JPS61277151A - Sealing method for thin and flat type lithium cell - Google Patents

Abstract

PURPOSE:To eliminate the necessity of providing a new armor member such as another armor film by employing the positive/negative electrode current collectors of cell as the armor. CONSTITUTION:Thermoadhesive film 3 is laminated on at least one circumferential section 4 of positive and negative electrode current collectors 2 facing each other through a barrier layer or a separator 7 then the circumferential section 4 is thermally sealed. Since the positive/negative electrode current collectors 2 are employed as the armor, new armor such as another armor film is not required. Consequently, it can be made thin and the size can be reduced economically.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for sealing a flat thin lithium battery.

More details include not only small size and thinness but also electrolyte resistance, t
The present invention relates to a sealing method with good Fi wetness.

[Conventional technology]

Currently, with advances in electronics technology, various types of consumer and industrial equipment are becoming smaller and thinner. In response to this demand, electronic equipment manufacturers are increasingly demanding particularly thin batteries.

Conventionally, the only thin batteries that have been put into practical use are ones that use an aqueous solution of neutral salt as an electrolyte9, but thin batteries that use non-aqueous electrolytes have problems with sealing materials and sealing methods, so they are currently under development. It's on its way. Electronic device manufacturers are currently developing thinner batteries with a thickness of less than 1 ton to accommodate various devices that are becoming smaller and thinner.

For example, metallic lithium or Li as the bipolar current collector
A flat thin lithium battery has been developed that uses -AI alloy and uses a non-aqueous electrolyte solution in which LiCIO4 is dissolved in an organic solvent as an electrolyte.

[Problem that the invention seeks to solve]

However, although such conventional flat thin lithium batteries have excellent battery characteristics, they have a problem with moisture resistance. In other words, there are disadvantages such as moisture infiltration, electrolyte and current collector reacting with water, causing corrosion and foaming of the exterior material.
We were not able to obtain anything with a long lifespan.

[Means for solving problems]

The present invention has been made in view of these conventional problems, and uses the positive and negative electrode current collectors of batteries as they are as exterior packaging.
By heat-sealing the peripheral edge, which will become the sealing part, with a heat-adhesive film made of plastic containing oxygen-containing functional groups, we have dramatically improved electrolyte resistance and moisture resistance, and solved the above problems. The purpose is

The present invention will be explained in detail below based on the drawings.

A flat and thin type product characterized in that a thermally adhesive film 3 is laminated on the peripheral edge part 4 of at least one of the positive and negative electrode current collectors 2 that face each other with a separator 7 interposed therebetween, and the first peripheral edge part 4 is heat-sealed. This is a method for sealing lithium batteries.

The thermoadhesive resin 3 is firmly thermally bonded to the metal current collectors 2 of both electrodes, is stable against non-aqueous electrolytes, and is used to seal stain ponds by thermal fusion. Next, the oxygen-containing functional group-containing plastics used as thermal adhesive films or resins are plastics containing carboxyl groups, hydroquine groups, acetoxy groups, etc., such as ethylene-(meth)acrylic acid copolymers and ionomers. , those that originally have carboxyl groups in their molecules, ethylene-
The above functional groups can be obtained by graft polymerizing maleic anhydride or the like onto a saponified vinyl acetate copolymer, polyethylene, polypropylene, ethylene-α olefin copolymer, or ethylene-methyl (meth)acrylate or ethyl ester copolymer. It includes things that you have given. Thickness is 1~
300μ is good.

As the current collectors 2 for the positive and negative electrodes, nickel foil or stainless steel foil is used, and in order to load the positive electrode 5, negative electrode 6, and separator 7 inside, it is preferable to mold them in advance. The thickness is preferably 1 to 200 μm, and the best from 10 to 40 μm in terms of moldability and functionality.

Methods for laminating the thermally adhesive film 3 on the positive and negative electrode current collectors 2 include urethane-based, polyester-based, Evokin-based,
They can be bonded together using a curable adhesive such as a polyamide adhesive, or they can be bonded to the peripheral edge by heat fusion using a hot-melt adhesive, an adhesive resin, or the like. Alternatively, the heat-adhesive resin 3 can be directly heat-sealed to the peripheral edges 4 of the positive and negative electrode current collectors, or the heat-adhesive film 3 can be placed on the peripheral edges 4 and heat-sealed. MnO as the positive electrode
2 or CF (graphite fluoride). As a negative electrode, lithium or Li-A7! Use alloys.

Second, the separator was a nonwoven fabric made of polypropylene, and was made of an electrolytic solution in which LiCA'04 was dissolved in propylene carbonate, an electrolytic solution in which Li CI Oa was dissolved in γ-butyrolactone, or lithium fluoroborate was dissolved in γ-butyrolactone. Used by impregnating with electrolyte.

[For production]

- According to the present invention, since the positive and negative electrode current collectors 2 of the battery are used as the exterior packaging, there is no need to provide a new packaging material such as a separate exterior film.

Therefore, it is possible to easily make the device more economical, smaller, and thinner than conventional devices. Furthermore, in the present invention, the peripheral portion 4 serving as the sealing portion is heat-sealed with a heat-adhesive film or resin 3, and the heat-adhesive film or resin 3 is made of an oxygen-containing functional material having good electrolyte resistance and moisture resistance. Group-containing plastics are used. Oxygenated functional group-containing plastics have excellent thermal adhesion to themselves and to metals, allowing for complete sealing.

As described above, it is possible to economically and completely seal a flat, thin lithium battery that has good electrolyte resistance and moisture resistance and excellent battery performance.

〔Example〕

Example 1 Nickel foil with a thickness of 30 μm, which is the current collector for the positive and negative electrodes, is molded in advance, and a 40 μm film of ethylene-ethyl acrylate copolymer containing an acetoxyl group is attached to the periphery of the nickel foil.
m is heat-sealed to form a packaging material for a flat, thin lithium battery.

A lithium battery having a configuration as shown in FIG. 1 was prepared using the above-mentioned packaging material. The separator 7 is a nonwoven fabric made of polypropylene impregnated with an electrolytic solution in which LLCIO4 is dissolved in propylene carbonate. Further, MnO2 was used for the positive electrode 5 and Li was used for the negative electrode 6, and the peripheral portions were heat-sealed to form a lithium battery.

The flat, thin lithium battery produced in the manner described above was able to be made extremely thin without foaming or corrosion due to evaporation of the electrolyte or infiltration of moisture.

It was a flat, thin lithium battery with a thickness of 0.5N.

Furthermore, the electrolyte resistance was good, with no decrease in adhesive strength with metal, and the performance as a battery was maintained over a long period of time.

Comparative Example Comparative Example 1 Two-layer foils with a thickness of 30 μm, which are current collectors for the positive and negative electrodes, are molded in advance, and an acid-modified low-density polyethylene film 40 is heat-sealed to the periphery of the foil to form a flat thin lithium battery. Used as packaging material.

A lithium battery having a configuration as shown in FIG. 1 was prepared using the above-mentioned packaging material. The separator 7 is a nonwoven fabric made of polypropylene, and is made of propylene carbonate.
It is used by impregnating it with an electrolytic solution in which a is dissolved. Further, MnO2 was used for the positive electrode 5 and Li was used for the negative electrode 6, and the peripheral portions were heat-sealed to form a lithium battery.

The thickness of the flat thin lithium battery produced as described above was 0.57H1.

Comparative Example 2 A nickel foil with a thickness of 301 rrrL, which is a current collector for positive and negative electrodes, is molded in advance, and an acid-modified polypropylene film of 40 ttrn is heat-sealed to the periphery of the nickel foil to obtain a packaging material for a flat and thin η-lithium battery. .

A lithium battery having a configuration as shown in FIG. 1 was prepared using the above-mentioned packaging material. The separator 7 is a nonwoven fabric made of polypropylene, and Li(lOa
It is used by impregnating it with an electrolyte solution in which it is dissolved. Also, positive electrode 5
MnO2 was used for the negative electrode 6, Li was used for the negative electrode 6, and the peripheral portion was heat-sealed to form a lithium battery.

The thickness of the flat thin lithium battery produced as described above was 0.5M.

The flat thin lithium battery of the present invention prepared in Example 1 was
shall be. Further, the flat thin lithium batteries of Comparative Example 1 and Comparative Example 2 are designated as B and C, respectively. These A, B,
Five samples of C were each stored in an atmosphere of 80° C. and 90 SRH, and gas generation, performance deterioration, etc. were observed. 10
Days later, B.

C expanded due to gas generation, and some even burst. Further, when disassembled, there was no change at all in A, and parts of B and C had peeled off, and they had completely lost their performance as batteries.

Next, the amount of moisture intrusion into the interior (moisture resistance) was compared and measured.

Heat-seal the peripheral edges of two pieces of 60-square Ni foil using the respective sealing resins used in A, B, and C above.
Electrolyte solution (1 mol Li CI Oa
After injecting 300 μl of dipropylene carbonate), seal the tube. The 10 samples made as described above were placed in an atmosphere of 80℃ and 90SRH.
Stored for 0 days, took out 200 μl, and electrolyzed As seen from the table above, the acetoxyl group-containing ethylene-ethyl acrylate copolymer used in Battery A, which is the sealing resin (thermal adhesive resin), is extremely moisture-proof. Excellent sex.

〔Effect of the invention〕

As explained above, according to the flat thin lithium battery sealing method of the present invention, since the positive and negative electrode current collectors 2 of the battery are used as the exterior packaging, a new packaging material such as a separate exterior film is provided. There's no need. Therefore, it has the effect that it is more economical than the conventional one and can be made smaller and thinner more easily. Furthermore, in the present invention, the peripheral edge portion 4 serving as the sealing portion is heat-sealed with a heat-adhesive film or resin 3, and the heat-adhesive film or resin 3 is resistant to electrolyte.

We use plastics containing oxygen-containing functional groups that also have good moisture resistance. Oxygenated functional group-containing plastics have excellent thermal adhesion to themselves and to metals, allowing for complete sealing.

As described above, there is an effect that a flat, thin lithium battery having good electrolyte resistance and moisture resistance and excellent battery performance can be economically and completely sealed.

[Brief explanation of drawings]

FIG. 1 shows a flat thin lithium battery sealed by the sealing method of the present invention. A negative electrode current collector, 3 a heat-adhesive film or resin, 4 a peripheral portion corresponding to a sealing part, 5 a positive electrode, 61 a negative electrode, and 7 a separator.

Claims (3)

[Claims] (1) A flat thin lithium battery characterized in that a thermal adhesive film or resin is laminated on the periphery of at least one of positive and negative electrode current collectors facing each other with an isolation layer interposed therebetween, and the periphery is heat-sealed. Sealing method. (2) The method for sealing a flat thin lithium battery according to claim 1, wherein a plastic containing an oxygen-containing functional group is used as the heat-adhesive film or resin. (3) A flat thin lithium battery according to claim 2, which uses an ethylene-ethyl acrylate copolymer to which carboxyl groups, hydroxyl groups, and acetoxy groups are added by graft polymerization as the oxygen-containing functional group-containing plastic. Sealing method.