JPH01313850A - Battery - Google Patents

Abstract

PURPOSE:To reduce a short circuit failure and a self-discharge by using a separator at least partially containing floss silk. CONSTITUTION:A manganese dioxide sintered/molded sheet is used for a positive electrode active material, metal lithium is used for a negative electrode 3 active material, propylene carbonate is used for the solvent of an electrolyte, 1M lithium perchlorate is used for the solute, a floss silk-mixed sheet made of floss silk fibers and Manila hemp fibers is used for a separator 4. The floss silk-contained separator has large strength and is dense even if it is thin. A cell with little self-discharge and good voltage holding characteristic is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a primary or secondary battery, and particularly to a separator disposed between a positive electrode and a negative electrode of these batteries.

[Conventional technology] In recent years, card-type electronic desktop calculators and electronic wristwatches have been introduced.

2. Description of the Related Art As electronic devices such as IC cards become smaller and thinner, there is an increasing demand for the development of flat batteries such as button-shaped, coin-shaped, and paper-shaped batteries. In particular, ultra-thin flat batteries with a thickness of 0.5 ms or less are desired as batteries for card-type electronic devices such as card-type calculators and IC cards.

As such a flat battery, for example, a paper type battery as shown in FIG. 1 has been proposed. The battery 1 shown in FIG. 1 is a primary or secondary battery, and for example, a separator 4 is provided between a positive electrode 2 made of a positive electrode active material, a conductive material, and a binder, and a negative electrode 3 made of metallic lithium. The positive electrode 2 is fixed to the inner surface of one exterior metal case 5 via, for example, a conductive adhesive (not shown), and the negative electrode 3 is similarly fixed to the inner surface of the other exterior metal case 6 with a conductive adhesive (not shown). They are fixed together with an adhesive, a frame-shaped insulator 7 is inserted between the outer metal cases 5 and 6, and the inside is filled with an electrolytic solution.

In the above-mentioned paper-type, button-type, or coin-type batteries, the separator is generally a sheet-like material made by mixing paper, polyethylene nonwoven fabric, polyester nonwoven fabric, or a mixture thereof with glass fibers having a diameter smaller than that of these fibers. It is known to use porous paper.

[Problem to be Solved by the Invention 1] A separator is formed by punching out a sheet-like material, but especially in the case of a separator made of a large amount of glass fiber (20 to 60%), the sheet-like material naturally contains glass. Due to the presence of fibers, the punching die for the separator is subject to severe wear, resulting in increased costs due to die replacement.

It is also known to use vegetable fiber paper such as kraft paper or Manila hemp paper as a separator, but this has the disadvantage that the self-discharge of the battery is large. Increasing the thickness of the separator reduces self-discharge, but increases internal resistance, which is not desirable.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a battery having a separator containing cotton.

The raw material for cotton cotton is cocoon, and the thickness of the fibers is as thin as 172 to 1/100 of Manila hemp, and the fibers have complicated bending and uneven thickness, so they are difficult to cut, beat, and make paper. Even in the case of pure cotton, the amount of electrolyte retained is improved, and since it is dense, the electrical resistance value can be reduced when soaked with electrolyte, and the mechanical strength can be reduced. When mixed with vegetable fibers such as manila hemp or kraft to strengthen the paper, the cotton fibers become tightly entwined in the gaps between the thick fibers of manila hemp or kraft, forming extremely thin gaps, making it difficult to isolate. The withstand voltage of the paper separator is improved.

The separator according to the present invention is made of pure cotton fiber,
Other vegetable fibers 1 Consist of fibers mixed with synthetic resin fibers, glass fibers, or mixed fibers thereof.

The separator according to the present invention, which is made of a woven or nonwoven fabric containing cotton, is thin but strong (and dense, so a battery using such a separator has
Self-discharge is small, and in the case of a secondary battery, the voltage holding characteristic, which indicates the degree of voltage maintenance when left unloaded after charging, is good. Furthermore, since the separator has good electrolyte retention properties, the reliability of the battery is improved.

The separator according to the present invention includes the above-mentioned button type, coin type,
It can also be applied to paper-type and rolled-up batteries, and -
It can be used as a single sheet or as a stack of multiple sheets.

The following can be exemplified as the primary and secondary batteries according to the present invention. - As a secondary battery, for example, the positive electrode is made of MnO* or CFn, the negative electrode is made of Li,
The solvent of the electrolytic solution is dimethoxyethane or γ-butyrolactone, and the solute is L i Cll0 or L i B F
A. For example, in a secondary battery, the positive electrode is made of carbon, polyaniline, PbO* or NiO, the negative electrode is made of Li alloy, PB or Cd, and the solvent of the electrolyte is propylene carbonate, γ-butyrolactone, or water.
The solute is LiBFa, H, or SO.

[Examples] Examples of batteries using the separator according to the present invention will be described below.

(Example 1) A manganese dioxide bound sheet was used as the positive electrode active material, metallic lithium was used as the negative electrode active material, a 30 μm thick stainless steel (SUS430) sheet was used as the exterior metal case on the positive electrode side, and A nickel sheet with a thickness of 30 μm is used for the exterior metal case, a heat-melt adhesive deformed polyethylene resin is used as the sealing insulator, propylene carbonate is used as the solvent for the electrolyte, and 1M lithium perchlorate is used as the solute. Cotton fiber 70wL as a separator
A paper-type lithium battery with a size of 23 mm x 29 mm was prepared using cotton-mixed paper with a thickness of 40 μm consisting of 30 wt % Manila hemp fibers and 30 wt % Manila hemp fibers.

(Example 2) 100 wt% cotton fiber with a thickness of 40 μm as a separator
I used the one from The rest is the same as in Example 1.

(Example 3) As a separator, a 100 μm thick cotton mixed paper consisting of 70 wt% cotton fibers and 30 wt% polypropylene resin fibers was used. The rest is the same as in Example 1.

(Comparative Example) As a separator, 100 wt % of polypropylene resin fibers with a thickness of 1100 u were used. The rest is the same as in Example 1.

Next, apply pressure of 13 kg to each paper type battery from above and below.
The open circuit voltage was examined after 100 hours by maintaining the atmosphere at a temperature of 80°C and a relative temperature of 90 to 95% while applying an external pressure of /am''.The results are shown in Table 1. A battery with an open circuit voltage of 3.0 V or less during assembly was considered to be a short-circuit defect.

Table 1 Electrical Properties [Effects of the Invention] As described above, a battery using a separator containing at least a portion of cotton cotton can reduce short-circuit failures and self-discharge.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a battery according to the present invention. In the figure, 1... - battery, 2... positive electrode, 3... negative electrode, 4
...Separator, 5.6-...Case, 7...Insulator patent applicant Elna Co., Ltd.

Claims (1)

[Claims] (1) A battery in which a separator containing at least a portion of cotton cotton is disposed between a positive electrode and a negative electrode.