadiene styrene block Copolymer or its hydrogenated product, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene /
Thermoplastic elastomeric polymer such as butadiene / ethylene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated product thereof; syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer Polymers, soft resinous polymers such as propylene / α-olefin copolymers; fluorinated polymers such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers, etc. Molecule: a polymer composition having ion conductivity of alkali metal ions (particularly lithium ions), and the like. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 3% by mass or more, and usually 50% by mass or less, 30% by mass. % Or less is preferable, 10 mass% or less is more preferable, and 8 mass% or less is more preferable. When the ratio of the binder is within the above range, the positive active substance can be sufficiently retained, and the mechanical strength of the positive electrode is maintained, which is preferable from the viewpoint of cycle characteristics, battery capacity, and conductivity.

(4) Liquid medium The liquid medium for forming the slurry may be a solvent capable of dissolving or dispersing the positive electrode active material, the conductive material, the binder, and the thickener used as necessary. For example, the type is not particularly limited, and either an aqueous solvent or an organic solvent may be used.

  Examples of the aqueous medium include water, a mixed medium of alcohol and water, and the like. Examples of organic media include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, 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 And amides such as dimethylacetamide; aprotic polar solvents such as hexamethylphosphalamide and dimethyl sulfoxide. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

(5) Thickener When using an aqueous medium as a liquid medium for forming a slurry, it is preferable to make a slurry using a thickener and a latex such as styrene butadiene rubber (SBR). A thickener is usually used to adjust the viscosity of the slurry.

  The thickener is not limited as long as the effect of the present invention is not significantly limited. Specifically, 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.

  Furthermore, when using a thickener, the ratio of the thickener to the active material is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.6% by mass or more, Usually, it is 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass or less. If it falls below the above range, applicability may be remarkably reduced, and if it exceeds the above range, the ratio of the active material in the positive electrode active material layer is lowered, the battery capacity is reduced, and the resistance between the positive electrode active materials. May increase.

(6) Consolidation The positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material. The density of the positive electrode active material layer is preferably 1 g · cm ⁻³ or more, more preferably 1.5 g · cm ⁻³ or more, further preferably 2 g · cm ⁻³ or more, and preferably 4 g · cm ⁻³ or less. 3.5 g · cm ⁻³ or less is more preferable, and 3 g · cm ⁻³ or less is more preferable.

  If the density of the positive electrode active material layer exceeds the above range, the permeability of the non-aqueous electrolyte solution to the vicinity of the current collector / active material interface may decrease, and the charge / discharge characteristics at a high current density may decrease. Moreover, when less than the said range, the electroconductivity between active materials may fall and battery resistance may increase.

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

  Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, foam metal, etc. A carbon thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred. In addition, you may form a thin film suitably in mesh shape.

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

  The ratio of the thickness of the current collector and the positive electrode active material layer is not particularly limited, but the value of (thickness of the positive electrode active material layer on one side immediately before electrolyte injection) / (thickness of the current collector) is Usually, it is 20 or less, preferably 15 or less, more preferably 10 or less, and the lower limit is usually 0.5 or more, preferably 0.8 or more, more preferably 1 or more. Above this range, the current collector may generate heat due to Joule heat during high current density charge / discharge. Below this range, the volume ratio of the current collector to the positive electrode active material increases and the battery capacity may decrease.

<2-5. Separator>
Usually, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the nonaqueous electrolytic solution of the present invention is usually used by impregnating the separator.

  There is no restriction | limiting in particular about the material and shape of a separator, As long as the effect of this invention is not impaired remarkably, a well-known thing can be employ | adopted arbitrarily. Among them, a resin, glass fiber, inorganic material, etc. formed of a material that is stable with respect to the non-aqueous electrolyte solution of the present invention is used, and a porous sheet or a nonwoven fabric-like material having excellent liquid retention properties is used. Is preferred.

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

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, more preferably 30 μm or less. If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. On the other hand, if it is thicker than the above range, not only the battery performance such as the rate characteristic may be lowered, but also the energy density of the whole non-aqueous electrolyte secondary battery may be lowered.

  Furthermore, when using a porous material such as a porous sheet or a nonwoven fabric as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Moreover, it is 90% or less normally, 85% or less is preferable and 75% or less is more preferable. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

  Moreover, although the average pore diameter of a separator is also arbitrary, it is 0.5 micrometer or less normally, 0.2 micrometer or less is preferable, and it is 0.05 micrometer or more normally. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.

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

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

<2-6. Battery design>
[Electrode group]
The electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed via the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape via the separator. Either may be used. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, and 80% or less. preferable. When the electrode group occupancy is below the above range, the battery capacity decreases. Also, if the above range is exceeded, the void space is small, the battery expands, and the member expands or the vapor pressure of the electrolyte liquid component increases and the internal pressure rises. In some cases, the gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.

[Current collection structure]
The current collecting structure is not particularly limited, but in order to more effectively realize the improvement of the discharge characteristics by the non-aqueous electrolyte solution of the present invention, it is necessary to make the structure to reduce the resistance of the wiring part and the joint part. preferable. Thus, when internal resistance is reduced, the effect of using the non-aqueous electrolyte solution of this invention is exhibited especially favorable.

In the case where the electrode group has the laminated structure described above, a structure formed by bundling the metal core portions of the electrode layers and welding them to the terminals is preferably used. When the area of one electrode increases, the internal resistance increases. Therefore, it is also preferable to reduce the resistance by providing a plurality of terminals in the electrode. When the electrode group has the winding structure described above, the internal resistance can be lowered by providing a plurality of lead structures for the positive electrode and the negative electrode, respectively, and bundling the terminals.

[Protective element]
As the above-mentioned protective element, PTC (Positive Temperature Coefficient) whose resistance increases when abnormal heat generation or excessive current flows, temperature fuse, thermistor, current flowing in the circuit due to sudden increase in internal pressure or internal temperature of the battery when abnormal heat generation occurs For example, a valve (current cutoff valve) that shuts off the current can be used. It is preferable to select a protective element that does not operate under normal use at a high current. From the viewpoint of high output, it is more preferable to design the protective element so as not to cause abnormal heat generation or thermal runaway even without the protective element.

[Exterior body]
The non-aqueous electrolyte secondary battery of the present invention is usually configured by housing the non-aqueous electrolyte, the negative electrode, the positive electrode, the separator, and the like in an exterior body. There is no restriction | limiting in this exterior body, A well-known thing can be arbitrarily employ | adopted unless the effect of this invention is impaired remarkably.

  Specifically, the material of the exterior body is not particularly limited as long as it is a substance that is stable with respect to the non-aqueous electrolyte used. Usually, for example, nickel-plated steel sheet, stainless steel, aluminum or aluminum alloy, metals such as nickel, titanium, magnesium alloy, or a laminated film (laminate film) of resin and aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.

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

  The shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

  EXAMPLES Hereinafter, although an Example and a reference example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.

Example 1
[Production of negative electrode]
As a thickener and a binder, 98 parts by mass of a carbonaceous material, 1 part by mass of an aqueous dispersion of sodium carboxymethylcellulose (concentration of 1% by mass of sodium carboxymethylcellulose) and an aqueous dispersion of styrene-butadiene rubber (of styrene-butadiene rubber) 1 part by mass was added and mixed with a disperser to form a slurry. The obtained slurry was applied to a copper foil having a thickness of 10 μm, dried, and rolled with a press. The active material layer was 30 mm wide, 40 mm long, 5 mm wide, and 9 mm long uncoated. It cut out into the shape which has a part, and was set as the negative electrode.

[Production of positive electrode]
94% by mass of Li (Ni _0.5 Mn _0.3 Co _0.2 ) O ₂ as a positive electrode active material, 3% by mass of acetylene black as a conductive material, and polyvinylidene fluoride (PV) as a binder
dF) 3% by mass was mixed in an N-methylpyrrolidone solvent to form a slurry. The obtained slurry was applied on one side of an aluminum foil having a thickness of 15 μm previously coated with a conductive additive, dried, and roll-pressed with a press machine. The size of the active material layer was 30 mm in width and length. A positive electrode was cut out into a shape having an uncoated portion of 40 mm, a width of 5 mm, and a length of 9 mm.

[Preparation of electrolyte]
Under a dry argon atmosphere, LiPF ₆ dried in a mixture (volume ratio 20:40:40) of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) has a ratio of 1.2 mol / L. The electrolyte solution was adjusted by dissolution as described above. The electrolyte solution was mixed with 1 part by weight of vinylene carbonate and 3 parts by weight of monofluoroethylene carbonate to obtain a basic electrolyte solution 1. Example 1 was mixed with 0.3 parts by mass of 1,3-bis (trifluoromethyl) benzene (A1) and 1 part by mass of lithium difluorophosphate (LiPO ₂ F ₂ ). An electrolyte solution was prepared.

[Manufacture of lithium secondary batteries]
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, and the positive electrode to prepare a battery element. The battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness: 40 μm) were coated with a resin layer so that the positive and negative terminals of the battery element protruded from the bag, and then the electrolyte solution was It poured into the bag, vacuum-sealed, and the sheet-like battery of Example 1 which will be in a full charge state by 4.3V was produced.

[Evaluation of initial discharge capacity]
A lithium secondary battery is charged to 4.3 V at a constant current corresponding to 0.2 C at 25 ° C. in a state of being sandwiched between glass plates in order to improve adhesion between electrodes, and then a constant current of 0.2 C Was discharged to 2.8V. This is done for two cycles to stabilize the battery. In the third cycle, after charging to 4.3V with a constant current of 0.2C, charging is performed until the current value reaches 0.05C with a constant voltage of 4.3V. The battery was discharged to 2.8 V at a constant current of 0.2C. Then, after charging to 4.3V with a constant current of 0.2C in the fourth cycle, charging is performed until the current value reaches 0.05C with a constant voltage of 4.3V, and 2. with a constant current of 0.2C. It discharged to 8V and calculated | required the initial stage discharge capacity.

[Evaluation of high temperature storage swelling]
The battery after the evaluation of the initial discharge capacity was immersed in an ethanol bath, the volume was measured, and this was the volume before high-temperature storage. After charging to 4.3 V at a constant current corresponding to 0.2 C at 25 ° C., storing it at 60 ° C. for 10 days, allowing the battery to cool to room temperature, and immersing it in an ethanol bath to measure the volume. Was the volume after high-temperature storage, and the amount of gas generated from the volume change before and after high-temperature storage was determined. The relative value (%) when the gas amount of Comparative Example 1 is 100 is shown in Table 1.

[Evaluation of capacity maintenance rate]
A battery whose volume was measured after storage at high temperature was discharged to 2.8 V at a constant current of 0.2 C at 25 ° C., charged to 4.3 V at a constant current of 0.2 C, and a current value of 0.05 C at a constant voltage. The test was conducted until the battery was discharged and discharged at a constant current of 0.2 C to 2.8 V, and the discharge capacity after high-temperature storage at 0.2 C was determined. The storage capacity retention rate (%) was determined from the following formula.
Storage capacity retention rate (%) = (discharge capacity after high temperature storage) / (initial discharge capacity) × 100
Table 1 shows the relative values (%) when Comparative Example 1 is 100.0.

(Comparative Example 1)
A sheet-like lithium secondary battery of Comparative Example 1 was produced and evaluated in the same manner as in Example 1 except that the basic electrolyte 1 described above was used as it was. The results are shown in Table 1.

(Comparative Example 2)
In the same manner as in Example 1, except that 0.3 parts by mass of 1,3-bis (trifluoromethyl) benzene (A1) is mixed with the basic electrolytic solution 1 described above, the sheet-like lithium secondary material of Comparative Example 2 is used. A secondary battery was prepared and evaluated. The results are shown in Table 1.

(Comparative Example 3)
A sheet-like lithium secondary battery of Comparative Example 3 was produced and evaluated in the same manner as in Example 1 except that 1 part by mass of lithium difluorophosphate was mixed with the basic electrolytic solution 1 described above. The results are shown in Table 1.

As is apparent from Table 1, it can be seen that Example 1 is superior to Comparative Examples 2 to 4 in terms of storage swelling (smaller numerical values indicate less swelling) and storage capacity retention rate.
Here, the storage blister of Comparative Example 2 using 1,3-bistrifluoromethylbenzene is -11% with respect to Comparative Example 1. In Comparative Example 3 using LiPO ₂ F ₂ is -25% with respect to Comparative Example 1. From this, it is estimated that when both 1,3-bistrifluoromethylbenzene and LiPO ₂ F ₂ are introduced, a storage swell of −36% is achieved with respect to Comparative Example 1. However, in Example 1 in which both 1,3-bistrifluoromethylbenzene and LiPO ₂ F ₂ were actually used, the storage swelling was −44% compared to Comparative Example 1, and a specific effect exceeding the estimated value was exhibited. I understand that
Further, the storage capacity retention rate of Comparative Example 2 using 1,3-bistrifluoromethylbenzene is −1% with respect to Comparative Example 1. Further, Comparative Example 3 using LiPO ₂ F ₂ is + 0.9% with respect to Comparative Example 1. From this, it is presumed that when both 1,3-bistrifluoromethylbenzene and LiPO ₂ F ₂ are introduced, a storage capacity retention rate of −0.1% is obtained with respect to Comparative Example 1. However, in Example 1 where both 1,3-bistrifluoromethylbenzene and LiPO ₂ F ₂ were actually used, the storage capacity retention rate was + 2% compared to Comparative Example 1, and a specific effect exceeding the estimated value was obtained. It turns out that it expresses.
From these contrasts, it can be seen that the combination of the compound of the formula (1) and the second electrolyte contributes to the reduction of the storage swelling and the improvement of the storage capacity retention rate due to specific effects, and provides excellent battery performance.

(Example 2)
[Production of positive electrode]
90% by mass of Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ as a positive electrode active material, 5% by mass of acetylene black as a conductive material, and polyvinylidene fluoride (PVdF) 5 as a binder % By mass was mixed in N-methylpyrrolidone solvent to make a slurry. The obtained slurry was applied on one side of an aluminum foil having a thickness of 15 μm previously coated with a conductive additive, dried, and roll-pressed with a press machine. The size of the active material layer was 30 mm in width and length. A positive electrode was cut out into a shape having an uncoated portion of 40 mm, a width of 5 mm, and a length of 9 mm.

[Preparation of electrolyte]
Under a dry argon atmosphere, LiPF ₆ dried in a mixture (volume ratio 30:30:40) of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) was adjusted to a ratio of 1 mol / L. It melt | dissolved and adjusted the electrolyte solution. To this electrolytic solution, 0.5 parts by mass of vinylene carbonate and 1.5 parts by mass of lithium bis (oxalate) borate (LiBOB) were mixed to obtain a basic electrolytic solution 2. 2 parts by mass of 1,3-bis (trifluoromethyl) benzene (A1) was mixed with the basic electrolyte solution 2 to prepare an electrolyte solution of Example 2.

[Manufacture of lithium secondary batteries]
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, and the positive electrode to prepare a battery element. This battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness 40 μm) were covered with a resin layer so that the positive and negative terminals protruded from the bag, and then the electrolyte was injected into the bag. Then, a sheet-like battery of Example 2 that was fully charged at 4.3 V was prepared by vacuum sealing.

[Evaluation of initial discharge capacity]
A lithium secondary battery is charged to 4.3 V at a constant current corresponding to 0.2 C at 25 ° C. in a state of being sandwiched between glass plates in order to improve adhesion between electrodes, and then a constant current of 0.2 C Was discharged to 2.8V. This is done for two cycles to stabilize the battery. In the third cycle, after charging to 4.3V with a constant current of 0.2C, charging is performed until the current value reaches 0.05C with a constant voltage of 4.3V. The battery was discharged to 2.8 V at a constant current of 0.2C. Then, after charging to 4.3V with a constant current of 0.2C in the fourth cycle, charging is performed until the current value reaches 0.05C with a constant voltage of 4.3V, and 2. with a constant current of 0.2C. It discharged to 8V and calculated | required the initial stage discharge capacity.

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

[Evaluation of initial -10 ° C input characteristics]
The battery for which the evaluation of the initial discharge capacity was completed was charged at 25 ° C. with a constant current of 0.2 C so as to be half the initial discharge capacity. This was charged at 0.5 C, 1.0 C, 1.5 C, 2 C, and 2.5 C at -10 ° C., and the voltage at 10 seconds was measured. The current value at 4.3 V was obtained from the current-voltage straight line, and 4.3 × (current value at 4.3 V) was defined as the output (W).

[Evaluation of cycle characteristics]
After the evaluation of the initial discharge capacity is completed, the battery is charged to 4.3 V with a constant current of 1 C, charged to a current value of 0.05 C with a constant voltage of 4.3 V, and then charged with a constant current of 1 C. Discharged to 8V. This was performed at 45 ° C. for 300 cycles. The cycle discharge capacity retention ratio (%) was determined from (discharge capacity at 300th cycle) ÷ (discharge capacity at the first cycle) × 100. Table 2 shows the relative values (%) when Comparative Example 1 is 100.0.

[Evaluation of -10 ° C output characteristics after cycling]
The battery for which the evaluation of the cycle characteristics was completed was charged at 25 ° C. with a constant current of 0.2 C so as to be half the initial discharge capacity. This was discharged at 0.5 C, 1.0 C, 1.5 C, 2 C, and 2.5 C at −10 ° C., and the voltage at 10 seconds was measured. A current value at 2.8 V was obtained from the current-voltage straight line, and 2.8 × (current value at 2.8 V) was defined as output (W). The cycle output retention rate (%) was calculated from (−10 ° C. output after cycle test) ÷ (initial −10 ° C. output) × 100. Table 2 shows the relative values (%) when Comparative Example 4 is 100.0.

[Evaluation of -10 ° C input characteristics after cycling]
The battery for which the evaluation of the cycle characteristics was completed was charged at 25 ° C. with a constant current of 0.2 C so as to be half the initial discharge capacity. This was charged at 0.5 C, 1.0 C, 1.5 C, 2 C, and 2.5 C at -10 ° C., and the voltage at 10 seconds was measured. The current value at 4.3 V was obtained from the current-voltage straight line, and 4.3 × (current value at 4.3 V) was used as the input (W). The cycle input retention rate (%) was determined from (input at −10 ° C. after cycle test) ÷ (initial −10 ° C. input) × 100. Table 2 shows the relative values (%) when Comparative Example 1 is 100.0.

(Comparative Example 4)
A sheet-like lithium secondary battery of Comparative Example 4 was produced and evaluated in the same manner as in Example 2 except that the basic electrolytic solution 2 described above was used as it was. The results are shown in Table 2.

(Comparative Example 5)
A sheet-like lithium secondary battery of Comparative Example 5 was produced and evaluated in the same manner as Example 2 except that 2 parts by mass of monofluorobenzene (A2) was mixed with the basic electrolyte solution 2 described above. . The results are shown in Table 2.

(Comparative Example 6)
A sheet-like lithium secondary battery of Comparative Example 6 was produced and evaluated in the same manner as in Example 2 except that 2 parts by mass of trifluoromethylbenzene (A3) was mixed with the basic electrolytic solution 2 described above. It was. The results are shown in Table 2.

(Comparative Example 7)
A sheet-like lithium secondary battery of Comparative Example 7 was produced and evaluated in the same manner as in Example 2 except that 1 part by mass of lithium tetrafluoroborate (LiBF ₄ ) was mixed with the basic electrolytic solution 2 described above. went. The results are shown in Table 2.

* "Other compounds", LiPF _6, the second electrolyte is a compound other than the compound of formula (1).

As can be seen from Table 2, Example 2 is superior to Comparative Example 4 in all items of cycle discharge capacity retention rate, cycle output retention rate, and cycle input retention rate.
On the other hand, in Comparative Example 5 using fluorobenzene which is not a compound of formula (1), the cycle output retention rate and the cycle input retention rate are higher than in Comparative Example 4, but the cycle discharge capacity retention rate is inferior to that in Comparative Example 4. . Moreover, Comparative Example 6 using trifluoromethylbenzene which is not a compound of Formula (1) is inferior in all items to Comparative Example 4. Furthermore, since Comparative Example 7 in which the type of electrolyte other than lithium hexafluorophosphate was increased did not use the compound of Formula (1), it was inferior to Example 2 in all items. From these comparisons, it can be seen that the compound of formula (1) contributes to raising the cycle capacity retention rate, cycle output characteristics, and cycle input characteristics, and provides excellent battery performance.

[Preparation of electrolyte]
Under a dry argon atmosphere, LiPF ₆ dried in a mixture (volume ratio 30:30:40) of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) was adjusted to a ratio of 1 mol / L. It melt | dissolved and adjusted the electrolyte solution. To this electrolyte solution, 0.5 parts by mass of vinylene carbonate, 1.5 parts by mass of lithium bis (oxalate) borate (LiBOB), and 1 part by mass of lithium fluorosulfonate (FSO ₃ Li) are mixed. Electrolytic solution 3 was obtained. The basic electrolyte solution 3 was mixed with 0.75 parts by mass of 1,3-bis (trifluoromethyl) benzene (A1) to prepare an electrolyte solution of Example 3.

[Manufacture of lithium secondary batteries]
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, and the positive electrode to prepare a battery element. This battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness: 40 μm) were coated with a resin layer so that the positive and negative terminals protruded from the bag, and then the electrolyte was injected into the bag. Then, the sheet-like battery of Example 3 that was fully charged at 4.3 V was prepared by vacuum sealing.

[Evaluation of initial discharge capacity]
A lithium secondary battery is charged to 4.3 V at a constant current corresponding to 0.2 C at 25 ° C. in a state of being sandwiched between glass plates in order to improve adhesion between electrodes, and then a constant current of 0.2 C Was discharged to 2.8V. This is done for two cycles to stabilize the battery. In the third cycle, after charging to 4.3V with a constant current of 0.2C, charging is performed until the current value reaches 0.05C with a constant voltage of 4.3V. The battery was discharged to 2.8 V at a constant current of 0.2C. Then, after charging to 4.3V with a constant current of 0.2C in the fourth cycle, charging is performed until the current value reaches 0.05C with a constant voltage of 4.3V, and 2. with a constant current of 0.2C. Discharged to 8V.

[Evaluation of high temperature storage swelling]
The battery for which the initial discharge capacity evaluation was completed was immersed in an ethanol bath, and the volume before storage was measured. After charging to 4.3 V at a constant current corresponding to 0.2 C at 25 ° C., storing it at 60 ° C. for 28 days, allowing the battery to cool to room temperature, immersing it in an ethanol bath, measuring the volume, The amount of gas generated from the volume change before and after storage was determined. The relative values (%) when Comparative Example 7 is 100 are shown in Table 3.

Example 4
In the same manner as in Example 3, except that 1.5 parts by mass of 1,3-bis (trifluoromethyl) benzene (A1) is mixed with the basic electrolytic solution 3 described above, the sheet-like lithium secondary battery of Example 4 is mixed. A secondary battery was prepared and evaluated. The results are shown in Table 3.

(Example 5)
In the same manner as in Example 3, except that 0.75 parts by mass of 1,4-bis (trifluoromethyl) benzene (A4) is mixed with the basic electrolytic solution 3 described above, the sheet-like lithium secondary battery of Example 5 is mixed. A secondary battery was prepared and evaluated. The results are shown in Table 3.

(Example 6)
In the same manner as in Example 3 except that 1.5 parts by mass of 1,4-bis (trifluoromethyl) benzene (A4) is mixed with the basic electrolytic solution 3 described above, the sheet-like lithium secondary battery of Example 6 is mixed. A secondary battery was prepared and evaluated. The results are shown in Table 3.

(Comparative Example 8)
A sheet-like lithium secondary battery of Comparative Example 8 was produced and evaluated in the same manner as in Example 3 except that the basic electrolyte solution 3 was used as it was. The results are shown in Table 3.

(Comparative Example 9)
A sheet-like lithium secondary battery of Comparative Example 9 was produced and evaluated in the same manner as in Example 3 except that 2 parts by mass of monofluorobenzene (A2) was mixed with the basic electrolytic solution 3 described above. . The results are shown in Table 3.

(Comparative Example 10)
A sheet-like lithium secondary battery of Comparative Example 10 was produced and evaluated in the same manner as in Example 3 except that 1 part by mass of trifluoromethylbenzene (A3) was mixed with the basic electrolytic solution 3 described above. It was. The results are shown in Table 3.

  As is apparent from Table 3, implementation using 1,3-bis (trifluoromethyl) benzene or 1,4-bis (trifluoromethyl) benzene, which is a compound of formula (1), and a second electrolyte It can be seen that Examples 3 to 6 are superior to Comparative Example 8 in storage blistering. Further, in Comparative Examples 9 to 10 using fluorobenzene or trifluoromethylbenzene which is not a compound of the formula (1), the storage swelling is inferior to that of Comparative Example 7. From these contrasts, it can be seen that the compound of formula (1) greatly contributes to the reduction of storage swelling and gives excellent battery performance.

  Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

According to the non-aqueous electrolyte solution of the present invention, the cycle capacity maintenance rate during durability of the non-aqueous electrolyte secondary battery during cycle operation or high-temperature storage, input / output characteristics (input / output maintenance rate) after cycling, battery Can improve blistering and is useful. Therefore, the non-aqueous electrolyte solution of the present invention and the non-non-aqueous electrolyte secondary battery using the same can be used for various known applications. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, etc. , Walkie Talkie, Electronic Notebook, Calculator, Memory Card, Portable Tape Recorder, Radio, Backup Power Supply, Motor, Automobile, Motorcycle, Motorbike, Bicycle, Lighting Equipment, Toy, Game Equipment, Clock, Electric Tool, Strobe, Camera, Home Backup power supply, business backup power supply, load leveling power supply, natural energy storage power supply, lithium ion capacitor and the like.

Claims (15)

A non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent for dissolving the electrolyte, comprising lithium hexafluorophosphate, lithium oxophosphate, lithium salt containing FSO ₂ and lithium salt containing oxalate complex as the electrolyte A non-aqueous electrolyte containing at least one second electrolyte selected from the group, and further containing a compound of the following general formula (1).


(However, R _f represents a saturated aliphatic hydrocarbon group having 1 to 6 carbon atoms bonded to an aromatic ring, and at least one hydrogen atom is substituted with a fluorine atom. Q is bonded to an aromatic ring. The number of saturated aliphatic hydrocarbon groups is an integer of 2 or more and 4 or less, and the structures of R _f may be the same or different.   The non-aqueous electrolyte solution according to claim 1, wherein the second electrolyte contains a lithium oxophosphate. The non-aqueous electrolyte solution according to claim 1 or 2, wherein the second electrolyte contains an FSO ₂ group-containing lithium salt.   4. The non-aqueous electrolyte solution according to claim 1, wherein the second electrolyte includes an oxalate complex-containing lithium salt. 5.   The content of the compound of the general formula (1) is 0.01% by mass or more and 5% by mass or less with respect to the whole non-aqueous electrolyte solution, according to any one of claims 1 to 4. The non-aqueous electrolyte described. 6. The compound according to claim 1, wherein the compound of the general formula (1) has a carbon number of R _f of 1 or more and 4 or less, and q is 2 or more and 3 or less. Non-aqueous electrolyte.   The nonaqueous electrolytic solution according to any one of claims 1 to 6, wherein the compound of the general formula (1) is 1,3-bis (trifluoromethyl) benzene.   The non-aqueous electrolyte solution according to claim 1, wherein the compound of the general formula (1) is 1,4-bis (trifluoromethyl) benzene.   The nonaqueous electrolytic solution according to any one of claims 1 to 8, further comprising a carbonate having at least one of a carbon-carbon unsaturated bond and a fluorine atom.   The carbonate having at least one of the carbon-carbon unsaturated bond and the fluorine atom is at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, ethynyl ethylene carbonate, and fluoroethylene carbonate, The non-aqueous electrolyte solution according to claim 9.   The non-aqueous electrolyte according to any one of claims 1 to 10, wherein the non-aqueous electrolyte contains one or more selected from the group consisting of cyclic carbonates, chain carbonates, and chain esters. Electrolytic solution.   A nonaqueous electrolyte secondary battery comprising: a negative electrode and a positive electrode capable of inserting and extracting lithium ions; and the nonaqueous electrolyte solution according to any one of claims 1 to 11.   The negative electrode has a current collector and a negative electrode active material layer on the current collector, and the negative electrode active material layer includes a silicon simple metal, an alloy and a compound, a tin simple metal, an alloy and a compound, and a carbonaceous material. The non-aqueous electrolyte secondary battery according to claim 12, further comprising at least one selected from the group consisting of lithium-titanium composite oxides.   The positive electrode has a current collector and a positive electrode active material layer on the current collector. The positive electrode active material layer includes a lithium / cobalt composite oxide, a lithium / cobalt / nickel composite oxide, and a lithium / manganese composite oxide. A lithium-cobalt-manganese composite oxide, a lithium-nickel composite oxide, a lithium-nickel-manganese composite oxide, and at least one selected from the group consisting of lithium-cobalt-nickel-manganese composite oxides The non-aqueous electrolyte secondary battery according to claim 12 or 13, characterized by the above. The positive electrode has a current collector and a positive electrode active material layer on the current collector, and the positive electrode active material layer is made of LixMPO ₄ (M is a transition metal of group 4 to group 11 of the fourth period of the periodic table). At least one element selected from the group consisting of x, 0 <x <1.2),
The non-aqueous electrolyte secondary battery according to claim 12 or 13.