JPH046071B2 - - Google Patents

Description

[Detailed description of the invention] <Technical field> The present invention relates to a flat thin organic electrolyte battery.

<Description of prior art and development progress> Conventionally, flat and thin batteries using manganese dioxide as the positive electrode active material, zinc as the negative electrode active material, and a neutral salt electrolyte have been commercially available under the trade name of "Paper Battery," for example. It's here. A cross-sectional view of this flat, thin battery is approximately as shown in FIG.

That is, in FIG. 1, the negative electrode (zinc plate) 11
A separator 12 impregnated with an aqueous solution of zinc perchlorate, which is an electrolytic solution, and a positive electrode mixture (a mixture of manganese dioxide and carbon black) 13 are interposed between the electrode current collector 14 and the positive electrode current collector 14, and the whole is covered with an outer covering material 10. It's packaged. Note that a window is partially opened in this outer packaging material 10, and the positive electrode current collector 14 exposed through this window becomes a positive electrode terminal 15, which is sandwiched between the negative electrode 11 and the outer packaging material 10. The metal plate serves as a negative terminal 16.

In FIG. 1, the outer wrapper 10 is depicted as a single layer sheet;
As shown in the enlarged sectional view of the figure, from the outside, the heat-resistant film 21 / adhesive 22 / aluminum foil 23 /
Adhesive 24/Heat-resistant resin film 25/Adhesive 2
6/ It is a multilayer sheet in which metal adhesive resin 27 is laminated.

Incidentally, recent advances in electronics such as ICs and LSIs have been remarkable, and electronic precision equipment that uses these devices is increasingly required to be highly accurate and multi-functional. High energy density and long-term reliability are required. Furthermore, small portable devices with low power consumption, such as calculators and cameras, are being designed to be more fashionable and more functional, such as dramatically smaller size and weight. Therefore, it must be small and lightweight,
The above-mentioned flat and thin battery is extremely superior in terms of being thin and fashionable;
It does not necessarily mean that the energy density is the best.

To date, the battery with the highest energy density is said to be a lithium battery. This lithium battery is metal lithium or lithium-
It uses a lithium-based alloy such as an aluminum (Li-Al) alloy as a negative electrode active material and a non-aqueous electrolyte, and has the following characteristics (a) to (c).

(a) Metallic lithium has a standard electrode potential E=-
It has the lowest potential of all substances at 3.045V, and the lowest electrochemical equivalent of 0.26g/Ah among solid substances, making it a high-voltage battery (more than 3V) and a very high energy density. It could be a battery.

(b) Since it uses an organic electrolyte, it has a wide operating temperature range.

(c) It can be expected to have a long shelf life of 5 years or more. Therefore, if it were possible to manufacture a flat thin lithium battery instead of the conventional flat thin manganese dioxide/zinc battery, it would be possible to produce a flat thin lithium battery that has high voltage, high energy density, long-term storage, and is small, lightweight, and thin. A fashionable battery can be obtained. Therefore, a rough cross-sectional view of the expected flat thin lithium battery is as shown in FIG. 3, for example. That is, the positive electrode current collector 31 and the negative electrode current collector 35 are each heat-sealed to the outer packaging material 30 which is folded into two sheets or two. This positive electrode current collector 31 and negative electrode current collector 35
A positive electrode mixture 32, a separator 33 impregnated with an organic electrolyte, and a negative electrode 34 made of lithium or a lithium-based alloy are sandwiched between them in this order.

However, the outer packaging material 3 of flat thin lithium batteries
Unlike the conventional manganese dioxide/zinc-based flat thin battery outer covering material 10, extremely excellent moisture resistance and resistance to organic electrolytes are required. Further, as with conventional flat thin batteries, it goes without saying that thermal adhesion to the current collectors 31 and 35 is required.

In view of these circumstances, the inventors of the present invention have so far produced and studied various outer packaging materials.

For example, if the conventional outer packaging material 10 in which an inner adhesive resin is laminated using an adhesive is used as is,
The organic electrolyte penetrates into the heat-resistant resin film 25.
and the metal adhesive resin 27, and between the heat-resistant resin film 25 and the aluminum foil 23.

Similar peeling or deterioration of adhesive strength due to penetration of organic electrolyte also occurred when urethane-based adhesives or epoxy-based adhesives were used. From these experimental results, it can be concluded that so-called adhesives such as solvent-based adhesives and non-solvent adhesives swell due to the penetration of organic electrolytes, which deteriorates their adhesive strength and makes them easier to peel off. I had no choice.

Therefore, the present inventors prototyped the outer wrapping material 40 using only a heat-fusible resin without using an adhesive on the inner side of the aluminum foil of the outer wrapping material 30. This is shown in the sectional view of FIG. 4, and is a laminated material 40 having a layered structure of heat-resistant film 41/adhesive 42/aluminum foil 43/thermal adhesive resin 44 in order from the outside.

Note that since the organic electrolyte does not penetrate beyond the aluminum foil 43, the heat-resistant film 4
1 and the aluminum foil 43 can be bonded together using a suitable adhesive. Here, heat-fusible resin 4
Examples of 4 include ethylene-(meth)acrylic acid derivative copolymer, ethylene-glycidyl(meth)acrylate-vinyl acetate terpolymer, and polyolefin graft-modified with unsaturated carboxylic acid. Polyolefin graft-modified with unsaturated carboxylic acid was superior in terms of fusion strength and stability over time, and polypropylene graft-modified with unsaturated carboxylic acid was particularly excellent.

In this way, by using the laminated material 40 shown in FIG.
Although the problem of deterioration of the adhesion between the outer envelope material 30 and the adhesive strength due to penetration of the organic electrolyte was solved, on the other hand, a new problem occurred by using the laminated material 40 shown in FIG. I did it. That is, the current collectors 31 and 35 and the aluminum foil 43 in the laminated material 40 were short-circuited.

There were two causes for the short circuit. One is that when the laminated material 40 is used as the outer covering material 30 and is heat-sealed to the current collectors 31 and 35, a small pinhole is created in the heat-sealable resin 44, and the aluminum in the laminated material 40 is formed through the heat-sealed resin 44. This causes a short circuit to the foil 43.

Another cause of the short circuit is that when the outer covering material 30 is heat-sealed together, the current collectors 31 and 35 break the heat-sealing resin 44 at the seal edges and short-circuit with the aluminum foil 43. That's what happens. This state is shown in the partial sectional view of FIG. The x in the figure is the torn part.

In order to prevent this short circuit, it was thought that it would be best to interpose another sheet between the aluminum foil 43 and the heat-sealing resin 44, which would not cause pinholes due to the heat during heat-sealing. This is shown in the cross-sectional view of FIG. 6, where 61 is nylon, ethylene-vinyl alcohol copolymer, polyester (polyethylene terephthalate), or polyolefin having a higher melt viscosity than the heat-fusible resin 44 during heat-sealing. It is a film such as.

However, since nylon and ethylene-vinyl alcohol copolymers have hygroscopic properties and absorb moisture from their end surfaces, there was a risk that lithium or lithium-based alloys used as negative electrode active materials would react with the invading moisture. Polyester is not hygroscopic and has excellent resistance to organic solvents, but heat-fusible resin 44 and polyester usually do not have heat-fusibility (polyester-based heat-fusible resin can be heat-fused to polyester, but , it swelled in the organic electrolyte), and sufficient adhesive strength could not be obtained.

Polyester may be used as the film 61, and an adhesive may be used between the heat-sealing resin 44 and the film 61, but as described above, the adhesive peels off due to penetration of the organic electrolyte.

The problem seemed intractable. However, the present inventors solved this problem by using a heat-resistant resin film with metals or inorganic substances deposited on both sides. The heat-fusible resin has heat-fusibility to metals and inorganic materials.

<Summary of the Invention> That is, the present invention provides a method in which a positive electrode current collector and a negative electrode current collector are respectively heat-sealed to an outer wrapping material folded into two sheets or folded in two, and the positive electrode current collector and negative electrode current collector are bonded together. A positive electrode mixture, a separator impregnated with an organic electrolyte, and a negative electrode are sandwiched between the layers, and the outer casing materials are bonded and sealed around the periphery. In a flat thin organic electrolyte battery in which a positive electrode current collector and a negative electrode current collector are exposed, this outer covering material is made of a heat-resistant film, aluminum foil, and a multilayer inner adhesive layer from the outside. , this inner surface adhesive layer consists of at least a three-layer structure in which a heat-resistant resin film with metal or inorganic material deposited on both sides is placed between the aluminum-side heat-fusible resin and the innermost heat-sealable resin, and this inner surface Provided is a flat and thin organic electrolyte battery characterized in that adhesive layers are laminated and integrated by heat fusion.

According to the present invention, the heat-resistant resin film is arranged on the inner surface adhesive layer inside the aluminum foil of the outer covering material, so that even if a pinhole occurs in the internal heat-sealing resin, it will not collect with the aluminum foil. In addition to preventing electrical contact with the electric body, since no adhesive is used to bond the heat-resistant resin film, it is possible to prevent deterioration of adhesive strength due to penetration of organic electrolyte.

<Embodiment of the invention> The details of the present invention will be explained below with reference to Examples.
FIG. 7 of the drawings shows a cross-sectional view of an outer wrapping material according to an embodiment of the present invention. In the figure, 71 indicates a heat-resistant film made of polyester, nylon, or the like. This prevents the occurrence of pinholes and corrosion in the aluminum foil 73, and also provides heat-sealing workability to the outer wrapping material 70. This heat-resistant film 71 and aluminum foil 73 are bonded together via an adhesive or an adhesive film 72.

Further, 75 is a heat-resistant resin film having metal or inorganic material deposited on both sides, and for example, a polyester film (polyethylene terephrate film) is suitable. Aluminum is the metal to be vapor deposited,
Gold, silver, chromium, copper, and inorganic substances to be vapor-deposited include, for example, silicon dioxide, silicon monoxide, titanium oxide, and indium oxide.

The innermost heat-fusible resin 76 may be made of metals and inorganic materials such as ethylene-(meth)acrylic acid copolymer, ethylene-glycidyl(meth)acrylate-vinyl acetate, and polyolefin graft-modified with unsaturated carboxylic acid. A heat-fusible resin having adhesive properties can be used, but as mentioned above, a polyolefin graft-modified with an unsaturated carboxylic acid is preferable because of its resistance to organic electrolytes.
In particular, 0.01 to 10 parts by weight of α,β-unsaturated carboxylic acid such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, maleic anhydride, etc. is graft polymerized to 100 parts by weight of ethylene or propylene monomer. Preferably.

Further, as the aluminum foil side heat-fusible resin 74, any resin that can be used as the innermost heat-fusible resin 76 can be used, but polyethylene or the like can also be used.

Aluminum foil (for example, thickness 9μ or more) 73,
The aluminum side heat-fusible resin 74, the heat-resistant resin film 75 with metal or inorganic material vapor-deposited on both sides, and the innermost heat-fusible resin 76 are laminated and integrated by heat fusion without using an adhesive. It is necessary.

The cross-sectional view of a flat, thin battery obtained using this outer wrapping material 70 is similar to that shown in FIG. The negative electrode current collectors 35 are each heat-sealed. The thermal fusion temperature at this time is preferably 150 to 200°C. Titanium, stainless steel, aluminum, or the like is used for the positive electrode current collector 31, and nickel, stainless steel, or the like is used for the negative electrode current collector 35. Moreover, its thickness is 30-80μ. The positive electrode mixture layer 32 consists of a positive electrode active material, carbon black as a conductive material, and a binder. Metal oxides such as manganese dioxide, metal sulfides, or carbon fluoride are used as the positive electrode active material. Polytetrafluoroethylene is used as the binder. On the other hand, the negative electrode 34 is made of lithium or a lithium-based alloy such as a lithium-aluminum alloy. Separator 33
is a nonwoven fabric such as polypropylene. The organic electrolyte used is one in which an inorganic salt such as lithium fluoride or lithium perchlorate is dissolved in an aprotic organic solvent having a high dielectric constant and low viscosity such as r-butyrolactone.

As described above, according to the present invention, pinholes are formed in the heat-fusible resin layer when heat-sealing the outer wrapping material and the current collector and when heat-sealing the outer wrapping materials together. Even if it occurs,
The presence of the heat-resistant resin film prevents electrical contact between the current collector and the aluminum foil, thereby preventing a short circuit between the outer wrapping material and the current collector. In addition, the layers of the outer covering material, current collector, and outer covering material have strong adhesive strength, and peeling does not occur due to penetration of the organic electrolyte.

In addition, since a heat-resistant resin film with metal or inorganic material vapor-deposited on both sides is used as the intermediate layer, the strength of the outer covering material is improved, and the vapor-deposited layer improves the permeability of the organic electrolyte. For this reason, polyethylene can be used as the heat-fusible resin on the aluminum side, increasing the range of resin selection and strength tolerance.

The present invention will be explained below with reference to Examples and Comparative Examples.

<Example> 500 on both sides of a 12μ thick polyester film
~600〓 of aluminum is vapor-deposited, one side of which is melt-extruded coated with polyethylene graft-modified with maleic anhydride, and the coated surface is coated with a laminated aluminum material with a layer structure of "polyester film/adhesive/aluminum foil". The foil surfaces were overlapped and heat fused. Next, polyethylene graft-modified with maleic anhydride was melt-extruded coated on the other surface of this aluminum vapor-deposited surface to form "Polyester Film 71/Adhesive 7".
2/Aluminum foil 73/Modified polyethylene 7
An outer covering material having a layer structure of 4/polyester film 75 with aluminum vapor-deposited on both sides/modified polyethylene 76 was obtained. When this adhesive strength was investigated, the lowest adhesive strength was between polyester film 75, which had aluminum deposited on both sides, and modified polyethylene 76, at 150 to 500 g/15 mm. Therefore, it can be seen that in this outer packaging material, each layer is firmly adhered to each other, and peeling between each layer is unlikely to occur over time or even when the battery is bent.

When a thin battery was made using this outer casing material, there was no short circuit between the outer casing material and the current collector due to electrode punctures or pinholes, and there was no short circuit between the outer casing material and the current collector at 60°C.
Even after storage for three months at a relative humidity of 95%, there was no deterioration in battery characteristics and the battery remained in good condition.

Furthermore, after bending the edges of a thin battery made using this outer packaging material 50 times in preparation for use, the packaging material was stored for 3 months at 60% relative humidity and 95% relative humidity. There were 2% defects due to cracks in the aluminum foil in the material, but the rest were in good condition with no deterioration. Note that cracks in the aluminum foil mean that moisture may enter and react with lithium or lithium alloys.

<Comparative Example> Example 1 except that a polyester film on which aluminum was not vapor-deposited was used instead of a polyester film on which aluminum was vapor-deposited on both sides.
An outer packaging material was manufactured in the same manner as in the above. When we investigated the adhesive strength of this outer covering material, we found that the adhesive strength was the lowest between polyester film and modified polyethylene.
It was 20-50g/15mm. Therefore, the polyester film and the modified polyethylene are likely to separate, and as described below, they will separate over time or by bending.

When a thin battery was created using this outer packaging material in the same manner as in the example, the battery characteristics were good immediately after creation, but when stored at 60°C and 95% relative humidity, it was stored for 3 days. The internal resistance began to increase, the polyester film and the modified polyethylene peeled off, and the moisture that entered made all the products unusable within a month.

Moreover, in the case where the edge portion was bent, peeling occurred between the polyester film and the modified polyethylene during the operation, making it unusable.

[Brief explanation of drawings]

Figures 1 and 2 are cross-sectional views of a conventional manganese dioxide/zinc-based flat thin battery and its outer packaging material;
Figure 3 is a cross-sectional view of a flat, thin battery with lithium as the negative electrode, Figures 4 and 6 are cross-sectional views of conventional outer packaging materials, and Figure 5 is a cross-sectional view of a flat, thin battery with lithium as a negative electrode. Partial sectional view, FIG. 7 is a sectional view of the outer wrapping material of the present invention. 10, 30, 40, 60, 70...outer packaging material,
21,41,71...Heat-resistant film, 22,2
4, 26, 42, 72...adhesive, 23, 43,
73... Aluminum foil, 44... Heat-fusible resin, 74... Aluminum foil side heat-fusible resin, 7
5...Heat-resistant resin film with aluminum vapor-deposited on both sides, 76...Innermost heat-fusible resin, 31...
...Positive electrode current collector, 32... Positive electrode mixture, 33... Separator, 34... Negative electrode, 35... Negative electrode current collector.

Claims (1)

[Claims] 1. A positive electrode current collector and a negative electrode current collector are heat-sealed to the outer wrapping material folded into two sheets or two, respectively, and between the positive electrode current collector and the negative electrode current collector, In order, the positive electrode mixture, the separator impregnated with an organic electrolyte, and the negative electrode are sandwiched, and the outer packaging materials are adhered and sealed around them, and a window is provided in a part of the outer packaging material. In flat, thin organic electrolyte batteries in which the positive electrode current collector and negative electrode current collector are exposed, this outer covering material consists of a heat-resistant film, aluminum foil, and a multilayer inner adhesive layer from the outside. The layer consists of at least a three-layer structure in which a heat-resistant resin film with metal or inorganic material vapor-deposited on both sides is arranged between the heat-fusible resin on the aluminum side and the heat-fusible resin on the innermost surface, and this inner adhesive layer A flat, thin organic electrolyte battery characterized by being integrated into layers by fusion bonding. 2. The flat and thin organic electrolyte battery according to claim 1, wherein the heat-resistant film is a polyester film.