JP2002025613A - Nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery with high capacity and high safety even when abnormalities are generated such as in overcharge. SOLUTION: This nonaqueous secondary battery has a positive electrode, a negative electrode, and an electrolyte, and sulfolene or its derivative is included in the electrolyte. The content of the sulfolene or its derivative in the electrolyte is preferable to be 0.05-10 wt.% in the solvent component of the electrolyte, and as a negative electrode active material, a carbon material having an average particle size of 8-20 μm is preferable. This is preferably applied to the nonaqueous secondary battery having a discharge capacity per volume of an electrode stack of 130 mAh/cm3 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous secondary battery, and more particularly, to a non-aqueous secondary battery having a high capacity and a high safety when an abnormality such as overcharging occurs.

[0002]

2. Description of the Related Art Demand for non-aqueous secondary batteries represented by lithium ion secondary batteries tends to increase due to their large capacity, high voltage, high energy density and high output. With the expansion of the range of use, studies for further increasing the capacity have been continued, and it has been pointed out that the safety is reduced as a result. Investigations have been made to solve this decrease in safety by improving various components such as an electrode structure, a charge / discharge circuit, an electrolyte composition, and an active material composition.

[0003]

However, when the present inventors have improved the discharge capacity per unit volume of the electrode laminate in order to further increase the capacity of the non-aqueous secondary battery, When the value is 130 mAh / cm ³ or more, it has been found that conventional safety measures do not ensure sufficient safety in the event of an abnormality such as overcharging, resulting in a battery with poor safety.

The present invention solves the above-mentioned problems of the conventional non-aqueous secondary battery, and provides a non-aqueous secondary battery having high capacity and high safety in the event of an abnormality such as overcharging. The purpose is to do.

[0005]

The present invention has solved the above-mentioned problems in a non-aqueous secondary battery having a positive electrode, a negative electrode, and an electrolyte by including sulfolene or a derivative thereof in the electrolyte.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, in the present invention, a description will be given of the reason why the above-described configuration makes it possible to obtain high security even in the event of an abnormality such as overcharging. The form will be described.

First, in order to increase the capacity of the battery, for example, the density of the mixture layer of the negative electrode is set to 1.4 g / cm ³ or more, and the discharge capacity per unit volume of the electrode laminate is 130 mAh / cm ^3.
In the case described above, the reaction between the positive electrode or the negative electrode and the electrolytic solution (liquid electrolyte) is apt to occur, and when an abnormality such as overcharging occurs, there is a high risk that the battery will ignite or burst due to heat generation.

However, when sulfolene or a derivative thereof is contained in the electrolyte, a film based on sulfolene or a derivative thereof is formed on the surface of the positive electrode at the time of occurrence of an abnormality such as overcharging or application of an abnormal voltage, thereby increasing the impedance. In addition, the reaction between the positive electrode or the negative electrode and the electrolytic solution (liquid electrolyte) is suppressed, and heat generation due to the reaction of the battery can be suppressed. In addition, it is possible to prevent an excessive current from flowing due to an increase in impedance due to the coating based on the sulfolene or a derivative thereof, thereby improving safety. On the other hand, since the heat is generated due to the rise in the impedance, the temperature rise start time of the battery at the time of occurrence of an abnormality such as overcharging is accelerated, and gas is generated due to decomposition of sulfolene or a derivative thereof, thereby causing an abnormality such as overcharging. After reaching the state, the internal pressure of the battery rises in a short time. as a result,
In a battery provided with a safety mechanism that cuts off current when the internal pressure rises, the time required for the safety mechanism to operate is shortened, safety is more reliably ensured, and safety is further enhanced.

The sulfolene and derivatives thereof used in the present invention include, for example, 2-sulfolene, 3-sulfolene, 2-methyl-2-sulfolene, 3-methyl-2-sulfolene, 2-methyl-3-sulfolene, Methyl-
3-sulfolene, 2,5-dimethyl-2-sulfolene,
Examples include 2,3-dimethyl-2-sulfolene, 2,3-dimethyl-3-sulfolene, and 3,4-dimethyl-3-sulfolene.

In the present invention, the content of sulfolene or a derivative thereof in the electrolyte is preferably 0.05 to 10% by weight in the solvent component of the electrolyte. That is, by setting the content of sulfolene or its derivative in the electrolyte to be 0.05% by weight or more in the solvent component of the electrolyte, the overcharge of the battery or the like causes the positive electrode or the negative electrode and the electrolytic solution (liquid electrolyte) to react with each other. The effect of suppressing the reaction and suppressing the heat generation of the battery is increased, and the internal pressure is easily increased,
Since the operation of a safety mechanism such as a current interrupt device can be hastened, favorable results regarding safety can be obtained. The content of the sulfolene or a derivative thereof in the electrolyte is more preferably 0.5% by weight or more, more preferably 1% by weight or more, in the solvent component of the electrolyte. On the other hand, when the content of sulfolene or a derivative thereof is increased, the discharge capacity tends to slightly decrease.Therefore, from the viewpoint of achieving a high capacity, the content of the sulfolene or the derivative thereof in the electrolyte is determined by the content of the electrolyte. The content is preferably 10% by weight or less, more preferably 5% by weight or less, even more preferably 2% by weight or less in the solvent component.

In the present invention, the volume of the electrode laminate is
Bulk volume in a battery such as a battery in which a positive electrode, a negative electrode and a separator are laminated, or a battery in which a positive electrode, a negative electrode and a separator are wound (a battery in which an electrolyte substitutes for a separator such as a gel polymer electrolyte has a positive electrode, a negative electrode, And the bulk volume of the gel-like polymer electrolyte in the battery), which is wound as the latter,
The through hole at the center of the wound body based on the winding shaft used for winding is not included in the volume. In short, it is the sum of the bulk volumes occupied by the positive electrode, the negative electrode, and the separator (or the gel polymer electrolyte) in the battery.

The three volumes of the positive electrode, the negative electrode, and the separator (or the gel polymer electrolyte) are important factors that determine the capacity of the battery. Regardless of the size of the battery, the discharge per unit volume of the electrode stack is By calculating the capacity (discharge capacity / volume of the electrode stack), the capacity density of the batteries can be compared. In addition, the discharge capacity at that time is determined by the general operating conditions of the battery [for example, in a non-aqueous secondary battery using LiCoO ₂ as a positive electrode active material and a carbon material as a negative electrode active material, 1 C at 25 ° C. (A current that can discharge the battery in 1 hour), charging by a combination of constant current charging and constant voltage charging up to 4.2V (charging time is 2.5 hours) and discharging at 0.2C to 3V] It is represented by the capacity of

The electrolyte used in the present invention may be either a liquid electrolyte or a gel polymer electrolyte. In the present invention, the effect is particularly remarkable when a liquid electrolyte is used. Will be described in detail with reference to the term "electrolyte solution" with respect to this liquid electrolyte.

In the present invention, the electrolytic solution is prepared, for example, by dissolving an electrolyte salt such as a lithium salt in a non-aqueous solvent such as an organic solvent. An ester is preferably used as the solvent. Particularly, a chain ester is preferably used because it lowers the viscosity of the electrolytic solution and increases the ionic conductivity. Examples of such a chain ester include chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, chain alkyl esters such as methyl propionate, and chain phosphate triesters such as trimethyl phosphate. Among them, chain carbonates are particularly preferable.

It is preferable to use the following ester having a high dielectric constant (ester having a dielectric constant of 30 or more) in combination with the above-mentioned chain ester because load characteristics and the like are improved. Examples of such an ester having a high dielectric constant include ethylene carbonate, propylene carbonate, butylene carbonate, and γ-butyrolactone.
In particular, those having a cyclic structure are preferred, cyclic carbonates are particularly preferred, and ethylene carbonate is most preferred.

The ester having a high dielectric constant is preferably 50% by weight or less in the total solvent of the electrolytic solution, more preferably 4% by weight.
0% by weight or less. The improvement of the properties by the ester having a high dielectric constant becomes remarkable when the ester having a high dielectric constant becomes 10% by weight or more in the total solvent of the electrolytic solution, and becomes more remarkable when the ester reaches 20% by weight. The amount of the chain ester mixed therewith is preferably 50% by weight or more, more preferably 60% by weight or more in the total solvent of the electrolytic solution.

Examples of solvents that can be used in combination with the above esters include 1,2-dimethoxyethane, 1,3-dioxolan, tetrahydrofuran, 2-methyl-tetrahydrofuran, diethyl ether and the like. In addition, an amine-based or imide-based organic solvent, a sulfur-containing or fluorine-containing organic solvent, and the like can also be used.
These solvents can be used alone or in combination of two or more.

Lithium used for preparing electrolyte
As an electrolyte salt such as a salt, for example, LiClO_Four, L
iPF₆, LiBF_Four, LiAsF₆, LiCF_ThreeSO
_Three, LiC_FourF₉SO_Three, LiCF_ThreeCO_Two, Li_TwoC
_TwoF_Four(SO_Three)_Two, LiN (CF_ThreeSO_Two)_Two, Li
C (CF_ThreeSO_Two)_Three, LiC_nF_{2n + 1}SO_Three(N ≧
2), LiN (RfOSO_Two)_Two[Where Rf is
Or a mixture of two or more thereof.
But especially LiPF₆And LiC_FourF₉SO _ThreeSuch
Is preferred. Electrolyte such as lithium salt in electrolyte
The concentration of the salt is not particularly limited, but 0.3 m
ol / l or more is preferable, and 0.4 mol / l or more is more preferable.
It is preferably 1.7 mol / l or less,
1.5 mol / l or less is more preferable.

In the present invention, the content of sulfolene and its derivatives in the electrolyte is expressed in terms of% by weight in the solvent component of the electrolyte, but all the solvent components are liquid at room temperature. You don't need to. For example, some sulfolene or its derivatives are solid at room temperature, but when they are dissolved in a solvent, they become a solution. Therefore, in the present invention, they are also called solvent components. In other words, for example, when the electrolyte is an electrolytic solution, when the electrolyte is separated into an electrolyte salt such as a lithium salt directly involved in ion conduction and another, a solvent other than the electrolyte salt such as a lithium salt is used as a solvent. Ingredients. When the electrolyte is a gel polymer electrolyte, when the electrolyte is divided into an electrolyte salt such as a lithium salt directly involved in ion conduction and a gelling agent and other than the above, the electrolyte salt such as a lithium salt and a gel are separated. A substance other than the agent is used as a solvent component.

The preparation of the electrolyte solution containing sulfolene or a derivative thereof may be performed, for example, by dissolving an electrolyte salt such as a lithium salt in a solvent, and then adding and mixing the sulfolene or a derivative thereof, or After mixing the solvent and the sulfolene or a derivative thereof, the reaction may be performed by dissolving an electrolyte salt such as a lithium salt therein, or the sulfolene or a derivative thereof and the electrolyte salt such as a lithium salt may be simultaneously added to the solvent. It may be performed by adding and mixing.

The gel polymer electrolyte corresponds to a gel obtained by gelling an electrolytic solution with a gelling agent. For the gelation, for example, a linear polymer such as polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile or the like is used. Copolymer, a polyfunctional monomer (eg, pentaerythritol tetraacrylate,
For example, tetrafunctional or higher acrylates such as ditrimethylolpropane tetraacrylate, ethoxylated pentaerythritol tetraacrylate, dipentaerythritol hydroxypentaacrylate, dipentaerythritol hexaacrylate, and tetrafunctional or higher methacrylate similar to the above acrylates are used. However, in the case of a monomer, a polymer obtained by polymerizing the above-mentioned monomer acts as a gelling agent, instead of the monomer itself gelling the electrolytic solution.

When the electrolytic solution is gelled using the polyfunctional monomer as described above, if necessary, a polymerization initiator such as benzoyls, benzoin alkyl ethers, benzophenones, and benzoylphenylphosphine oxides may be used. , Acetophenones, thioxanthones, anthraquinones, etc., and also alkylamines, amino esters, etc., as sensitizers for the polymerization initiator. When the gel polymer electrolyte is divided into an electrolyte salt such as a lithium salt and a gelling agent as described above, the polymerization initiator and the sensitizer are also included in the gelling agent. Just think about it.

In order to make the gel polymer electrolyte contain sulfolene or a derivative thereof, the electrolyte before gelation may contain sulfolene or a derivative thereof as described above.

The positive electrode is produced, for example, by forming a positive electrode mixture layer containing a positive electrode active material on at least a part of a positive electrode current collector.

As the positive electrode active material, various materials can be used without any particular limitation. However, a transition metal oxide containing lithium is preferable because of its high energy density and excellent reversibility. Is, for example, LiCoO
₂ , lithium manganese oxides such as LiMn ₂ O ₄ , lithium nickel oxides such as LiNiO ₂ , mixtures thereof, and those in which some of their constituent elements are replaced by other elements Is preferably used. However, the positive electrode active material is not limited to those exemplified above, for example, one-dimensional chain structure, two-dimensional layered structure, three-dimensional channel structure, cobalt having a amorphous structure, nickel, vanadium, manganese,
What is necessary is just to select suitably from lithium composite oxides, such as iron oxide, or a substance containing lithium, such as chalcogen or a conductive polymer.

For the positive electrode, for example, a conductive auxiliary such as graphite, carbon black, acetylene black and the like, and a binder are added to the above-mentioned positive electrode active material, if necessary, and mixed.
A paste is formed using a solvent (the binder may be dissolved in the solvent in advance and then mixed with the positive electrode active material, etc.), and the obtained positive electrode mixture-containing paste is applied to the positive electrode current collector and dried. It is produced by forming a positive electrode mixture layer and, if necessary, subjecting it to pressure molding. However, the manufacturing method of the positive electrode is not limited to the above-described example, and another method may be used.

The positive electrode current collector used for the positive electrode is preferably a metal foil containing aluminum as a main component, and its purity is preferably 98% by weight or more and less than 99.9% by weight. In an ordinary lithium ion secondary battery, an aluminum foil having a purity of 99.9% by weight or more is used as a positive electrode current collector. In the present invention, a thin metal foil having a thickness of 15 μm or less is used for high capacity. Is preferred. Therefore, it is preferable to have a strength that can be used even if it is thin, and in order to secure such strength, the purity is preferably less than 99.9% by weight. Particularly preferred metals to be added to aluminum are iron and silicon. Iron is preferably 0.5% by weight or more, more preferably 0.7% by weight or more, and preferably 2% by weight or less, more preferably 1.3% by weight or less. Silicon is preferably at least 0.1% by weight, more preferably at least 0.2% by weight, and preferably at most 1.0% by weight, more preferably at most 0.3% by weight. These iron and silicon need to be alloyed with aluminum, and do not exist as impurities in aluminum.

The tensile strength of the positive electrode current collector is preferably 150 N / mm ² or more, more preferably 1 N / mm ^2.
80 N / mm ² or more. Further, the positive electrode current collector used in the present invention preferably has an elongation of 2% or more, more preferably 3% or more. This is because as the discharge capacity per unit volume of the electrode stack increases,
Since the expansion of the positive electrode mixture layer during charging increases, the expansion causes stress in the positive electrode current collector, which tends to cause cracks and cuts. Thereby, the stress is relieved, and the cracks and cuts can be prevented, so that the cycle characteristics are improved. However, if it gets too thin,
Since there is a possibility of cutting due to insufficient strength of the positive electrode current collector during manufacturing, the thickness of the positive electrode current collector is 5 μm
Above, especially 8 μm or more is practically suitable.

The surface of the positive electrode current collector is preferably roughened on one side, and the wound body is preferably configured such that the rough surface is disposed on the outer peripheral side during winding.
This is because the discharge capacity per unit volume of the electrode laminate is 13
At 0 mAh / cm ³ or more, the active material is more likely to be degraded on the outer peripheral side than on the inner peripheral side of the positive electrode. Since it becomes a factor that lowers safety, such as increasing the size, by arranging the rough surface of the current collector on the outer peripheral side, the adhesiveness of the mixture layer on the outer peripheral surface is increased to suppress deterioration, and the positive electrode This is for equalizing the deterioration. The average roughness of the rough surface is R
a (center line average roughness specified in JIS B0601) is preferably from 0.1 to 0.5 μm, more preferably from 0.2 to 0.3 μm. The average roughness of the opposite surface (glossy surface) is R
a is preferably 0.2 μm or less, more preferably 0.1 μm or less.

Examples of the binder used for producing the positive electrode include polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene diene rubber, fluoro rubber, styrene butadiene rubber, cellulose resin,
Examples thereof include polyacrylic acid, which can be used alone or as a mixture of two or more.

The active material used for the negative electrode may be any material capable of doping and undoping lithium ions. Examples of the active material include graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, Carbon microbeads,
Examples include carbon materials such as carbon fiber and activated carbon. Especially 2
Mesocarbon microbeads fired at 500 ° C. or more are preferable because they have good cycle characteristics even when a negative electrode mixture layer is formed at a high density. In addition, alloys such as Si, Sn, and In, or S that can be charged and discharged at a low potential close to Li
Oxides such as i and Sn, nitrides of Li and Co, and the like can also be used as the negative electrode active material.

When a carbon material is used as the negative electrode active material,
The carbon material preferably has the following characteristics. That is, with respect to the inter-plane distance d ₀₀₂ of the (002) plane,
0.35 nm or less is preferable, and 0.34 nm or less is more preferable.
5 nm or less. The average particle size of the carbon material is preferably 8 to 20 μm, particularly preferably 10 to 15 μm. This is based on the reason that the density can be increased and the capacity can be increased by reducing the particle size, but the safety is reduced when the particle size is too small. Further, the purity of the carbon material is preferably 99.9% by weight or more.

For the negative electrode, for example, if necessary, the same binder as in the case of the positive electrode is added to the negative electrode active material and mixed to prepare a negative electrode mixture, which is dispersed in a solvent to form a paste (binder). May be previously dissolved in a solvent and then mixed with the negative electrode active material, etc.), the negative electrode mixture-containing paste is applied to a negative electrode current collector made of copper foil or the like, dried, and dried. It is produced by forming a negative electrode mixture layer in a part and subjecting it to a pressure molding step as necessary. However, the method for manufacturing the negative electrode is not limited to the method described above, and may be another method.

As the negative electrode current collector, for example, copper foil,
Metal foils such as nickel foils and stainless steel foils, and nets of these metals are used, but copper foils are particularly suitable. For the negative electrode current collector, a material having one surface roughened may be used for the same reason as in the case of the positive electrode current collector.

When a carbon material is used for the negative electrode, the density of the negative electrode mixture layer is preferably set to 1.4 g / cm ³ or more in order to increase the capacity.

The separator is not particularly limited. For example, polyolefin-based separators such as a microporous polyethylene film, a microporous polypropylene film, and a microporous ethylene-propylene copolymer film having a thickness of 20 μm or less include: Even if it is thin, it has sufficient strength and can increase the filling amount of the positive electrode active material, the negative electrode active material, and the like, and thus is particularly preferably used in the present invention.

[0037]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

Example 1 Methyl ethyl carbonate and ethylene carbonate were mixed at a weight ratio of 67:33, and Li was added to the mixed solvent.
The PF ₆ was dissolved in a proportion of 1.4 mol / l, 3 of the solid in such a manner that the content of a solvent component is 2 wt% therein
-An electrolyte was prepared by adding and dissolving sulfolene.

Separately from the above, flaky graphite as a conductive aid is added to LiCoO ₂ at a weight ratio of 100: 6 and mixed, and this mixture and polyvinylidene fluoride are mixed with N-methyl-2-
A solution that had been previously dissolved in pyrrolidone was mixed to prepare a positive electrode mixture-containing paste. The amount of this polyvinylidene fluoride is 10% by weight with respect to LiCoO ₂ .
0: 3.8 (3.8 parts by weight of polyvinylidene fluoride relative to 100 parts by weight of LiCoO ₂ ). After the obtained positive electrode mixture-containing paste was passed through a 70-mesh net to remove large pieces, a coating amount of 24.5 mg was applied to both surfaces of a 15 μm-thick positive electrode current collector made of a metal foil containing aluminum as a main component. / Cm ² (however, the amount of the positive electrode mixture after drying) is applied uniformly, dried to form a positive electrode mixture layer, and then pressed and formed by a roller press machine to obtain a predetermined size. After cutting, the lead body was welded to obtain a belt-shaped positive electrode.

The metal foil mainly composed of aluminum used as the positive electrode current collector was composed of 1% by weight of iron and 0.1% of silicon.
Contains 5% by weight, the purity of aluminum is 98% by weight
That was all. The tensile strength of the metal foil mainly composed of aluminum used as the positive electrode current collector is 185 N /
mm ² , the average roughness Ra of the rough surface was 0.2 μm, the average roughness Ra of the glossy surface was 0.04 μm, and the elongation was 3%.

Next, mesocarbon microbeads [However, the interplanar spacing d _{00 2} of (002) plane 0.337nm
And the size Lc of the crystallite in the c-axis direction is 95 nm,
Graphite-based carbon material having an average particle size of 15 μm and a purity of 99.9% by weight or more]
The mixture was mixed with a solution previously dissolved in -methyl-2-pyrrolidone to prepare a paste containing the negative electrode mixture. The amount of this polyvinylidene fluoride was 92: 8 by weight with respect to the graphite-based carbon material (8.7 parts by weight of polyvinylidene fluoride per 100 parts by weight of the graphite-based carbon material). After passing the obtained negative electrode mixture-containing paste through a 70-mesh net to remove large ones, the applied amount was 12.0 mg on both surfaces of a negative electrode current collector made of a strip-shaped copper foil having a thickness of 10 μm.
/ Cm ² (however, the amount of the negative electrode mixture after drying) is applied uniformly, and dried to form a negative electrode mixture layer.
After being pressure-formed by a roller press, it was cut into a predetermined size, and the lead body was welded to obtain a strip-shaped negative electrode. The density of the negative electrode mixture layer in this negative electrode was 1.5 g / c.
m ³ .

The strip-shaped positive electrode was overlaid on the strip-shaped negative electrode via a separator made of a microporous polyethylene film having a thickness of 20 μm, and spirally wound to form an electrode laminate having a spirally wound structure. At that time, the roughened surface of the positive electrode current collector made of a metal foil containing aluminum as a main component was made to be on the outer peripheral side. The volume of the electrode laminate was 11.4 cm ³ . Thereafter, the electrode laminate was filled in a cylindrical battery case having a bottom with an outer diameter of 18 mm, and the positive electrode and the negative electrode were welded to a lead body.

Next, the above-mentioned electrolytic solution was injected into the battery case, and after the electrolytic solution sufficiently permeated into the separator and the like, sealing was performed, preliminary charging and aging were performed, and the structure as shown in the schematic diagram of FIG. A cylindrical non-aqueous secondary battery was manufactured.

Referring to the battery shown in FIG. 1, reference numeral 1 denotes the positive electrode and 2 denotes the negative electrode. However, FIG. 1 does not show a current collector used for manufacturing the positive electrode 1 and the negative electrode 2 in order to avoid complication. And
The positive electrode 1 and the negative electrode 2 are spirally wound through a separator 3 to form an electrode laminate having a spirally wound structure, which is housed in a battery case 5 together with the electrolyte 4 made of the specific electrolytic solution. I have.

The battery case 5 is made of stainless steel as described above, and an insulator 6 made of polypropylene is arranged at the bottom of the battery case 5 prior to insertion of the spirally wound electrode laminate. The sealing plate 7 is made of aluminum and has a disk shape, provided with a thin portion 7a at the center thereof, and as a pressure inlet 7b around the thin portion 7a for applying the internal pressure of the battery to the explosion-proof valve 9. Holes are provided. The projection 9a of the explosion-proof valve 9 is welded to the upper surface of the thin portion 7a to form a welded portion 11. In addition, the thin portion 7a provided on the sealing plate 7 and the protruding portion 9a of the explosion-proof valve 9 are illustrated only in a cut plane so as to be easily understood in the drawings, and a contour line behind the cut plane is shown. Is not shown. Further, the thin portion 7a of the sealing plate 7 and the projection 9 of the explosion-proof valve 9 are provided.
The welded portion 11 with "a" is illustrated in an exaggerated state rather than the actual one so that the drawing can be easily understood.

The terminal plate 8 is made of rolled steel, has a nickel-plated surface, and has a hat-like shape with a brim-shaped peripheral portion. The terminal plate 8 is provided with a gas outlet 8a. The explosion-proof valve 9 is made of aluminum and is in the shape of a disk. A projection 9a having a tip is provided on the power generation element side (the lower side in FIG. 1) at the center thereof, and a thin wall 9b is provided. And
As described above, the lower surface of the protruding portion 9a is welded to the upper surface of the thin portion 7a of the sealing plate 7 to form a welded portion 11. The insulating packing 10 is made of polypropylene and has an annular shape. The insulating packing 10 is disposed above the peripheral portion of the sealing plate 7, and the explosion-proof valve 9 is disposed above the insulating packing 10, and insulates the sealing plate 7 from the explosion-proof valve 9. The gap between the two is sealed so that the liquid electrolyte does not leak from between the two. The annular gasket 12 is made of polypropylene, and the lead body 13 is made of aluminum. The sealing plate 7 and the positive electrode 1 are connected to each other. An insulator 14 is disposed on the electrode laminate, and the negative electrode 2 and the bottom of the battery case 5 are connected. Are connected by a lead body 15 made of nickel.

In this battery, the thin portion 7 of the sealing plate 7
a and the projecting portion 9a of the explosion-proof valve 9 come into contact at the welded portion 11,
Since the peripheral portion of the explosion-proof valve 9 and the peripheral portion of the terminal plate 8 are in contact with each other, and the positive electrode 1 and the sealing plate 7 are connected by the lead 13 on the positive electrode side, in a normal state, the positive electrode 1 and the terminal plate 8 Means a lead body 13, a sealing plate 7, an explosion-proof valve 9, and their welded parts 1
1 provides an electrical connection and functions normally as an electrical circuit.

If an abnormal situation occurs in the battery, such as the battery generating heat due to overcharging, and gas is generated inside the battery and the internal pressure of the battery rises, the internal pressure rises and the central part of the explosion-proof valve 9 is raised. Is deformed in the direction of the internal pressure (upward direction in FIG. 1), and a shearing force acts on the thin portion 7a of the sealing plate 7 integrated with the welded portion 11 to break the thin portion 7a. Alternatively, the welding portion 11 between the projecting portion 9a of the explosion-proof valve 9 and the thin portion 7a of the sealing plate 7 peels off to cut off the current, and then the thin portion 9b provided on the explosion-proof valve 9 is broken to release gas to the terminal plate. The battery 8 is designed to be able to be discharged from the battery through the gas discharge port 8a to prevent the battery from being ruptured.

Example 2 A cylindrical non-aqueous secondary battery was manufactured in the same manner as in Example 1 except that the content of 3-sulfolene in the solvent component of the electrolytic solution was changed to 1% by weight.

Example 3 A cylindrical non-aqueous secondary battery was manufactured in the same manner as in Example 1 except that the content of 3-sulfolene in the solvent component of the electrolytic solution was changed to 5% by weight.

Example 4 A cylindrical non-aqueous secondary battery was manufactured in the same manner as in Example 1 except that the content of 3-sulfolene in the solvent component of the electrolytic solution was changed to 10% by weight.

Example 5 Mesocarbon microbeads having an average particle diameter of 10 μm (provided that the distance d ₀₀₂ between (002) planes is 0.335 nm)
And the size Lc of the crystallite in the c-axis direction is 95 nm,
A graphite non-aqueous secondary battery was produced in the same manner as in Example 1, except that a graphite-based carbon material having a characteristic of a purity of 99.9% by weight or more was used as the negative electrode active material.

Comparative Example 1 Except that 3-sulfolene was not contained in the electrolyte,
A cylindrical non-aqueous secondary battery was produced in the same manner as in Example 1.

The batteries of Examples 1 to 5 and Comparative Example 1 were discharged at a constant current of 1800 mA (1 C) to 3.0 V, charged at 1800 mA, and maintained at a constant voltage of 4.2 V. The battery was charged for 5 hours. Then, replace the battery with 1
Discharge to 800 V at 3.0 V, measure discharge capacity,
The discharge capacity per unit volume of the electrode stack (discharge capacity / volume of the electrode stack) was determined based on the discharge capacity. Table 1 shows the results.

Further, the batteries of Examples 1 to 5 and Comparative Example 1 were charged to 50% in advance and then subjected to an overcharge test to evaluate the characteristics. The overcharge test is
1800mA for each battery using 18V power supply
(1C) Assuming an abnormal operation that does not occur normally, in which the current of 1C is continuously forced to flow, a current interrupting device accompanying a rise in temperature at that time and an increase in internal pressure (safety mechanism)
During the operation, the maximum temperature reached by the battery was measured. The results are shown in Table 1 as the temperature rise start time at the time of overcharge, the operation time of the current interrupter at the time of overcharge, and the maximum temperature of the battery at the time of overcharge, together with the discharge capacity per unit volume of the electrode laminate.

[0056]

[Table 1]

As shown in Table 1, the battery of Comparative Example 1 in which 3-sulfolene was not contained in the electrolytic solution had the maximum temperature of the battery at the time of overcharging of 97 ° C. In the batteries of Examples 1 to 5 in which sulfolene was contained in the electrolytic solution, the maximum temperature of the batteries at the time of overcharging was as low as 61 to 71 ° C. Further, in the batteries of Examples 1 to 5, the temperature rise started earlier than in the battery of Comparative Example 1, and the current interrupting device was activated earlier. This is because in the batteries of Examples 1 to 5, the temperature rise started earlier than in the battery of Comparative Example 1 due to the increase in impedance due to the coating formed on the positive electrode surface, and the internal pressure increased due to the decomposition of 3-sulfolene. As a result, the current interrupter operates faster than the battery of Comparative Example 1, and on the other hand, the reaction between the positive electrode or the negative electrode and the electrolytic solution is suppressed, so that the temperature rise due to the reaction heat is suppressed, and as a result,
It is considered that the maximum temperature of the battery at the time of overcharging was lower than that of the battery of Comparative Example 1.

As described above, in the batteries of Examples 1 to 5 of the present invention, the discharge capacity per unit volume of the electrode laminate was 130 m.
Despite having a high capacity of Ah / cm ³ or more, the battery had higher safety than the battery of Comparative Example 1 corresponding to a conventional battery.

[0059]

As described above, according to the present invention, it is possible to provide a non-aqueous secondary battery having a high capacity and a high safety when an abnormality such as overcharge occurs.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of a non-aqueous secondary battery according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Electrolyte

 ──────────────────────────────────────────────────の Continued on the front page (72) Hiroyuki Togi, 1-88 Ushitora, Ibaraki-shi, Osaka Prefecture Inside Hitachi Maxell Co., Ltd. (72) Kazunobu Matsumoto 1-188 Ushitora, Ibaraki-shi, Osaka, Japan Hitachi Maxell Co., Ltd. (72) Inventor Yasuji Shimada 346-1, Miyanishi, Harima-cho, Kako-gun, Hyogo Prefecture Sumitomo Seika Co., Ltd. Gas Engineering Laboratory F-term (reference) AM06 AM07 BJ02 BJ14 HJ01 HJ05 HJ19 5H050 AA03 AA08 AA15 BA17 CA08 CB07 FA17 HA01 HA05 HA19

Claims (4)

[Claims] 1. A non-aqueous secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte contains sulfolene or a derivative thereof. 2. The nonaqueous secondary battery according to claim 1, wherein the solvent component of the electrolyte contains 0.05 to 10% by weight of sulfolene or a derivative thereof. 3. The non-aqueous secondary battery according to claim 1, wherein a discharge capacity per unit volume of the electrode laminate is 130 mAh / cm ³ or more. 4. The negative electrode active material has an average particle size of 8 to 20 μm.
The non-aqueous secondary battery according to any one of claims 1 to 3, wherein m carbon materials are used.