JPH0587946B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a metal sheet forming a current collector that enables a long life and high reliability of a thin battery, and a thin battery using the same. The present invention relates to a manufacturing method, and particularly to a metal sheet of lead or lead-based alloy on which an adhesive layer is formed, and a method of manufacturing a thin battery using the same.

[Conventional technology]

With the spread of small devices such as portable devices,
Demand for inexpensive, thin, sealed secondary batteries is increasing. As a method for making the battery thinner, for example, there is a sealed secondary battery described in Japanese Patent Application No. 185085/1985 previously filed by the applicant of the present invention.

In this secondary 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 the space between each end face of the positive electrode plate and the negative electrode plate is filled with an electrolyte containing sulfuric acid. The positive electrode plate and the negative electrode plate are formed by coating or filling a positive electrode current collector and a negative electrode current collector with a positive electrode active material and a negative electrode active material, respectively.

The metal sheet for the current collector may only be surface roughened, or it may be coated with one or two layers of the same resin as the film substrate or a resin such as ethylene/acrylic acid/maleic anhydride terpolymer. It is a metal sheet with a layered structure.

By adopting the above-mentioned structure, the positive electrode current collector and negative electrode current collector do not deteriorate due to oxidation corrosion from the surface in contact with the film substrate, so even if the electrode thickness becomes thinner, the battery life does not decrease. This makes it possible to make the battery thinner without having to do so.

Furthermore, even in a sealed battery in which the positive and negative plates are fixed on different film substrates, the current collector surface that comes into contact with the film substrate is protected from being exposed to sulfuric acid contained in the electrolyte. It is similar to the battery.

As the plastic film substrate on which the electrode plates of these batteries are installed, polyolefin resin films such as polyethylene and polypropylene, which are acid-resistant polymers, are used. Examples of adhesives used in polyolefin resin films include films of ethylene/acrylic acid/maleic anhydride terpolymer described in Japanese Patent Application No. 1-168531 previously filed by the present applicant. There is an adhesive.

This plastic film substrate also serves as a battery case. A plastic film made of the same material as the plastic film substrate is provided on the top surface, and the outer peripheries of the upper and lower films are heat-sealed to form a sealed structure, which improves the economical manufacturability of the battery.
This enables reliability and weight reduction.

[Problem to be solved by the invention]

However, although polyolefin resin films or film adhesives such as polyethylene and polypropylene adhere to current collectors made of lead or lead-based alloys, the adhesion gradually weakens when exposed to sulfuric acid contained in the electrolyte. The problem is that the peel strength decreases.

One method for solving this problem is a multilayer metal sheet described in Japanese Patent Application No. 1-299865 previously filed by the present applicant. This sheet is a multilayer metal sheet made by sequentially applying epoxy resin and chlorinated polyethylene to a metal sheet for the current collector, and it is a reliable metal sheet for the current collector and the plastic film substrate that also serves as the battery case. This enables highly durable adhesion. However, since the adhesive temperature at which high adhesive strength is developed is only in a narrow temperature range around 150°C, there is a problem in that the reproducibility of adhesive strength is affected by the environmental temperature.

The present invention has been made in view of the above-mentioned problems, and provides a metal sheet for thin batteries and a metal sheet for a thin battery that improves the adhesion between the metal sheet of the current collector and the polyolefin resin film substrate and makes it possible to extend the life of the battery. The object of the present invention is to provide a method for manufacturing a thin battery using the same.

[Means to solve the problem]

In order to achieve such an object, the multilayer metal sheet of the present invention has a positive electrode plate and a negative electrode plate disposed on the same plane of a film substrate, and the gap between the positive electrode plate and the negative electrode plate is filled with an electrolyte. In a metal sheet for a current collector used to form the positive electrode plate and negative electrode plate of a thin battery formed into a bag shape by heat-sealing the outer periphery of two film substrates so as to cover the electrode plate group, The metal sheet has an epoxy resin layer on the surface of the metal thin layer and at least one of a chlorinated polypropylene containing a maleic anhydride skeleton or a mixed composition layer of chlorinated polypropylene containing a maleic anhydride skeleton and diglycidyl ether. It is characterized by being coated in one layer.

Further, in the method for manufacturing a thin battery of the present invention, a positive electrode plate and a negative electrode plate are arranged on the same plane of a film substrate, and a gap between the positive electrode plate and the negative electrode plate is covered with an electrode plate group filled with an electrolyte. In the thin battery manufacturing method in which the outer circumferences of two film substrates are heat-sealed to form a bag shape, an epoxy resin layer is formed on the surface of each metal sheet for a current collector forming the positive electrode plate and the negative electrode plate. a step of applying at least one layer of a chlorinated polypropylene layer containing a maleic anhydride skeleton or a mixed composition layer of a chlorinated polypropylene containing a maleic anhydride skeleton and diglycidyl ether; The method is characterized by including a step of thermocompression bonding the coated layer and the film substrate at 130 to 210°C.

[Function] In the present invention, an epoxy resin layer is formed on a metal sheet for a current collector, and chlorinated polypropylene containing a maleic anhydride skeleton or chlorine containing a maleic anhydride skeleton is further applied on the epoxy resin layer. A mixed composition of chlorinated polypropylene and diglycidyl ether (hereinafter abbreviated as MA-containing chlorinated polypropylene) layer is formed, and the epoxy resin layer and MA
A three-layer mixture of metal, epoxy resin, and MA-containing chlorinated polypropylene is formed by forming chemical bonds with the MA-containing chlorinated polypropylene layer through the maleic anhydride skeleton in the MA-containing chlorinated polypropylene.
It is a metal sheet with a multilayer structure based on a layered structure.

The epoxy resin is preferably one that has good adhesion to the metal for the current collector, and in the case of lead batteries, it must have particularly good sulfuric acid resistance.
It is desirable to use an amine-based curing agent for curing the epoxy resin.

It is important that the metal sheet surface of the current collector to which the epoxy resin is applied be previously subjected to general blasting and cleaning treatments. A mixture of a base epoxy resin and a curing agent is applied to a surface-treated metal sheet using a bar coater at room temperature, and cured at a desired temperature and curing time.

Epoxy resin has poor adhesion to plastic film substrates such as polyethylene and polypropylene, so it has poor adhesion to both.
A toluene solution of MA-containing chlorinated polypropylene is applied to the epoxy resin surface using a bar coater and dried to produce a multilayer metal sheet.

The thus produced multilayer metal sheet for a current collector can be firmly adhesively fixed by being pressure-bonded to a film substrate. MA-containing chlorinated polypropylene can exhibit the highest adhesive strength, particularly when the resin on the adhesive surface of the film substrate is polypropylene.

The curing conditions for the epoxy resin described above may be such that the temperature and curing time are such that the epoxy resin is solidified but not completely cured. By choosing such temperature and curing time, MA
The cyclic skeleton of the maleic anhydride skeleton in the chlorinated polypropylene contained can react with the epoxy group of the epoxy resin or the amine group of the curing agent to form strong adhesive strength.

The thickness of the epoxy resin layer may range from 5 μm to several tens of μm, and the thickness of the MA-containing chlorinated polypropylene layer may be approximately 5 μm, resulting in a multilayer metal sheet that exhibits sufficient adhesive strength.

The conditions for thermocompression bonding the multilayer metal sheet to the film substrate using a heat sealer or press machine are as follows: If the bonding surface of the film substrate is polypropylene resin, the temperature must be below the melting point of polypropylene.
Maximum adhesive strength is obtained when thermocompression bonding is performed in the range of 130°C to 220°C, which is above the melting point of polypropylene.

[Example] Examples for confirming the performance of the multilayer metal sheet of the present invention are shown below.

Example 1 FIG. 1 is a diagram illustrating an example of the multilayer metal sheet of the present invention. Here, 1 is a metal layer, 2 is an epoxy resin layer, and 3 is an MA-containing chlorinated polypropylene layer. A lead sheet with a thickness of 100 μm was used as the metal layer 1, and after its surface was blasted, it was cleaned in acetone using an ultrasonic cleaner.

Next, a 4:1 mixture of epoxy resin base and curing agent was applied to metal layer 1, and the mixture was heated to 60℃ for 60 minutes.
After curing for minutes, the epoxy resin layer 2 with a thickness of about 30 μm
was formed.

Next, apply a toluene solution of MA-containing chlorinated polypropylene to epoxy layer 2 and air dry it to reduce the thickness.
A 6 μm MA-containing chlorinated polypropylene layer 3 was formed.

The surface of the MA-containing chlorinated polypropylene layer 3 of the multilayer metal sheet thus formed and the film substrate made of polypropylene were adhered using a heat sealer at a pressure of 1 kg/cm ² for 10 seconds, and the 180 degree peel strength was measured. did.

Peel strength reaches maximum value when bonding temperature is 150℃
It showed 500g/cm. The peel strength at various bonding temperatures is as shown in Figure 2.
The results showed high values in the range of 210℃.

Next, a film substrate was placed on the multilayer metal sheet, the three sides were sealed under the above conditions (adhesion for 10 seconds at a pressure of 1 kg/cm ² ), and 40% sulfuric acid was injected into it and sealed into a bag shape. Leave it for a month to 180% of the seal area.
The peel strength was measured, but the peel strength was
500 g/cm, and no decrease in peel strength was observed.

Example 2 A multilayer metal sheet was prepared in the same manner as in Example 1, except that the MA-containing chlorinated polypropylene layer 3 was formed using a mixed composition of chlorinated polypropylene containing a maleic anhydride skeleton and bisphenol diglycidyl ether. Formed. The 180 degree peel strength using this product was 600 g/cm at 150°C, which is a high value.

Next, a comparative example for comparison with Examples 1 and 2 will be shown.

Comparative Example 1 The surface of a 100 μm thick lead sheet was subjected to blasting and cleaning treatment, and was adhered to a film substrate with a polypropylene layer as an adherend at a temperature of 220°C using a heat sealer in the same manner as in Example 1. .

The 180 degree peel strength at that time was 100 g/cm, which was a low value. In addition, the peel strength after being exposed to sulfuric acid for one week as in Example 1 was 5 g/cm,
Furthermore, the peel strength decreased.

Comparative Example 2 A metal sheet was produced in the same manner as in Comparative Example 1, except that a 100 μm thick lead sheet coated with a resin of ethylene/acrylic acid/maleic anhydride terpolymer was used, and was adhered to a film substrate.

The 180 degree peel strength at that time was 450 g/cm, which was a good value. However, the peel strength after one week of exposure to sulfuric acid in the same manner as in Example 1 was
It was 100g/cm and decreased.

It goes without saying that the multilayer metal sheets of Examples 1 and 2 can be applied to both primary batteries and secondary batteries.

〔Effect of the invention〕

As explained above, in the present invention, chlorinated polypropylene having a maleic anhydride skeleton that chemically bonds with an epoxy resin having good sulfuric acid resistance is used.
It was applied sequentially to the metal sheet for the current collector that forms the electrode plate, resulting in a metal sheet with a multilayer structure.
This has the advantage that highly reliable adhesive strength can be obtained between the film substrate, which is also a battery case, and the metal sheet, which is a current collector.

Furthermore, since the adhesive strength can be achieved at a temperature below the melting point of polypropylene, there is an advantage that deformation of the film substrate is prevented and, therefore, electrode positional displacement of the thin battery does not occur.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a multilayer metal sheet according to a first embodiment of the present invention, and FIG. 2 is a diagram showing the peel strength of the multilayer metal sheet shown in FIG. 1 with respect to bonding temperature. 1...Metal layer, 2...Epoxy resin layer, 3...
MA-containing chlorinated polypropylene layer.

Claims (1)

[Scope of Claims] 1. A positive electrode plate and a negative electrode plate are arranged on the same plane of a film substrate, and two films are arranged in a gap between the positive electrode plate and the negative electrode plate so as to cover a group of electrode plates filled with electrolyte. In a metal sheet for a current collector used to form the positive electrode plate and the negative electrode plate of a thin battery formed into a bag shape by heat-sealing the outer periphery of a substrate, the metal sheet is attached to the surface of the thin metal layer. It is characterized by being coated with an epoxy resin layer and at least one of a chlorinated polypropylene containing a maleic anhydride skeleton or a mixed composition layer of chlorinated polypropylene containing a maleic anhydride skeleton and diglycidyl ether. Multilayer metal sheet for thin batteries. 2 A positive electrode plate and a negative electrode plate are arranged on the same plane of a film substrate, and the outer periphery of the two film substrates is heat-sealed so as to cover the electrode plate group filled with electrolyte in the gap between the positive electrode plate and the negative electrode plate. A method for manufacturing a thin battery formed into a bag shape by applying an epoxy resin layer to a metal sheet surface for each current collector forming the positive electrode plate and the negative electrode plate, a step of applying at least one layer of a chlorinated polypropylene layer or a mixed composition layer of chlorinated polypropylene containing a maleic anhydride skeleton and diglycidyl ether, and combining this applied layer with the film substrate.
A method for manufacturing a thin battery, comprising a step of thermocompression bonding at 130 to 210°C.