JP2003077431A - Enclosed type cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary cell usable for a long time even under a circumstance of rapid temperature change. SOLUTION: The enclosed type cell with a power generation element body including a cathode, an anode, and nonaqueous electrolyte stored in a cell can made of metal material, the inside of which is enclosed by a sealing member with a gasket made of resin interposed at an opening of the cell can, has an asphalt layer fitted via a rubber layer on a surface of the gasket made of resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed type battery, and more particularly to a sealed type lithium ion secondary battery that can be used for a long period of time even under an environment of abrupt temperature change.

[0002]

2. Description of the Related Art A sealed battery is one in which a power generating element is enclosed in a battery can. For example, a lithium ion secondary battery is known. Lithium ion secondary batteries are capable of increasing their capacity because they use lithium ions, and have recently become widely used as power sources for mobile phones, electronic terminals, and the like. In particular, an electrode material that greatly contributes to the performance improvement of a lithium ion secondary battery, such as LiCoO ₂ or Li for a positive electrode.
NiO ₂ or the like is used in the negative electrode, lithium metal or its alloy,
Carbon materials have been developed and studied, and electric characteristics such as discharge capacity have been improved.

By the way, a power generation element of a lithium ion secondary battery generally sends and receives a positive electrode, a negative electrode, an insulating separator interposed between the positive electrode and the negative electrode, and lithium ions between the positive electrode and the negative electrode. It is composed of a non-aqueous electrolyte solution. In many cases, the carbonate-based organic material is mainly used as the electrolytic solution. Therefore, from the viewpoint of preventing leakage and increasing the internal pressure of the battery due to gasification of the electrolytic solution, the battery can of the lithium-ion secondary battery is stainless,
A metal material such as iron is used. The battery can contains a positive electrode, a negative electrode, and a power generation element body containing a non-aqueous electrolyte solution, and a gasket made of resin is interposed in the opening of the battery can to seal the inside of the battery with a sealing member to seal the battery can. Although the battery is a type battery, such a gasket is required to have a sealing property in order to prevent the non-aqueous electrolyte from flowing out.

For example, Japanese Patent Application Laid-Open No. 7-130341 discloses that the storability is improved in a non-use state, and even in a use state (charging, large current discharge, pulse discharge is performed in a changing ambient temperature). In order to provide a non-aqueous battery with little deterioration, a block copolymer of propylene and ethylene having a copolymerization ratio of ethylene of 2 to 20% by weight (particularly a flexural modulus of 1 is used as a gasket material.
Gaskets containing from 2000 to 18000 kilograms per square centimeter) are disclosed.

Further, in Japanese Patent Laid-Open No. 10-199495, there is no need to apply a sealant on the gasket surface.
In order to further improve the sealing performance of the gasket itself, the gasket has an annular base portion that can be interposed over the entire circumference of the opening between the joint surfaces of the sealing member and the battery can wall around the opening, and the entire circumference around the opening. There is disclosed a mode in which a mountain range-shaped projection portion which is continuous along a closed loop is drawn.

In the invention of Japanese Patent Laid-Open No. 10-302741, glass fiber or a thermoplastic elastomer is added as a gasket interposed between a positive electrode can and a negative electrode can for the purpose of liquid leakage under high temperature environment of reflow solder. The straight chain type PPS is used.

Further, in the invention of Japanese Patent Application Laid-Open No. 2001-126684, there is a need for preventing leakage of non-aqueous electrolyte, reduction of non-aqueous electrolyte batteries, and deterioration of battery performance due to inflow of water.
As a material for the sealing gasket, a mixed material of resin and rubber having a specific compression set is used.

However, even if these gaskets were used, there were still cases where there was a problem with the sealability. That is, when the lithium-ion secondary battery is used in an environment where the temperature changes abruptly, for example, when the lithium-ion secondary battery is installed in a portable wireless device and the user of the portable wireless device uses it in a cold region, If the battery is taken out of a room with heating to the outside of -20 ° C and there is a sudden change in environmental temperature, the battery can shrinks and the resin gasket hardens, causing a slight gap between the battery can and the gasket. There is a problem that a gap is generated and moisture in the air enters the battery or the electrolyte solution flows out.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sealed battery which has excellent long-term reliability and can be used for a long period of time even in an environment of abrupt temperature change. That is, the inventors of the present invention have earnestly studied the cause of the above problems, and have obtained the following findings. 1) When the environment is changed from a high temperature environment to a low temperature environment, the battery can made of a metal material undergoes heat shrinkage, and the resin gasket hardens to reduce the elastic force. 2) The battery can made of a metal material is thermally shrunk, and the resin gasket is hardened so that the elastic force is reduced, so that a slight gap is generated between the battery can and the gasket. 3) The gap is largely due to the fine irregularities on the surface of the battery can. 4) The gap between the battery can and the gasket should become larger due to repeated rapid environmental changes in high temperature and low temperature environments. There was found. Therefore, in order to prevent the deterioration of the sealing characteristics, the present invention is made based on the finding that it is effective to provide an asphalt layer on the surface of a gasket made of a resin through a rubber layer for the resin gasket. Came to.

[0010]

Means for Solving the Problems: (1) A power generation element body containing a positive electrode, a negative electrode and a non-aqueous electrolyte is housed in a battery can made of a metal material, and a resin is provided in an opening of the battery can. A sealed battery in which the inside of the battery is hermetically sealed by a sealing member with a gasket made of, and a asphalt layer is provided on the surface of the gasket made of resin with a rubber layer interposed therebetween. battery. (2) The sealed battery according to (1), wherein the gasket made of resin is polypropylene resin. (3) The sealed battery according to (1) or (2) above, which is a lithium-ion secondary battery. Will be solved by.

[0011]

1 is a schematic diagram showing a sealed battery of the present invention. In a sealed battery, a power generation element body 2 containing a positive electrode, a negative electrode and a non-aqueous electrolyte is housed in a battery can 1 made of a metal material having an opening, and a gasket 3 made of resin is provided in the opening of the battery can. The inside of the battery is hermetically sealed by the sealing member 4 with the interposing. As shown in the figure, the structure of the sealed battery of the present invention is a structure in which the opening of the battery can 1 is closed by the sealing member 4. The battery can 1 is a tubular body having one end face having an opening 1B and the other end face having a bottom face 1C, and the sealing member 4 is fitted in the opening of the battery can 1.

As shown in the figure, the battery can wall 1A around the opening is bent so as to include a "U-shaped" cross-sectional shape, and that portion holds the outer peripheral edge portion 4A of the sealing member over the entire circumference. . A gasket 3 is used so as to intervene between the portion where the battery can wall 1A is gripping the outer peripheral edge portion 4A of the sealing member, that is, the joint surface between the battery can wall 1A and the outer peripheral edge portion 4A of the sealing member. Therefore, high sealing performance is obtained.

The sealing member 4 referred to in the present invention can be regarded as one lid that closes the opening of the battery can when the sealed battery is completed, but it is not usually a single member but the outermost surface. In addition to the terminal plate, in many cases, various plate-shaped members for safety structure that release internal gas when the internal pressure rises are laminated on the inner side thereof. In the present invention, these are not divided into details, and one in which one or more parts are gathered together at the opening of the battery can to form a lid is referred to as a sealing member. In FIG. 1, the sealing member 4 is illustrated as a single member.

FIG. 2 is a sectional view of the gasket of the present invention. Rubber layer 3 on gasket base material 3A made of resin
B and the asphalt layer 3C are sequentially laminated, and the asphalt layer 3A is exposed on the outermost layer surface.

The power generating element containing the positive electrode, the negative electrode and the non-aqueous electrolyte is housed in a battery can, and any known positive electrode, negative electrode and non-aqueous electrolyte can be used. The material of the battery can is a nickel-plated iron plate, stainless steel (SUS304, SUS304L, SUS304N,
SUS316, SUS316L, SUS430, SUS
444), nickel-plated stainless steel (the same), aluminum or aluminum alloys, nickel, copper, titanium, and other metal materials. The shape of the battery can is a bottomed cylindrical shape, a bottomed long cylindrical shape, a free bottom rectangular cylindrical shape, or the like. The wall thickness of the battery can is 1
A range of 00 to 500 microns is suitable. In terms of increasing the internal volume, it is advisable to reduce the wall thickness to about 50 to 150 microns. In this case, the bottom of the can should be curved or 300 to 5
It is preferable to prevent deformation due to internal pressure, for example, by increasing the thickness to 00 microns. Further, in order to increase the strength of the thinned can, the material is preferably the above-mentioned stainless steel, carbon steel or titanium alloy, and in the sense of being thinner, superplastic stainless steel is preferable. The battery can may be plated.
In particular, a nickel-plated battery can has excellent electrochemical stability and corrosion resistance.

The gasket is made of a resin material, for example,
Thermoplastic polymers such as polypropylene, polyethylene, polyvinyl chloride, poly 4-methylpentene-1, polyvinyl chloride, ethylene vinyl acetate copolymer, nylon, polyester, polyamide imide, polyimide, polysulfone, polyether sulfone, polyphenylene oxide Heat resistant resins such as polyphenylene ether, polyphenylene sulfide, polyetherimide, polyether ketone, polyacetal, polycarbonate, fluororesin, polyallyl ether nitrile, and polybenzimidazole are exemplified. Of these, polypropylene is preferable from the viewpoint of water permeability and heat resistance.

In the present invention, an asphalt layer is provided on the surface of the gasket made of the resin via a rubber layer. That is, asphalt, which is easily plastically deformed, fills the fine irregularities of the battery can to improve the sealing property at normal temperature, and the rubber layer interposed between the resin gasket and the asphalt layer has its elastic force. As a result, a slight gap does not occur between the battery can and the gasket even when the temperature changes suddenly.

As a method for sequentially forming a rubber layer and an asphalt layer on a gasket made of resin, a rubber material is dissolved in an organic solvent such as toluene or xylene, dip-coated or applied, and then dried to form a rubber layer. After being formed, asphalt may be dissolved in an organic solvent such as toluene or xylene, dip-coated or applied, and then dried to form an asphalt layer. When forming an asphalt layer using an organic solvent, the excess asphalt solution should be blown off by centrifugal force or compressed air after forming the asphalt layer so that the rubber layer previously formed is not dissolved by the organic solvent. Is preferred.

The thickness of the rubber layer is 5 μm to 200 μm, preferably 10 μm to 100 μm, and if it is less than 5 μm, the sealing property tends to deteriorate. If it exceeds 200 μm, the strength tends to be insufficient. The thickness of the asphalt layer is 1 μm to 100 μm, preferably 5 μm.
It is 50 μm. If it is less than 1 μm, the sealing property tends to deteriorate, and if it exceeds 100 μm, the strength tends to be insufficient.

As the rubber material used in the present invention, known materials can be used. For example, any one of rubber latex (styrene butadiene rubber, butadiene rubber, chloroprene rubber, ethylene propylene rubber or a mixture thereof is used as a cationic surface active agent. Suspension with water in water), non-silicone rubber (natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), 1,2-polybutadiene (1,2-BR), styrene-butadiene rubber ( SBR), chloroprene rubber (CR), nitrile rubber (NBR), butyl rubber (IIR), ethylene-propylene rubber (EPM, EPDM), chlorosulfonated polyethylene (CSM), acrylic rubber (ACM, AN)
M)) etc.

Asphalt materials used in the present invention include:
Chemistry Dictionary, page 193 (Publisher, Kyoritsu Shuppan Co., Ltd.
Known materials such as natural asphalt described in October 26, 2006, 26th edition) or petroleum asphalt produced from petroleum can be used.

The gasket made of the resin used in the present invention should be improved in sealing resistance under high temperature environment.
It is preferable to add and blend a copper damage inhibitor. As the copper damage inhibitor, a known material can be used, for example,
2,2'-oxamido-bis [ethyl-3- (3,5-
Oxalic acid derivatives such as di-t-butyl-4-hydroxyphenyl) propionate], salicylic acid derivatives such as 3- (N-salicyloyl) amino-1,2,4-triazole, N, N′-bis [3 ( 3,5-t-butyl-4
A hydrazide derivative such as -hydroxyphenyl) propionyl] hydrazine can be used, and these may be used alone or in combination of two or more. Among these, the effect of the present invention becomes more remarkable when a salicylic acid derivative such as 3- (N-salicyloyl) amino-1,2,4-triazole and hydrotalcites are used in combination.

The copper damage inhibitor is preferably blended in an amount of 0.01 to 1 part by weight based on 100 parts by weight of the resin.
If it is less than 0.01 parts by weight, the long-term sealing property tends to be poor, and if it is 1 part by weight or more, the elastic force of the resin tends to be low and the sealing function tends to be low.

Examples of the present invention will be described below. [Example 1] (Preparation of positive electrode sheet) 3 parts by weight of polyvinylidene fluoride as a binder was dissolved in 50 parts by weight of N-methyl-2-pyrrolidone, and LiCoO ₂ as a positive electrode active material was dissolved in the solution.
After adding 91 parts by weight, 5 parts by weight of massive graphite as a conductive agent and 1 part by weight of Ketjenblack, and kneading, a thickness of 20
It was applied to both sides of a micron aluminum foil current collector. After the above coated material was dried, it was compression-molded by a roller press machine and further cut into a width of 55 mm to prepare a strip-shaped positive electrode sheet.

(Preparation of Negative Electrode Sheet) 5 parts by weight of polyvinylidene fluoride as a binder was dissolved in 60 parts by weight of N-methyl-2-pyrrolidone, and 95 parts by weight of fibrous graphite as a negative electrode active material was mixed with the solution. Then, it was applied to both surfaces of a 14-micron-thick copper foil current collector. After drying the coated material, it was compression-molded by a roller press machine and further cut into a strip having a width of 57 mm to prepare a strip-shaped negative electrode sheet. The positive electrode sheet and the negative electrode sheet are spirally wound so that they face each other with a microporous polypropylene / polyethylene / polypropylene three-layer separator interposed therebetween, and this wound product also serves as a negative electrode terminal and is made of nickel-plated iron with a bottom. It was stored in a cylindrical battery can. Further, 1 mol / liter of lithium hexafluorophosphate was added to ethylene carbonate / propylene carbonate / diethyl carbonate / ethyl methyl carbonate / dimethyl carbonate (volume ratio 11: 9:
4:29:47) A solution prepared by dissolving a mixed solvent was injected into a battery can as a non-aqueous electrolyte. Cylindrical battery (height 65 mm, outer diameter 18 mm, capacity 1600 mAh) by caulking the battery lid that also serves as the positive electrode terminal through the following 5 types of gaskets
It was created. The positive electrode terminal was connected to the positive electrode sheet, and the negative electrode can was connected to the negative electrode sheet in advance inside the battery by a lead tab.

(Preparation of Gasket) Polypropylene (BC03B manufactured by Nippon Polychem) is used as a material, and a gasket (outer diameter 17.2 mm, inner diameter 12.6 mm) is formed by injection molding.
Was prepared, and 100 g of butyl rubber was added to 1 liter of toluene.
Dip-coat with dissolved solution, then 40
It was dried at ℃ for 1 hour to form a rubber layer (thickness 18 μm). Further, 50 g of asphalt is dissolved in 1 liter of toluene, dip-coated, and then at 60 ° C. for 1 hour.
After drying for an hour, an asphalt layer (thickness 6 μm) was formed.

Example 2 The same as Example 1 except that the butyl rubber used in Example 1 was replaced with nitrile rubber.

[Example 3] A copper damage inhibitor (3- (N-salicyloyl)) was used in place of the polypropylene used in Example 1.
Polypropylene containing 0.1% by weight of amino-1,2,4-triazole (BC03 manufactured by Nippon Polychem)
Same as Example 1 except that C) was used as the material.

Comparative Example 1 The same as Example 1 except that the rubber layer was not formed.

Comparative Example 2 The same as Example 1 except that the asphalt layer was not formed.

[Gas Leakage Resistance Test] 1) Heat Cycle Test Batteries were stored at -20 ° C. for 2 hours, immediately stored at 60 ° C. for 2 hours, and immediately thereafter stored again at -20 ° C. for 2 hours. After repeating this 10 times, a hole having a diameter of 1 mm is made in the bottom of the battery can, and nitrogen gas is introduced from the hole until the internal pressure becomes 15 kg / cm 2. Soap water was applied to the gasket portion of such a battery, and the presence or absence of gas leakage due to generation of bubbles was visually confirmed. 2) After storing the cold-resistant battery at -30 ° C for 12 hours and at 25 ° C for 1 hour, make a hole with a diameter of 1 mm in the bottom of the battery can and add nitrogen gas from the hole until the internal pressure becomes 15 kg / cm 2. Introduce.
Soap water was applied to the gasket portion of such a battery, and the presence or absence of gas leakage due to generation of bubbles was visually confirmed, and (number of gas leakage samples / number of test samples) was examined.

[Discharge Capacity Test] 1. Charged at a constant current of 6A until the charging voltage reaches 4.2V, then 4.2V.
The battery is charged at a constant voltage until the total charging time reaches 2.5 hours, and then discharged at 0.32 A until the terminal voltage becomes 3V. Further, after a pause of 1 hour after discharging, charging is performed under the same conditions, and then high rate discharging with a discharging current of 3.2 A is performed until the voltage between terminals becomes 3V. At that time, 0.32
Discharge capacity (a value) in discharge at A, discharge capacity (b value) in discharge at 3.2 A, and their ratio (b /
a value).

[0033]

[Table 1]

[0034]

According to the present invention, it is possible to provide a lithium ion secondary battery which can be used or stored for a long period of time even in an environment where the temperature changes abruptly.

[0035]

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a sealed battery of the present invention.

FIG. 2 is a cross-sectional view of a gasket used in the sealed battery of the present invention.

[Explanation of symbols]

1 battery can 2 Power generation element 3 gasket 3A resin base material 3B rubber layer 3C asphalt layer 4 Sealing member

Claims (3)

[Claims] 1. A power generation element body containing a positive electrode, a negative electrode and a non-aqueous electrolyte is housed in a battery can made of a metal material, and a gasket made of a resin is interposed at the opening of the battery can by a sealing member. What is claimed is: 1. A sealed battery in which the inside of the battery is sealed, wherein an asphalt layer is provided on the surface of a gasket made of resin with a rubber layer interposed therebetween. 2. The sealed battery according to claim 1, wherein the gasket made of resin is polypropylene resin. 3. The lithium ion secondary battery according to claim 1.
Alternatively, the sealed battery according to claim 2.