JPS59148277A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To increase binding action of aluminum substrate and improve cycle life by using a negative electrode comprising a lithium-aluminum alloy using a molded body of aluminum fiber as a substrate. CONSTITUTION:A negative electrode 1 comprising lithium-aluminum alloy using a molded body of aluminum fiber as a substrate is pressed to a negative current collector 3 which is bonded to the inner bottom surface of a negative can 2. The negative electrode 1 is prepared in such a way that an aluminum fiber molded body as a cathode and a lithium plate as an anode are immersed in a nonaqueous electrolyte prepared by dissolving 1mol/l lithium perchlorate in the equal volume mixture of propylene carbonate and 1, 2 dimethoxyethane and 0.2-2mA of current is made flow between both electrodes till charging capacity reaches 100mAH to form lithium-aluminum alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial application field The present invention provides a non-aqueous non-aqueous electrode comprising a negative electrode using lithium as an active material and a positive electrode using molybdenum trioxide, vanadium pentoxide, titanium sulfide, etc. as an active material. This invention relates to electrolyte secondary batteries.

Conventional technology The problem with this type of battery is that the lithium, which is the negative electrode active material, grows like a tree on the surface of the negative electrode during charging and comes into contact with the positive electrode, causing an internal short circuit, resulting in extremely short charge/discharge cycles. It is.

As a countermeasure to this problem, it has been proposed that the negative electrode be made of a lithium-aluminum alloy.

This is because in the case of lithium alone, when lithium is ionized and eluted during discharge, the negative electrode surface becomes uneven, and during subsequent charging, lithium is deposited intensively on the convex parts and grows in a dendritic shape. This is because, in the case of a lithium-aluminum alloy, lithium restores itself to form an alloy with aluminum, which is the base of the negative electrode, during charging, so that the dendritic growth of lithium is suppressed.

Therefore, the conventionally used lithium alone /L/
Since the Minilam alloy is obtained by adding aluminum powder to lithium and reacting it, the negative electrode may fall off with repeated charging and discharging, resulting in a shortened cycle life (a drawback).

In other words, when lithium is ionized and eluted due to discharge, the aluminum base remains in the negative electrode, but since this aluminum base is powder-molded, the bonding strength between the powders is poor, and the bond between the powders is weak. It falls off from the negative electrode.

(c) Purpose of the Invention The present invention focuses on the above-mentioned problems in conventional batteries, and aims to increase the bonding strength of the aluminum substrate and measure the direction of the C cycle life.

B) Structure of the Invention The present invention has been made to achieve the above object, and includes a positive electrode, a negative electrode made of a lithium-aluminum alloy having a molded body of aluminum fibers as a base, and a non-aqueous electrolyte. This project proposes a non-aqueous electrolyte secondary battery.

(Autopsy example Embodiments of the present invention will be described below based on the drawings.

8 and 11) in FIG. 1 are lithium-
The negative electrode is made of an aluminum alloy (a specific example will be described later), and is pressed into a negative electrode current collector (31) that is fixed to the inner bottom surface of the negative electrode can (2).

14) is a positive electrode in which titanium sulfide as an active material is mixed with an acetylene black conductive agent and a fluororesin binder at a ratio of 80:
It is molded from a mixture mixed at a ratio of 10:10 (mass ratio), and is pressed into contact with the inner bottom surface of the positive electrode can (51).

(6) A separator made of polypropylene nonwoven fabric, which contains propylene carbonate and
．． A non-aqueous electrolytic solution containing 1 mol/l of lithium perchlorate dissolved in a volumetric mixed solvent of 2-dimethoxyethane was impregnated. (7) is an insulating backing that electrically insulates the positive and negative electrode cans, and the battery dimensions are 250 mm in diameter and 2.8 mm thick.

Next, an example of creating a negative electrode will be described in detail.

Creation example 1゜Aluminum fiber (0.1 am it x 5 m)
A molded body formed by molding a fin with a diameter of 15 to 17M0 and a thickness of 0.4 to 1.0 at a pressure of 1 to 3 tons/d is used as a cathode, a lithium plate is used as an anode, and these cathode and anode plates are made of propylene carbonate and 1. It was immersed in a non-aqueous electrolyte in which 1 mol/l of lithium perchlorate was dissolved in a mixed solvent of equal volume with 2 dimethoxyethane, and then charged with a current of 0.2 to 2 mA.
A lithium-aluminum alloy is created by applying current under OmAH conditions, and this is used as a negative electrode.

A battery of the present invention using this negative electrode is designated as A.

Preparation Example 2 The molded body of the aluminum fiber group in Preparation Example 1 was wrapped in a lithium sheet and heated for 60 [
React at J℃ for several hours, then cool to obtain lithium-
An aluminum alloy is used as the negative electrode.

A battery of the present invention using this negative electrode is designated as A'.

Figure 2 shows the cycle characteristics of the present invention battery (At (At), in which (B) is a comparative battery ■ whose negative electrode is a lithium-aluminum alloy formed using aluminum powder, and (C) is lithium alone. This is the case of comparative battery H using a negative electrode composed of the following: These comparative batteries differ only in the negative electrode and are otherwise the same as the battery of the present invention.

The cycle conditions are a charging current of 2 mA and a charge end voltage of 4.
0V, and the discharge current is 2 mA, and the discharge final voltage is 1°5.
v.

(f) Effects of the invention As is clear from FIG. 2, the invention battery fA) (Al and comparative battery 1
(B) is a comparative battery using lithium alone as the negative electrode (C)
Furthermore, among lithium-aluminum alloys, especially when a molded body of aluminum fibers is used as the base material, as in the battery (A) of the present invention, the cycle life is dramatically improved. I can see that it improves.

The reason for this is that the negative electrode in the second battery of the present invention is composed of a lithium-aluminum alloy based on a molded body of aluminum fibers, so even when lithium is ionized and eluted due to discharge, the remaining aluminum remains. This is thought to be due to the fact that since the base body is a state in which aluminum fiber groups are intertwined, the bonding force between aluminum is strong (and there is no problem such as collapse of the electrode).

As mentioned above, the present invention greatly contributes to improving the cycle characteristics of non-aqueous electrolyte secondary batteries using lithium as a negative electrode active material.

[Brief explanation of drawings]

FIG. 1 is a half-sectional view of a battery according to the present invention, and FIG. 2 is a comparison diagram of cycle characteristics between the battery according to the present invention and a comparative battery. ([)... Negative electrode, (21... Negative electrode can, (3)...
Negative electrode current collector, (4)...positive electrode, (5)...positive electrode can,
(6) Separator, (7) Insulating backing, fA) fA) Invention battery, fB) (C)...
・Comparison battery. Applicant Sanyo Electric Co., Ltd. Agent Patent Attorney Shizuo Sano e

Claims (1)

[Claims] ■ A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode made of a lithium-aluminum alloy having a molded body of aluminum fibers as a base, and a non-aqueous electrolyte.