JPH08167413A - Nonaqueous electrolyte battery - Google Patents

Abstract

PURPOSE: To improve liquid absorptivity and electric conductivity of a positive electrode pellet, and heighten a discharge characteristic by coating a positive electrode active material with expanded graphite. CONSTITUTION: Lithium 3 being a negative electrode active material is press- fitted to an inner wall of a sealing plate 2 also serving as a negative electrode terminal. An opening tip part of a battery case 1 also serving as a positive electrode terminal is calked inward and the peripheral edge of the sealing plate 2 is so fastened through a gasket 4 that a port is sealed. A positive electrode active material is coated with expanded graphite having an average particle diameter of 20μm to 80μm being a conductive material having binding performance, and is used as a positive electrode pellet 6 in which a binding agent such as a fluororesin does not substantially exist. So, a uniform mixed condition is held, and the positive electrode pellet can be molded without adding a binding agent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a non-aqueous electrolyte battery, and more particularly to a positive electrode active material thereof.

[0002]

_2. Description of the Related Art Generally, for a positive electrode of a non-aqueous electrolyte battery, an active material composed of manganese dioxide, copper oxide, metal oxides such as FeS and FeS ₂ , metal sulfides and fluorinated graphite, acetylene black, After kneading a conductive material such as Ketjen black or graphite and a binder such as fluororesin,
A mixed material molded body (hereinafter referred to as a positive electrode pellet) obtained by pressure-molding a dry and pulverized powder 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 quickly impregnated with the electrolytic solution. However, there is a problem that it is difficult to take out a large current because the current is blocked. In addition, it is difficult to produce a positive electrode pellet only with acetylene black, Ketjen black or graphite and manganese dioxide, which have weak binding properties.

[0004]

In order to solve such a problem, the present invention is to coat a positive electrode active material with expanded graphite having an average particle size of 20 μm or more and 80 μm or less, which is a conductive material having a binding property. It is characterized by being 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, the positive electrode active material is coated with expanded graphite, so that a uniform mixed state of these can be maintained, and a binder is added depending on the binding property of the expanded graphite. The positive electrode pellets can be molded without any problem. Further, since no binder is used, the liquid absorption 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 vertical cross-sectional view of a lithium-manganese dioxide-based coin type non-aqueous electrolyte battery of the present invention.

In the figure, 1 is a battery case made of stainless steel which also serves as a positive electrode terminal, 2 is a sealing plate which also serves as a negative electrode terminal made of stainless steel, and lithium 3 which is a negative electrode active material is pressure-bonded to its inner wall. . Reference numeral 4 is a gasket made of polypropylene, 5 is a separator made of polypropylene non-woven fabric impregnated with a non-aqueous electrolyte, 6 is a positive electrode pellet which is a feature of the present invention, 7 is a sealant layer of the battery case 1 also serving as a positive electrode terminal. The tip end of the opening is caulked inward, and the peripheral edge of the sealing plate 2 is tightened via the gasket 4, thereby forming a hermetic sealing.

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 that the compounding ratio was 100: 7 (weight ratio), and the mixture was stirred and mixed to cover the manganese dioxide with the expanded graphite. Dry with hot air at ℃. After drying, since there is a lumpy mixture, the mixture is pulverized and adjusted to a size of 250 μm or less, the powder is pressure-molded at ² to 4 ton / cm ² , and dried again at 250 ° C. with hot air to obtain a positive electrode pellet. The expanded graphite used at this time had an average particle size of 10 μm or more and 100 μm or less. Further, as a comparative battery, the same as the present invention except that Ketjen Black was added as a conductive agent and 6% by weight of a fluororesin was added as a binder to the mixture.
A coin-type lithium battery having a height of 16 mm was prepared. To investigate the performance of a coin-type lithium battery, the ambient temperature 2
A high-load continuous discharge characteristic test with a load of 1 kΩ at 0 ° C. and a battery voltage during pulse discharge with an environmental temperature of 20 ° C. and a load of 400Ω for 15 seconds were measured. The result of the high load continuous discharge characteristic test is shown in FIG. 2, and the result of the battery voltage measurement when the load is discharged for 400 Ω for 15 seconds is shown in FIG. In these figures, the battery of the example is A and the battery of the comparative example is B. The test results revealed the following.

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

This is because, in the battery of the present invention, the binder which does not participate in power generation and conductivity does not exist 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 investigate the moldability of the positive electrode mixture of the present invention, the defective molding rate of the mixture when changing the particle size of the expanded graphite coated with manganese dioxide is shown in (Table 1). .

[0012]

[Table 1]

As is clear from (Table 1), it was found that when manganese dioxide was coated with expanded graphite having an average particle size of less than 20 μm and greater than 80 μm, the formability was significantly reduced. When the average particle size is less than 20 μm, a coating film cannot be formed sufficiently on the surface of manganese dioxide, resulting in molding failure. When the average particle size is greater than 80 μm, segregation due to aggregation of expanded graphite and formation of manganese dioxide on the surface occur. It is considered that molding is defective because an excessive coating of expanded graphite is not formed and a uniform coating is not formed.

That is, the average particle size of the expanded graphite coated with manganese dioxide is preferably 20 μm or more and 80 μm or less,
Particularly, 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, the defective molding rate of the mixture is shown in Table 2 when the expanded graphite having an average particle size of 40 μm was used and the ratios of the particle size of 10 μm or less and 100 μm or more were changed.

[0016]

[Table 2]

As is clear from (Table 2), the particle size is 10
It was found that when manganese dioxide was coated with expanded graphite in which particles having a particle size of less than or equal to 100 μm and a total of 10% or more were coated with manganese dioxide, the formability was significantly reduced. Particle size is 10
If 10% or more of particles having a size of μm or less are present, a sufficient film cannot be formed on the surface of manganese dioxide, resulting in defective molding.
When 10% or more of particles having a particle diameter of 100 μm or more are present, it is considered that molding defects are caused by aggregation of expanded graphite and excessive coating on the surface of manganese dioxide. In this respect, 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, by coating the positive electrode active material with expanded graphite, positive electrode pellets can be molded without using a binder such as fluororesin. it can.

As a result, the liquid absorption and conductivity of the positive electrode pellets can be improved, and a non-aqueous electrolyte battery having excellent discharge characteristics can be provided.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a coin-type non-aqueous electrolyte battery of the present invention.

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

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

[Explanation 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 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A non-aqueous electrolyte battery comprising a positive electrode active material, a negative electrode active material, and a non-aqueous electrolytic solution, wherein the positive electrode active material is coated with a conductive material having a binding property. 2. The binding conductive material has an average particle size of 2
The non-aqueous electrolyte battery according to claim 1, which is expanded graphite having a size of 0 μm or more and 80 μm or less. 3. The expanded graphite having a binding property has a particle size of 10 μm.
m or less is 10% or less of the total amount and is 90 μm
The non-aqueous electrolyte battery according to claim 2, wherein the above amount 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.