JPH0447900Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] This invention relates to a thin lithium battery.

[Prior Art] Hitherto, lithium batteries have generally been sealed by crimping synthetic resin packing onto a metal sealing plate by caulking a metal can.

However, when adopting such a sealing structure, the limit is to reduce the thickness of the battery to approximately 1.0 mm, which is required as battery-applied devices become smaller and lighter in recent years. It was not possible to make thin batteries with a thickness of about 0.5 mm, which has become popular.

Therefore, in order to meet such demands, as shown in FIG.
0 is interposed in the center between the positive electrode plate 1 and the negative electrode plate 5 made of metal, and the peripheral edge of the positive electrode plate 1 and the peripheral edge of the negative electrode plate 5 are bonded and sealed with hotmelt adhesive 6. It has been proposed to create thin batteries (for example, at the 25th Battery Symposium (Nagoya, Showa)).
November 13-14, 1959) Collection of lecture abstracts, No. 288-295
page).

[Problem that the invention attempts to solve]

However, in a battery sealed with a hot melt adhesive as described above, the hot melt adhesive 6 that bonds the positive electrode plate 1 and the negative electrode plate 5 is exposed to the outside of the battery at the outer peripheral edge of the battery. During use, moisture, oxygen, etc. from outside the battery permeate the layer of hot melt adhesive 6 and enter the battery, react with lithium, form a passive film on the negative electrode 4, and reduce the internal resistance of the battery. There is a problem in that it causes a decrease in battery performance.

[Means for solving problems]

This idea solves the problems of the prior art described above, and by covering the exposed part of the hot melt adhesive used for sealing with a gas barrier film, it protects against moisture and oxygen outside the battery. This prevents nitrogen and the like from penetrating the hot melt adhesive layer and entering the battery, thereby preventing deterioration in battery performance during storage or use.

That is, in the present invention, a power generating element is interposed between a positive electrode plate and a negative electrode plate, and the peripheral edge of the positive electrode plate and the peripheral edge of the negative electrode plate are bonded and sealed with hot melt adhesive outside the peripheral edge of the power generating element. The present invention relates to a thin lithium battery characterized in that the outer periphery of the battery main body formed by this process is covered with a gas barrier film to prevent the hot melt adhesive from being exposed to the outside of the battery.

In the present invention, the gas barrier film used to prevent the hot melt adhesive used for sealing from being exposed to the outside of the battery includes, for example, an acrylonitrile thermoplastic resin film,
Modified polyvinyl alcohol film, ethylene-
Examples include vinyl alcohol copolymer resin films. For example, the oxygen gas permeability of these gas barrier films is as follows:
These gas barrier films have an oxygen gas permeability of 0.1 to ^13c.c./cm 2.2hr.atm, and have an oxygen gas permeability of 7000 to 10000c.c./cm (general packaging film, polyethylene film). ^cm2・24hr・atm),
Polypropylene film (oxygen gas permeability 2100~
3600c.c./cm ² / 24hr / atm), etc., the gas permeability is lower, and even a thin one of about 20 to 60 μm can exhibit its full effect, making it very suitable for making thin batteries. It is.

Some of these gas barrier films have adhesive properties to metals by themselves, while others do not have adhesive properties to metals by themselves and require an adhesive to be used. Although they do not have adhesion to metals by themselves, some are supplied in a laminated state with a film that has adhesion to metals.

A typical example of the above-mentioned gas barrier film that itself has adhesive properties to metals is the aforementioned acrylonitrile-based thermoplastic resin film, which is commercially available from Mitsui Toatsu Chemical Co., Ltd. under the trade name Zekron. has been done. A specific example of a gas barrier film that does not have adhesive properties to metals by itself is the aforementioned ethylene-vinyl alcohol copolymer resin film, which is commercially available from Kuraray Co., Ltd. under the trade name EVAL FILM. . Specific examples of gas barrier films that do not have adhesive properties to metals by themselves but are laminated with films that have adhesive properties to metals include:
It is a laminated film of the above-mentioned modified polyvinyl alcohol film and polypropylene film, and is commercially available from Tokuyama Soda Co., Ltd. under the trade name Varistar.

〔Example〕

Next, the present invention will be explained in more detail with reference to examples.

Example 1 A modified polyolefin hot melt adhesive (manufactured by Mitsubishi Yuka Co., Ltd., product name) was applied to the peripheral edge of a 15 mm x 15 mm square stainless steel plate with a thickness of 0.5 mm.
MODIC) is pre-coated, and the central part is coated with titanium disulfide as a positive electrode active material and LiB as a positive electrode.
(C ₆ H ₅ ) ₄・3 A mixture of 27.8% by weight of DME, 59.1% by weight of PC, and 13.1% by weight of RMMA with a gel electrolyte in a weight ratio of 50:50 was prepared in a 10 mm x 10 mm size with a thickness of 0.25 mm.
It was painted on. In the gel electrolyte, DME is 1,2-dimethoxyethane, PC is propylene carbonate, and RMMA is polymethyl methacrylate for imparting viscosity.

Next, a 25 μm thick microporous polypropylene film (Polyplastic Co., Ltd.) was placed on the positive electrode made of the mixture of titanium disulfide and gel electrolyte.
A sealator impregnated and coated with the same gel electrolyte as above is placed on a sheet (manufactured by Jyuraguard, trade name), and on top of it, the same modified polyolefin-based hot melt adhesive as above is pre-coated on the periphery, and a thick layer is placed in the center as a negative electrode. A 15 mm x 15 mm square stainless steel plate with a thickness of 0.05 mm was placed on which an 8 mm x 8 mm square lithium plate with a ^thickness of 0.1 mm was crimped. The battery main body portion was prepared by heating for 10 seconds to thermally fuse and seal the precoated hot melt adhesives.

The outer periphery of the battery body produced as described above, that is, the outer periphery end surface of the battery main body, the upper surface of the negative electrode plate and the lower surface of the positive electrode plate near the outer periphery end surface are
25 μm acrylonitrile thermoplastic resin gas barrier film (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name: Zeclon, oxygen gas permeability 13 c.c./cm ² , 24 hr.
atm) and heated at 150°C for 10 seconds under a pressure of 1 kg/cm ² to heat-seal the gas barrier film to the outer periphery of the battery body to prevent the hot melt adhesive from being exposed to the outside. was created. The width of the gas barrier film covering the upper surface of the negative electrode can and the lower surface of the positive electrode can are measured from the outer edge of the battery body.
It is 1.5mm. A battery produced in this manner is shown in FIG.

In FIG. 1, 1 is a positive electrode plate made of a stainless steel plate, 2 is a positive electrode made of titanium disulfide and a gel electrolyte, and 3 is a separator made of microporous polypropylene film. 4 is a negative electrode made of lithium, 5 is a negative electrode plate made of a stainless steel plate, 6 is a hot melt adhesive for sealing which adheres the peripheral edge of the positive electrode plate 1 and the peripheral edge of the negative electrode plate 5,
As mentioned above, a modified polyolefin hot melt adhesive is used. Reference numeral 11 denotes the battery main body, which includes the positive electrode 2, separator 3 and negative electrode 4 as described above.
A hot melt adhesive 6 is applied to the periphery of the positive electrode plate 1 and the periphery of the negative electrode plate 5 with the power generation element 10 interposed therebetween.
It is formed by adhesive sealing. 7
is a gas barrier film that covers the outer periphery of the battery main body portion 11;
The outer peripheral end surface of the negative electrode plate 5 and the lower surface of the positive electrode plate 1 near the outer peripheral end surface are coated with a hot melt adhesive 6.
This prevents the battery from being exposed to the outside.

Example 2 A battery main body part was produced in the same manner as in Example 1,
Erylene-vinyl alcohol copolymer resin gas barrier whose outer periphery is pre-coated with a hot melt adhesive (manufactured by Mitsui Dupont Polychemical Co., Ltd., trade name: Himilanfil) on the side that will become the inner surface when coated with a thickness of 35 μm. Sex film (Kuraray Co., Ltd.)
Manufactured by Eval Film, Oxygen gas permeability
0.5 cc/cm ² ·24 hr · atm) and heated at 150°C for 10 seconds under a pressure of 1 kg · cm ² to heat-seal.

Example 3 A battery main body part was produced in the same manner as in Example 1,
Its outer periphery is covered with a gas barrier film (manufactured by Tokuyama Soda Co., Ltd., trade name: Barrier Star, thickness of modified polyvinyl alcohol part) consisting of a laminate film of modified polyvinyl alcohol and polypropylene with a thickness of 60 μm.
30μm, oxygen gas permeability ^3c.c./cm2・24hr・atm)
Cover with the polypropylene side facing the inner surface, and
Heat fusion was carried out by heating at 180° C. for 10 seconds under a pressure of Kg/cm ² .

Comparative Example A battery was produced in the same manner as in Example 1, except that the outer periphery of the battery main body was not covered with a gas barrier film. That is, a battery main body portion was produced in the same manner as in Example 1, and this was used as a battery.

The batteries of Examples 1 to 6 and the batteries of Comparative Example were
The batteries were stored for a predetermined period under conditions of no humidification at 60°C and 90% relative humidity, and the increase in internal resistance of each battery was examined. Figure 3 shows the results when stored at 60°C and non-humidified conditions, and Figure 4 shows the results when stored at 60°C and 90% relative humidity.

As shown in Figures 3 and 4, this invention prevents the hot melt adhesive used for sealing from being exposed to the outside of the battery by covering the outer periphery of the battery body with a gas barrier film. Example 1 of
Batteries No. 3 to 3 showed a smaller increase in internal resistance than the comparative example battery, which is a conventional battery. in this way,
The fact that the battery of the present invention shows little increase in internal resistance when stored under non-humidified conditions indicates that the gas barrier film prevents the electrolyte solvent from leaking out to the outside of the battery. The fact that the battery of this invention has a small increase in internal resistance when stored under humidified conditions of 90% relative humidity means that the gas barrier film prevents moisture, oxygen, etc. from entering the battery from outside. It shows that it will be done.

In the example, the power generation element 10 includes a positive electrode made of a mixture of a gel electrolyte and a positive electrode active material;
Although a power generation element consisting of a separator impregnated with a gel electrolyte and a negative electrode was used, the present invention is not limited to this case, and may be made of, for example, a positive electrode, a solid electrolyte layer, and a negative electrode.

[Effect of idea]

As explained above, in the present invention, the gas barrier film prevents the hot melt adhesive used for sealing from being exposed to the outside of the battery, allowing moisture, oxygen, etc. from outside the battery to be absorbed by the hot melt adhesive. To provide a thin lithium battery with good storage characteristics by preventing electrolyte solvent from permeating the layer and entering the battery, and preventing electrolyte solvent from permeating the hot melt adhesive layer and escaping to the outside of the battery. I was able to do that.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the thin lithium battery of the present invention, and FIG. 2 is a sectional view showing a conventional thin lithium battery. Figure 3 shows the increase in internal resistance of the battery of the present invention and the conventional battery when stored at 60°C with no humidity, and Figure 4 shows the battery of the present invention and the conventional battery at 60°C and relative humidity. FIG. 3 is a diagram showing an increase in internal resistance with storage under 90% conditions. DESCRIPTION OF SYMBOLS 1... Positive electrode plate, 2... Positive electrode, 3... Separator, 4... Negative electrode, 5... Negative electrode plate, 6... Hot melt adhesive, 7... Gas barrier film, 1
0...Power generation element, 11...Battery main body part.

Claims (1)

[Claims for Utility Model Registration] (1) A power generating element 10 is interposed between the positive electrode plate 1 and the negative electrode plate 5, and the peripheral edge of the positive electrode plate 1 and the peripheral edge of the negative electrode plate 5 are located outside the peripheral edge of the power generating element 11. The outer periphery of the battery main body part 11 formed by adhering and sealing the parts with a hot melt adhesive 6 is covered with a gas barrier film 7 to prevent the hot melt adhesive 6 from being exposed to the outside of the battery. A thin lithium battery characterized by: (2) The gas barrier film 7 is an acrylonitrile-based thermoplastic resin film, an ethylene-
The thin lithium battery according to claim 1, which is a vinyl alcohol copolymer resin film or a modified polyvinyl alcohol film.