JPH0547368A - Sealed secondary battery and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a battery with a long life and no leak of an electrolyte by covering a current collector metal with epoxy resin, forming a chlorinated polyolefin layer on it, and sticking them to a film substrate via a polyolefin adhesive. CONSTITUTION:A polyolefin adhesive layer 8 is provided on the polyolefin 5 of the first film substrate 4, and a terminal portion constituted of a chlorinated polyolefin layer 3, an epoxy resin layer 2, and a current collector metal 1 is stuck to the substrate 4. An epoxy resin layer 10 and the chlorinated polyolefin layer 3 are formed to cover the metal 1 of a terminal seal section. The polyolefin layer of the same second film substrate 11 as the substrate 4 formed on the layer 3 is stuck to the layer 3 by heat pressure. The adhesion between the current collector metal 1 and the polyolefin resin film substrate 4 is improved, thus a battery having a long life and no leak of an electrolyte from the terminal section is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed secondary battery capable of achieving a long service life and high reliability of a sealed secondary battery, particularly a terminal of a current collector made of lead or lead-based alloy. The present invention relates to a terminal sealing portion structure having excellent sulfuric acid resistance and sealing property in a portion.

[0002]

2. Description of the Related Art With the spread of small devices such as portable devices, the demand for inexpensive and thin sealed secondary batteries is increasing. As a thinning method, for example, Japanese Patent Application No. 63-1
There is a sealed secondary battery described in No. 85085.
In this battery, a positive electrode plate and a negative electrode plate are arranged side by side on the same plane of a plastic film substrate, and a space between each end surface of the positive electrode plate and the negative electrode plate is filled with an electrolyte containing sulfuric acid.
By adopting this structure, the method of advancing the field of the battery reaction due to charging and discharging is not the reaction between the electrode surfaces but the reaction between the electrode end surfaces in the direction parallel to the electrode surfaces. This protects the current collector located at the center of the electrode surface against deterioration, and thus enables reduction in thickness without decreasing battery life even if the electrode thickness is reduced. As a plastic film substrate material on which the electrode plates of this battery are arranged side by side, a polyolefin resin such as polyethylene, polypropylene, ethylene / acrylic acid / maleic anhydride terpolymer, which is an acid resistant polymer, is used. The plastic film substrate also serves as a battery case, the same plastic film as the plastic film substrate is provided on the upper surface, and the upper and lower films include an electrode terminal portion sandwiching the metal plate of the current collector, and the outer periphery thereof is heated. It is sealed to form an airtight structure, which enables economical manufacturing, reliability and weight saving of the battery.

[0003]

However, although the polyolefin-based resin film is in close contact with a current collector made of, for example, lead or a lead-based alloy, it is exposed to sulfuric acid as an electrolyte, moisture in the atmosphere, etc. There is a problem that the adhesive strength gradually weakens and the peel strength decreases.
The present invention has been made in view of the above-mentioned problems, and improves the adhesion between the metal plate of the current collector and the polyolefin-based resin film substrate, and the terminal of the sealed secondary battery that enables the long life of the battery. It is to provide a sealing part structure.

[0004]

In order to solve the above-mentioned problems, the terminal structure according to the present invention is a chlorinated polyolefin or maleic anhydride skeleton containing an epoxy resin and a maleic anhydride skeleton on a metal plate of a current collector. It is characterized in that it has a multi-layered terminal part structure in which a mixed composition of a chlorinated polyolefin containing a and other chlorinated polymer is sequentially applied. In the conventional terminal structure, the metal plate of the current collector is surface-roughened, and the resin of the adhesive such as ethylene / acrylic acid / maleic anhydride terpolymer or chlorinated polyolefin is further formed on the film substrate film. It was a structure in which they were heat-sealed, but in the product of the present invention, the metal plate of the current collector is further coated with an epoxy resin having good acid resistance and water resistance, and a maleic anhydride skeleton is further added. Applying a chlorinated polyolefin resin that has, to cause a chemical bond between the epoxy resin and the chlorinated polyethylene resin through the maleic anhydride skeleton, and by fusing it with the polyolefin adhesive of the film substrate, further collecting current This is different from the prior art in that it has a multi-layered terminal portion structure based on a structure formed by applying epoxy resin or chlorinated polyolefin to the body.

As the epoxy resin, one having good adhesion to the metal of the current collector, and particularly good sulfuric acid resistance in the case of a lead battery, is required. It is important to subject the metal plate surface to general blasting and cleaning treatment in advance. The surface-treated metal sheet is diluted with a mixture of an epoxy resin main agent and a curing agent in a solvent such as methyl ethyl ketone and applied at room temperature, and then cured at an arbitrary temperature and time. Epoxy resin has poor adhesion to plastic film substrates such as polyethylene and polypropylene, so use chlorinated polyolefin such as chlorinated polyethylene and chlorinated polypropylene that has adhesiveness to both, and use epoxy resin for the metal sheet. After the coating and curing, the toluene solution of the chlorinated polyolefin is further applied and dried to form the adhesive layer. The current collector terminal portion thus produced can be easily fused with the film substrate, and the metal plate of the current collector and the film substrate can be firmly bonded and fixed. When chlorinated polyethylene is used among the chlorinated polyolefins, linear low-density polyethylene is particularly suitable as the resin on the adhesive surface of the film substrate, and the highest adhesive strength can be exhibited.

Next, the epoxy resin applied on the collector metal fixed to the film substrate may be applied so as to cover the entire collector metal including the side surfaces so that the polyolefin resin does not come into contact with the collector metal. It is important for ensuring the acid resistance of the body metal surface.

The curing conditions for the epoxy resin may be selected such that the temperature and time are such that the epoxy resin is solidified and not completely cured. As a result, the cyclic skeleton of the maleic anhydride skeleton contained in the chlorinated polyolefin can react with the epoxy group of the epoxy resin or the amine group of the curing agent to form a strong adhesive force. The thickness of the epoxy resin layer should be 5 μm to several tens of μm, and the thickness of the chlorinated polyethylene layer should be 5 μm.
If it has a certain thickness, it becomes an adhesive layer that exhibits a sufficient adhesive force. The temperature of about 130 ° C. to about 200 ° C. is desirable for the conditions for thermocompression bonding to the film substrate with a heat sealer or a press.

[0008]

EXAMPLE Next, an example for confirming the reliability of the terminal portion sealing property of the sealed secondary battery of the present invention will be described. FIG. 1 is a view for explaining a structure of a positive electrode or negative electrode terminal sealing portion of a sealed secondary battery of the present invention, where 1 is a collector metal, 2 is an epoxy resin, 3 is a chlorinated polyolefin, and 4 is a 1 is a film substrate, 5 is a polyolefin, 6 is polyethylene terephthalate, 8 is a polyolefin adhesive, 9 is an epoxy resin, 10 is a chlorinated polyolefin, and 11 is a second film substrate. The surface of the current collector metal 1 of each of the positive electrode and the negative electrode is blasted and washed, and then the epoxy resin 2 having good sulfuric acid resistance is applied and heat-treated at 60 ° C for 50 minutes to form an epoxy resin layer having a thickness of about 20 µm Formed. Next, using chlorinated polypropylene as the chlorinated polyolefin 3, the toluene solution is applied and dried,
A chlorinated polypropylene layer was formed. This was punched into a positive electrode pattern and a negative electrode pattern, and the chlorinated polypropylene layer of the produced positive electrode plate and negative electrode plate and the polypropylene layer of the first film substrate were bonded by thermocompression bonding at a temperature of about 150 ° C. At that time, the portion corresponding to the terminal sealing portion is formed by thermocompression bonding after further forming a chlorinated polypropylene layer as the polyolefin adhesive 8 on the polypropylene layer as the polyolefin 5 of the first film substrate 4 to a thickness of about 6 μm. Glued.

Next, an epoxy resin 9 is applied so as to wrap the collector metal 1 and heat treated at 60 ° C. for 50 minutes, and then chlorinated polypropylene as the chlorinated polyolefin 10 is applied and dried. .. Then, a second film substrate having the same structure as the first film substrate is formed so that an electrode and an electrolyte containing 46% sulfuric acid are prepared and the first film substrate on which these electrode groups are arranged is wrapped. The terminal portion was covered and heat-sealed at a temperature of 210 ° C. using a heat sealer so that the polypropylene of the second film substrate and the chlorinated polypropylene were fused to each other, and the terminal sealing portion shown in FIG. 1 was produced. The secondary battery manufactured in this manner has a capacity of 70 mAh at a 20-hour rate of 25 ° C. and 2.4.
Cycle life test of discharge under the conditions of constant voltage of 5V, maximum charge current 17.5mA, charge time 6 hours and discharge current 17.5mA, discharge end voltage 1.7V, rest time 1 hour. As a result, no decrease in capacity was observed for 200 cycles.

As a comparative example, the same procedure as in the example was carried out except that the step of wrapping the current collector metal 1 with the epoxy resin 9 was omitted and the current collector metal 1 was directly coated with chlorinated polypropylene as the chlorinated polyolefin 10. To produce a sealed secondary battery. The capacity was 70 mAh, and when a cycle life test was conducted in the same manner as in the example, the capacity after 200 cycles was reduced to 40 mAh. Further, the surface of the current collector metal of the positive electrode terminal was changed from lead color to black of lead oxide, which is considered to be generated by immersion in sulfuric acid.

[0011]

As described above, according to the present invention, the current collector metal of the terminal portion of the sealed secondary battery is covered with the epoxy resin having good sulfuric acid resistance and water resistance, and then the epoxy resin and the film. A chlorinated polyolefin having a maleic anhydride skeleton capable of having a strong adhesive force with both the polyolefin resin of the substrate is formed on the polyolefin resin layer, and the polyolefin resin layer is provided on the inside of the battery. Since it has a terminal sealing portion structure in which the portion is heat-sealed, there is no leakage of the electrolytic solution from the terminal portion, and a sealed secondary battery having a long life can be manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a terminal sealing portion structure of a sealed secondary battery of the present invention.

[Explanation of symbols]

1 is a collector metal, 2 is an epoxy resin, 3 is a chlorinated polyolefin, 4 is a first film substrate, 5 is a polyolefin, 6 is polyethylene terephthalate, 7 is aluminum, 8 is a polyolefin adhesive, and 9 is an epoxy resin. ,
10 is a chlorinated polyolefin, 11 is a second film substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinori Hasuda 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Inventor Keiji Akakudo 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A positive electrode plate and a negative electrode plate are disposed on the same plane of a film substrate, an electrolyte is filled in a gap between the positive electrode plate and the negative electrode plate, and the positive electrode plate is provided on an upper surface of the first film substrate. A second film substrate, which is the same as the first film substrate, is disposed so as to cover the negative electrode plate and the electrolyte, and the outer peripheries of the first and second film substrates are heat-sealed to form a hermetically sealed structure. In a secondary battery, the metal of the terminal portion is sequentially covered with a chlorinated polyolefin containing an epoxy resin and a maleic anhydride skeleton, and the terminal sealing portion is obtained by heat-sealing the terminal portion with the first and second film substrates. A sealed secondary battery having a structure. 2. A polyolefin adhesive layer of chlorinated polyolefin or the like is previously formed on the first film substrate, and a chlorinated polyolefin layer of a terminal portion composed of it and a chlorinated polyolefin layer / epoxy resin layer / collector metal. Then, an epoxy resin layer and a chlorinated polyolefin layer are sequentially formed so as to cover the collector metal surface of the terminal sealing portion, and then the second layer is formed on the chlorinated polyolefin layer.
A method for producing a sealed secondary battery, characterized in that the film substrate of (1) is placed, and the polyolefin layer of the second film substrate is bonded by thermocompression bonding to form a terminal sealing portion.