JP3216451B2 - Non-aqueous electrolyte battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonaqueous electrolyte battery, and more particularly to a positive electrode active material thereof.

[0002]

_2. Description of the Related Art In general, a positive electrode of a non-aqueous electrolyte battery includes acetylene black, acetylene black, a metal oxide such as manganese dioxide, copper oxide, FeS, FeS2, and a metal sulfide and graphite fluoride. After kneading a conductive material such as Ketjen Black or graphite and a binder such as fluororesin,
A mixture molded body (hereinafter, referred to as a positive electrode pellet) obtained by press-molding a powder obtained by drying and pulverization is used.

[0003]

However, since the binder such as fluororesin has low conductivity and liquid absorbing ability, the internal resistance of the positive electrode itself cannot be reduced or the positive electrode pellet is rapidly impregnated with the electrolytic solution. Therefore, there is a problem that it is difficult to take out a large current. In addition, it is difficult to produce a positive electrode pellet using only acetylene black, Ketjen black, graphite and manganese dioxide having weak binding properties.

[0004]

In order to solve such a problem, the present invention provides a method of coating a positive electrode active material with expanded graphite having an average particle diameter of 20 μm or more and 80 μm or less, which is a conductive material having a binding property. And is characterized in that it is used as a positive electrode pellet substantially free of a binder such as a fluororesin.

[0005]

In the non-aqueous electrolyte battery of the present invention, since the positive electrode active material is covered with expanded graphite, a uniform mixed state thereof can be maintained, and a binder is added by the binding property of the expanded graphite. A positive electrode pellet can be formed without any trouble. Furthermore, since no binder is used, the liquid absorbing property and conductivity of the positive electrode pellet can be improved to improve the performance of the battery.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a lithium-manganese dioxide-based coin-shaped non-aqueous electrolyte battery of the present invention.

In FIG. 1, reference numeral 1 denotes a battery case also serving as a positive electrode terminal made of stainless steel, and 2 denotes a sealing plate also used as a negative electrode terminal made of stainless steel. . 4 is a gasket made of polypropylene, 5 is a separator made of a nonwoven fabric impregnated with a non-aqueous electrolyte, 6 is a positive electrode pellet characteristic of the present invention, 7 is a sealant layer, and a battery case 1 also serving as a positive electrode terminal The hermetic sealing is performed by caulking the opening front end inward and tightening the peripheral edge of the sealing plate 2 via the gasket 4.

Next, the positive electrode mixture of the present invention will be described.
First, the expanded graphite is uniformly dispersed in distilled water while stirring. Next, manganese dioxide, which is a positive electrode active material, was added to the expanded graphite so as to have a compounding ratio of 100: 7 (weight ratio), and the mixture was stirred and mixed to coat the manganese dioxide with the expanded graphite. Dry with hot air at ℃. After drying, there is also a bulk mixture, which is pulverized and adjusted to a size of 250 μm or less, and this powder is molded under pressure at ² to 4 ton / cm ² and dried again at 250 ° C. with hot air to obtain positive electrode pellets. The expanded graphite used had an average particle size of 10 μm or more and 100 μm or less. The comparative battery was the same as the present invention except that Ketjen black was added as a conductive agent and fluorocarbon resin as a binder was added at 6% to the mixture.
A coin-type lithium battery having a height of 16 mm was prepared. To check the performance of the coin-type lithium battery, the ambient temperature 2
A high-load continuous discharge characteristic test at 0 ° C. and a load of 1 kΩ and a battery voltage at the time of pulse discharge at 400 ° C. for 15 seconds at an environmental temperature of 20 ° C. were measured. FIG. 2 shows the results of the high-load continuous discharge characteristic test, and FIG. 3 shows the results of measuring the battery voltage when the load was discharged at 400Ω for 15 seconds. In these figures, the battery of the example is A, and the battery of the comparative example is B. The following results became clear from the test results.

From FIG. 2, the battery voltage of the present invention is higher at the time of high load discharge than the battery of the comparative example, and the discharge capacity is also improved. FIG. 3 also shows that the battery of the present invention has a smaller voltage drop in the closed-circuit voltage characteristics than the battery of the comparative example.

[0010] This is because the battery of the present invention does not contain a binder that is not involved in power generation and conductivity in the mixture, so that the electrochemical reaction inside the mixture proceeds as compared with the battery of the comparative example. It can be estimated that it is easy to do.

Next, in order to examine the moldability of the positive electrode mixture of the present invention, the molding failure rate of the mixture when the particle size of the expanded graphite coated with manganese dioxide was changed is shown in Table 1. .

[0012]

[Table 1]

As is clear from Table 1, it was found that the moldability when the expanded graphite having an average particle size of less than 20 μm and larger than 80 μm was coated on manganese dioxide was remarkably reduced. When the average particle size is less than 20 μm, a film cannot be formed sufficiently on the manganese dioxide surface, and molding failure occurs. When the average particle size is more than 80 μm, segregation due to agglomeration of expanded graphite and manganese dioxide surface. It is considered that excessive coating of the expanded graphite occurs and a uniform coating is not formed, resulting in poor molding.

In other words, the average particle size of the expanded graphite covering the manganese dioxide is preferably 20 μm or more and 80 μm or less.
In particular, when the average particle size of the expanded graphite was 30 μm or more and 60 μm or less, more stable positive electrode pellets were obtained.

Next, Table 2 shows the molding failure rate of the mixture when the ratio of the particle size of 10 μm or less and 100 μm or more was changed using expanded graphite having an average particle size of 40 μm.

[0016]

[Table 2]

As is clear from Table 2, the particle size is 10
It was found that when the manganese dioxide was coated with expanded graphite in which particles having a particle size of 100 μm or less and a particle size of 100 μm or more were present in total, the moldability was significantly reduced. Particle size 10
When particles having a particle size of μm or less exist in an amount of 10% or more, a sufficient film is not formed on the surface of manganese dioxide, and molding defects occur,
If 10% or more of the particles having a particle diameter of 100 μm or more are present, it is considered that molding defects are caused by aggregation of the expanded graphite and excessive coating on the manganese dioxide surface. In this regard, similar results were obtained for those having different average particle sizes.

[0018]

As described above, in the non-aqueous electrolyte battery of the present invention, the positive electrode pellet can be molded without using a binder such as fluororesin by coating the positive electrode active material with expanded graphite. it can.

As a result, it is possible to improve the liquid absorption and conductivity of the positive electrode pellet, and to provide a non-aqueous electrolyte battery having excellent discharge characteristics.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a coin-type nonaqueous electrolyte battery of the present invention.

FIG. 2 is a graph showing the results of a high-load continuous discharge characteristic test of a battery of the present invention and a battery of a comparative example.

FIG. 3 is a graph showing test results of closed-circuit voltage characteristics of the battery of the present invention and a battery of a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Lithium 4 Gasket 5 Separator 6 Positive electrode pellet 7 Sealant layer

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kunihide Miura 1006 Kazuma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-59-112568 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01M 4/02-4/06 H01M 4/50-4/62 H01M 6/16 H01M 10/40

Claims (4)

(57) [Claims] 1. A cathode active material, anode active material, a nonaqueous electrolyte
A non-aqueous electrolyte cell according to the basic configuration, the positive electrode active material is coated with a conductive material having a binding property, said electrically
A non-aqueous electrolyte battery characterized by using expanded graphite as an electric material . 2. The expanded graphite has an average particle size of not less than 20 μm and not more than 8 μm.
Non-aqueous electrolyte battery according to claim 1, wherein 0μm is below. 3. Rise脹化graphite, those having a particle diameter of 10μm or less is 10% or less of the total amount, and the non-aqueous electrolyte battery according to claim 2, wherein 90μm or more of is 10% or less of the total amount. 4. The non-aqueous electrolyte battery according to claim 1, wherein the positive electrode active material is manganese dioxide.