JPH11345599A - Sheet type electrochemical element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the strength at which the external connection terminals of a sheet type electrochemical element such as a lithium ion battery are secured to a sheath. SOLUTION: This electrochemical element includes a structure whereby an electrode-electrolyte structure having electrodes placed on both sides of a polymer solid electrolyte is sealed in a sheath 6, and the inner surface of the sheath 6 is formed of a polyolefin film 6b. Each side of each external connection terminal 7, 8 connected to the electrodes has an acid-denatured polyolefin 9 applied to its portion sealed by the sheath, and the sealed portion is heat sealed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-type electrochemical element such as a sheet-type battery, an electric double-layer capacitor, and the like, and a method of manufacturing the same. The present invention relates to a chemical element and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, secondary batteries using a carbon material, tin oxide, silicon oxide or the like as a negative electrode active material called a lithium ion secondary battery have been studied for use in various electronic products and electric vehicles. I have. These lithium ion secondary batteries use a so-called electrolytic solution in which an electrolyte salt is dissolved in a liquid solvent. Batteries using an electrolytic solution have the advantage of low internal resistance, but, on the other hand, have the problem of liability to leak and ignition. To address such problems, for example, a gel polymer solid electrolyte comprising a polymer, an electrolyte salt and a solvent has recently been spotlighted. Some of these gel-like polymer solid electrolytes have a conductivity close to that of a liquid and exhibit a value on the order of 10 ⁻³ S · cm ⁻¹ .

A battery using a solid polymer electrolyte does not leak because it does not use a liquid electrolyte. Therefore,
Unlike a conventional battery using a liquid electrolyte, it is not necessary to mechanically caulk with a metal container and a polymer packing therebetween. The polymer solid electrolyte battery can prevent liquid leakage by using a laminate film composed of a polymer film and a metal foil as an exterior (container).

[0004]

However, depending on the type of the polymer forming the laminate film as the exterior, the adhesion between the external connection terminal connected to the battery electrode and the laminate film is insufficient and the external The connection terminals were not fixed properly.

Although a laminated film can be used as an exterior in an electric double layer capacitor or the like using a solid polymer electrolyte, the same problem occurs.

The present inventors have studied various polymers in order to improve the above-mentioned drawbacks. As a result, the present inventors have examined various types of polymers, and found that sheet-type electrochemical devices such as batteries and electric double-layer capacitors using this kind of polymer solid electrolyte. The sheet-type electrochemical element using an external connection terminal coated with an acid-modified polyolefin is a sheet-type electrochemical element whose inner surface is a polyolefin, which can be used as an exterior body of the laminate film. It has been found that the fixing strength of the external connection terminal is sufficiently large because of its excellent performance.

Japanese Patent Application Laid-Open No. Hei 8-287889 proposes a two-layer resin film in addition to a laminate film as an exterior body, but does not improve the fixing strength of external connection terminals. .

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide a sheet-type electrochemical element in which the strength of fixing an external connection terminal to an exterior body and a method of manufacturing the same are provided.

Other objects and novel features of the present invention will be clarified in embodiments described later.

[0010]

In order to achieve the above object, a sheet-type electrochemical element of the present invention has an electrode / electrolyte structure in which electrodes are disposed on both sides of a solid polymer electrolyte and is sealed in an outer package. In the configuration, the inner surface of the outer package is made of polyolefin, and an acid-modified polyolefin is applied to portions sealed on both surfaces of the external connection terminals connected to the electrodes by the outer package.

In the sheet-type electrochemical device, a through hole is formed in a sealing portion of the external connection terminal on both sides sealed by the exterior body, and the exterior body surface and the external connection terminal are formed at the portion. It may be configured to perform heat fusion.

The method of manufacturing a sheet-type electrochemical device according to the present invention is characterized in that an external connection terminal is connected to the electrode of the electrode / electrolyte structure in which electrodes are arranged on both sides of the polymer solid electrolyte; An acid-denatured polyolefin is applied to the sealing portion of the exterior body on both sides, and the electrode / electrolyte structure is sealed in the interior of the polyolefin exterior body, and the interior surface of the exterior body and the external connection terminal are heated. It is characterized by being fused.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a sheet-type electrochemical device and a method for manufacturing the same according to the present invention will be described below with reference to the drawings.

An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an enlarged cross-sectional view of a main part of a sheet-type lithium ion secondary battery as an electrochemical element, and FIG. 2 is a front cross-sectional view of the entire configuration of the sheet-type lithium ion secondary battery. It is one. FIG. 3 is a plan view of the same, and FIG. 4 is a plan view of a current collector. In these figures, 1 is a positive electrode,
Reference numeral 2 denotes a negative electrode, 3 denotes a separator of a polymer solid electrolyte interposed between the positive and negative electrodes, and a positive electrode 1 is provided with an aluminum current collector 4 and a negative electrode 2 is provided with a copper current collector 5 laminated and integrated. , And the battery body 10 (electrode / electrolyte structure). As shown in FIG. 4, the current collectors 4, 5 have tongue pieces 4a, 5a for connecting the external connection terminals 7, 8, to which the external connection terminals 7, 8 are respectively welded. The current collector 4 and the external connection terminal 7 to be welded to the same are made of the same metal material (or a material that is easily welded). Similarly, the current collector 5 and the external connection terminal 8 are made of the same metal material (or welded). It is preferable that the material is easy to use.

The outer package (sealed container) 6 is a laminated bag of a metal foil 6a such as an aluminum foil, a polyolefin (polypropylene or the like) film 6b inside the metal foil 6a and an insulating film 6c such as a polyamide or polyester outside the metal foil. The inner surface is a polyolefin film 6b.
Further, an acid-modified polyolefin (such as acid-modified polypropylene) 9 is applied to portions of the external connection terminals 7 and 8 which are sealed by the outer package 6 on both surfaces. Then, the battery element body 10 to which the external connection terminals 7 and 8 are welded is housed in the exterior body 6 of a laminate bag having polyolefin as an inner surface,
The opening (the hatched portion in FIG. 3) of the exterior body 6 is sealed (heat-sealed) by heating and pressurizing the opening (the hatched portion in FIG. 3) with the distal ends of the external connection terminals 7 and 8 drawn out.

An acid-modified polypropylene, which is one type of the acid-modified polyolefin, is sold by Mitsui Chemicals, Inc. under the trade name “UNISTOL (liquid polyolefin adhesive)”. The acid-modified polyolefin has a carboxyl group in the molecule and therefore has good adhesion to metals (aluminum, copper, iron, stainless steel, etc.), polyolefins, and the like. Also, the heat resistance is excellent. The application of the acid-modified polyolefin 9 to the external connection terminals 7 and 8 is performed by spraying a dispersion in which the acid-modified polyolefin is dispersed in toluene or the like to a necessary portion of the terminal (a portion sealed with an exterior body) by spraying or the like. I just need.

According to this embodiment, the inner surface of the outer package 6 is made of polyolefin, and the acid-modified polyolefin 9 is arranged between the polyolefin and the external connection terminals 7 and 8, so that the outer package 6 is Because of the excellent adhesion to the terminals 7 and 8, the terminals 7 and 8 can be sufficiently fixed for practical use, and the tensile strength can be improved.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to a case where a sheet type lithium ion secondary battery is constructed.

[Example 1] As an acid-modified polypropylene which is a kind of acid-modified polyolefin, Mitsui Chemicals, Inc.
"UNISTOR R-200" was used. Unistal R
-200 is a dispersion in which acid-modified polypropylene fine particles are dispersed in toluene. Unistall R-2
00 was sprayed onto aluminum foil and nickel foil having a width of about 4 mm, a length of about 40 mm, and a thickness of 0.1 mm. After the application, the film was put in a drying oven at 200 ° C. for 10 minutes and adhered. These foils become the external connection terminals 7 and 8.

The electrode 1 was prepared by a doctor blade method in which the positive electrode 1 was composed of an active material LiCoO ₂ , a conductive auxiliary carbon black (HS-100, manufactured by Denki Kagaku Kogyo), and a binder PVDF (polyvinylidene fluoride). . The negative electrode 2 was made of a material composed of active material mesocarbon microbeads (MCMB), a conductive aid HS-100, and a binder PVDF by a doctor blade method. The separator 3 is PVDF,
An article made of SiO ₂ was prepared by a doctor blade method. The positive electrode and the negative electrode were cut into a rectangular shape having a width of 31 mm and a length of 41 mm. The separator was cut into a rectangular shape having a width of 33 mm and a length of 43 mm. The current collectors 4 and 5 (the composition of ethylene acrylic acid copolymer and carbon black are applied to expanded metal made of aluminum and copper) have a rectangular shape having a width of 29 mm and a length of 39 mm as shown in FIG. The terminal connection portion was cut while leaving a tongue piece having a width of 7 mm and a length of 8 mm.

The fabrication of the battery body 10 was performed as follows.
First, the positive electrode 1 and the separator 3 were laminated and laminated by hot pressing. Laminating condition is 130 ° C, pressure 3kgcm
^The pressure was increased by ^-2 for 2 minutes. A negative electrode was laminated thereon and laminated similarly. A current collector 4 made of aluminum was laminated on the positive electrode and similarly laminated. The negative electrode 2 was similarly laminated with a copper current collector 5.

An aluminum terminal 7 was welded to the aluminum current collector 4 of the battery body 10 and a nickel terminal 8 was welded to the copper current collector 5. This was immersed for 1 hour in 330 ml of an electrolytic solution obtained by dissolving 1 M of LiPF _{6 in} a mixed solvent of EC (ethylene carbonate) and DMC (dimethyl carbonate) at a volume ratio of 1: 2. After taking out the battery body from the electrolyte, the electrolyte adhering to the electrode surface was wiped off. This battery element absorbed the electrolytic solution and became a gel state. The battery body is formed of an exterior body 6 made of polypropylene on the inner surface.
(Laminate bag of aluminum foil, polypropylene film and polyethylene terephthalate), and the opening was heat-sealed (heat-sealed) to produce a sheet-type lithium ion secondary battery. As shown in Table 1 below, the battery of Example 1 using the terminal obtained by applying acid-modified polypropylene to the external connection terminals 7 and 8 as the acid-modified polyolefin 9 has excellent tensile strength of the external connection terminals 7 and 8. I was

Table 1 Sample Terminal Tensile Strength (kgf) Example 1 Aluminum 3.1 〃 3.2 〃 3.0 ニ ッ ケ ル Nickel 13.0 〃 11.5 〃 10.2 Example 2 Aluminum 3. 5 〃 〃 4.0 ４ 〃 4.5 ニ ッ ケ ル Nickel 14.0 〃 １４ 14.5 〃． 15.0 Comparative Example 1 Aluminum 1.3 〃 1.7 〃 1.0 〃 Nickel 1.4 2.3 〃 1.7

[Example 2] A sheet mold was used in the same manner as in Example 1 except that external connection terminals 7 and 8 having a large number of small through holes 11 were used in the sealed portion of the exterior body as shown in FIG. A lithium ion secondary battery was manufactured. FIG.
The same reference numerals are given to the same or corresponding parts as in Example 1. The battery of Example 2 had excellent tensile strength as shown in Table 1 above. It is considered that the reason for this is that, when the exterior body 6 and the external connection terminals 7 and 8 are heat-sealed, the polypropylene on the interior surface of the exterior body gets into the through-hole 11.

Comparative Example 1 A sheet-type lithium ion secondary battery was manufactured in the same manner as in Example 1 except that an external connection terminal not coated with an acid-modified polyolefin was used.
As shown in Table 1, the battery of Comparative Example 1 was inferior in tensile strength to Example 1.

In the above-described embodiments and examples, the case where the battery is formed as the electrode / electrolyte structure is exemplified. However, the present invention can be applied to a sheet type electrochemical element such as an electric double layer capacitor. . In an electric double layer capacitor, a polarizable electrode using activated carbon or the like as an active material may be used instead of the positive electrode and the negative electrode.

The acid-modified polyolefin is available from Chuo Rika Kogyo Co., Ltd. under the trade name "Aquatex" and Sumitomo Seika Co., Ltd. in addition to the trade name "UNISTOL" from Mitsui Chemicals, Inc.
Some are sold as liquid polyolefin-based adhesives under the trade names “Seporjon”, “Siixen”, and “CSM latex”, and these can also be used.

Although the embodiments of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited to the embodiments and various modifications and changes can be made within the scope of the claims. There will be.

[0029]

As described above, according to the present invention,
By coating the external connection terminal with an acid-modified polyolefin such that the inner surface of the outer package is polyolefin and the acid-modified polyolefin is interposed between the polyolefin and the external connection terminal, the outer package and the external connection terminal Can be improved, and the fixing strength of the external connection terminal can be improved, and the fixing of the external connection terminal is sufficiently strong for practical use.

Further, if a through hole is provided in a part of the external connection terminal, and the exterior body and the external connection terminal are heat-sealed at the part of the through hole, the exterior body is provided in the through hole. The polyolefin on the surface is engaged, and the fixing strength of the external connection terminal is improved.

[Brief description of the drawings]

FIG. 1 is an essential part enlarged sectional view showing a case where a sheet-type lithium ion secondary battery is configured according to an embodiment (Example 1) of the present invention.

FIG. 2 is a front sectional view showing the entire configuration of the embodiment (Example 1).

FIG. 3 is a plan view of the same.

FIG. 4 is a plan view showing a current collector used in the embodiment (Example 1).

FIG. 5 is an enlarged sectional view of a main part of a second embodiment of the present invention.

FIG. 6 is a plan view of an external connection terminal used in a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4,5 Current collector 6 Outer case 7,8 External connection terminal 9 Acid-modified polyolefin 10 Battery element 11 Through hole

 ──────────────────────────────────────────────────の Continuing on the front page (72) Katsuo Naoi Inventor, TDK Corporation, 1-13-1 Nihonbashi, Chuo-ku, Tokyo

Claims (3)

[Claims] 1. A sheet-type electrochemical element in which an electrode / electrolyte structure in which electrodes are arranged on both sides of a polymer solid electrolyte is hermetically sealed in an outer case, wherein the inner surface of the outer case is made of polyolefin and connected to the electrode. An acid-modified polyolefin is coated on both sides of the terminal for external connection sealed by the outer package. 2. A through-hole is formed in a portion of the external connection terminal sealed by the exterior body on both sides, and the exterior interior surface and the external connection terminal are heat-sealed at the portion. The sheet-type electrochemical device according to claim 1. 3. An external connection terminal is connected to the electrode of the electrode / electrolyte structure in which electrodes are arranged on both sides of the solid polymer electrolyte, and an acid-denatured portion of the external connection terminal is sealed by the outer package on both surfaces. A sheet-type electric device, characterized in that a polyolefin is applied, and the electrode / electrolyte structure is sealed inside with a polyolefin exterior, and the exterior interior surface and the external connection terminal are heat-sealed. Manufacturing method of chemical element.