JP2001155767A - Non-aqueous electrolyte and lithium secondary cell using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary cell which has excellent cell characteristics such as a cycle characteristic, an electric capacity or charging maintenance characteristic and excellent safety. SOLUTION: A non-aqueous electrolyte dissolves an electrolytic salt in a non-aqueous solvent, wherein an octane derivative represented by a following formula I is contained in the non-aqueous electrolyte: where, R1 represents alkyl group of 1-6 carbon atoms, alkenyl group of 2-6 carbon atoms, alkynyl group of 2-6 carbon atoms cycloalkyl group of 3-6 carbon atoms or aryl group. R2 represents alkyl group of 1-6 carbon atoms, alkenyl group of 2-6 carbon atoms, alkynyl group of 2-6 carbon atoms cycloalkyl group of 3-6 carbon atoms, aryl group, acyl group of 2-10 carbon atoms alkanesulfonyl group of 1-6 carbon atoms, arylsulfonyl group of 6-10 carbon atoms or ester group of 2-10 carbon atoms. Also, the lithium secondary cell using the non-aqueous electrolyte is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel lithium battery capable of providing a lithium secondary battery having excellent battery characteristics such as cycle characteristics, electric capacity, storage characteristics and the like and excellent safety. The present invention relates to a non-aqueous electrolyte and a lithium secondary battery using the same.

[0002]

2. Description of the Related Art In recent years, lithium secondary batteries have been widely used as power sources for driving small electronic devices and the like. Lithium secondary batteries are mainly composed of a positive electrode, a non-aqueous electrolyte, and a negative electrode. In particular, a lithium secondary battery using a lithium composite oxide such as LiCoO ₂ as a positive electrode and a carbon material or lithium metal as a negative electrode has been developed. It is preferably used. As the non-aqueous electrolyte for the lithium secondary battery, ethylene carbonate (EC), propylene carbonate (P
Carbonates such as C) are preferably used.

[0003]

However, while lithium secondary batteries have the advantage of high energy density and high battery voltage, there have been cases where safety is not sufficient under severe conditions. For example, when an internal short circuit or the like occurs due to some abnormality, thermal runaway occurs due to a large current that flows instantaneously, and there is a risk of explosion or ignition. In addition, when overcharging is performed so as to exceed a normal operating voltage, lithium is excessively extracted at the positive electrode, and lithium may be precipitated at the negative electrode in some cases. When the electrode becomes thermally unstable as described above, the electrolyte is decomposed and gas is generated due to an oxidation reaction of the electrolyte on the positive electrode surface, a reduction reaction of the electrolyte by the deposited lithium on the negative electrode surface, and the like. At the same time, a thermal runaway may occur, causing a risk of explosion or fire. Further, the same danger arises when the device is placed in a high-temperature environment or dropped into a fire for some reason. Such a safety problem was particularly serious when lithium metal was used for the negative electrode.

[0004] To solve the problem of battery safety, the following measures have been taken. For example, a PTC element increases the internal resistance when the temperature rises to ensure safety, and a safety valve incorporates a safety mechanism into the battery structure, such as a method that shuts off current when the internal pressure of the battery rises. is there. Further, as a method of interrupting the current at a high temperature, there is a method of using a porous polymer separator that melts at a high temperature. In this case, when the battery undergoes thermal runaway, the separator melts, the internal resistance of the battery increases, and safety is ensured. However, even if the separator is melted, if the internal resistance of the electrolytic solution itself is low, current flows through gaps between the separators, which is not sufficient in terms of safety.

[0005] In order to further enhance the safety, studies have been made from the viewpoint of the electrolytic solution.
No. 78635 proposes a battery using 1,3-dioxolane, which polymerizes at a temperature exceeding 100 ° C. or a voltage higher than the operating voltage window of the battery, as an electrolyte. This is because if the battery is subjected to the extreme conditions of abnormally high temperature or abnormal overcharge, the electrolyte will polymerize and increase the internal resistance of the battery, resulting in a decrease in current flow. That is, the temperature in the battery decreases. However, in this publication, the operating voltage of the battery is as low as 2.0 to 3.4 V, and 1,3-dioxolan, which is disclosed as a polymerizable electrolyte, undergoes polymerization at a voltage of 4.0 V or more. However, there is a problem that the battery cannot be used at 4.2 V used in the lithium battery. In addition, there is a problem that a lithium salt containing arsenic that is harmful to humans and the environment, LiAsF ₆ , is used as an electrolyte.

The present invention solves the above-mentioned problems relating to the non-aqueous electrolyte for a lithium secondary battery, has excellent cycle characteristics of the battery, and further has excellent battery characteristics such as electric capacity and storage characteristics in a charged state. It is an object of the present invention to provide a non-aqueous electrolyte for a lithium secondary battery which can constitute a lithium secondary battery having excellent safety, and a lithium secondary battery using the same.

[0007]

According to the present invention, there is provided a non-aqueous electrolytic solution in which an electrolyte salt is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolytic solution contains an oxetane derivative. It relates to an electrolytic solution. The oxetane derivative in this case is represented by the following general formulas (I) and (II)

[0008]

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Wherein R ¹ represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, or an aryl group. R ² represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group, and 2 carbon atoms. Acyl group having 10 to 10 carbon atoms, alkane sulfonyl group having 1 to 6 carbon atoms, arylsulfonyl group having 6 to 10 carbon atoms, ester group having 2 to 10 carbon atoms)

[0010]

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(Wherein R ³ and R ⁴ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms,
It represents an alkynyl group having 2 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group. ) Is preferred.

Further, the present invention relates to a lithium secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolyte contains an oxetane derivative. It relates to a lithium secondary battery characterized by the above-mentioned. The oxetane derivative in this case is represented by the following general formulas (I) and (II)

[0013]

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(Wherein R ¹ represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group) R ² represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, an aryl group, and 2 carbon atoms. Acyl group having 10 to 10 carbon atoms, alkane sulfonyl group having 1 to 6 carbon atoms, arylsulfonyl group having 6 to 10 carbon atoms, ester group having 2 to 10 carbon atoms)

[0015]

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(Wherein R ³ and R ⁴ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms,
It represents an alkynyl group having 2 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group. ) Is preferred.

The oxetane derivative of the present invention has a high dielectric constant, a low melting point, and does not decompose on a positive electrode or a negative electrode at a voltage of about 4 V. It shows excellent characteristics as an electrolyte solvent of the above. In addition, since the oxetane derivative is polymerized at a high temperature to increase the internal resistance of the battery, the current can be interrupted when the internal temperature of the battery rises sharply, and an electrolyte having excellent safety can be provided.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In the oxetane derivative represented by the above general formula (I) contained in a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent, R ¹ and R ² are methyl group, ethyl group An alkyl group having 1 to 6 carbon atoms such as a group, propyl group, butyl group, pentyl group and hexyl group is preferred. The alkyl group may be a branched alkyl group such as an isopropyl group, an isobutyl group or an isopentyl group, or a cycloalkyl group such as a cyclopropyl group or a cyclohexyl group. Further, it may be an alkenyl group having 2 to 6 carbon atoms such as vinyl group, 1-propenyl group and allyl group, or an alkynyl group having 2 to 6 carbon atoms such as ethynyl group and 2-propynyl group. Further, an aryl group such as a phenyl group and a p-tolyl group may be used. Further, R ² may be an acyl group having 2 to 10 carbon atoms such as an acetyl group, a propionyl group, an acryloyl group and a benzoyl group, and a methanesulfonyl group,
It may be an alkanesulfonyl group having 1 to 6 carbon atoms or an arylsulfonyl group having 6 to 10 carbon atoms, such as a sulfonyl group such as an ethanesulfonyl group and a benzenesulfonyl group. Further, a methoxycarbonyl group, an ethoxycarbonyl group,
An ester group having 2 to 10 carbon atoms such as a phenoxycarbonyl group and a benzyloxycarbonyl group may be used.

In the dioxetane derivative represented by the general formula (II), R ³ and R ^{4 each} have 1 to 6 carbon atoms such as methyl, ethyl, propyl, butyl, pentyl and hexyl. Are preferred. The alkyl group may be a branched alkyl group such as an isopropyl group, an isobutyl group or an isopentyl group, or a cycloalkyl group such as a cyclopropyl group or a cyclohexyl group. Further, an alkenyl group having 2 to 6 carbon atoms such as a vinyl group, a 1-propenyl group and an allyl group may be used, and an ethynyl group,
An alkynyl group having 2 to 6 carbon atoms such as a propynyl group may be used. Further, an aryl group such as a phenyl group and a p-tolyl group may be used.

Oxetane derivative represented by the above general formula (I)
Specific examples of the conductor include, for example, R ¹Is a methyl group
Include 3-methyl-3-methoxymethyloxetane [R
¹= Methyl group, R^Two= Methyl group], 3-methyl-3-ethoxy
Xymethyloxetane [R¹= Methyl group, R^Two= Ethyl
Group], 3-methyl-3-propoxymethyloxetane
[R¹= Methyl group, R^Two= N-propyl group], 3-methyl
-3-butoxymethyloxetane [R¹= Methyl group, R^Two
= N-butyl group], 3-methyl-3-isopropoxyme
Cyloxetane [R¹= Methyl group, R^Two= Isopropyl
Group], 3-methyl-3-cyclohexyloxymethylo
Xetane [R¹= Methyl group, R^Two= Cyclohexyl group],
3-methyl-3-allyloxymethyloxetane [R¹
= Methyl group, R^Two= Allyl group], 3-methyl-3- (2
-Propynyl) oxymethyloxetane [R¹= Methyl
Group, R^Two= 2-propynyl group], 3-methyl-3-fe
Nonoxymethyloxetane [R¹= Methyl group, R^Two= Pheni
Group), 3-methyl-3-acetoxymethyloxetane
[R¹= Methyl group, R^Two= Acetyl group], 3-methyl-3
-Propionyloxymethyloxetane [R¹= Methyl
Group, R^Two= Propionyl group], 3-methyl-3-benzo
Iloxymethyloxetane [R¹= Methyl group, R^Two= Ba
Benzoyl group], 3-methyl-3-methanesulfonyloxy
Cimethyloxetane [R¹= Methyl group, R^Two= Methanesul
Honyl group], 3-methyl-3-benzenesulfonyloxy
Cimethyloxetane [R¹= Methyl group, R^Two= Benzens
Rufonyl group], 3-methyl-3-methoxycarbonylo
Xymethyloxetane [R¹= Methyl group, R^Two= Methoxy
Carbonyl group], 3-methyl-3-ethoxycarbonyl
Oxymethyloxetane [R¹= Methyl group, R^Two= Etoki
Sicarbonyl group], 3-methyl-3-butoxycarbonyl
Roxymethyloxetane [R¹= Methyl group, R^Two= N-
Butoxycarbonyl group], 3-methyl-3-phenoxy
Carbonyloxymethyloxetane [R¹= Methyl group,
R^Two= Phenoxycarbonyl group].
Also, R¹Is an ethyl group,
Toximethyloxetane [R¹= Ethyl group, R^Two= Methyl
Group], 3-ethyl-3-ethoxymethyloxetane [R
¹= Ethyl group, R^Two= Ethyl group], 3-ethyl-3-pro
Poxymethyl oxetane [R¹= Ethyl group, R^Two= N-p
Ropyl group], 3-ethyl-3-butoxymethyloxeta
[R¹= Ethyl group, R^Two= N-butyl group], 3-ethyl
-3-isopropoxymethyloxetane [R¹= Ethyl
Group, R^Two= Isopropyl group], 3-ethyl-3-cyclo
Hexyloxymethyloxetane [R¹= Ethyl group, R^Two
= Cyclohexyl group], 3-ethyl-3-allyloxy
Methyl oxetane [R¹= Ethyl group, R^Two= Allyl group],
3-ethyl-3- (2-propynyl) oxymethyloxy
Cetane [R¹= Ethyl group, R^Two= 2-propynyl group], 3
-Ethyl-3-phenoxymethyloxetane [R¹= D
Tyl group, R^Two= Phenyl group], 3-ethyl-3-aceto
Xymethyloxetane [R¹= Ethyl group, R^Two= Acetyl
Group], 3-ethyl-3-propionyloxymethyloxy
Cetane [R¹= Ethyl group, R^Two= Propionyl group], 3-
Ethyl-3-benzoyloxymethyloxetane [R¹
= Ethyl group, R^Two= Benzoyl group], 3-ethyl-3-
Methanesulfonyloxymethyloxetane [R¹= Echi
R group, R^Two= Methanesulfonyl group], 3-ethyl-3-
Benzenesulfonyloxymethyloxetane [R¹= D
Tyl group, R^Two= Benzenesulfonyl group], 3-ethyl-
3-methoxycarbonyloxymethyloxetane [R¹
= Ethyl group, R^Two= Methoxycarbonyl group], 3-ethyl
Ru-3-ethoxycarbonyloxymethyloxetane
[R¹= Ethyl group, R^Two= Ethoxycarbonyl group], 3-
Ethyl-3-butoxycarbonyloxymethyloxeta
[R¹= Ethyl group, R^Two= N-butoxycarbonyl
Group], 3-ethyl-3-phenoxycarbonyloxime
Cyloxetane [R¹= Ethyl group, R^Two= Phenoxycal
Bonyl group].

Specific examples of the dioxetane derivative represented by the general formula (II) include, for example, 3,3'-
[Oxybis (methylene)] bis (3-methyl) oxetane [R ³ = methyl group, R ⁴ = methyl group], 3,3′-
[Oxybis (methylene)] bis (3-ethyl) oxetane [R ³ = ethyl group, R ⁴ = ethyl group], 3,3′-
[Oxybis (methylene)] bis (3-butyl) oxetane [R ³ = n-butyl group, R ⁴ = n-butyl group], 3,
3 ′-[oxybis (methylene)] bis (3-isopropyl) oxetane [R ³ = isopropyl group, R ⁴ = isopropyl group], 3,3 ′-[oxybis (methylene)] bis (3-allyl) oxetane [R ³ = allyl group, R ⁴ = allyl group], 3,3 ′-[oxybis (methylene)] bis [3- (2-propynyl)] oxetane [R ³ = 2-propynyl group, R ⁴ = 2-propynyl group ], 3, 3'-
[Oxybis (methylene)] bis (3-cyclopropyl) oxetane [R ³ = cyclopropyl group, R ⁴ = cyclopropyl group], 3,3 ′-[oxybis (methylene)]
Bis (3-phenyl) oxetane [R ³ = phenyl group,
R ⁴ = phenyl group]. If the content of the oxetane derivative represented by the general formula (I) and the general formula (II) is excessively large, sufficient battery characteristics may not be obtained. Even if polymerization occurs, sufficient internal resistance to interrupt the current cannot be obtained. Therefore, its content is preferably in the range of about 3 to 50% by weight based on the weight of the non-aqueous electrolyte.

Further, since the oxetane derivative is polymerized by proton acids or Lewis acids PF ₅ or the like, such as small amount of HF in the electrolytic solution, a small amount of amine as a polymerization inhibitor,
It is preferable to add nitrogen compounds such as amides or ureas. Examples of the polymerization inhibitor to be used include amines such as trimethylamine, triethylamine, and the like.
Tri-n-propylamine, tri-n-butylamine,
Tri-iso-butylamine, tri-n-pentylamine, tri-n-hexylamine, tri-n-octylamine, triphenylamine, tribenzylamine, 1-
Examples include methylpyrrolidine, 1-methylpyrrole, 1-methylpiperidine, pyridine, quinoline, N, N-dimethylaniline and the like. Among amides, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-
Dimethylbenzamide, 1-methyl-2-pyrrolidone,
N-methyl-ε-caprolactam and the like. Further, among ureas, 1,1,3,3-tetramethylurea,
1,1,3,3-tetraethylurea, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4
5,6-tetrahydro-2 (1H) -pyrimidinone and the like. The amount of the polymerization inhibitor is not particularly limited,
If the amount is too large, sufficient battery characteristics may not be obtained, and if the amount is too small, polymerization may occur even at room temperature. Therefore, the content is preferably in the range of about 0.05 to 10% by weight based on the weight of the non-aqueous electrolyte.

The non-aqueous solvent used in the present invention is preferably a solvent comprising a high dielectric constant solvent and a low viscosity solvent. Examples of the high dielectric constant solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC).
Preferred examples thereof include cyclic carbonates. One of these high dielectric constant solvents may be used, or two or more thereof may be used in combination.

Examples of the low-viscosity solvent include dimethyl carbonate (DMC) and methyl ethyl carbonate (M
EC), chain carbonates such as diethyl carbonate (DEC), tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane And lactones such as γ-butyrolactone, nitriles such as acetonitrile, esters such as methyl propionate, and amides such as dimethylformamide. These low-viscosity solvents may be used alone or in combination of two or more. The high dielectric constant solvent and the low viscosity solvent are arbitrarily selected and used in combination. The high dielectric constant solvent and the low viscosity solvent are used in a volume ratio (high dielectric constant solvent: low viscosity solvent) of usually 1: 9 to 4: 1, preferably 1: 4 to 7: 3. You.

The electrolyte salt used in the present invention includes, for example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiN
(SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC
Compounds not containing As, such as (SO ₂ CF ₃ ) _3, may be mentioned. These electrolytes may be used alone,
Two or more types may be used in combination. These electrolytes are used after being dissolved in the above non-aqueous solvent at a concentration of usually 0.1 to 3M, preferably 0.5 to 1.5M.

The non-aqueous electrolytic solution of the present invention is prepared, for example, by mixing the above-mentioned high dielectric constant solvent or low-viscosity solvent, dissolving the above-mentioned electrolyte, and adding a small amount of amines as a polymerization inhibitor. Is obtained by dissolving the oxetane derivative represented by the general formula (I) or (II).

The non-aqueous electrolyte of the present invention is used as a component of a lithium secondary battery. The constituent members other than the non-aqueous electrolyte constituting the secondary battery are not particularly limited, and various constituent members conventionally used can be used.

For example, as the positive electrode active material, a composite metal oxide of lithium and at least one metal selected from the group consisting of cobalt, manganese, nickel, chromium, iron and vanadium is used. Examples of such a composite metal oxide include LiCoO ₂ , LiMn ₂ O ₄ ,
LiNiO ₂ , LiNi _0.8 CO _0.2 O _{2 and the} like. One of these positive electrode active materials may be selected and used, or two or more thereof may be used in combination.

The positive electrode is prepared by kneading the positive electrode active material with a conductive agent such as acetylene black and carbon black, a binder such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), and a solvent to form a positive electrode mixture. After that, this positive electrode material is applied to an aluminum foil or a stainless steel lath plate as a current collector, dried and pressed, and then heat-treated under a vacuum at a temperature of about 50 ° C. to 250 ° C. for about 2 hours. It is produced by doing.

Examples of the negative electrode active material include lithium metals, lithium alloys, and carbon materials having a graphite type crystal structure capable of inserting and extracting lithium (pyrolytic carbons, cokes,
Materials such as graphites (artificial graphite, natural graphite, etc.), organic polymer compound burners, carbon fibers] and composite tin oxide are used. In particular, the spacing (d) of the lattice plane (002)
It is preferable to use a carbon material having a graphite type crystal structure in which ( ₀₀₂ ) is 0.335 to 0.340 nm. One of these negative electrode active materials may be selected and used, or two or more thereof may be used in combination. In addition,
A powder material such as a carbon material is used as a negative electrode mixture by kneading with a binder such as ethylene propylene diene terpolymer (EPDM), polytetrafluoroethylene (PTFE), or polyvinylidene fluoride (PVDF). The method for producing the negative electrode is not particularly limited, and the negative electrode can be produced by the same method as the above-described method for producing the positive electrode.

The structure of the lithium secondary battery is not particularly limited. A coin-type battery having a positive electrode, a negative electrode and a single-layer or multi-layer separator, and a cylindrical battery having a positive electrode, a negative electrode and a roll-shaped separator And a prismatic battery. As the separator, a known microporous polyolefin membrane, woven fabric, nonwoven fabric, or the like is used.

[0032]

(Preparation of non-aqueous electrolyte)

A non-aqueous solvent of EC: DMC (volume ratio) = 1: 2 was prepared,
LiPF ₆ was dissolved therein to a concentration of 1 M to prepare a non-aqueous electrolyte.
0.1% by weight of pyridine as a polymerization inhibitor, 3-ethyl-3-butoxymethyloxetane [R ¹ = ethyl group, R ²
= N-butyl group] was added to give 20% by weight.

[Preparation of Lithium Secondary Battery, Measurement of Battery Characteristics, and Heating Experiment] LiCoO ₂ (cathode active material)
0% by weight, 10% by weight of acetylene black (conductive agent) and 10% by weight of polyvinylidene fluoride (binder), and a mixture obtained by adding a 1-methyl-2-pyrrolidone solvent to the mixture. The composition was applied on an aluminum foil, dried, molded under pressure, and heat-treated to prepare a positive electrode. 90% by weight of artificial graphite (negative electrode active material) and 10% by weight of polyvinylidene fluoride (binder) were mixed, and a 1-methyl-2-pyrrolidone solvent was added thereto. , Dried, press-molded, and heat-treated to prepare a negative electrode. Then, using a separator made of a polypropylene microporous film, the above nonaqueous electrolyte was injected to prepare a coin battery (diameter 20 mm, thickness 3.2 mm). Using this coin battery, at a constant current and a constant voltage of 0.8 mA at room temperature (20 ° C.), the battery was charged to a final voltage of 4.2 V for 5 hours, and then a final voltage of 0.8 mA was applied under a constant current of 0.8 mA. The battery was discharged to 7 V, and the charging and discharging were repeated. When the battery characteristics after 20 cycles were measured, the discharge capacity retention ratio when the initial discharge capacity was 100% was 80.2%. Also,
Low temperature characteristics were also good. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery. In addition, this electrolyte is
Heated to 30 ° C. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown and gelled.

Example 2 As an oxetane derivative, 3,3 '-[oxybis (methylene)] bis (3-ethyl) oxetane (R ³ = ethyl group, R ⁴ = ethyl group) was used, and pyridine was used as a polymerization inhibitor. An electrolyte was prepared in the same manner as in Example 1 except that 0.15 wt% was used, and a coin battery was manufactured. The discharge capacity retention rate at 20 cycles was measured. The discharge capacity retention rate was 81.5%. Was. This electrolyte was heated to 130 ° C. in a closed system. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown and solid. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 3 As an oxetane derivative, 3,3 ′-[oxybis (methylene)] bis (3-ethyl) oxetane [R ³ = ethyl group, R ⁴ = ethyl group] was 10 wt% based on the total electrolyte. Except for using the same, an electrolytic solution was prepared in the same manner as in Example 1 to prepare a coin battery, and the discharge capacity retention rate in 20 cycles was measured. The discharge capacity retention rate was 85.8%. This electrolyte was heated to 130 ° C. in a closed system. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown and gelled. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 4 As an oxetane derivative, 3,3 ′-[oxybis (methylene)] bis (3-ethyl) oxetane [R ³ = ethyl group, R ⁴ = ethyl group] was 5 wt% based on the total electrolyte. A coin battery was prepared by preparing an electrolyte solution in the same manner as in Example 1 except that 0.07 wt% of pyridine was used as a polymerization inhibitor, and a discharge capacity retention ratio was measured in 20 cycles. The rate was 93.2%.
This electrolyte was heated to 130 ° C. in a closed system. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown and gelled. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 5 As an oxetane derivative, 3,3 ′-[oxybis (methylene)] bis (3-ethyl) oxetane [R ³ = ethyl group, R ⁴ = ethyl group] was 5 wt% based on the total electrolyte. Use triethylamine as a polymerization inhibitor 0.07w
Except for using t%, an electrolytic solution was prepared in the same manner as in Example 1 to prepare a coin battery, and the discharge capacity retention rate was measured in 20 cycles. As a result, the discharge capacity retention rate was 90.1%. This electrolyte was heated to 130 ° C. in a closed system. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown and gelled. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 6 A non-aqueous solvent of EC: MEC (volume ratio) = 1: 2 was prepared.
A non-aqueous electrolyte was prepared by dissolving LiPF ₆ to a concentration of 1 M, and pyridine was added to the solution in an amount of 0.1 wt% with respect to the total electrolyte.
-Acetoxymethyloxetane [R ¹ = ethyl group, R ² =
Acetyl group] was added so as to be 10% by weight with respect to the total electrolytic solution. Using this non-aqueous electrolyte, a coin battery was fabricated in the same manner as in Example 1, and the battery characteristics were measured.
The discharge capacity retention rate after the cycle was 87.1%. This electrolyte was heated to 130 ° C. in a closed system. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown and gelled. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 7 A non-aqueous solvent of EC: DEC (volume ratio) = 1: 2 was prepared.
A non-aqueous electrolyte was prepared by dissolving LiPF ₆ to a concentration of 1 M, and pyridine was added to the solution in an amount of 0.1 wt% with respect to the total electrolyte.
-Methanesulfonyloxymethyloxetane [R ¹ = ethyl group, R ² = methanesulfonyl group] was added so as to be 10% by weight based on the total electrolyte. Using this non-aqueous electrolyte, a coin battery was fabricated in the same manner as in Example 1, and the battery characteristics were measured. As a result, the discharge capacity retention after 20 cycles was 88.7%. Further, this electrolytic solution was used in a closed system for 13 hours.
Heated to 0 ° C. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown and gelled. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 8 As an oxetane derivative, 3-ethyl-3-methoxycarbonyloxymethyloxetane [R ¹ = ethyl group, R ²
= Methoxycarbonyl group] to the total electrolyte
%, An electrolytic solution was prepared in the same manner as in Example 1 to prepare a coin battery, and the discharge capacity retention rate was measured in 20 cycles. As a result, the discharge capacity retention rate was 90.3%. This electrolyte was heated to 130 ° C. in a closed system. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown and gelled. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 9 A non-aqueous solvent of EC: PC: DMC (volume ratio) = 1: 1: 2 was prepared, and LiPF ₆ was dissolved therein to a concentration of 1M to prepare a non-aqueous electrolyte. After that, pyridine was added to be 0.1 wt% with respect to the total electrolyte solution, and
3 '-[oxybis (methylene)] bis (3-ethyl)
Oxetane [R ³ = ethyl group, R ⁴ = ethyl group] was added so as to be 10% by weight based on the total electrolyte. Using this non-aqueous electrolyte, a coin battery was prepared in the same manner as in Example 1,
When the battery characteristics were measured, the discharge capacity retention ratio after 20 cycles was 84.4%. This electrolyte was heated to 130 ° C. in a closed system. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown and gelled. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 10 As the negative electrode active material, natural graphite was used in place of artificial graphite, and 3,3 ′-[oxybis (methylene)] bis (3-ethyl) oxetane [R ³ =
Ethyl group, R ⁴ = ethyl group] to 10 w
Except for using t%, an electrolytic solution was prepared in the same manner as in Example 1 to prepare a coin battery, and the discharge capacity retention rate in 20 cycles was measured. The discharge capacity retention rate was 83.8%. This electrolyte was heated to 130 ° C. in a closed system. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown and gelled. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 11 As a positive electrode active material, LiMn ₂ O ₄ was used instead of LiCoO _2.
And 3,3 ′-[oxybis (methylene)] bis (3-ethyl) oxetane [R ³ = ethyl group, R ⁴ = ethyl group] was used as an oxetane derivative in an amount of 10 wt% based on the total electrolyte. Otherwise, an electrolytic solution was prepared in the same manner as in Example 1 to produce a coin battery, and the discharge capacity retention rate was measured at 20 cycles.
It was 0%. This electrolyte was heated to 130 ° C. in a closed system. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown and gelled.
Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 12 Lithium metal was used in place of artificial graphite as the negative electrode active material, and 3,3 ′-[oxybis (methylene)] bis (3-ethyl) oxetane [R ³
= Ethyl group, R ⁴ = ethyl group]
A coin battery was prepared by preparing an electrolytic solution in the same manner as in Example 1 except that wt% was used, and the discharge capacity retention rate in 20 cycles was measured. The discharge capacity retention rate was 89.5%.
Met. This electrolyte was heated to 130 ° C. in a closed system. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown and gelled. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

Example 13 A lithium-aluminum alloy was used as the negative electrode active material instead of artificial graphite, and oxetane derivatives were
3 '-[oxybis (methylene)] bis (3-ethyl)
A coin battery was prepared in the same manner as in Example 1 except that oxetane [R ³ = ethyl group, R ⁴ = ethyl group] was used in an amount of 10 wt% based on the total electrolyte, and a discharge capacity at 20 cycles was prepared. When the retention rate was measured, the discharge capacity retention rate was 88.9%. This electrolyte was heated to 130 ° C. in a closed system. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown and gelled. Table 1 shows the coin battery fabrication conditions and battery characteristics.
Shown in

Comparative Example 1 A coin battery was prepared by preparing an electrolytic solution in the same manner as in Example 1 except that 1,3-dioxolan was used instead of the oxetane derivative, and the discharge capacity retention ratio at 20 cycles was measured. However, the discharge capacity retention ratio was 39.0%. This electrolyte was heated to 130 ° C. in a closed system. After cooling to room temperature, the state of the electrolytic solution was observed, and the color of the electrolytic solution was changed to brown, but was still liquid. Table 1 shows the manufacturing conditions and battery characteristics of the coin battery.

The present invention is not limited to the described embodiments, and various combinations can be easily inferred from the spirit of the invention. In particular, the combinations of the solvents in the above examples are not limited. Further, while the above embodiments relate to coin batteries, the present invention is also applicable to cylindrical and prismatic batteries.

[0048]

According to the present invention, since the oxetane derivative which is stable against redox is used, even at a high voltage of 4.0 V or more, the battery characteristics such as the cycle characteristics, electric capacity and charge storage characteristics of the battery are obtained. It is possible to provide an excellent lithium secondary battery. In addition, the oxetane derivative contained in the non-aqueous electrolyte rapidly polymerizes when used under severe conditions or when the battery temperature rises due to overcharging or the like. As a result, the current is cut off, and the temperature inside the battery decreases, so that the present invention can provide a lithium secondary battery with excellent safety.

[0049]

[Table 1]

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H029 AJ03 AJ04 AJ05 AJ12 AK18 AL03 AL06 AL07 AL12 AM02 AM03 AM04 AM05 AM07 CJ08 HJ02

Claims (4)

[Claims] 1. A non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolyte contains an oxetane derivative. 2. An oxetane derivative represented by the following general formula (I) and general formula (II): (Wherein, R ¹ is an alkyl group having 1 to 6 carbon atoms, 2 to 2 carbon atoms)
An alkenyl group having 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group. R ² is an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms,
To 6 cycloalkyl groups, aryl groups, 2 to 10 carbon atoms
An acyl group having 1 to 6 carbon atoms, an arylsulfonyl group having 6 to 10 carbon atoms, and 2 to 10 carbon atoms
Ester group) (Wherein R ³ and R ⁴ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms,
Alkynyl group, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group. 2. The non-aqueous electrolyte according to claim 1, which is at least one member selected from the group consisting of: 3. A lithium secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolyte contains an oxetane derivative. Rechargeable lithium battery. 4. An oxetane derivative represented by the following general formula (I) and general formula (II): (Wherein, R ¹ is an alkyl group having 1 to 6 carbon atoms, 2 to 2 carbon atoms)
An alkenyl group having 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group. R ² is an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms,
To 6 cycloalkyl groups, aryl groups, 2 to 10 carbon atoms
An acyl group having 1 to 6 carbon atoms, an arylsulfonyl group having 6 to 10 carbon atoms, and 2 to 10 carbon atoms
Ester group) (Wherein R ³ and R ⁴ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms,
Alkynyl group, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group. 4. The lithium secondary battery according to claim 3, which is at least one member selected from the group consisting of: