JPH1173991A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

(57) [Problem] To improve the cycle characteristics of a non-aqueous electrolyte secondary battery by preventing oxidative deterioration of a non-aqueous electrolyte layer. SOLUTION: In a non-aqueous electrolyte secondary battery including a positive electrode, a non-aqueous electrolyte layer, and a negative electrode capable of inserting and extracting lithium, an antioxidant is added to the non-aqueous electrolyte layer. In the example, Li
100 parts by weight of a non-aqueous solvent solution of BF ₄ (electrolyte salt) was added with tetratetrakis (methylene-3- (3,5-) as an antioxidant.
0.1 parts by weight of di-t-butyl-4-hydroxyphenol) -propionate) methane was added to obtain an electrolyte. A battery was manufactured using a predetermined positive electrode, the electrolyte solution, and a negative electrode of a Li plate. In a comparative example, a battery without the antioxidant was prepared. As a result, the battery cycle characteristics of the example were significantly improved as compared with those of the comparative example.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery using a novel non-aqueous electrolyte containing an antioxidant.

[0002]

2. Description of the Related Art A lithium secondary battery using a non-aqueous electrolyte has been rapidly developed for consumer use as a battery having a high voltage and a high capacity density. Examples of the non-aqueous electrolyte include LiB in a polar solvent such as γ-butyrolactone, sulfolane, tetrahydrofuran, dimethoxyethane, and dioxolane.
F ₄ , LiPF ₆ , LiAsF ₆ , LiClO ₄ , Li
CF ₃ obtained by mixing and dissolving an electrolyte salt such as SO ₃ is used.

[0003]

However, the solvent of such a non-aqueous electrolyte has a low withstand voltage in many cases. When charge and discharge are repeated, the solvent is decomposed, gas is generated, or decomposition of the electrode is generated. An object may be attached. As a result, the internal impedance rises, and the discharge characteristics decrease.
There has been a problem that the storage characteristics and cycle characteristics of the battery deteriorate due to a decrease in charge / discharge efficiency and a decrease in energy density.

In order to solve these problems, an attempt is made to suppress a decrease in energy density after charging and discharging by using a carbonate-based solvent such as diethyl carbonate having a high withstand voltage (Japanese Patent Laid-Open No. 2-10666). And so on. It has also been proposed to use a derivative obtained by partially substituting an ether solvent such as tetrahydrofuran. Further, by adding TCNQ (7,7,8,8-tetracyanoquinodimethane), deterioration of the electrolytic solution can be prevented (JP-A-8-222268), or an electron donating compound such as pyrene can be added. Attempts have been made to prevent the deterioration of the electrolytic solution by doing so (Japanese Unexamined Patent Publication No. 8-195199), but at present it cannot be said that a sufficient effect has been obtained.

In addition, not only the electrolyte solution deteriorates, but also the polymer solid electrolyte, which is a polymer material, deteriorates due to cycling and high potential holding, resulting in a reduction in molecular weight and a decrease in mechanical strength, resulting in a short circuit. There is a fear that the internal impedance may increase or the cycle characteristics may be deteriorated due to anxiety, or furthermore, the decomposition impurities may adhere to the electrodes. Similarly, in the polymer gel electrolyte containing the electrolyte solution and the electrolyte salt, both the electrolyte solution and the polymer solid electrolyte cause a problem, and there is a concern that the cycle characteristics are deteriorated and the mechanical strength is reduced. .

Accordingly, an object of the present invention is to prevent the electrolyte constituting the non-aqueous electrolyte secondary battery from being oxidized and deteriorated, thereby improving the cycle characteristics of the electrolytic solution and the cycle characteristics of the polymer solid electrolyte and the polymer gel electrolyte. It is another object of the present invention to provide a non-aqueous electrolyte secondary battery that has little deterioration in mechanical strength.

[0007]

Means for Solving the Problems The present inventors have conducted various studies to achieve the above object, and as a result, it has been found that by adding an antioxidant to the electrolyte layer, capacity deterioration due to charge / discharge cycles can be suppressed. It has been found that the deterioration of the mechanical strength of the polymer solid electrolyte and the polymer gel electrolyte can be suppressed.

The antioxidant is effective in preventing the decomposition of the electrolytic solution at the positive electrode, particularly at high potential, and at the negative electrode, the electrolytic solution reacts with Li, impurities, moisture and the like to decompose. Therefore, it is considered that the antioxidant contributes to the prevention of the capacity deterioration due to the charge / discharge cycle.

In the polymer gel electrolyte, oxygen contained in the polymer matrix of the polymer matrix, peroxy radicals generated by peroxides, radicals, and the like, and polymer radicals generated by heat, etc., initiate the oxidation reaction. It is considered that the oxidation reaction proceeds as a starting point.
Due to this oxidation reaction, the molecular weight of the polymer matrix is reduced or decomposed, or the internal impedance is increased due to by-products on the electrode or adhesion of the decomposed product. It is presumed that the deterioration of the cycle characteristics and the cycle characteristics may occur. Therefore, by containing an antioxidant, the progress of oxidation of the polymer matrix can be suppressed, and decomposition and the like can be suppressed. In particular, when a compound having a tertiary amine skeleton is contained, there is also an effect that oxidation of the electrolytic solution can be prevented.

Particularly, when LiPF ₆ is contained as an electrolyte salt in consideration of safety and toxicity, an antioxidant is used,
In particular, by using a compound having a tertiary amine skeleton, the thermal stability of LiPF ₆ is also effective.

As described above, the present inventors have made intensive studies and found that the electrolyte layer contains an antioxidant, that is, the nonaqueous electrolyte, the polymer electrolyte, or the polymer gel electrolyte contains the antioxidant. By doing so, it has been found that a nonaqueous electrolyte secondary battery having good cycle characteristics and little mechanical strength deterioration can be obtained, and the present invention has been accomplished.

That is, the invention according to claim 1 provides a non-aqueous electrolyte secondary battery comprising at least a positive electrode, a non-aqueous electrolyte layer, and a negative electrode capable of inserting and extracting lithium, wherein the non-aqueous electrolyte layer contains an antioxidant. A non-aqueous electrolyte secondary battery characterized in that:

[0013] The non-aqueous electrolyte secondary battery according to claim 2 is
In claim 1, the non-aqueous electrolyte layer is made of a non-aqueous electrolyte.

A non-aqueous electrolyte secondary battery according to claim 3 is
In claim 1, the non-aqueous electrolyte layer is made of a polymer gel electrolyte.

A non-aqueous electrolyte secondary battery according to claim 4 is
In claim 1, the non-aqueous electrolyte layer is made of a solid polymer electrolyte.

A non-aqueous electrolyte secondary battery according to claim 5 is
The non-aqueous electrolyte layer according to claim 2, 3 or 4, wherein at least LiPF ₆ is contained as an electrolyte salt.

A non-aqueous electrolyte secondary battery according to claim 6 is
Claims 1, 2, 3, 4 or 5, wherein the antioxidant is contained in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the nonaqueous electrolyte layer (excluding the antioxidant). Features.

A non-aqueous electrolyte secondary battery according to claim 7 is
In claim 6, the antioxidant is a compound having a tertiary amine in the skeleton.

[0019]

Embodiments of the present invention will be described below. Examples of the antioxidant used in the present invention include: (1) tetrakis (methylene-3- (3,5-di-t-
Butyl-4-hydroxyphenol) -propionate) methane, 2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-p-cresol, 2,
2'-methylenebis (6-t-butyl-4-methylphenol), 4,4'-butylenebis (3-t-butyl-
3-methylphenol), 4,4'-thiobis (6-t
-Butyl-3-methylphenol), α-tocophenol, 2,2,4-trimethyl-6-hydroxy-7-t
Phenolic compounds such as -butyl chroman; (2) 2,5-di-t-octylhydroquinone;
6-di-n-dodecylhydroquinone, 2-n-dodecyl-5-chlorohydroquinone, 2-t-octyl-5
Hydroquinone compounds such as -methylhydroquinone; (3) organic phosphorus compounds such as phosphorus triphenylated, phosphorus tris (dinonylphenyl) phosphorized, and phosphorylated tricresole; (4) dilauryl-3,3'-thiodipropionate ,
Sulfur compounds such as disterial-3,3'-thiodipropionate; (5) N-phenyl-N'-isopropyl-p-phenylenediamine, N, N'-diphenyl-p-phenylenediamine, N, N, N ', N'-tetramethylethylenediamine, N, N, N', N'-tetramethyltrimethylenediamine, tetramethyl-p-phenylenediamine, triethylamine, diphenylamine, triphenylamine, ethylenediamine, 1-methyl-2-piperidone , 1-methyl-2-pyridinone, N, N-dimethylpropionamide, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,2)
6,6-pentamethyl-4-piperidyl) sebacate,
1- (2- (3- (3,5-di-t-butyl-4-hydrophenyl) propionyloxy) ethyl) -4-
(3,3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy) -2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,
Examples thereof include, but are not limited to, amine compounds such as 6-tetramethylpiperidine and 2,2,6,6-tetramethyl-4-piperidinol (amines, amides, hindered amines, etc.).

In particular, the effect of improving the cycle characteristics of the electrolyte;
In consideration of the effect of improving the mechanical strength of the polymer matrix of the polymer solid electrolyte and the polymer gel electrolyte, phenol compounds, organic phosphorus compounds, and amine compounds are preferred. In particular, compounds having a tertiary amine skeleton such as triethylamine, triphenylamine, bis (1,2,2,2)
(6,6-pentamethyl-4-piperidyl) sebacate and the like are not limited thereto, and they are effective in preventing deterioration of the polymer matrix and are also effective in preventing light deterioration, and are therefore preferable.

The amine-based compound, there are particularly effective in thermal stabilization of thermally rather unstable electrolyte salts such as LiPF _6, also such as LiAsF _6, LiPF _6, but no problem in toxicity It is particularly effective for thermal stabilization of a thermally unstable electrolyte salt. The antioxidant may be used alone or in combination of two or more as needed. The content of the antioxidant is 0.01 to the electrolyte.
-5 wt%, preferably 0.1-2 wt%
More preferably, it is contained. Content is 0.01wt%
If less, the antioxidant effect is low. On the other hand, the content is 5w
If it exceeds t%, problems in electrical characteristics such as a decrease in battery capacity due to storage often occur.

The method of adding an antioxidant to the electrolyte layer includes (1) dissolving the antioxidant in an organic solvent, and then directly adding an electrolyte salt to the dissolved solution to form an electrolytic solution; Dissolving the agent in an organic solvent, impregnating the polymer solid electrolyte or dissolving and mixing the polymer solid electrolyte, and then distilling off the solvent; (3) impregnating the polymer solution with the antioxidant-added electrolytic solution in Gelation by cross-linking may be mentioned, but the method is not limited to these methods.

Next, the configuration of the battery of the present invention will be described. The battery of the present invention comprises at least a positive electrode, a non-aqueous electrolyte layer, and a negative electrode capable of inserting and extracting lithium. The positive electrode active material used in the battery of the present invention is TiS ₂ , M
Examples include transition metal oxides such as oS ₂ , Co ₂ S ₅ , V ₂ O ₅ , MnO ₂ , and CoO ₂ , transition metal chalcogen compounds, and composite oxides of lithium and any one of cobalt, nickel, and manganese.

As the composite oxide, a composite oxide having a layered structure represented by LiMO ₂ such as lithium cobalt oxide and lithium nickel oxide, or LiM ₂ O
_And a composite oxide having a spinel structure represented by No. 4 (JP-B-63-59507, JP-B-8-21).
431). These composite oxides can be synthesized by firing at a high temperature using carbonates, hydroxides, nitrates and the like as starting materials, and have an average particle size of 10 μm or less, preferably 8 μm or less.

Further, a conductive agent can be added to the positive electrode. As the conductive agent to be added, one-dimensional graphite, which is a thermal polymer of an organic substance, carbon fluoride, graphite, or an electric conductivity of 10 ⁻² S / cm. Conductive polymer having a certain degree. Specific examples of the conductive polymer include polyaniline, polypyrrole, polyazulene, polyphenylene, polyacetylene, polyphthalocyanine, and poly-3.
-Polymers such as methylthiophene, polypyridine, polydiphenylbenzidine and derivatives thereof.
In particular, in the case of polyaniline, it is also effective as a positive electrode active material.

Further, these active materials may be used in combination of several kinds. Positive electrodes using these active materials include dimethylformamide, N-methylpyrrolidone,
A high-concentration coating liquid mixed and dispersed in a solvent such as tetrahydrofuran or the like can be prepared by coating and drying on a current collector. Examples of the dispersing method include those using a roll mill, a ball mill, a barren mill, and the like, and examples of the applying method include a wire bar method, a blade coater method, and a spray method.

As the positive electrode current collector used in the present invention, for example, a metal sheet such as stainless steel, gold, platinum, nickel, aluminum, molybdenum, titanium, etc., a metal foil, a metal net, a punching metal, an expanded metal, or a metal plating Examples thereof include nets and nonwoven fabrics made of fibers, metal-deposited wires, metal-containing synthetic fibers, and the like. These also apply to the negative electrode. Among them, it is particularly preferable to use aluminum or stainless steel in consideration of electrical conductivity, chemical / electrochemical stability, economy, workability, and the like.

As the negative electrode material used in the battery of the present invention, an alkali metal such as Li or Na, a lithium alloy such as Li-Al, a conductive polymer such as polyacene, polypyridine or polyparaphenylene, or a carbonaceous material is used. Can be Among them, carbonaceous materials are mainly used from the viewpoint of safety and the like. Examples of the carbonaceous negative electrode active material include graphite (graphite), pitch coke, synthetic polymer, and fired body of natural polymer. In the present invention, a synthetic polymer such as phenol or polyimide, or an insulating or semiconductive carbon body obtained by firing a natural polymer in a reducing atmosphere at 400 to 800 ° C., coal, pitch, a synthetic polymer, or a natural polymer is used. A conductive carbon body, coke, pitch, a synthetic polymer, a natural polymer obtained by firing in a reducing atmosphere at 800 to 1300 ° C., obtained by firing in a reducing atmosphere at a temperature of 2000 ° C. or higher; and A graphite-based carbon body such as natural graphite is used.

As a method for forming a sheet of a carbon body, as described above, a method of forming a sheet by a wet papermaking method using a carbon body and a binder, or a coating material in which an appropriate binder is mixed with a carbon material is used. What is used and what forms a sheet by a coating method can be adopted. An electrode can be manufactured by supporting a carbon body on the current collector by a method such as application, adhesion, and pressure bonding by the above method.

Further, as electrolyte salts constituting the electrolyte layer, LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiS
bF ₆ , LiClO ₄ , LiCF ₃ CO ₃ , LiCF ₃
SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ S
O ₂ ) ₃ , LiC (CH ₃ ) (CF ₃ SO ₂ ) ₂ , Li
CH (CF ₃ SO ₂ ) ₂ , LiCH ₂ (CF ₃ S
O ₂ ), LiC ₂ F ₅ SO ₃ , LiN (C ₂ F ₅ S
O ₂ ) ₂ , LiB (CF ₃ SO ₂ ) _{2 and the} like.
There is no particular limitation. Note that these electrolyte salts may be used as a mixture. LiPF ₆ is particularly preferred because of its high ionic conductivity and safety, and low toxicity.

Examples of the non-aqueous electrolytic solution include those dissolved in a non-aqueous solvent. The concentration of the electrolyte salt in the non-aqueous electrolytic solution varies depending on the electrode and the electrolytic solution used.
7.0 mol / l, particularly preferably 1.0 to 5.0 mol / l.

As the non-aqueous solvent constituting the electrolytic solution, for example, ethylene carbonate, propylene carbonate,
Butylene carbonate, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, sulfolane, dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,2-dimethoxyethane, 1,2-ethoxymethoxyethane, methylglyme, methyl Examples include triglyme, methyltetraglyme, ethylglyme, butylglyme, and the like, but are not limited thereto, and these nonaqueous solvents can be used alone or as a mixture of two or more.

Further, the present invention has a great effect when using a polymer solid electrolyte or a polymer gel electrolyte. Polymer solid electrolytes such as polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyacrylonitrile, etc. are used as polymer matrices, and composites in which electrolyte salts are dissolved, or ion dissociating groups such as low molecular weight polyethylene oxide, crown ether, etc. Macromolecules grafted to chains.

Examples of the polymer gel electrolyte include a thermoplastic gel composition comprising a polymer such as polyvinylidene fluoride, polyacrylonitrile and polyethylene oxide, a non-aqueous solvent and an electrolyte salt, and a polysiloxane having an ethylene oxide chain in a side chain. Or a crosslinked polymer having an ethylene oxide chain in a side chain or a main chain, for example, a gel composition comprising a polymer matrix, a nonaqueous solvent, and an electrolyte salt by crosslinking such as urethane, acrylic, and epoxy. It is not limited.

In the battery of the present invention, a separator can be used. As the separator, it is preferable to use a separator having low resistance to ion movement of the electrolyte solution and excellent in holding the solution. Examples of such a separator include a nonwoven fabric filter made of glass fiber, a filter, a polymer fiber such as polyester, Teflon, polyflon, and polypropylene, and a nonwoven fabric filter in which glass fiber is mixed with such a polymer fiber.

[0036]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.
The non-aqueous solvent and the electrolyte salt are sufficiently purified and have a water content of 100%.
ppm or less, and a battery grade which was further deoxygenated and denitrified, was used, and all operations were performed in an inert gas atmosphere. In the following Reference Examples and Examples, "parts" indicate parts by weight.

Reference Example 1 Nonaqueous Electrolyte 1 Propylene carbonate / dimethoxyethane (1/1:
LiBF ₄ was dissolved in a mixed solvent (non-aqueous solvent) (volume ratio) to obtain a LiBF ₄ solution having a concentration of 2.0 mol / l. To 100 parts of this solution, 0.1 part of tetrakis (methylene-3- (3,5-di-t-butyl-4-hydroxyphenol) -propionate) methane as an antioxidant (0.1 part) was added.
1 wt%) was used as an electrolytic solution (for forming a non-aqueous electrolyte layer). In this case, the addition ratio of the antioxidant to 100 parts of the nonaqueous electrolyte layer (excluding the antioxidant) is 0.1 part.

Reference Example 2 Nonaqueous Electrolyte 2 Ethylene carbonate / diethyl carbonate (1 /
LiPF ₆ was dissolved in a mixed solvent (non-aqueous solvent) (1: 1: volume ratio) to obtain a LiPF ₆ solution having a concentration of 1.0 mol / l. An electrolyte (for forming a non-aqueous electrolyte layer) was prepared by adding 0.2 parts (0.2 wt%) of triethylamine as an antioxidant to 100 parts of this LiPF ₆ solution. in this case,
The addition ratio of the antioxidant to 100 parts of the nonaqueous electrolyte layer (excluding the antioxidant) is 0.1 part.

Reference Example 3 Nonaqueous Electrolyte 3 Ethylene carbonate / dimethyl carbonate (1 /
1: LiN the mixed solvent (non-aqueous solvent) by volume) (CF ₃
SO ₂ ) ₂ dissolved in LiN at a concentration of 1.5 mol / l
A (CF ₃ SO ₂ ) ₂ solution was prepared. To 100 parts of this solution, 5 parts of bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate (5.0 wt.
%) Was used as an electrolytic solution (for forming a non-aqueous electrolyte layer).

Reference Example 4 Polymer Gel Electrolyte 1 80 parts of the non-aqueous electrolyte prepared in Reference Example 3 was heated to 60 ° C., and 20 parts of polyvinylidene fluoride having a molecular weight of about 150,000 was added thereto as a polymer solid electrolyte. After the addition and mixing, the mixture was cooled and solidified to 10 ° C. to obtain a polymer gel electrolyte (for forming a non-aqueous electrolyte layer). In this case, the ratio of the antioxidant to 100 parts of the nonaqueous electrolyte layer (excluding the antioxidant) is about 3.8.
Department.

Reference Example 5: Polymer gel electrolyte 2 LiPF ₆ was dissolved in a mixed solvent (non-aqueous solvent) of ethylene carbonate / propylene carbonate / dimethoxyethane (5/2/3: volume ratio) to give a concentration of 1. 0 mol / l
Of LiPF ₆ was prepared. An electrolyte obtained by adding 0.5 part of triphenylamine as an antioxidant to 80 parts of this solution was heated to 70 ° C., and 20 parts of polyacrylonitrile having a number average molecular weight of about 100,000 was added and mixed. The mixture was cooled and solidified at 10 ° C. to obtain a polymer gel electrolyte (for forming a non-aqueous electrolyte layer). In this case, the non-aqueous electrolyte layer 100
The addition ratio of the antioxidant to parts (excluding the antioxidant) is 0.5 part.

Reference Example 6: Positive electrode 1 0.3 part of polyvinylidene fluoride was dissolved in 10 parts of N-methylpyrrolidone, and LiMn ₂ O having an average particle diameter of 5 μm was further dissolved.
₄ and 9 parts of conductive graphite were added and mixed and dispersed in a homogenizer under an argon gas atmosphere to prepare a coating for a positive electrode. This was applied on a 20 μm thick Al foil using a wire bar in the air,
After drying for minutes, a positive electrode having a thickness of 60 μm was prepared.

Reference Example 7: Positive electrode 2 A mixed solution of 450 ml of a 5.9 N (normal) H ₂ SO ₄ aqueous solution and 20.4 g of aniline was cooled to 5 ° C. or lower. A mixed solution of 50 ml of a 5.9 N H ₂ SO ₄ aqueous solution and 11.5 g of ammonium persulfate was added dropwise thereto. After completion of the dropwise addition, the mixture was stirred at 3 to 5 ° C. for 2 hours and filtered. The obtained solid particles were sufficiently washed with water and then with methanol to obtain polyaniline. 20 mol of this polyaniline
% Hydrazine monohydrate in methanol, stirred for one day, filtered, washed and dried to obtain a polyaniline powder having a weight average molecular weight Mw of 2.0 × 10 ⁴ . One part of this polyaniline was dissolved in 10 parts of N-methylpyrrolidone, 9 parts of LiMn ₂ O ₄ having an average particle size of 5 μm and 0.5 part of conductive graphite were added, and the mixture was homogenized under an argon gas atmosphere. By mixing and dispersing, a paint for a positive electrode was prepared. Using a wire bar in the air, a 20 μm thick A
l on a foil, dried at 100 ° C for 15 minutes,
A 0 μm positive electrode was produced.

REFERENCE EXAMPLE 8 Negative electrode 1 2 parts of polyvinylidene fluoride were replaced with N-methylpyrrolidone 58
And 40 parts of a coke calcined product at 2500 ° C. was added and mixed and dispersed under an argon gas atmosphere by a roll mill method to prepare a negative electrode coating material. This was applied on a copper foil having a thickness of 20 μm using a doctor blade in the air, and
After drying at 0 ° C. for 20 minutes, a negative electrode having a thickness of 85 μm was prepared.

Example 1 A secondary battery was manufactured using the positive electrode manufactured in Reference Example 6, the non-aqueous electrolyte layer manufactured using the electrolyte solution of Reference Example 1, and a counter electrode of a Li plate. went. In the charge / discharge test, Hokuto Denko's “HJ-201B charge / discharge measurement device” was used.
And the battery voltage was 4.2 at a current of 1.0 mA / cm ^2.
Charge to V, pause for 10 minutes, 1.0 mA / cm ²
The charge / discharge operation of discharging the battery voltage to 3.3 V with a current of 10 and resting for 10 minutes was repeated, and the battery cycle characteristics at this time were examined. The results are shown in Table 1 below.

Example 2 A secondary battery was manufactured using the positive electrode manufactured in Reference Example 6, the nonaqueous electrolyte layer made of the electrolytic solution manufactured in Reference Example 3, and a counter electrode of a Li plate. Was subjected to a charge / discharge test. Table 1 shows the results of evaluating the characteristics of this battery.

Example 3 A secondary battery was manufactured using the positive electrode manufactured in Reference Example 7, the nonaqueous electrolyte layer made of the electrolytic solution manufactured in Reference Example 2, and a counter electrode of a Li plate. Was subjected to a charge / discharge test. Table 1 shows the results of evaluating the characteristics of this battery.

Example 4 A secondary battery was produced in the same manner as in Example 3 using the positive electrode produced in Reference Example 6, the nonaqueous electrolyte layer produced using the polymer gel electrolyte of Reference Example 4, and the counter electrode of a Li plate. Was prepared, and a charge / discharge test and an elastic modulus measurement of the nonaqueous electrolyte layer were performed. The results of the charge / discharge test are shown in [Table 1], and the initial elastic modulus of the non-aqueous electrolyte layer and the elastic modulus of the electrolyte after 100 cycles are shown in [Table 2].

In the measurement of the elastic modulus, the elastic moduli of the polymer solid electrolyte and the polymer gel electrolyte were measured using a dynamic viscoelasticity tester (MR-300, manufactured by Raylogy Co., Ltd.). The elastic modulus was measured for the following reason. When a polymer solid electrolyte or a polymer gel electrolyte is used as a component (electrolyte layer) in a battery, a separator is not usually used. Therefore, when the modulus of elasticity of the electrolyte layer is low, the positive and negative electrodes are pressed by pressure from outside the battery. There is a concern that a short circuit will occur between them. Therefore, the elastic modulus was taken up as one of the evaluation items of the components in the battery. This elastic modulus is 10 ² d
It is preferably at least yn / cm ² .

Example 5 A battery was manufactured in the same manner as in Example 3 using the positive electrode manufactured in Reference Example 7, the nonaqueous electrolyte layer made of the polymer gel electrolyte manufactured in Reference Example 5, and the counter electrode of a Li plate. Then, a charge / discharge test and an elastic modulus measurement were performed. The results are shown in [Table 1] and [Table 2].

Example 6 Using the positive electrode produced in Reference Example 6, the nonaqueous electrolyte layer made of the polymer gel electrolyte produced in Reference Example 4, and the negative electrode produced in Reference Example 8, the same procedure as in Example 3 was carried out. A battery was prepared, and a charge / discharge test and an elastic modulus measurement were performed. These results are shown in [Table 3] and [Table 2].

Comparative Example 1 In Reference Example 1, tetrakis (methylene-3) was added to the electrolytic solution.
-(3,5-Di-t-butyl-4-hydroxyphenol) -propionate) A battery was prepared in the same manner as in Example 1 except that methane was not added, and the same electrolytic solution was used. The cycle characteristics were evaluated. The results are shown in [Table 1].

Comparative Example 2 In the reference example 3, bis (1,2,2,6,6
-Pentamethyl-4-piperidyl) sebacate was added in the same manner as in Example 2 except that 20 parts of sebacate was added. In this case, the amount of the antioxidant in 120 parts of the electrolytic solution (including the antioxidant) is 20 parts (16.7 wt%). The results are shown in [Table 1].

Comparative Example 3 In Reference Example 2, 0.001 part (0.001 wt.) Of triethylamine was added to 100 parts of the nonaqueous solvent solution.
%) Was carried out in the same manner as in Example 3. The results are shown in [Table 1].

Comparative Example 4 The same procedure as in Example 4 was carried out except that bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate was not added to the polymer gel electrolyte produced in Reference Example 4. The results are shown in [Table 1] and [Table 2].

Comparative Example 5 An experiment was carried out in the same manner as in Example 5 except that triphenylamine was not added to the polymer gel electrolyte produced in Reference Example 5. The results are shown in [Table 1] and [Table 2].

Comparative Example 6 The same procedure as in Example 6 was carried out except that bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate was not added to the polymer gel electrolyte prepared in Reference Example 4. The results are shown in [Table 3] and [Table 2].

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3]

[0061]

As apparent from the above description, the following effects can be obtained according to the present invention. (1) Claims 1-4 Since the non-aqueous electrolyte layer contains an antioxidant, the non-aqueous electrolyte layer is prevented from being oxidized and deteriorated, so that a non-aqueous electrolyte secondary battery having good cycle characteristics can be obtained. I can do it. Further, when the non-aqueous electrolyte layer is made of a polymer gel electrolyte, or when the non-aqueous electrolyte layer is made of a polymer solid electrolyte, the oxidative deterioration is prevented, and the cycle characteristics are good and the mechanical strength is high. A non-aqueous electrolyte secondary battery with little deterioration can be obtained. (2) Claim 5 Since LiPF ₆ as an electrolyte salt has high safety, a non-aqueous electrolyte secondary battery of particularly high quality can be obtained. (3) Claim 6 When the antioxidant is contained in the nonaqueous electrolyte layer in an amount of 0.01 to 5 wt%, the effect of preventing the nonaqueous electrolyte layer from being oxidized and degraded is enhanced. (4) In the case where the non-aqueous electrolyte layer is composed of a polymer gel electrolyte or the non-aqueous electrolyte layer is composed of a polymer solid electrolyte, a compound having a tertiary amine in the skeleton is used as an antioxidant. This increases the effect of preventing the deterioration of the polymer matrix of each of the polymer gel electrolyte and the polymer solid electrolyte, so that the effect of preventing a decrease in mechanical strength is increased and the effect of preventing light deterioration is also obtained.

Claims (7)

[Claims] 1. A non-aqueous electrolyte secondary battery comprising at least a positive electrode, a non-aqueous electrolyte layer, and a negative electrode capable of inserting and extracting lithium, wherein the non-aqueous electrolyte layer contains an antioxidant. Rechargeable battery. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte layer comprises a non-aqueous electrolyte. 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte layer comprises a polymer gel electrolyte. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte layer comprises a solid polymer electrolyte. 5. The non-aqueous electrolyte secondary battery according to claim 2, 3 or 4, wherein the non-aqueous electrolyte layer contains at least LiPF ₆ as an electrolyte salt. 6. The antioxidant according to claim 1, wherein the antioxidant is contained in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the nonaqueous electrolyte layer (excluding the antioxidant). A non-aqueous electrolyte secondary battery characterized in that: 7. The method of claim 6, wherein the antioxidant has 3
A non-aqueous electrolyte secondary battery comprising a compound having a secondary amine.