JPS5856467B2 - Battery manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an organic electrolyte battery using a light metal as a negative electrode active material.

More specifically, the present invention aims to improve a method for manufacturing batteries using an electrolyte gelled with polymethyl methacrylate, a polymer that is soluble in organic electrolytes but does not directly participate in battery reactions.

Batteries currently on the market as power sources for electronic devices are:
Silver batteries and mercury batteries are the mainstream, but because these use an aqueous solution of caustic potash or caustic soda as an electrolyte,
It inherently has creep properties.

In addition, due to the interaction with the electrode potential, liquid leakage may occur if stored for a long period of time even at room temperature, potentially causing serious damage to the equipment in use.

On the other hand, in organic electrolyte batteries, the electrolyte is non-aqueous and uses a highly viscous solvent, and past experimental results show that they are extremely unlikely to leak compared to batteries using alkaline electrolytes. However, when stored at high temperatures, leakage may occur due to improper sealing, which is not uncommon.

Leakage has a serious impact on the performance of the device, so it is considered more important than battery performance.

Therefore, the most effective way to eliminate leakage is to immobilize the electrolyte.

Generally, when an electrolyte is immobilized, the ionic conductivity tends to decrease and the battery output also tends to decrease, so it is important to determine how to immobilize the electrolyte while minimizing the decrease in ionic conductivity.

As a method for immobilizing the electrolyte, the present inventors proposed a method of producing a gel using polymethyl methacrylate.

This gel is obtained as follows.

First, 20 to 40% by weight of polymethyl methacrylate is added to an electrolytic solution in which polymethyl methacrylate is dissolved, such as a predetermined concentration electrolytic solution of propylene carbonate or r-butyrolactone lithium borofluoride or lithium perchlorate.
When heated to 100°C, it becomes a sol.

When this is cooled, a jelly-like gel is formed.

Even when this gel is stored at 60°C, no syneresis phenomenon is observed, so batteries using this gel electrolyte do not leak.

Polymethyl methacrylate gel is electrochemically stable and has an ionic conductivity of approximately 10-3 Ω-1 cm.
, 1, which is about two orders of magnitude larger than that of solid electrolytes such as lithium iodide, and is sufficient in terms of battery performance.

However, it is somewhat sticky and adhesive due to the cohesive energy caused by its molecular structure, so it is somewhat difficult to cut it into thin pieces like agar, for example, and place it between the positive and negative electrodes.

Therefore, methods such as applying it to a polypropylene nonwoven fabric and placing it between the positive and negative electrodes have been considered, but the process for assembling the battery is complicated.

In view of the above points, the present invention provides a method for manufacturing a battery that is easy to assemble and has excellent performance.

That is, an electrolytic solution in which polymethyl methacrylate constituting the gel electrolyte is mixed and dispersed is injected into a battery container, sealed, and then heated to form a gel and fix the electrolyte.

According to the method of the present invention, in the battery assembly process,
Since there is no need to handle sticky substances such as sol or gel, a leak-free battery can be obtained using almost the same manufacturing method as when using a conventional liquid electrolyte.

Hereinafter, the present invention will be explained with reference to examples thereof.

Example 1 In FIG. 1, 1 is a case made of stainless steel, 2 is a sealing plate made of the same material, and 3 is a grid welded to the inner surface of the sealing plate. A lithium sheet 4 as a negative electrode is placed on the surface of this grid. It is crimped.

5 is a positive electrode containing gel, 100 parts by weight of fluorocarbon;
10 parts by weight of acetylene black, 20 parts by weight of fluororesin binder
22 parts by weight and polymethyl methacrylate microspheres (diameter 0.05-0.15 mm) with a molecular weight of 700,000 to 750,000.
．． 0.31 g of a mixture of 5 parts by weight was molded into a disk shape.

6 is a titanium grid welded to the inner surface of the case 1.

7 is a liquid retaining material made of a polypropylene woven fabric, and 8 is a separator made of a polypropylene nonwoven fabric.

The method for manufacturing this battery is as follows.

First, the sealing plate is turned upside down, lithium is pressure-bonded to the grid 3, and the liquid retaining material 7 is placed on top of it.

Next, the polymethyl methacrylate microspheres 459 are dispersed in 30 cc of a propylene carbonate solution in which 1 mol/l of lithium borofluoride is dissolved, and when 0.3 cc of this is poured onto the liquid retaining material, polymer microspheres are formed. remains on the liquid retaining material.

This L is covered with the separator 8, the positive electrode molded body 5, and the case 1, and sealed.

9 is a polypropylene gasket molded integrally with the sealing plate.

The positive electrode absorbs about 0.15 cc of electrolyte. When this battery is heated at 70° C. overnight, polymethyl methacrylate dissolves and gels inside the battery, forming a substantially uniform gel with a polymer concentration of about 30% by weight.

Example 2 As a positive electrode, 0.26% of a positive electrode mixture having the same components and composition as Example 1 except that polymethyl methacrylate was not mixed was used.
9 molded into a disk shape is used.

Then, 0.30 cc of the polymethyl methacrylate microspheres 459 dispersed in 15 cc of a propylene carbonate solution containing 1 mol/l of lithium borofluoride was poured into the solution in the same manner as in Example 1, and the cap was sealed. to configure the battery,
Heat treatment was performed at 70°C overnight.

A gel was formed inside the battery as in Example 1.

Comparative Example In a conventional battery, a positive electrode was impregnated under reduced pressure with a heated sol of a mixture of propylene carbonate solution containing 1 mol/l of lithium borofluoride and polymethyl methacrylate.

A similar thermosol is also applied to the liquid retaining material and cooled to form a gel.

The other configurations are the same as in the first embodiment.

Examples 1 and 2 and Comparative Example Batteries A, B-, and C-2
The electrical characteristics at 0°C are shown in the table below, and the electrical characteristics at 20°C are as follows:
Figure 2 shows the discharge characteristics of Ω.

As is clear from the following results, the battery according to the present invention is superior in performance to batteries manufactured using conventional methods.

This is thought to be due to the excellent adhesion of the gel electrolyte to the positive and negative electrodes, and the uniformity of the gel inside the battery.

Further, according to the present invention, the manufacturing process can be streamlined compared to the case where a conventional gel electrolyte is used, since almost the same process as that for a battery using a conventional liquid organic electrolyte is required.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal cross-sectional view of a fluorocarbon-notium battery according to an embodiment of the present invention, and FIG. 2 shows discharge characteristics of batteries produced by various manufacturing methods. 4... Negative electrode, 5... Positive electrode, 7... Liquid-containing material, 8... Separator.

Claims (1)

[Claims] 1. A method for manufacturing a battery comprising a negative electrode using a light metal as an active material, an organic electrolyte gelled with polymethyl methacrylate, and a positive electrode, the step of obtaining the gelled electrolyte comprising:
1. A method for manufacturing a battery, comprising injecting an organic electrolyte in which polymethyl methacrylate is mixed and dispersed into a battery container, sealing the container, and then heating the container to gel it.