JPS63969A - Nonaqueous electrolyte cell - Google Patents

Abstract

PURPOSE:To improve a long period high-temperature preservation property and a long period discharge reliability, by adding an organic carbonic acid or its salt to a nonaqueous electrolyte. CONSTITUTION:To a nonaqueous electrolyte which is made by dissolving lithium boron-fluoride or lithium perchlorate as a solvent to gamma-butyrolactone propylene carbonate, dimethoxyethane, or their mixture solvent, for example, an organic carbon acid, its lithium salt, or its sodium salt is added. In this case, the adding amount of the organic carbonic acid or its salt shall be 100 to 600 PPM.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a non-aqueous electrolyte battery.

BACKGROUND OF THE INVENTION Lithium batteries are currently widely used, which are composed of an active metal such as lithium as a negative electrode active material, carbon fluoride or manganese dioxide as a positive electrode active material, and a non-aqueous electrolyte.

Problems to be Solved by the Invention However, this type of battery has a problem in that its internal resistance increases abnormally when it is stored at a high temperature of 60° C. or higher or when subjected to a weak long-term discharge κ of several μA or less.

Although the cause is not clear, the lithium surface is oxidized due to a chemical reaction between the active negative electrode active material, such as lithium, and the non-aqueous electrolyte, becoming passivated by an oxide film, and as the oxide film grows, the film gradually thickens. It is thought that this causes the internal resistance to rise.

The present invention aims to improve battery characteristics during long-term high-temperature storage and long-term discharge by forming a chemically stable compound film against non-aqueous electrolytes on the surface of an active metal, such as lithium, which is an active material for the negative electrode. This is the purpose.

Means for Solving the Problems In order to achieve the above objects, the present invention uses K, a non-aqueous electrolyte such as γ-butyrolactone (hereinafter referred to as γ-BL), propylene carbonate (hereinafter referred to as PC) or dimethoxyethane (hereinafter referred to as DM). Organic carboxylic acids or their lithium salts or sodium salts are added to a non-aqueous electrolyte in which lithium fluoroborate or lithium perchlorate is dissolved in a mixed solvent thereof or a mixed solvent thereof. The amount of the organic carboxylic acid or its salt added here is preferably 100 to 600 PPM.

Effect By adopting the configuration of the present invention, storage deterioration at high temperatures of 60'C or higher or long-term weak current discharge deterioration of several μA or less can be prevented, and battery characteristics can be improved.

Example The details of the present invention will be explained below using examples.

FIG. 1 shows a fluorocarbon monolithium battery. 1 in the figure shows a positive electrode mixture made of expanded titanium metal, which is made by adding carbon powder such as graphite or carbon plank as a conductive material to fluorinated carbon as an active material, and fluororesin as a binder. It is a positive electrode attached to an electric body. 2 is a negative electrode in which expanded metal made of nickel is embedded in a lithium sheet. The positive and negative electrodes are spirally wound through a separator 3 made of a polypropylene nonwoven fabric, and housed in a battery case 4 made of a nickel-plated steel plate which also serves as a negative electrode terminal. 5 is a positive terminal plate made of titanium, 6 is a cap made of stainless steel, and 7 is a gasket made of polypropylene. A lead 8 is made of titanium and electrically connects the positive electrode and the positive terminal plate 5.

The following electrolyte solution was used in the battery configured as described above.

■ Conventional electrolyte solution in which 1 mol/l of lithium borofluoride is dissolved in γ-BL.

(2) Electrolytic solution of the present invention in which 500 PPM of n-butyl formate is dissolved in Electrolytic Solution 1.

Two types of AA size cylindrical lithium batteries were manufactured using the above electrolyte. Figure 2 shows the discharge characteristics at a constant resistance of 8Ω at 20°C immediately after manufacture. In the figure, 1 is a conventional product using an electrolytic solution marked ○, and 2 is a product of the present invention using an electrolytic solution marked ▪. Furthermore, the same type of battery was stored at 70° C. for one month and then discharged under the same conditions as immediately after manufacture, and the results are shown in FIG.

As is clear from FIGS. 2 and 3, there is no difference in the discharge characteristics of the batteries immediately after manufacture, but as shown in FIG. 2 shows almost the same discharge characteristics as the immediately manufactured battery shown in Figure 2, and shows almost no deterioration during storage, but with conventional batteries, the battery characteristics deteriorate significantly after storage, and the difference is particularly noticeable. This is particularly clear in FIG. 3, which shows the battery characteristics after storage at 70'C for one month, and in the initial discharge characteristics shown in FIG. This is thought to be due to the difference in the thickness of the oxide film formed on the lithium surface, and in electrolyte 2, the hydrogen H of the carboxylic acid does not separate from the lithium surface on the lithium surface using the reaction formula shown below, and the oxide film forms on the lithium surface. It is thought that it is interfering with the formation. Therefore, the thickness of the lithium oxide film on the surface is considered to be thinner overall than in the case of O electrolyte. Therefore, the internal resistance of each battery before and after storage was measured, and the results were as shown in Table 1 below.

Table 1 Note that the internal resistance was measured using 1 KHz alternating current. Also, 70'0 when the total amount of n-butyl formate added was changed.
The measurement results of internal resistance after one month are shown in Table 2 below.

(Margins below) Table 2 As shown above, adding n-butyl formate in the range of 100 to 600 PPM was effective in suppressing battery deterioration.

In addition, at 46°C with a battery using the electrolyte of O,■
Table 3 shows the results of measuring the internal resistance during IMΩ long-term discharge.
Shown below.

(Margins below) Table 3 As described above, when butyl n-formate was added, it was effective in suppressing internal deterioration even during long-term discharge.

In addition to this example, similar effects were obtained using organic carboxylic acids such as acetoacetic acid, isobutyric acid, and glutaric acid.

Effects of the Invention As is clear from the above description, by adding an organic carboxylic acid or its salt to the non-aqueous electrolyte, it provides excellent characteristics in long-term high-temperature storage and long-term discharge reliability.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the battery of the present invention, Figure 2 is a diagram showing the initial discharge characteristics of the battery, and Figure 3 is a diagram showing the battery characteristics after storage for 7 o'C I months. ...Positive electrode mixture, 2...Negative electrode, 3...7 parts, 4...Case, 5...Positive terminal plate,
6... Canop, 7... Gasket, 8
...Lead. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (3)

[Claims] (1) A nonaqueous electrolyte battery using lithium or a lithium alloy as a negative electrode and a fluorocarbon, a metal oxide, or a mixture thereof as a positive electrode, in which an organic carboxylic acid or a salt thereof is added to the nonaqueous electrolyte. A non-aqueous electrolyte battery characterized by: (2) Addition amount of organic carboxylic acid is 100 to 600 PPM
A non-aqueous electrolyte battery according to claim 1. (3) The non-aqueous electrolyte battery according to claim 1 or 2, using any one of n-butyl formate, acetoacetic acid, isobutyric acid, and glutaric acid as the organic carboxylic acid.