JPH0221557A - Thin battery - Google Patents

Abstract

PURPOSE:To prevent the capacity change of a battery even if bending stress is applied by fixing parts of power generating elements with a frame made of a plastic sheet, and bonding the periphery of the frame to parts of outer jackets through connecting layers in airtightness. CONSTITUTION:Power generating elements 11 are bonded to a plastic frame 10 having a hot-melt adhesive layer 16. The power generating elements 11 and the plastic frame 10 are interposed between a pair of outer jackets 9, 9 each of which has a hot-melt layer 16, and melt-bonded with peripheral hot-melt adhesive layers 16 in airtightness. The outer jacket is the stack comprising a polypropylene hot-melt adhesive layer 12, a nylon layer 13, an aluminium layer 14, and a polyester layer 15, and two outer jackets are bonded through the hot-melt adhesive layers 12. The capacity change of a battery is prevented even if bending stress is applied.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a thin battery, particularly a sheet type secondary battery.

[Prior Art] In recent years, high energy density secondary batteries using conductive polymer materials such as polyacetylene, polypyrrole, and polyaniline have been developed. In particular, the above-mentioned polymeric materials can be processed into flexible sheet-type electrodes, so they are attracting attention as electrodes for sheet-type or card-type batteries.
There are many difficulties in developing mounting methods and in terms of battery reliability, and in particular, the method of fixing the power generation element has only been studied for sheet-type metal cans.

Furthermore, even if the weight of the electrode material can be reduced, the energy density per weight of the entire battery decreases due to the weight of other constituent materials. Lithium, lithium alloy (Li-Al) can be used as the negative electrode material of the electrode.

When using Li-3i) or polymeric materials that can be n-doped (polyparaphenylene, polythiophene, polyacetylene, etc.), the negative electrode is unstable and will deteriorate if moisture permeates through the exterior material. do. Also, propylene carbonate, ethylene carbonate, dimethoxyethane, γ-butyllactone, sulfolane, THF
When using a non-aqueous solvent such as 2-methyl THF, there are problems such as a decrease in adhesion over time, and difficulties in immobilization such as keeping the distance between the positive and negative electrodes constant. there were.

In particular, in the case of combination with the above-mentioned conductive polymer active material, in battery systems using unstable negative electrode materials and non-aqueous solvents containing highly concentrated electrolytes, the reliability of the bonding part with the exterior material is low,
This is a particularly important problem for thin secondary batteries.

[Problems to be Solved by the Invention] The present invention has discovered a reliable structure for the exterior material and adhesive layer of a non-aqueous secondary battery using such a polymer material.

[Means for Solving the Problems] In order to solve the above problems, the present invention has a configuration in which at least the positive electrode is conductive between a pair of aluminum/plastic film laminated sheets formed into a predetermined contour shape. In a secondary battery that holds a power generation element made of a polymeric material, a part of this power generation element is fixed to a frame made of sheet-like plastic, and the periphery of the frame is sealed with a part of the exterior material by an adhesive layer. It is a thin battery that is glued to the

That is, the material of the exterior material is a laminate of aluminum and plastic film, the adhesive layer of the exterior material is a polyolefin such as heat-fusible polyethylene, polypropylene, or a copolymer containing a propylene structure, and the internal battery is It has been discovered that a battery with a configuration in which the positive electrode, negative electrode, separator, etc. as elements are fixed to a sheet-like framework, and this sheet-like framework is fixed inside the exterior material, exhibits excellent reliability as a battery. It is something.

To explain in detail with reference to the drawings, as shown in FIG. a pair of exterior materials 9 having a fusion layer 16;
9, and these are sealed and fused by the surrounding heat-sealing layer 1B.

As shown in FIG. 2, the structure of the fusing cloth and the sheathing material 9 is such that a plastic frame 10 to which the power generation element 11 is fixed is sealed by a pair of sheathing materials 9, 9.

The exterior material 9 includes a polypropylene heat-sealing layer 12 and a nylon layer 1
3. Aluminum layer! 4. A laminate consisting of a polyester layer 15, which is tightly adhered by the heat sealing layer 12.

The structure of the power generating element 11 is, for example, as shown in FIG. 3, in which a current collector 7 and a positive electrode 2 made of a conductive polymer material 8 are sandwiched between negative electrodes 1 with a separator 3 in between.

The negative electrode l is a laminate of a nickel foil 5 and a lithium foil 6.

A power generation element consisting of a positive electrode 1, a negative electrode 2, and a separator 3 is folded as shown in FIG. 4, and is fixed to a plastic frame 10 and connected to a terminal 4 as shown in FIG.

Plastic packaging materials have conventionally been widely used for packaging retort foods, but when used in batteries, especially non-aqueous batteries, the physical properties required are different from those for foods. For example, hot-melt resins such as ethylene-vinyl acetate copolymers, polyamides, and polyesters are not suitable as exterior materials for batteries because they swell with electrolyte and are relatively permeable to moisture.

The plastic exterior material that encloses the power generation element of a battery is, in principle, a laminate (laminate sheet) of an aluminum sheet and a plastic film. Aluminum sheets have a high moisture-proofing effect and low gas permeability, so they are suitable as exterior materials for the above-mentioned non-aqueous solvent batteries that generate little gas.

The aluminum layer needs to have a thickness of 4 μm or more, and preferably 25 μm or less for flexible mounting.

As the material for the plastic layer, polyethylene, polypropylene, polyester, polyimide, etc. are used, and -axially or biaxially stretched polyester film is particularly suitable.

The appropriate thickness of this polyester film is 12 to 150 μm.

The thermal adhesive layer is particularly important in the present invention.

As a material for this thermal adhesive layer, polypropylene, especially -axially stretched CPP, has excellent adhesive strength and adhesive strength at high temperatures.

The plastic sheet frame in the present invention has a thickness of 20 to 5
00 μm plastic sheets punched into square or circular shapes are suitable, and in addition to polyolefins such as polyethylene and polypropylene, materials with excellent chemical resistance such as polycarbonate, polyvinyl chloride, acetal resin, fluororesin, polyester, and polyimide are suitable. It is made of material and is used to secure power generation elements. It is preferable that the power generating element is fixed at the periphery of the plastic sheet frame by a stone contacting material, and in particular, the electrode terminal portion is fixed on the sheet frame. Further, it is preferable that the plastic frame is tightly sealed with a part or all of the exterior sealing part by heat sealing.

The polymer active material, which is an element of the present invention, is a conductive polymer material polymerized by an electrolytic polymerization method or a chemical oxidation polymerization method, and has an electrical conductivity of IO's/cm or more during charging. Such polymer materials include polypyrrole, polyphenylene, polythiophene, polyaniline,
Examples include polydiphenylbenzidine, polycarbazole, polyvinylcarbazole, and substituted products thereof.

These materials can be used as electrode active materials in the form of films, or can be fixed on metal foils such as Al5Ni, carbon fiber sheets, etc. (directly polymerized and composited by electrolytic polymerization) to form sheet-like electrodes.

These electrode active materials are used as a positive electrode or a negative electrode, and Li or an alloy such as Li-At or Li-8i is used as the negative electrode by reinforcing it with a nickel sheet or the like.

The positive and negative electrodes are separated by a sheet separator made of glass fiber paper, polyester, polypropylene, etc., or a solid or semi-solid electrolyte, and if necessary, propylene carbonate, ethylene carbonate, dimethoxyethane, 2 methyl THF, or sulfolane is used. , γ-butyllactone and other solvents, LiB F 4 , LiP
F6, LiClO4, LiSbF6, KPF6, K
B F < , N a P F & , K B F
Alkali metal salts such as 4, TBABF4, TBACI0
4, TBAPF&, TEABF4, TEAC104 (T
Organic salts such as BA (tetrabutylammonium) and TEA (tetraethylammonium) are added.

The power generation element obtained as described above is flexible and becomes an important component of a sheet type secondary battery.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 200 holes/c with a diameter of 200 μm by electroplating method
A 20 μm thick nickel sheet with a density of n+2 was prepared.

Cut this sheet into 5cm wide and 15cm long, and
A current collector was prepared by blasting with 100 mesh silicon carbide emery particles at a pressure of 1 kg.

0.1M balatoluenesulfonic acid and 0.1M balatoluenesulfonic acid were used as the polymerization solution.
Using an acetonitrile solution containing 1M pyrrole,
A polypyrrole film having a thickness of 15 μi (2.5 c/cm 2 ) was deposited on both sides of the current collector by the constant potential electrolytic polymerization method in step 4, and this was used as a positive electrode.

As a separator, polypropylene pore filter (
Polyplastics Co., Ltd., product name: DURAGUARD 5511 (7
5 μm thick) was used. The negative electrode used was a 70 μl thick lithium foil pressed onto a 10 μm thick nickel foil. A 5 mm x 50 mm x 0.3+ ua polypropylene sheet was punched out to produce a plastic frame with a width of 5I.

A power generating element consisting of a positive electrode, a negative electrode, and a separator was folded inside this plastic frame as shown in FIG. 4 to produce a battery having the structure shown in FIG. 1.

The exterior material consists of a four-layer structure of polyester/aluminum/nylon/polypropylene fused stone layer, and is 100 mm thick.
A μm film was used.

After assembling the sheet battery with the above configuration, L with a concentration of 3M
i Inject an electrolytic solution in which BF4 is dissolved in a 1:1 mixed solution of propylene carbonate and dimethoxyethane using a syringe, and then seal the periphery of the battery by heat pressure bonding.
A potential with a size of 50 mm x 50 mm x 0.8 mm was created.

This battery was subjected to a 30° bending test 100 times, and its performance and leakage properties were tested before and after the test.

No liquid leakage was observed even after the folding test was performed 100 times.

In the battery performance test, charging and discharging were performed at a constant current of 1 fflA.

The results are shown in the table below.

Example 2 A polymerization solution containing 0.5M aniline and 5.5NH2SO4 dissolved in water was used, and a current collector was used as a working electrode.
A 50 mm x 50 IX 0 film was prepared in the same manner as in Example 1, except that a 20 μm thick polyaniline film was deposited on both sides of the current collector by 5 V vs S CE to form a sheet-like positive electrode.
．． A battery with a size of 7 mm was produced.

This battery was subjected to the same test as in Example 1. The results are shown in the table below. No liquid leakage was observed even after the folding test was performed 100 times.

Example 3 The structure was the same as in Example 2, except that an electrode was formed on one side of the current collector and used to manufacture a battery as shown in FIGS. 1 and 2.

This battery was tested in the same manner as in Example 1.

The results are shown in the table below.

Comparative Example The power generation element in Example 2 was enclosed in an exterior material as it was.

In this battery, liquid leakage was observed after 43 bending tests.

This battery was tested in the same manner as in Example 1, and the results are shown in the table below.

[Effects of the Invention] As explained above, the battery of the present invention is highly flexible and has high reliability because the battery capacity does not change even when bending stress is applied.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of the thin battery of the present invention, and FIG.
Figure 3 is a partial schematic cross-sectional view showing the configuration of the power generating element; Figure 4 is a schematic cross-sectional view showing the overall configuration of the power generating element. It is. ■... Negative electrode, 2... Positive electrode, 3... Separator, 4
Terminal, 5 Nickel foil, 6 Lithium foil, 7 Current collector, 8 Conductive polymer material, 9 Exterior material, 10 Plastic frame , 11・
... Power generation element, 12 ... Polypropylene heat-sealing layer, 13 ... Nylon layer, 14 ... Aluminum layer, 1
5...Polyester layer.

Claims (1)

[Claims] Between the exterior material consisting of a pair of aluminum/plastic film laminated sheets formed into a predetermined contour shape,
In a secondary battery in which at least the positive electrode holds a power generation element made of a conductive polymer material, a part of this power generation element is fixed to a frame made of sheet-like plastic, and the periphery of the frame is attached to the exterior material by an adhesive layer. A thin battery characterized by being sealed in a sealed state.