JPS59128779A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To increase cycle life by using lighium or lithium alloy obtained by preliminaryily performing charge-discharge treatment as a negative electrode. CONSTITUTION:Lithium or lithium-aluminum alloy using as a negative electrode 4 is preliminarly discharged by the capacity equivalent to 10% of capacity of a positive electrode, then a battery is assembled. Cycle life of this battery is remarkably increased compared with a battery using lithium or lithium-aluminum alloy which no preliminary charge-discharge treatment is prepared. By preliminary charge-discharge treatment, inactive film on the surface of the negative electrode is removed, and sponge-like lithium is formed thereon. Since expansion of the negative electrode caused by repeated charge-discharge cycling is suppressed, compression to a separator 9 is decreased. Therefore, shortage of electrolyte caused by squeeze out of electrolyte from the separator 9 is prevented.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a negative electrode using lithium or an alloy containing lithium as an active material, and molybdenum trioxide, panazicum pentoxide, titanium or niobium sulfide, selenide, etc. The present invention relates to a non-aqueous electrolyte secondary battery including a positive electrode having as an active material and a non-aqueous electrolyte.

(B) Conventional technology Conventional batteries of this type have problems with cycle characteristics, the main causes of which are the deterioration of the performance of lithium or an alloy containing lithium, which is the negative electrode active material, and the amount of electrolyte in the separator due to charge/discharge cycles. In reduction.

That is, in the process of rolling and crimping lithium or an alloy plate containing lithium to be a negative electrode to a predetermined size, LiQH%Li is applied to the surface.
Inert adsorbed substances such as 2O, Li2CO5, and Li3N are generated. During repeated charging and discharging, some of this inert film dissolves in the electrolyte, decomposing the organic solvent that makes up the electrolyte, and lithium precipitates on the surface that remains during charging, creating so-called dendrites. It turns out.

In addition, as a result of repeated charging and discharging, highly porous and spongy lithium lithium is formed on the surface of the negative electrode, increasing its thickness, which, together with the expansion of the positive electrode, compresses the separator, squeezing out the electrolyte in the separator. This will lead to a decrease in battery performance.

(c) Purpose of the Invention The present invention aims to eliminate the defects in the conventional batteries mentioned above and to improve the cycle stability of this type of battery.

B) Structure of the Invention The present invention comprises a negative electrode using lithium or gold containing lithium as an active material, a positive electrode, and a non-aqueous electrolyte. A non-aqueous electrolyte secondary battery characterized by using an alloy containing the following.

(e) Examples Examples of the present invention will be described in detail below.

FIG. 1 shows a half-sectional view of the battery of the present invention, in which (1) and (2) are positive and negative electrode cans made of stainless steel, which are separated by an insulating backing (3) made of polypropylene. 44
) is a negative electrode made of a lithium plate that has been previously charged and discharged as will be described later, and is crimped to a negative electrode current collector 151 fixed to the inner bottom surface of the negative electrode can (2).

1 (5) A positive electrode containing a titanium disulfide active material, an Ayachire black conductive agent and a fluororesin binder at a ratio of 80:10:1.
A mixture mixed at a ratio of 0 (weight ratio) is placed in a positive electrode fixing ring 17) and is pressed against a positive electrode assembly (8) fixed to the inner bottom surface of the positive electrode can (1). +9) This is a separator made of polypropylene nonwoven fabric, and this separator contains 1 mole of lithium perchlorate in a mixed solvent of propylene carbonate and 1,2 dimethoxyethane.
C is impregnated with a dissolved non-aqueous electrolyte.

Then, a positive electrode-dominated battery (capacity 120 mAH) was fabricated with a negative electrode capacity of 200 mAH and a positive electrode capacity of 120 mAH. This battery is called A.

The negative electrode used was one that had been preliminarily charged and discharged by the following procedure.

That is, a lithium plate with a thickness of 0.5fi and a diameter of 18.0wm is crimped to the inner bottom surface of the negative electrode can, and the counter electrode (positive!ii)
A lithium plate was used as the electrolyte, and 1 mol/j of lithium perchlorate was dissolved in a mixed solvent of propylene carbonate and 1.2 dimethoxyethane as the electrolyte. Next, the battery is charged under the same conditions to preliminarily charge and discharge 10% of the positive electrode capacity (12 mAH).

In addition, a lithium-aluminum-cum alloy with a molar ratio of lithium and aluminum cum of -8:85:15 was used as the negative electrode, and this alloy was assembled by pre-charging and discharging it to a capacity equivalent to 10% of the positive electrode capacity in the same manner as described above. Let the battery be B.

On the other hand, for comparison, comparative batteries C and D were prepared using lithium and lithium-aluminum alloy as negative electrodes, which are not charged or discharged.

Figure 2 shows the charge/discharge cycle characteristics of these batteries, and the cycle conditions are a charging current of 2 mA, a charge end voltage of 4, Ov,
The discharge current was 2 mA, and the discharge end voltage was 1.5 V.

(F) Effects of the Invention As is clear from FIG. 2, the battery of the present invention has significantly improved cycle characteristics compared to the comparative battery.

Considering the reason for this, the negative electrode in the battery of the present invention is preliminarily subjected to charging/discharging treatment, and this treatment removes inert particles on the surface of the negative electrode, and the negative electrode is already charged/discharged at the time of battery assembly. When the battery is used, a spongy lithium is formed and carbon is present, which suppresses the expansion of the negative electrode caused by repeated charging and discharging during battery use, suppressing the compressive force on the separator and squeezing out the electrolyte from the separator. This is because there is no inconvenience and there is no fear of electrolyte shortage.

[Brief explanation of the drawing]

FIG. 1 is a half-sectional view of the battery of the present invention, and FIG. 2 is a comparison diagram of cycle characteristics. (1)...Positive electrode can, (2)...Negative electrode can, (3)...
・Insulating banking, (4)...Negative electrode, (6)...Positive electrode, (9)...Separator, fA) (B)...Battery of the present invention, <C) ID)...Conventional battery .

Claims (1)

[Claims] ■ It is equipped with a negative electrode whose active material is lithium or an alloy containing lithium, a positive electrode, and a non-aqueous electrolyte, and it is preferable to use lithium or an alloy containing lithium that has been preliminarily charged and discharged as the negative electrode. Characteristic non-aqueous electrolyte secondary battery.