JP2018055934A - Nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery using an electrolyte solution containing a compound having a nitrile group, and superior in the balance between a viscosity and a relative dielectric constant, which is superior in high-temperature preservation characteristic, and in which the pull-out of a hydrogen atom at an α-position of the compound having a nitrile group as a result of a reaction with an impurity can be suppressed.SOLUTION: A nonaqueous secondary battery comprises a positive electrode, a negative electrode, and a nonaqueous electrolyte. The nonaqueous electrolyte comprises: a nonaqueous solvent including a compound having a nitrile group; and an additive agent which has a peak in a range of -50 to -70 ppm according toF-NMR analysis.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a non-aqueous secondary battery. Specifically, when using a non-aqueous solvent containing a compound having a nitrile group typified by acetonitrile, by preventing the extraction of α-position hydrogen due to reaction with impurities, excellent output characteristics and storage characteristics at high temperatures The present invention relates to a non-aqueous secondary battery that can achieve both of the above.

  Non-aqueous secondary batteries represented by lithium ion secondary batteries are characterized by light weight, high energy density, and high durability, and are widely used, for example, as power sources for portable devices. In recent years, electric vehicles; electric bicycles; power tools such as electric tools; Accordingly, lithium ion secondary batteries are required to have higher energy density, higher output, higher durability, and higher safety. In order to solve these problems, in non-aqueous lithium ion secondary batteries, characteristics are improved from various angles such as a main solvent, a lithium salt, and an additive.

One means for solving these problems is to add a compound having a nitrile group to a non-aqueous solvent in a non-aqueous secondary battery. Among them, acetonitrile has an excellent balance between viscosity and relative dielectric constant, and has a high potential as a solvent used in an electrolyte solution of a lithium ion secondary battery. However, acetonitrile has a fatal defect of electrochemically reducing and decomposing at the negative electrode, and thus has not been able to exhibit practical performance until now. Several improvements have been proposed for this problem.
The main improvement measures proposed so far are classified into the following three.

(1) Method for protecting negative electrode by combination with specific electrolyte salt, additive, etc. and suppressing reductive decomposition of acetonitrile For example, Patent Documents 1 and 2 include acetonitrile as a solvent as a specific electrolyte salt and an additive. There has been reported an electrolyte solution that reduces the influence of reductive decomposition of acetonitrile by combining with the above. In the early days of lithium ion secondary batteries, as disclosed in Patent Document 3, an electrolytic solution containing a solvent obtained by simply diluting acetonitrile with propylene carbonate and ethylene carbonate has been reported. However, in Patent Document 3, since the high-temperature durability performance is determined by evaluating only the internal resistance and battery thickness after high-temperature storage, information on whether or not the battery actually operates when placed in a high-temperature environment. Is not disclosed. In practice, it is extremely difficult to suppress the reductive decomposition of an electrolytic solution containing an acetonitrile-based solvent by simply diluting with ethylene carbonate and propylene carbonate. As a method for suppressing reductive decomposition of a solvent, a method of combining a plurality of electrolyte salts and additives as in Patent Documents 1 and 2 is realistic.

(2) A method of suppressing reductive decomposition of acetonitrile by using a negative electrode active material that occludes lithium ions at a potential nobler than the reduction potential of acetonitrile. For example, Patent Document 4 uses a specific metal compound for the negative electrode. Thus, it is reported that a battery avoiding reductive decomposition of acetonitrile can be obtained. However, in applications where the energy density of the lithium ion secondary battery is important, it is overwhelmingly advantageous to use a negative electrode active material that occludes lithium ions at a lower potential than the reduction potential of acetonitrile from the viewpoint of potential difference. Therefore, when the improvement measure of Patent Document 4 is applied in such an application, the range of usable voltages becomes narrow, which is disadvantageous. In addition, the technique of Patent Document 4 improves the problem that the life performance is greatly deteriorated when used at high temperatures because the non-aqueous electrolyte having high ion conductivity at low temperatures easily reacts with the positive electrode at high temperatures. It is not a thing.

(3) Method of maintaining a stable liquid state by dissolving a high concentration electrolyte salt in acetonitrile For example, Patent Document 5 discloses a lithium bis (trifluoromethanesulfonyl) imide (concentration of 4.2 mol / L). It is described that reversible lithium insertion / extraction from a graphite electrode is possible by using an electrolytic solution in which LiN (SO ₂ CF ₃ ) ₂ ) is dissolved in acetonitrile. Patent Document 6 discloses a cell using an electrolytic solution in which lithium bis (fluorosulfonyl) imide (LiN (SO ₂ F) ₂ ) is dissolved in acetonitrile so that the concentration is 4.5 mol / L. As a result of charge / discharge measurement, Li ⁺ insertion / extraction reaction to graphite was observed, and it was reported that discharge was possible at a high rate.

International Publication No. 2012/057311 International Publication No. 2013/062056 JP-A-4-351860 JP 2009-21134 A International Publication No. 2013/146714 JP 2014-241198 A

However, lithium ion secondary batteries containing acetonitrile are inferior in durability at high temperatures compared to existing lithium ion secondary batteries containing a carbonate solvent, and have not yet reached full-scale practical use. .
From the results of various verification experiments, the reason why the acetonitrile-based lithium ion secondary battery is inferior in high-temperature durability is considered as follows.
Under a high temperature environment, acetonitrile decomposes while extracting hydrogen atoms from methyl groups by reaction with impurities present in the lithium ion secondary battery. It is considered that the decomposition product promotes the elution of the positive electrode transition metal, thereby causing the deterioration of the lithium ion secondary battery.
Such a reaction with impurities is unavoidable if it is a nitrile compound having a hydrogen atom at the α-position, and is a high temperature environment in a non-aqueous secondary battery using a compound having a nitrile group as a non-aqueous electrolyte. In order to improve the following characteristics, it is considered essential to suppress this reaction.

  The present invention has been made in view of the above circumstances. Therefore, the present invention provides an α-position hydrogen of a compound having a nitrile group by reaction with an impurity in a non-aqueous secondary battery using an electrolytic solution containing a compound having a nitrile group excellent in the balance between viscosity and relative dielectric constant. An object of the present invention is to provide a non-aqueous secondary battery that suppresses the extraction of atoms and has excellent storage characteristics at high temperatures.

The inventors of the present invention have made extensive studies to solve the above-described problems. As a result, even in the case of a non-aqueous electrolyte solution containing a compound having a nitrile group as a non-aqueous solvent, when a specific compound is further contained as an additive, while maintaining the excellent output characteristics that are characteristic of acetonitrile The inventors have found that deterioration during high-temperature storage can be suppressed, and have completed the present invention.
That is, the present invention is as follows.

｛式中、（１）式中のＮ及び（２）式中のＯ上の二重点はそれぞれ孤立電子対を示し、矢印は配位結合を示し、（１）式中のＮ及び（２）式中のＰからそれぞれ発する直線及び二重線はそれぞれ結合手を示す。｝のそれぞれで示される構造を有する化合物からなる群のうち少なくとも１種の化合物を含み、かつ、その総含有量が前記非水系電解液に対して０．００１〜１０質量％である、［１］又は［２］に記載の非水系二次電池。 [1] A non-aqueous secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte solution,
The non-aqueous electrolyte includes a non-aqueous solvent containing a compound having a nitrile group and an additive having a peak at -50 to -70 ppm when analyzed by ¹⁹ F-NMR. Secondary battery.
[2] The non-aqueous secondary battery according to [1], wherein the non-aqueous electrolyte includes an organic lithium salt.
[3] The additive of the non-aqueous electrolyte solution includes the following general formulas (1) and (2):

{In the formula, N in the formula (1) and a double point on O in the formula (2) indicate a lone pair, an arrow indicates a coordination bond, and N and (2) in the formula (1) A straight line and a double line respectively originating from P in the formula indicate a bond. And at least one compound selected from the group consisting of compounds having a structure represented by each of the following formulas, and the total content thereof is 0.001 to 10% by mass with respect to the non-aqueous electrolyte solution: [1 ] Or the nonaqueous secondary battery as described in [2].

[4] The compound having the structure represented by the general formula (1) has any one of a pyridine skeleton, a quinoline skeleton, and an acridine skeleton, and the compound having the structure represented by the general formula (2) is an alkyl The nonaqueous secondary battery according to [3], which has any one of a group, an allyl group, and a trimethylsilyl group.
[5] The non-aqueous secondary battery according to any one of [1] to [4], wherein the compound having a nitrile group is a nitrile compound having a hydrogen atom at the α-position.
[6] The non-aqueous secondary battery according to [5], wherein the nitrile compound having a hydrogen atom at the α-position is acetonitrile.
[7] A non-aqueous electrolyte containing a non-aqueous solvent containing a compound having a nitrile group and an additive having a peak at −50 to −70 ppm when analyzed by ¹⁹ F-NMR.

  According to the present invention, there is provided a secondary battery having high storage characteristics at high temperatures while suppressing the extraction of α-position hydrogen atoms of a compound having a nitrile group by reaction with impurities and maintaining excellent output characteristics. Can be provided.

It is a top view which shows roughly an example of the non-aqueous secondary battery of this embodiment. It is the sectional view on the AA line of the non-aqueous secondary battery of FIG. 2 is a ¹⁹ F-NMR chart of a non-aqueous electrolyte prepared in Example 1. FIG. 6 is a ¹⁹ F-NMR chart of a nonaqueous electrolytic solution prepared in Example 8. FIG.

Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. In the present specification, numerical ranges described using “to” include numerical values described before and after.
The non-aqueous secondary battery of this embodiment is
A positive electrode, a negative electrode, and a non-aqueous electrolyte solution are provided,
The non-aqueous electrolyte contains a non-aqueous solvent containing a compound having a nitrile group and an additive having a peak at −50 to −70 ppm when analyzed by ¹⁹ F-NMR.

<1. Non-aqueous battery overall configuration>
The non-aqueous secondary battery of this embodiment is, for example,
A positive electrode containing a positive electrode material capable of inserting and extracting lithium ions as a positive electrode active material;
A negative electrode material capable of inserting and extracting lithium ions as a negative electrode active material, and a negative electrode containing one or more negative electrode materials selected from the group consisting of metallic lithium or lithium alloys;
It can be a lithium ion secondary battery comprising a non-aqueous electrolyte solution.
Specifically, the non-aqueous secondary battery of the present embodiment may be the non-aqueous secondary battery illustrated in FIGS. 1 and 2. Here, FIG. 1 is a plan view schematically showing a non-aqueous secondary battery, and FIG. 2 is a cross-sectional view taken along line AA of FIG.

The non-aqueous secondary battery 8 includes a laminated electrode body formed by laminating a positive electrode 5 and a negative electrode 6 with a separator 7 in a battery exterior 2 constituted by two aluminum laminate films 1, and a non-aqueous electrolyte solution ( (Not shown). The battery exterior 2 is sealed by heat-sealing the upper and lower aluminum laminate films 1 at the outer periphery thereof. The laminate in which the positive electrode 5, the separator 7, and the negative electrode 6 are sequentially laminated is impregnated with a nonaqueous electrolytic solution. However, in FIG. 2, in order to avoid the drawing from becoming complicated, each layer constituting the battery exterior 2 and each layer constituting the positive electrode 5 and the negative electrode 6 are not shown separately.
The aluminum laminate film 1 constituting the battery casing 2 is preferably one in which both surfaces of an aluminum foil are coated with a polyolefin resin.
The positive electrode 5 is connected to the positive electrode external terminal 3 through a lead body in the battery 8. Although not shown, the negative electrode 6 is also connected to the negative electrode external terminal 4 through the lead body in the battery 8. The positive electrode external terminal 3 and the negative electrode external terminal 4 are each drawn out to the outside of the battery exterior 2 so that they can be connected to an external device or the like, and the resin portion fused to them is It is heat-sealed together with one side of the battery casing 2.

In the non-aqueous secondary battery 8 shown in FIGS. 1 and 2, the positive electrode 5 and the positive electrode 6 each have one laminated electrode body, but the number of the positive electrodes 5 and the negative electrodes 6 can be increased depending on the capacity design. It can be increased as appropriate. In the case of a laminated electrode body having a plurality of positive electrodes 5 and negative electrodes 6, tabs having the same polarity may be joined by welding or the like, and then joined to one lead body by welding or the like and taken out of the battery. Examples of the same type of tab include an aspect constituted by an exposed portion of the current collector, an aspect constituted by welding a metal piece to the exposed portion of the current collector, and the like.
The positive electrode 5 includes a positive electrode active material layer made from a positive electrode mixture and a positive electrode current collector. The negative electrode 6 includes a negative electrode active material layer made from a negative electrode mixture and a negative electrode current collector. The positive electrode 5 and the negative electrode 6 are disposed so that the positive electrode active material layer and the negative electrode active material layer face each other with the separator 7 interposed therebetween.
Hereinafter, the positive electrode and the negative electrode are also abbreviated as “electrode”, the positive electrode active material layer and the negative electrode active material layer are collectively referred to as “electrode active material layer”, and the positive electrode mixture and the negative electrode mixture are also abbreviated as “electrode mixture”.
As each of these members, a material provided in a conventional lithium ion secondary battery can be used as long as each requirement in the present embodiment is satisfied. For example, the following materials may be used. Hereinafter, each member of the non-aqueous secondary battery will be described in detail.

<2. Non-aqueous electrolyte>
The non-aqueous electrolyte solution in this embodiment (hereinafter also simply referred to as “electrolyte solution”) has a non-aqueous solvent containing a compound having a nitrile group and a peak at −50 to −70 ppm when analyzed by ¹⁹ F-NMR. At least an additive having In addition to these, the electrolytic solution preferably contains a lithium salt.
The electrolytic solution in the present embodiment preferably does not contain moisture, but may contain a very small amount of moisture as long as the solution of the problem of the present invention is not hindered. The water content is preferably 0 to 100 ppm with respect to the total amount of the electrolytic solution.

<2-1. Non-aqueous solvent>
[Compound having nitrile group]
The non-aqueous solvent in the electrolytic solution in the present embodiment includes a compound having a nitrile group.
The compound having a nitrile group is preferably a nitrile compound having a hydrogen atom at the α-position.
Specific examples thereof include, for example, mononitriles represented by acetonitrile, propionitrile, butyronitrile, valeronitrile, and acrylonitrile;
Alkoxy group-substituted nitriles represented by methoxyacetonitrile and 3-methoxypropionitrile;
Malononitrile, succinonitrile, glutaronitrile, adiponitrile, 1,4-dicyanoheptane, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 2,6-dicyanoheptane, 1,8 Represented by -dicyanooctane, 2,7-dicyanooctane, 1,9-dicyanononane, 2,8-dicyanononane, 1,10-dicyanodecane, 1,6-dicyanodecane, and 2,4-dimethylglutaronitrile Dinitrile;
Cyclic nitriles represented by benzonitrile;
Etc. Of these, acetonitrile is particularly preferred.

Among the compounds having a nitrile group, a nitrile compound having a hydrogen atom at the α-position, particularly acetonitrile, has high ion conductivity, and can increase the diffusibility of lithium ions in the battery. Therefore, when the electrolytic solution contains acetonitrile, a collector in which lithium ions are difficult to reach at the time of discharge under a high load, particularly in a positive electrode in which the positive electrode active material layer is thickened to increase the filling amount of the positive electrode active material. Lithium ions can be diffused well to nearby regions. Therefore, a sufficient capacity can be extracted even during high-load discharge, and a non-aqueous secondary battery having excellent load characteristics can be obtained.
By using acetonitrile as the non-aqueous solvent of the non-aqueous electrolyte solution, as described above, the ionic conductivity of the non-aqueous electrolyte solution is improved, so that the quick charge characteristics of the non-aqueous secondary battery can be enhanced. In constant current (CC) -constant voltage (CV) charging of a non-aqueous secondary battery, the capacity per unit time in the CC charging period is larger than the charging capacity per unit time in the CV charging period. When acetonitrile is used as the non-aqueous solvent of the non-aqueous electrolyte, the CC chargeable area can be increased (the CC charge time can be increased), and the charge current can be increased, so the non-aqueous secondary battery can be charged. The time from the start to the fully charged state can be greatly shortened.

[Other non-aqueous solvents]
The non-aqueous solvent is not particularly limited as long as it contains a compound having a nitrile group, and may or may not contain other non-aqueous solvents.
The “non-aqueous solvent” in the present embodiment refers to a component excluding an additive having a peak at −50 to −70 ppm when analyzed by lithium salt and ¹⁹ F-NMR from the electrolyte. That is, in the case where the electrolyte contains an additive for electrode protection described later together with a solvent, a lithium salt, and an additive having a peak at −50 to −70 ppm when analyzed by ¹⁹ F-NMR, The solvent and the electrode protecting additive are collectively referred to as “non-aqueous solvent”. A non-aqueous solvent does not contain a lithium salt described later and an additive having a peak at −50 to −70 ppm when analyzed by ¹⁹ F-NMR.

Examples of the other non-aqueous solvents include alcohols such as methanol and ethanol; aprotic solvents and the like. Among these, an aprotic polar solvent is preferable.
Among the other non-aqueous solvents, specific examples of the aprotic solvent include, for example,
Ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, trans-2,3-butylene carbonate, cis-2,3-butylene carbonate, 1,2-pentylene carbonate, trans-2,3-pentylene carbonate, cis Cyclic carbonates represented by -2,3-pentylene carbonate and vinylene carbonate;
Cyclic fluorinated carbonates typified by fluoroethylene carbonate, 1,2-difluoroethylene carbonate, and trifluoromethylethylene carbonate;
Lactones represented by γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, and ε-caprolactone;
Sulfur compounds represented by sulfolane, dimethyl sulfoxide, and ethylene glycol sulfite;
Cyclic ethers represented by tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, and 1,3-dioxane;
A chain carbonate represented by ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, and methyl trifluoroethyl carbonate;
Linear fluorinated carbonates typified by trifluorodimethyl carbonate, trifluorodiethyl carbonate, and trifluoroethyl methyl carbonate;

Chain esters represented by methyl propionate;
Linear ethers represented by dimethoxyethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme, and tetraglyme;
A fluorinated ether represented by Rf ⁴ -OR ⁵ (Rf ⁴ is an alkyl group containing fluorine, and R ⁵ is an organic group which may contain fluorine);
In addition to ketones typified by acetone, methyl ethyl ketone, and methyl isobutyl ketone, halides typified by these fluorinated products are exemplified. These are used singly or in combination of two or more.

  Among these other non-aqueous solvents, it is more preferable to use one or more of cyclic carbonate and chain carbonate together with acetonitrile. Here, only one of those exemplified above as the cyclic carbonate and the chain carbonate may be selected and used, or two or more (for example, two or more of the cyclic carbonates exemplified above, Two or more of the exemplified chain carbonates or one or more of the exemplified cyclic carbonates and two or more of the exemplified chain carbonates may be used. Among these, ethylene carbonate, propylene carbonate, vinylene carbonate, or fluoroethylene carbonate is more preferable as the cyclic carbonate, and ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate is more preferable as the chain carbonate. It is more preferable to use a cyclic carbonate and a chain carbonate in combination.

Acetonitrile is electrochemically susceptible to reductive decomposition. Therefore, it is preferable to perform at least one of mixing this with another solvent and adding an electrode protective additive for forming a protective film on the electrode.
In order to increase the ionization degree of the lithium salt that contributes to charge / discharge of the non-aqueous secondary battery, the non-aqueous solvent preferably contains one or more cyclic aprotic polar solvents, and contains one or more cyclic carbonates. Is more preferable.
The content of acetonitrile is preferably 30 to 100% by volume, more preferably 35% by volume or more, based on the total amount of the non-aqueous solvent (including the electrode protection additive described later). More preferably, it is at least volume%. This value is more preferably 85% by volume or less, and still more preferably 66% by volume or less. When the content of acetonitrile is 30% by volume or more, ionic conductivity tends to increase and high output characteristics tend to be exhibited, and further, dissolution of the lithium salt can be promoted. When the content of acetonitrile in the non-aqueous solvent is within the above range, the storage characteristics and other battery characteristics tend to be further improved while maintaining the excellent performance of acetonitrile.

<2-2. Additives>
The electrolytic solution in the present embodiment is characterized by containing a compound having a peak at −50 to −70 ppm when analyzed by ¹⁹ F-NMR as an additive.
The compound having a peak at −50 to −70 ppm when analyzed by ¹⁹ F-NMR is preferably a compound having a structure in which a lone electron pair is coordinated to a phosphorus atom of phosphorus pentafluoride (PF ₅ ).
Phosphorus pentafluoride shows a peak at −70 to −80 ppm in ¹⁹ F-NMR analysis. In fact, when a lone pair of electrons is coordinated to the phosphorus atom of the phosphorus pentafluoride (PF ₅ ), the above peak shifts to the low magnetic field side. The chemical shift after the shift by coordination is, for example, about −50 to −70 ppm when a lone electron pair of a nitrogen atom or an oxygen atom is coordinated.
When the present inventors include a compound exhibiting such a chemical shift in ¹⁹ F-NMR analysis in the electrolytic solution, the α-position hydrogen atom of the compound having a nitrile group is extracted by reaction with impurities. As a result, the present invention has been found.

｛式中、（１）式中のＮ及び（２）式中のＯ上の二重点はそれぞれ孤立電子対を示し、矢印は配位結合を示し、（１）式中のＮ及び（２）式中のＰからそれぞれ発する直線及び二重線はそれぞれ結合手を示す。｝のそれぞれで示される構造を有する化合物を挙げることができ、これらのうちから選択される少なくとも１種の化合物を使用することが好ましい。 Examples of the compound having a peak at −50 to −70 ppm when analyzed by ¹⁹ F-NMR include the following general formulas (1) and (2):

{In the formula, N in the formula (1) and a double point on O in the formula (2) indicate a lone pair, an arrow indicates a coordination bond, and N and (2) in the formula (1) A straight line and a double line respectively originating from P in the formula indicate a bond. }, It is preferable to use at least one compound selected from these compounds.

The compound having the structure represented by the general formula (1) preferably has any of a pyridine skeleton, a quinoline skeleton, and an acridine skeleton.
Examples of the compound represented by the general formula (1) having a pyridine skeleton include pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2- (n-propyl) pyridine, 3- (n-propyl) pyridine, 4- (n-propyl) pyridine, 2-isopropylpyridine, 3-isopropylpyridine, 4-isopropylpyridine, 2- (n-butyl) pyridine 3- (n-butyl) pyridine, 4- (n-butyl) pyridine, 2- (1-methylpropyl) pyridine, 3- (1-methylpropyl) pyridine, 4- (1-methylpropyl) pyridine, 2 -(2-methylpropyl) pyridine, 3- (2-methylpropyl) pyridine, and 4- (2-methylpropyl) pyridine Compound lone electron pair of the nitrogen atom is coordinated to PF _5, each having such a;
Examples of the compound represented by the general formula (1) having a quinoline skeleton include quinoline, 2-methylquinoline, 3-methylquinoline, 4-methylquinoline, 5-methylquinoline, 6-methylquinoline, 7-methylquinoline, and 8-lone pair of the nitrogen atom, each having a methyl quinoline compounds such coordinated to PF _5;
Examples of the compound represented by the general formula (1) having an acridine skeleton include acridine, 2-methylacridine, 3-methylacridine, 4-methylacridine, 5-methylacridine, 6-methylacridine, 7-methylacridine, Compounds in which a lone pair of nitrogen atoms contained in each of 8-methylacridine and 9-methylacridine is coordinated to PF ₅ ;
Each can be mentioned.

The compound having the structure represented by the general formula (2) preferably has any of an alkyl group, an allyl group, and a trimethylsilyl group.
Examples of the compound represented by the general formula (2) having an alkyl group include a lone pair of oxygen atoms having a double bond contained in each of trimethyl phosphate, triethyl phosphate, and tributyl phosphate in PF ₅ . Coordinated compounds, etc .;
Examples of the compound represented by the general formula (2) having an allyl group include triallyl phosphate and the like;
Examples of the compound represented by the general formula (2) having a trimethylsilyl group include trimethylsilyl phosphate and the like;
Each can be mentioned.

Said compound is used individually by 1 type or in combination of 2 or more types.
There is no restriction | limiting in particular about content of the compound which has a peak in -50--70 ppm when it analyzes by ¹⁹ F-NMR in the electrolyte solution in this embodiment. However, it is preferably 0.001 to 10% by mass, more preferably 0.02 to 5% by mass, based on the total amount of the electrolytic solution (including the electrode protecting additive described later), and 0.02 to 5% by mass. More preferably, it is 05-3 mass%.
In this embodiment, by adjusting the content of the compound having a peak at −50 to −70 ppm within the above range, the basic function as a non-aqueous secondary battery is not impaired, and the nitrile group is included. Since the reaction between the compound and the impurity can be suppressed, an increase in internal resistance accompanying charge / discharge can be reduced.
By preparing a non-aqueous solvent with the above composition, all of high output performance under low temperature environment, storage characteristics at high temperature, and other battery characteristics tend to be even better. .

The ¹⁹ F-NMR analysis of the additive can be performed by the method described in the examples described later. The ¹⁹ F-NMR analysis may be performed using the additive as a sample, or a nonaqueous electrolytic solution containing the additive as a sample.
For example, in a ¹⁹ F-NMR analysis measured using a non-aqueous electrolyte as a sample, when a peak is observed at −50 to −70 ppm, it may be estimated that the electrolyte contains the predetermined additive of this embodiment. it can.

<2-3. Lithium salt>
The non-aqueous electrolyte solution in the present embodiment can contain a lithium salt, and it is preferable to do so.
The type of lithium salt contained in the non-aqueous electrolyte solution is not particularly limited, and may be any one type or two or more types of known lithium salts.
The lithium salt is preferably selected from inorganic lithium salts and organic lithium salts.

Specific examples of the inorganic lithium salt include, for example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiSbF ₆ , Li ₂ B ₁₂ F _b H _12-b [b is an integer of 0 to 3, preferably 1 An integer of ˜3], LiN (SO ₂ F) ₂ , LiClO ₄ , LiAlO ₄ , LiAlCl ₄ , LiB ₁₀ Cl ₁₀ , inorganic lithium salts that do not contain a fluorine atom in the anion, and the like.

Specific examples of the organic lithium salt include, for example,
LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (n ≧ 2), lower aliphatic carboxylic acid Li, An organic lithium salt such as lithium tetraphenylborate;
An organic lithium salt represented by LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 1 to 8] such as LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ ;
_{LiPF 5 (CF 3) LiPF n} (C p F 2p + 1) 6-n [n is an integer of 1 to 5, p is an integer of 1 to 8] The organic lithium salt represented by the like;
LiBF _q (C _s F _{2s + 1} ) _4-q such as LiBF ₃ (CF ₃ ) _4-q [q is an integer of 1 to 3, s is an integer of 1 to 8];
Lithium bis (oxalato) borate (LiBOB) represented by LiB (C ₂ O ₄ ) ₂ ;
Halogenated LiBOB; Lithium oxalate difluoroborate (LiODFB) represented by LiBF ₂ (C ₂ O ₄ );
Lithium bis (malonate) borate (LiBMB) represented by LiB (C ₃ O ₄ H ₂ ) ₂ ;
Organic lithium salts such as lithium tetrafluorooxalatophosphate represented by LiPF ₄ (C ₂ O ₄ ) and lithium difluorobis (oxalato) phosphate represented by LiPF ₂ (C ₂ O ₄ ) ₂ ;
A lithium salt combined with a polyvalent anion;
The following general formulas (2a), (2b), and (2c):
^{_{LiC (SO 2 R 6) (}} SO 2 R 7) (SO 2 R 8) (2a)
LiN (SO ₂ OR ⁹ ) (SO ₂ OR ¹⁰ ) (2b)
LiN (SO ₂ R ¹¹ ) (SO ₂ OR ¹² ) (2c)
{Wherein R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , and R ¹² may be the same as or different from each other, and represent a C 1-8 perfluoroalkyl group. An organic lithium salt represented by each of
Etc.

In order to improve the load characteristics and charge / discharge cycle characteristics of the non-aqueous secondary battery, it is preferable to use an organic lithium salt, more preferably an organic lithium salt having an oxalic acid group, and LiB (C ₂ It is particularly preferable to use one or more selected from the group consisting of O ₄ ) ₂ , LiBF ₂ (C ₂ O ₄ ), LiPF ₄ (C ₂ O ₄ ), and LiPF ₂ (C ₂ O ₄ ) _2. .
The above organic lithium salt may be contained in the negative electrode (negative electrode active material layer) in addition to being added to the nonaqueous electrolytic solution.

  The amount of the above organic lithium salt added to the non-aqueous electrolyte is from 1 L of non-aqueous solvent of the non-aqueous electrolyte (including the electrode protection additive described later) from the viewpoint of better ensuring the effect of its use. The amount is preferably 0.005 mol or more, more preferably 0.02 mol or more, and still more preferably 0.05 mol or more. However, if the amount of the organic lithium salt in the non-aqueous electrolyte is too large, it may be precipitated. Therefore, the amount of the organic lithium salt added to the non-aqueous electrolyte is less than 1.0 mol as the amount per liter of the non-aqueous solvent (including the electrode protection additive described later) of the non-aqueous electrolyte. It is preferably less than 0.5 mol, more preferably less than 0.2 mol.

  It is also a preferred aspect in this embodiment that an inorganic lithium salt is used in combination with an organic lithium salt. When the organic lithium salt and the inorganic lithium salt are used in combination, the total amount added to the non-aqueous electrolyte solution is the amount per liter of the non-aqueous solvent (including the electrode protection additive described later) of the non-aqueous electrolyte solution. 0.1 to 4.0 mol is preferable, 0.5 to 3.0 mol is more preferable, and 0.7 to 2.0 mol is still more preferable.

<2-4. Electrode protective additive>
The electrolytic solution in the present embodiment may contain an additive for protecting the electrode in addition to the additive having a peak at −50 to −70 ppm when analyzed by ¹⁹ F-NMR. In addition, as described above, when the electrolytic solution contains an electrode protecting additive, the electrode protecting additive is contained in a non-aqueous solvent. Therefore, the electrolytic solution contains a non-aqueous solvent containing an electrode protecting additive. It is sufficient that the solvent contains a compound having a nitrile group.
The electrode protecting additive is not particularly limited as long as it does not hinder the problem solving according to the present invention. You may substantially overlap with the substance which plays the role as a solvent which melt | dissolves lithium salt (namely, the above-mentioned non-aqueous solvent). The electrode protecting additive is preferably a substance that contributes to improving the performance of the electrolytic solution and the non-aqueous secondary battery in this embodiment, but also includes substances that are not directly involved in the electrochemical reaction.

As a specific example of the electrode protecting additive, for example,
4-fluoro-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, cis-4,5-difluoro-1,3-dioxolan-2-one, trans- 4,5-difluoro-1,3-dioxolan-2-one, 4,4,5-trifluoro-1,3-dioxolan-2-one, 4,4,5,5-tetrafluoro-1,3- Dioxolan-2-one and fluoroethylene carbonate represented by 4,4,5-trifluoro-5-methyl-1,3-dioxolan-2-one;
An unsaturated bond-containing cyclic carbonate represented by vinylene carbonate, 4,5-dimethylvinylene carbonate, and vinylethylene carbonate;
Lactones represented by γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, and ε-caprolactone;
Cyclic ethers represented by 1,4-dioxane;
Cyclic sulfur compounds represented by ethylene sulfite, propylene sulfite, butylene sulfite, pentene sulfite, sulfolane, 3-methylsulfolane, 1,3-propane sultone, 1,4-butane sultone, and tetramethylene sulfoxide;
Etc. These are used singly or in combination of two or more.

Since a compound having a nitrile group, which is a component of a non-aqueous solvent, is easily electrochemically reduced and decomposed, a non-aqueous solvent containing the compound having the nitrile group is used as an additive for forming a protective film on the negative electrode. It is preferable to include at least one cyclic aprotic polar solvent, and it is more preferable to include at least one unsaturated bond-containing cyclic carbonate.
There is no restriction | limiting in particular about content of the electrode protection additive in the electrolyte solution in this embodiment. However, the content of the electrode protective additive with respect to the total amount of the non-aqueous solvent (including the electrode protective additive) is preferably 0.1 to 30% by volume, and more preferably 2 to 20% by volume. Preferably, it is 5 to 15% by volume.
In this embodiment, deterioration of electrolyte solution is suppressed, so that there is much content of the additive for electrode protection. However, the lower the content of the electrode protecting additive, the higher the high output characteristics of the non-aqueous secondary battery in a low temperature environment. Therefore, by adjusting the content of the electrode protecting additive within the above-mentioned range, excellent performance based on the high ionic conductivity of the electrolytic solution can be obtained without impairing the basic function as a non-aqueous secondary battery. There is a tendency to make the most of it. By preparing the electrolytic solution with such a composition, all of the cycle performance of the non-aqueous secondary battery, the high output performance in a low temperature environment, and other battery characteristics tend to be further improved.

<2-5. Other optional additives>
In the present embodiment, for the purpose of improving the charge / discharge cycle characteristics of the non-aqueous secondary battery, high-temperature storage property, improving safety (for example, preventing overcharge, etc.), the non-aqueous electrolyte solution includes, for example, anhydrous acid, Sulfonic acid ester, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, tert-butylbenzene, phosphoric acid ester [ethyl diethylphosphonoacetate (EDPA): (C ₂ H ₅ O) ₂ (P═O) —CH ₂ ( C═O) OC ₂ H ₅ , tris (trifluoroethyl) phosphate (TFEP): (CF ₃ CH ₂ O) ₃ P═O, triphenyl phosphate (TPP): (C ₆ H ₅ O) ₃ P ═O etc.] and the like, and optional additives selected from derivatives of these respective compounds and the like can be appropriately contained. In particular, the phosphoric acid ester has an effect of suppressing side reactions during storage and is effective.

<3. Positive electrode>
The positive electrode 5 includes a positive electrode current collector and a positive electrode active material layer formed from a positive electrode mixture on the positive electrode current collector. The positive electrode 5 is not particularly limited as long as it functions as a positive electrode of a non-aqueous secondary battery, and may be a known one.

[Positive electrode current collector]
The positive electrode current collector is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. The positive electrode current collector may have a surface coated with a carbon coat or may be processed into a mesh shape. The thickness of the positive electrode current collector is preferably 5 to 40 μm, more preferably 7 to 35 μm, and still more preferably 9 to 30 μm.

[Positive electrode active material layer]
The positive electrode active material layer contains a positive electrode active material and optionally further contains a conductive additive and a binder.
The positive electrode active material layer preferably contains a material capable of inserting and extracting lithium ions as the positive electrode active material. It is preferable that a positive electrode active material layer contains a conductive support agent and a binder as needed with a positive electrode active material. The use of such a material is preferable because a high voltage and a high energy density tend to be obtained.
Examples of the positive electrode active material include the following general formulas (3a) and (3b):
Li _x MO ₂ (3a)
Li _y M ₂ O ₄ (3b)
{In the formula, M represents one or more metal elements including at least one transition metal element, x represents a number of 0 to 1.1, and y represents a number of 0 to 2. }, A lithium-containing compound represented by each of the above and other lithium-containing compounds.

As the lithium-containing compound represented by each of the general formulas (3a) and (3b), for example,
Lithium cobalt oxide typified by LiCoO ₂ ;
Lithium manganese oxides typified by LiMnO ₂ , LiMn ₂ O ₄ , and Li ₂ Mn ₂ O ₄ ;
Lithium nickel oxide typified by LiNiO ₂ ;
Li _z MO ₂ {M includes at least one transition metal element selected from Ni, Mn, and Co, and two or more metal elements selected from the group consisting of Ni, Mn, Co, Al, and Mg And z represents a number of more than 0.9 and less than 1.2}
Etc.

The lithium-containing compound other than the lithium-containing compound represented by each of the general formulas (3a) and (3b) is not particularly limited as long as it contains lithium. Examples of such a lithium-containing compound include a composite oxide containing lithium and a transition metal element, a metal chalcogenide containing lithium, a metal phosphate compound containing lithium and a transition metal element, and lithium and a transition metal element. (For example, Li _t M _u SiO ₄ , M is as defined in the general formula (3a), t is a number from 0 to 1, and u is a number from 0 to 2). From the viewpoint of obtaining a higher voltage, as the lithium-containing compound, in particular,
With lithium,
Selected from the group consisting of cobalt (Co), nickel (Ni), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), chromium (Cr), vanadium (V), and titanium (Ti) At least one transition metal element,
The composite oxide containing and a metal phosphate compound are preferable.

More specifically, the lithium-containing compound is more preferably a composite oxide containing lithium and a transition metal element or a metal chalcogenide having lithium and a transition metal element, and a metal phosphate compound having lithium. General formulas (4a) and (4b):
^{_{Li v M I D 2 (4a}} )
Li _w M ^II PO ₄ (4b)
{Wherein D represents oxygen or a chalcogen element, MI and MII each represent one or more transition metal elements, and the values of v and w depend on the charge / discharge state of the battery, and v is 0.05 to 1 .10, w represents a number from 0.05 to 1.10. }, Compounds represented by each of the above.
The lithium-containing compound represented by the above general formula (4a) has a layered structure, and the compound represented by the above general formula (4b) has an olivine structure. These lithium-containing compounds are obtained by substituting a part of the transition metal element with Al, Mg, or other transition metal elements for the purpose of stabilizing the structure, and include these metal elements in the grain boundaries. It is also possible that the oxygen atom is partially substituted with a fluorine atom or the like, or at least a part of the surface of the positive electrode active material is coated with another positive electrode active material.

As the positive electrode active material in the present embodiment, only the lithium-containing compound as described above may be used, or other positive electrode active material may be used in combination with the lithium-containing compound.
Examples of such other positive electrode active materials include metal oxides or metal chalcogenides having a tunnel structure and a layered structure; sulfur; a conductive polymer. Examples of the metal oxide or metal chalcogenide having a tunnel structure and a layered structure include MnO ₂ , FeO ₂ , FeS ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , TiS ₂ , MoS ₂ , and NbSe _2. And oxides, sulfides, selenides, and the like of metals other than lithium. Examples of the conductive polymer include conductive polymers represented by polyaniline, polythiophene, polyacetylene, and polypyrrole.

The other positive electrode active materials described above are used alone or in combination of two or more, and are not particularly limited. However, since it is possible to occlude and release lithium ions in a reversible manner and to achieve a high energy density, the positive electrode active material layer is at least one transition metal selected from Ni, Mn, and Co. It is preferable to contain an element.
When a lithium-containing compound and another positive electrode active material are used in combination as the positive electrode active material, the use ratio of both is preferably 80% by mass or more, and 85% by mass as the use ratio of the lithium-containing compound to the entire positive electrode active material. % Or more is more preferable.

Examples of the conductive aid include carbon black typified by graphite, acetylene black, and ketjen black, and carbon fiber. The content ratio of the conductive assistant is preferably 10 parts by mass or less, more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the positive electrode active material.
Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid, styrene butadiene rubber, and fluorine rubber. The content ratio of the binder is preferably 6 parts by mass or less, more preferably 0.5 to 4 parts by mass with respect to 100 parts by mass of the positive electrode active material.

  The positive electrode active material layer is formed by applying a positive electrode mixture-containing slurry, in which a positive electrode mixture obtained by mixing a positive electrode active material and, if necessary, a conductive additive and a binder in a solvent, is applied to a positive electrode current collector and dried (solvent removal) And is formed by pressing as necessary. There is no restriction | limiting in particular as such a solvent, A conventionally well-known thing can be used. For example, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, water and the like can be mentioned.

<4. Negative electrode>
The negative electrode 6 includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector from a negative electrode mixture. The negative electrode 6 is not particularly limited as long as it functions as a negative electrode of a non-aqueous secondary battery, and may be a known one.

[Negative electrode current collector]
The negative electrode current collector is made of a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. The negative electrode current collector may have a surface coated with a carbon coat or may be processed into a mesh shape. The thickness of the negative electrode current collector is preferably 5 to 40 μm, more preferably 6 to 35 μm, and still more preferably 7 to 30 μm.

[Negative electrode active material layer]
From the viewpoint that the negative electrode active material layer can increase the battery voltage, lithium ion as a negative electrode active material is 0.4 V vs. It is preferable to contain a material that can be occluded at a lower potential than Li / Li +. It is preferable that a negative electrode active material layer contains a conductive support agent and a binder as needed with a negative electrode active material.
Examples of the negative electrode active material include amorphous carbon (hard carbon), artificial graphite, natural graphite, graphite, pyrolytic carbon, coke, glassy carbon, organic polymer compound fired body, mesocarbon microbeads, carbon fiber, activated carbon In addition to carbon materials such as graphite, carbon colloid, and carbon black, metal lithium, metal oxide, metal nitride, lithium alloy, tin alloy, silicon alloy, intermetallic compound, organic compound, inorganic compound, metal complex And organic polymer compounds.
A negative electrode active material is used individually by 1 type or in combination of 2 or more types.

Examples of the conductive aid include carbon black typified by graphite, acetylene black, and ketjen black, and carbon fiber. The content ratio of the conductive assistant is preferably 20 parts by mass or less, more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material.
Examples of the binder include PVDF, PTFE, polyacrylic acid, styrene butadiene rubber, and fluorine rubber. The content ratio of the binder is preferably 10 parts by mass or less, more preferably 0.5 to 6 parts by mass with respect to 100 parts by mass of the negative electrode active material.

  The negative electrode active material layer is coated with a negative electrode mixture-containing slurry in which a negative electrode mixture obtained by mixing a negative electrode active material and, if necessary, a conductive additive and a binder is dispersed in a solvent, and dried (solvent removal). And it forms by pressing as needed. There is no restriction | limiting in particular as such a solvent, A conventionally well-known thing can be used. For example, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, water and the like can be mentioned.

<5. Separator>
The nonaqueous secondary battery 1 in the present embodiment preferably includes a separator 7 between the positive electrode 5 and the negative electrode 6 from the viewpoint of providing safety such as prevention of short circuit between the positive electrode 5 and the negative electrode 6 and shutdown. The separator 7 may be the same as that provided in a known non-aqueous secondary battery, and is preferably an insulating thin film having high ion permeability and excellent mechanical strength. Examples of the separator 7 include a woven fabric, a nonwoven fabric, and a synthetic resin microporous membrane. Among these, a synthetic resin microporous membrane is preferable.
As the synthetic resin microporous membrane, for example, a microporous membrane containing polyethylene or polypropylene as a main component or a polyolefin microporous membrane such as a microporous membrane containing both of these polyolefins is suitably used. Examples of the nonwoven fabric include a porous film made of a heat resistant resin such as glass, ceramic, polyolefin, polyester, polyamide, liquid crystal polyester, and aramid.
The separator 7 may have a configuration in which one type of microporous membrane is laminated or a plurality of microporous membranes may be laminated, or two or more types of microporous membranes may be laminated. The separator 7 may be configured to be laminated in a single layer or a plurality of layers using a mixed resin material obtained by melting and kneading two or more kinds of resin materials.

<6. Battery exterior>
Although the structure of the battery exterior 2 of the non-aqueous secondary battery 1 in this embodiment is not specifically limited, For example, the battery exterior of either a battery can or a laminate film exterior body can be used. As the battery can, for example, a metal can made of steel or aluminum can be used. As the laminate film outer package, for example, a laminate film having a three-layer structure of hot melt resin / metal film / resin can be used.
Laminate film exterior is in a state where two sheets are stacked with the hot-melt resin side facing inward, or folded so that the hot-melt resin side faces inward, and the end is sealed by heat sealing It can be used as an exterior body. When using the laminate film outer package, the positive electrode external terminal 3 (or the positive electrode terminal and a lead tab connected to the positive electrode terminal) is connected to the positive electrode current collector, and the negative electrode external terminal 4 (or the negative electrode terminal) is connected to the negative electrode current collector. You may connect the lead tab which connects with this negative electrode terminal. In this case, the laminate film outer package is sealed with the ends of the positive electrode external terminal 3 and the negative electrode external terminal 4 (or the positive electrode terminal and the negative electrode terminal, and the lead tab connected to each of them) drawn out of the outer package. You may stop.

<7. Manufacturing method of battery>
The non-aqueous secondary battery 8 in the present embodiment has the above-described non-aqueous electrolyte, the positive electrode 5 having a positive electrode active material layer on one or both surfaces of the current collector, and the negative electrode active material layer on one or both surfaces of the current collector. It can be produced by a known method using the negative electrode 6, the battery casing 2, and, if necessary, the separator 7.
First, the laminated body which consists of the positive electrode 5 and the positive electrode 6, and the separator 7 as needed is formed.
For example, an aspect in which a long positive electrode 5 and a negative electrode 6 are wound in a laminated state in which the long separator is interposed between the positive electrode 5 and the negative electrode 6 to form a laminate having a wound structure;
A mode of forming a laminate having a laminated structure in which a positive electrode sheet and a negative electrode sheet obtained by cutting the positive electrode 5 and the negative electrode 6 into a plurality of sheets having a certain area and shape are alternately laminated via a separator sheet. ;
It is possible to form a laminated body having a laminated structure in which long separators are folded in a zigzag manner, and positive electrode sheets and negative electrode sheets are alternately inserted between the zippered separators.

Next, the above-described laminated body is accommodated in the battery exterior 2 (battery case), the electrolytic solution according to the present embodiment is injected into the battery case, and the laminated body is immersed in the electrolytic solution and sealed. The nonaqueous secondary battery in this embodiment can be produced.
Alternatively, an electrolyte solution in a gel state is prepared in advance by impregnating a base material made of a polymer material with an electrolytic solution, and a sheet-like positive electrode 5, negative electrode 6, electrolyte membrane, and separator 7 as necessary. After forming the laminated body of a laminated structure using, the nonaqueous secondary battery 1 can be produced by being accommodated in the battery exterior 2.
The shape of the non-aqueous secondary battery 8 in the present embodiment is not particularly limited, and for example, a cylindrical shape, an elliptical shape, a rectangular tube shape, a button shape, a coin shape, a flat shape, a laminate shape, and the like are suitably employed.

  The non-aqueous secondary battery 8 in the present embodiment can function as a battery by initial charging. There are no particular restrictions on the method of initial charging. However, considering that the non-aqueous secondary battery 8 is stabilized by the decomposition of a part of the electrolytic solution at the time of the initial charge, the initial charge is 0. 0 for the purpose of effectively expressing this stabilization effect. It is preferable to be performed at 001 to 0.3C, more preferably at 0.002 to 0.25C, and still more preferably at 0.003 to 0.2C. It is also preferable that the initial charging is performed via a constant voltage charging in the middle. The constant current for discharging the rated capacity in 1 hour is 1C. By setting the voltage range in which the lithium salt is involved in the electrochemical reaction for a long time, SEI (Solid Electrolyte Interface: solid electrolyte interface) is formed on the electrode surface, and the effect of suppressing the increase in internal resistance including the positive electrode 5 In addition, the reaction product is not firmly fixed only to the negative electrode 6, and in some way, a good effect is given to members other than the negative electrode 6 (for example, the positive electrode 5, the separator 7, etc.). For this reason, it is very effective to perform the initial charge in consideration of the electrochemical reaction of the lithium salt dissolved in the non-aqueous electrolyte.

  The non-aqueous secondary battery 1 in the present embodiment can also be used as a battery pack in which a plurality of non-aqueous secondary batteries 1 are connected in series or in parallel. From the viewpoint of managing the charge / discharge state of the battery pack, the operating voltage range per unit is preferably 2 to 5 V, more preferably 2.5 to 5 V, and 2.75 V to 5 V. Particularly preferred.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to the above-mentioned embodiment. The present invention can be variously modified without departing from the gist thereof.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
Various evaluations were performed as follows.

(1) Production of positive electrode Lithium, nickel, manganese, and cobalt composite oxide (LiNi _0.5 Mn _0.2 Co _0.3 O ₂ ) as a positive electrode active material, acetylene black powder as a conductive assistant, and binder As a mixture, polyvinylidene fluoride (PVDF) was mixed at a mass ratio of 100: 3.5: 3 to obtain a positive electrode mixture. N-methyl-2-pyrrolidone as a solvent was added to the obtained positive electrode mixture and further mixed to prepare a positive electrode mixture-containing slurry. This positive electrode mixture-containing slurry was applied to one surface of a 15 μm-thick aluminum foil serving as a positive electrode current collector while adjusting the basis weight to be about 95.0 g / m ₂ . When applying the positive electrode mixture-containing slurry to the aluminum foil, an uncoated region was formed so that a part of the aluminum foil was exposed. Then, the positive electrode which consists of a positive electrode active material layer and a positive electrode electrical power collector was obtained by rolling so that the density of a positive electrode active material layer might be 1.90 g / cm < ³ > with a roll press.
Next, the positive electrode was cut so that the area of the positive electrode mixture layer was 30 mm × 50 mm and the exposed portion of the aluminum foil was included. And the aluminum lead piece for taking out an electric current was welded to the exposed part of aluminum foil, and the positive electrode with a lead was obtained by performing vacuum drying at 120 degreeC for 12 hours.

(2) Production of Negative Electrode Graphite as a negative electrode active material, carboxymethyl cellulose as a binder, and styrene butadiene latex as a binder are mixed at a mass ratio of 100: 1.1: 1.5, and a negative electrode mixture Got. An appropriate amount of water was added to the obtained negative electrode mixture and mixed well to prepare a negative electrode mixture-containing slurry. This slurry was applied with a constant thickness on one side of a copper foil having a thickness of 10 μm. When applying the negative electrode mixture-containing slurry to the copper foil, an uncoated region was formed so that a part of the copper foil was exposed. Then, the negative electrode which consists of a negative electrode active material layer and a negative electrode electrical power collector was obtained by rolling so that the density of a negative electrode active material layer might be 1.20 g / cm < ³ > with a roll press.
Next, this negative electrode was cut so that the area of the negative electrode mixture layer was 32 mm × 52 mm and the exposed portion of the copper foil was included. And the lead piece made from nickel for taking out an electric current was welded to the exposed part of copper foil, and the negative electrode with a lead was obtained by performing vacuum drying at 80 degreeC for 12 hours.

(3) Assembly of single-layer laminated battery The positive electrode with lead and the negative electrode with lead are stacked with a polyethylene microporous membrane separator (thickness: 21 μm) laminated so that the mixture application surface of each electrode faces each other. An electrode body was obtained. This laminated electrode body was accommodated in a 90 mm × 80 mm aluminum laminate sheet outer package, and vacuum-dried at 80 ° C. for 5 hours in order to remove moisture. Subsequently, after injecting the electrolytic solution into the exterior body, the exterior body is sealed, so that a single-layer laminate type non-aqueous secondary battery (hereinafter, referred to as the external structure shown in FIG. 1 and the cross-sectional structure shown in FIG. 2). This was also simply referred to as “single layer laminate battery”.
This single-layer laminated battery has a rated current value of 23 mAh and a rated voltage value of 4.2V.

(4) Evaluation of single-layer laminated battery For the single-layer laminated battery obtained as described above, first, a first charge / discharge treatment was performed according to the following procedure (4-1). Next, the output characteristics were measured according to the following procedure (4-2), and then the 4.0 V storage characteristics at 60 ° C. were evaluated according to the following procedure (4-3). Charging / discharging was performed using charging / discharging apparatus ACD-01 (trade name) manufactured by Asuka Electronics Co., Ltd. and a thermostat PLM-73S (trade name) manufactured by Futaba Kagaku Co., Ltd.
Here, 1C means a current value at which a fully charged battery is discharged at a constant current and is expected to be discharged in 1 hour. In the following, it means a current value that is expected to discharge from a fully charged state of 4.2 V to 3.0 V at a constant current and finish discharging in 1 hour.

(4-1) Initial charge / discharge treatment of single-layer laminate battery The ambient temperature of the single-layer laminate battery is set to 25 ° C., and the battery voltage is 4.2 V by charging with a constant current of 1.125 mA corresponding to 0.05C. Then, the battery was charged until it reached, and then charged at a constant voltage of 4.2 V for a total of 3 hours. Thereafter, the battery was discharged to 3.0 V with a constant current of 7.5 mA corresponding to 0.3 C.

(4-2) Output characteristics (discharge capacity maintenance rate)
The single-layer laminated battery after the first charge / discharge treatment was charged at a constant current of up to 4.2 V at a current value of 0.3 C at 25 ° C. and then charged at a constant voltage of 4.2 V for 1 hour. About the single-layer laminated battery after charge, it discharged by the constant current until it became 3.0V with each current value of 0.3C and 10C, and the discharge capacity in each current value was measured.
And the value which remove | divided 0.3C discharge capacity by 10C discharge capacity was made into the discharge capacity maintenance factor, and it represented with percentage.

(4-3) Storage characteristics (4.0 V storage characteristics at 60 ° C.)
The single-layer laminated battery after the measurement of the discharge capacity maintenance rate was charged at a constant current until it reached 4.0 V at a current value of 0.3 C at 25 ° C., and then charged at a constant voltage of 4.0 V for 1 hour. went. And the single layer laminated battery after this charge was stored for 30 days in a 60 degreeC thermostat. After 30 days, the single-layer laminated battery was taken out of the thermostat and returned to room temperature, and then the voltage after storage for 30 days of each laminate cell was measured to measure the 4.0-V storage characteristics of the single-layer laminated battery (after 30 days of storage). Cell voltage).

[Example 1]
Under an inert atmosphere, a mixed solvent consisting of 470 mL of acetonitrile, 380 mL of diethyl carbonate, 110 mL of vinylene carbonate, and 40 mL of ethylene sulfite was prepared as a non-aqueous solvent. Among these, vinylene carbonate and ethylene sulfite also function as an additive for electrode protection.
In the mixed solvent, 1.3 mol of LiPF ₆ and 0.1 mol of LiBOB were dissolved as a lithium salt. Furthermore, the nonaqueous electrolyte solution was obtained by adding 0.1 mass% of the compound 1 shown below as an additive with respect to the whole quantity of electrolyte solution.
The ¹⁹ F-NMR spectrum of this electrolytic solution was measured as follows.
C ₆ H ₂ F ₄ (-141.7 ppm) is used as the internal standard sample, CFCl ₃ is used as the lock solvent, the resonance frequency of the F component is 376.13 MHz, the scanning range is 0 to −200 ppm, and the number of integration is 256 times. The ¹⁹ F-NMR spectrum of the electrolyte was measured using a double tube method. The obtained ¹⁹ F-NMR chart is shown in FIG. As can be seen in FIG. 3, a peak was observed at -50 to -70 ppm.
Table 1 shows the results of evaluation of this laminated battery by the above method.

[Examples 2 to 13 and Comparative Examples 1 and 2]
In Example 1 above, the composition of the non-aqueous solvent, the amount of each lithium salt added, and the type and amount of the additive were as described in Table 1, respectively. The solution was prepared, and a single-layer laminated battery was prepared and evaluated using the electrolytic solution. In Example 13, two types of compounds were used in combination as additives.
The evaluation results are shown in Table 1.
FIG. 4 shows a ¹⁹ F-NMR chart obtained by the same method as in Example 1 for the non-aqueous electrolyte prepared in Example 8. As can be seen in FIG. 4, also in the non-aqueous electrolyte solution of Example 8, a peak was confirmed at −50 to −70 ppm.

Abbreviations of each component in the non-aqueous electrolyte solution in Table 1 have the following meanings.
[Non-aqueous solvent]
AN: acetonitrile DEC: diethyl carbonate VC: vinylene carbonate ES: ethylene sulfite EC: ethylene carbonate EMC: ethyl methyl carbonate [lithium salt]
LiPF ₆ : lithium hexafluorophosphate (LiPF ₆ )
LiBOB: Lithium bis (oxalato) borate (LiB (C ₂ O ₄ ) ₂ )
[Additives] Compound 1: Compound represented by the following formula (A1) Compound 2: Compound represented by the following formula (A2) Compound 3: Compound represented by the following formula (A3) Compound 4: Formula (A4) Compound 5: Compound represented by the following formula (A5) Compound 6: Compound represented by the following formula (A6)

The PN bond in the above formulas (A1) to (A3) and the bond between P of PF ₅ and O of P = O in the above formulas (A4) to (A6) are coordinate bonds, respectively. .

From the comparison between Comparative Example 1 and Comparative Example 2 and Examples 1 to 13, when the electrolytic solution containing acetonitrile was used, the output characteristics (discharge capacity) were compared with the case of using the electrolytic solution not containing acetonitrile. It was confirmed that the maintenance rate was significantly improved.
Furthermore, Examples 1-6 containing the compound which has a structure of the above-mentioned general formula (1), and general formula (2) with respect to the comparative example 2 which does not contain an additive in electrolyte solution containing a significant amount of acetonitrile. It was found that in Examples 7 to 13 containing a compound having the structure), the storage characteristics at high temperature (4.0 V storage characteristics) were improved. From this result, in the electrolytic solution containing a significant amount of acetonitrile, the addition of the compound having the structure of the general formula (1) or the general formula (2) greatly contributes to the improvement of storage characteristics at high temperatures. It became clear that
From the above results, it was verified that the non-aqueous secondary battery using the electrolytic solution of the present embodiment can maintain high temperature durability comparable to that when the existing electrolytic solution is used while realizing high output characteristics.

  The non-aqueous secondary battery of the present invention is, for example, a portable device such as a mobile phone, a portable audio device, a personal computer, an IC (Integrated Circuit) tag; a rechargeable battery for a vehicle such as a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle; It can be applied to a residential power storage system.

DESCRIPTION OF SYMBOLS 1 Aluminum laminated film 2 Battery exterior 3 Positive electrode external terminal 4 Negative electrode external terminal 5 Positive electrode 6 Negative electrode 7 Separator 8 Non-aqueous secondary battery

Claims (7)

A non-aqueous secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte,
The non-aqueous electrolyte includes a non-aqueous solvent containing a compound having a nitrile group and an additive having a peak at -50 to -70 ppm when analyzed by ¹⁹ F-NMR. Secondary battery.   The non-aqueous secondary battery according to claim 1, wherein the non-aqueous electrolyte includes an organic lithium salt. The additive of the non-aqueous electrolyte solution includes the following general formulas (1) and (2):

{In the formula, N in the formula (1) and a double point on O in the formula (2) indicate a lone pair, an arrow indicates a coordination bond, and N and (2) in the formula (1) A straight line and a double line respectively originating from P in the formula indicate a bond. }, And a total content thereof is 0.001 to 10% by mass with respect to the non-aqueous electrolyte solution. The nonaqueous secondary battery according to 1 or 2.   The compound having the structure represented by the general formula (1) has any one of a pyridine skeleton, a quinoline skeleton, and an acridine skeleton, and the compound having the structure represented by the general formula (2) is an alkyl group, allyl The nonaqueous secondary battery according to claim 3, which has any one of a group and a trimethylsilyl group.   The non-aqueous secondary battery according to claim 1, wherein the compound having a nitrile group is a nitrile compound having a hydrogen atom at the α-position.   The non-aqueous secondary battery according to claim 5, wherein the nitrile compound having a hydrogen atom at the α-position is acetonitrile. A non-aqueous electrolyte containing a non-aqueous solvent containing a compound having a nitrile group and an additive having a peak at -50 to -70 ppm when analyzed by ¹⁹ F-NMR.

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