JPS58111276A - Organic electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To suppress dendritic growth of a negative active mass of increase a charge-discharge cycle life by arrqnging a polyacethylene layer on the surface of a negative electrode using a light meal such as lithium, facing a positive electrode. CONSTITUTION:A polyacethylene layer 3 comprising a polyacethylene film is arranged on the surface of a negative electrode 1 using a light metal such as lithium as an active mass, facing a positive electrode 2. This negative electrode 1 and the positive electrode 2 prepared by mixing titanium sulfide used as an active mass with a conductive mass and a binder and molding them, and a separator 4 impregnated with an organic electrolyte prepared by dissolving lithium perchlorate acting as a solute into a mixed solvent of propylene carbonate and dimethoxy ethane are assembled to form a secondary battery. Thereby the reaction thet lithum ion is doped to polyacethylene takes place, and followed by depositing lithium metal. Therefore, deposition is made uniform, and dendritic growth of lithium is suppressed.

Description

[Detailed Description of the Invention] The present invention provides a negative electrode containing lithium, sodium, etc. as an active material, and a solute such as lithium persalt*, lithium borofluoride, etc. dissolved in an organic solvent such as propylene carbonate or r-butyl lactone. The present invention relates to an organic electrolyte secondary battery that includes an organic electrolyte and a positive electrode whose active material is molybdenum dioxide, vanadium pentoxide, titanium sulfide, or the like.

A problem with this type of battery is that during charging, for example, lithium, which is a negative electrode active material, grows in a dendritic manner on the negative electrode, causing an internal short circuit, so that the charge/discharge cycle is extremely short.

In order to solve these problems, it has been proposed, for example, to use a lithium alloy as the negative electrode active material. This proposal is based on the idea that dendritic growth of lithium is suppressed because lithium reacts with alloys with substrate gold II (aluminum, mercury, etc.) during charging.

However, even in this method, when charging is performed rapidly, the reduction reaction of lithium occurs rapidly, and the amount consumed by the alloy formation reaction cannot keep up, and as a result, lithium metal is deposited on the surface of the alloy layer. , furthermore, lithium metal is precipitated at t, resulting in dendritic growth of lithium.

In addition, when a deep discharge is performed, the adhesion of the alloy layer becomes weaker due to the decrease in lithium concentration, resulting in a short circuit due to deformation of the substrate itself or a short circuit caused by precipitation of lithium on the deformed substrate. This results in a decrease in battery tolerance.

The present invention has been made as a result of intensive studies in view of the problems listed in t. The purpose is to suppress dendritic growth and improve charge/discharge cycle performance.

The implementation of the present invention will be explained below based on the drawings.

Il+ is a negative electrode made by punching a lithium rolled plate into a specified size.
A polyacetylene layer (31) made of a polyacetylene model is disposed on the surface facing the positive electrode 121, which will be described later.The polyacetylene layer may be made of polyacetylene other than a film, for example. It may be formed by creating a paste mainly composed of powder and applying this paste to the surface of the negative electrode, and as long as the negative electrode +II and the negative electrode can αG are sufficiently electrically connected, the negative electrode side may be coated with polyacetylene as much as possible. Preferably, it is covered with a layer.

The positive electrode (2) is a pressure-molded mixture of 80% by weight of titanium sulfide as an active material, 0% by weight of acetylene fluorine as a conductive agent, and 10 gm of fluororesin as a binder, It is placed on the circular surface of the positive electrode can. (4) is a separator made of polypropylene nonwoven fabric, which contains perchlorine as a solute in a m-containing m-containing m-containing mixture of propylene ty-hot and dimethoxyethane. It is impregnated with an organic electrolyte made by dissolving lithium oxide (51
is an insulating puffing that isolates the positive and negative electrode cans.

Figure 3 shows the cycle characteristics of the battery of the present invention (AJ); in Figure 1, BJ is a comparative battery of 181 using a lithium negative electrode without a polyacetylene layer; The second using alloy negative electrode
The cases of comparative batteries are shown respectively.

The cycle conditions are: charge 1jIL@current 2111A for 15 days, release IILK current 2mA and discharge end voltage 1.
It was set to 5V. From FIG. 3, it can be seen that the cycle characteristics of the battery of the present invention are dramatically improved.

Considering the reason for this, it is important to understand that one battery of the present invention has one power! 2
As shown in the figure (first, when discharging, Li-
Lithium ions pass through the polyacetylene layer (31) due to the Li +s reaction.

Next, during charging, a reaction occurs in which lithium ions are first doped into polyacetylene according to the following reaction formula, as indicated by the solid line arrow.

(CB) n + X L i ” Melon (CH) n
・X L 1 This reaction progresses further, and as the voltage increases, lithium ions pass through the polyacetylene layer to the negative electrode 1.
A reaction occurs that precipitates metal lithium on 1+.

In this way, the reaction of L1++.-→Li does not occur directly on the surface of the negative electrode, but first a reaction occurs in which lithium ions or polyacetylene are doped.

Since it is then precipitated as metallic lithium through the polyacetylene layer, the result is L? y+,・
This is thought to be because the reduction reaction of Li proceeds smoothly and the deposition on the negative electrode is uniform.

As mentioned above, the present invention relates to an organic electrolyte secondary battery, by disposing a polyacetylene layer on at least the surface of the negative electrode facing the positive electrode.

It improves the cycle characteristics of Kusunoki batteries, and its industrial value is extremely large.

[Brief explanation of the drawing]

Figure 181 is a longitudinal cross-sectional view of the battery of the present invention, Figure @2 is a diagram for explaining the charging/discharging reaction mechanism of the negative electrode in the battery of the present invention, 1
FIG. 85 is a comparison diagram of cycle characteristics between the battery of the present invention and a comparative battery. +11... Negative electrode, I2... Positive electrode, (31... Polyacetylene layer. (41... Separator, 0/Negative electrode can, (201...
・Positive electrode can.

Claims (1)

[Claims] ■ A positive electrode, an organic electrolyte comprising at least one solvent and at least one solute, 'J'POA, fthorium rl
Which light metal is used as the active material and the negative electrode. The negative electrode has a small number (EiNIC) on the surface facing the positive electrode.
An organic electrolyte secondary battery that is equipped with a polyacetylene layer.