JPS61198556A - Lithium battery - Google Patents

Abstract

PURPOSE:To give high electron conductivity to a positive electrode by small amount of metal and obtain a lithium battery having small internal resistance and large discharge capacity by applying chemical plating of metal to positive active material powder. CONSTITUTION:By applying chemical plating of metal to positive active material powder having poor electron conductivity, high electron conductivity can be given to the active material powder in spite of smaller volume occupation compared with addition of nickel powder. Accordingly, a lithium battery having small internal resistance and large discharge capacity. For example, nickel, chromium, gold, or platinum is used as a metal for applying chemical plating to the positive active material. For example, V2O5, TiO2, V6O13, WO3 or CoO2 is used as the positive active material having poor electron conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to lithium batteries. More specifically, the present invention relates to a lithium battery that has high electronic conductivity, low internal resistance, and increased discharge capacity by applying electroless plating to a positive electrode active material having poor electronic conductivity.

[Conventional technology]

Conventionally, in lithium batteries that use positive electrode active materials with poor electronic conductivity such as vanadium pentoxide (V20r, ), nickel powder is added to the positive electrode active material as an electron conduction aid in order to give the positive electrode electron conductivity. (For example, B, C, H, 5teele etal
, +5olid 5tate Ionics, January 1
1,391 (1983)).

[Problem that the invention seeks to solve]

However, in order to impart sufficient electronic conductivity to the positive electrode by adding nickel powder as described above, it is necessary to add 35% by volume of the nickel powder in the positive electrode.
As a result, the amount of positive electrode active material per unit volume decreases, resulting in a decrease in effective energy density and a decrease in discharge capacity.

(Means for solving the problems) The present invention solves the problems of the prior art described above.
By electrolessly plating metal on positive electrode active material particles,
This objective was achieved by imparting high electronic conductivity to the positive electrode with a smaller volume occupancy than when nickel powder was added.

In other words, when the positive electrode active material particles are electrolessly plated with a metal such as nickel, the dispersion state of the metal such as nickel in the positive electrode is extremely good, and the contact between the positive electrode active material and the metal with electronic conductivity such as nickel occurs. Since the condition is good, it is thought that high electronic conductivity can be imparted to the positive electrode with a small amount of metal, thereby making it possible to obtain a lithium battery with low internal resistance and high discharge capacity.

Examples of metals to be electrolessly plated on the positive electrode active material include nickel, chromium, gold, and platinum. These metals have high electrical conductivity, are chemically stable, are not oxidized by the positive electrode active material, and exhibit high electronic conductivity in the positive electrode. Among the above-mentioned metals, nickel is preferably used in the present invention because it is chemically stable, cheaper than gold and platinum, and is economically advantageous.

The plating thickness by electroless plating is preferably 500 A or more because if it is too thin, sufficient electron conductivity cannot be exhibited.

If it is too thick, there will be no problem in terms of imparting electronic conductivity, but the amount of active material packed into the positive electrode will decrease accordingly, so it is usually preferable to keep the thickness to 1 μm or less.

The positive electrode active material contains positive electrode active materials with poor electronic conductivity, such as vanadium pentoxide (V2O3) and titanium dioxide (Ti).
02), vanadium trioxide (V6O13), tungsten trioxide (WO3), cobal dioxide 1-(Co02)
), lead iodide (Pb12), etc. are used. These generally have an electronic conductivity of 1 Ω-1 cm-1 or less,
Of course, it is also applicable to those having electronic conductivity greater than -.

〔Example〕

Next, the present invention will be explained in more detail by giving examples.

Example 1 A nonaqueous solvent lithium battery was manufactured using vanadium pentoxide particles having an average particle size of 30 μm electrolessly plated with nickel as a positive electrode material.

Electroless plating of nickel was carried out at 60° C. for 10 minutes while stirring vanadium pentoxide powder in a plating bath. A plating bath was prepared by dissolving 40 g of nickel sulfide, 24 g of sodium citrate, 14 g of sodium acetate, 20 g of sodium hypophosphite, and 5 g of ammonium chloride in 1 liter of water. The plating thickness was approximately 700.

After electroless plating, the vanadium pentoxide powder was washed with water, dried, and then filled in a predetermined amount into a mold to produce 200 kg of vanadium pentoxide powder.
/ C+A powder compaction diameter 13mm, thickness 1.5
A non-aqueous solvent lithium battery shown in FIG. 1 was fabricated using this as a positive electrode. The volume occupancy of nickel in the positive electrode was approximately 1% by volume.

In FIG. 1, 1 is a negative electrode made of lithium metal, and 2
is the positive electrode mentioned above. 3 is an electrolytic solution, and this electrolytic solution 3 contains a mixed solvent of 4-methyl-1,3-dioxolane, 1,2-dimethoxyethane, and hexamethylphosphoric triamide in a volume ratio of 60:35:5. , 1PF6
Imol/j! It was dissolved at a rate of . A non-aqueous electrolyte solution is used. 4 is a separator made of microporous polypropylene film, 5 is an electrolyte absorber made of polypropylene nonwoven fabric, and 6 is an annular gasket made of polypropylene. 7 is a negative electrode can made of stainless steel and has a nickel plated outer surface; 8 is a positive electrode can made of stainless steel and has a 2.7 kelp plated outer surface; 9 is a negative electrode current collector made of a stainless steel mesh; 10 is stainless steel. This is a positive electrode current collector made of a mesh.

Example 2 A non-aqueous solvent lithium battery was produced in the same manner as in Example 1, except that the time for electroless nickel plating on vanadium pentoxide was 30 minutes. The thickness of the plate was 3000X, and the volume occupancy of nickel in the positive electrode was about 3% by volume.

Example 3 A non-aqueous solvent lithium battery was produced in the same manner as in Example 1, except that the plating time for electroless nickel plating on vanadium pentoxide was 1 hour.The plating thickness was 6000X, and the nickel in the positive electrode The volume occupancy was about 6% by volume.

Comparative Example 1 Nickel powder was mixed with vanadium pentoxide powder, and 200
Powder molded at kg/cJ, diameter 13mm, thickness 1.5
A non-aqueous solvent lithium battery was produced in the same manner as in Example 1 using this as a positive electrode. The mixing ratio of nickel to pentoxide and vanadium was 25% by volume.

Comparative Example 2 A non-aqueous solvent lithium battery was produced in the same manner as Comparative Example 1 except that the mixing ratio of nickel to vanadium pentoxide was 30% by volume.

Comparative Example 3 A non-aqueous solvent lithium battery was produced in the same manner as Comparative Example 1 except that the mixing ratio of nickel to vanadium pentoxide was 35% by volume.

Comparative Example 4 A nonaqueous solvent lithium battery was produced in the same manner as Comparative Example 1 except that the mixing ratio of nickel to vanadium pentoxide was 45% by volume.

Table 1 shows the results of measuring the discharge capacity per unit volume and internal resistance per unit area for the batteries of Examples 1 to 3 and the batteries of Comparative Examples 1 to 4. The discharge capacity is the capacity when the final voltage is set to 2V and the battery is discharged with a current of 1mA/c+J. The internal resistance value was determined from the current-voltage curve. Each value is at 25°C.

In addition, the amount of electricity of the negative electrode active material was made to be in excess of the amount of electricity of the positive electrode active material in any of the batteries.

Table 1 (Note) *1- indicates that discharge is not possible.

As shown in Table 1, in the case of the example using electroless plating, the battery of Example 1 in which the volume occupancy rate of nickel is about 1% by volume already has a small internal resistance and an excellent discharge capacity. Ta.

On the other hand, in the case of the comparative example in which nickel powder was added, even the battery of comparative example 2, in which the amount of nickel added reached 30% by volume, had a high internal resistance and was unable to discharge. Although the battery of Comparative Example 3 containing 35% by volume of nickel powder can be discharged, it still has a higher internal resistance than Examples 2 and 3, and Comparative Example 4 in which the amount of nickel powder added is increased to 45% by volume. Even in this case, the internal resistance was higher than in Examples 2 and 3. In the batteries of Comparative Examples 3 and 4, since the amount of nickel powder added was large, the amount of positive electrode active material in the positive electrode molded body (diameter 13 mm, thickness 1°511II11) was reduced, and the discharge capacity was lower than that of the batteries of Examples. was much smaller.

In the examples, vanadium pentoxide was used as the positive electrode active material, but titanium dioxide (Ti02), trioxide vanadium (V6O13), tungsten dioxide (WO3), cobal dioxide (Co02), etc. An oxide, lead iodide (Pb12), or the like may also be used. In particular, oxides can be charged and discharged and produce high-voltage batteries, but because they have poor electronic conductivity, conventionally a large amount of nickel powder had to be added, resulting in a low discharge capacity. In contrast, in the present invention, high electronic conductivity can be imparted with a small amount of nickel, so the effects of the present invention are significantly exhibited when an oxide is used as a positive electrode active material.

〔Effect of the invention〕

As explained below, in the present invention, by applying electroless metal plating to the positive electrode active material particles, high electronic conductivity can be imparted to the positive electrode with a small amount of metal, and lithium can be produced with low internal resistance and large discharge capacity. We were able to provide batteries.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a lithium battery according to the present invention. ■... Negative electrode, 2... Positive electrode, 3... Electrolyte,
4...Separator

Claims (1)

[Claims] (1) A lithium battery using a positive electrode active material with poor electronic conductivity, characterized in that the positive electrode active material particles are electrolessly plated with metal to provide electronic conductivity.