JPH07211321A - Nonaqueous solvent battery - Google Patents

Abstract

PURPOSE:To provide a battery in which a defective caused by breakage or cutout of a porous carbon body in a positive electrode produced due to low mechanical strength is eliminated, discharge voltage is stabilized, and high rate performance is enhanced. CONSTITUTION:A nonaqueous solvent battery consists of a negative active material made of an alkali metal such as lithium and sodium, a positive electrode 3 using a porous carbon body 6 as the main constituent, and an electrolyte 14 whose main component is an oxyhalide, also serving as a positive active material. Carbon fibers with a fiber diameter of 8-25mum, a fiber length of 0.5-7.0mm, and a carbon content of 95wt.% or more are mixed with the porous carbon body 6 of the positive electrode 3. The mixing ratio of the carbon fiber is preferably 5-20wt.% based on the weight of the porous carbon body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a positive electrode for a non-aqueous solvent battery using an alkali metal as a negative electrode active material and an oxyhalide as a positive electrode active material.

[0002]

2. Description of the Related Art A porous carbon body which uses an alkali metal such as lithium or sodium as a negative electrode active material, uses an oxyhalide such as thionyl chloride or sulfuryl chloride as a solvent for an electrolytic solution and a positive electrode active material, and is inactive per se. The non-aqueous solvent battery, which is composed mainly of a positive electrode, has a large energy density, excellent storage characteristics, and a wide operating temperature range, and is often used as a backup power source for calculators, watches, and memories. ing.

The greatest feature of such a battery is that a liquid oxyhalide such as thionyl chloride is used as the positive electrode active material, and the liquid active material is electrochemically reduced on the porous positive electrode surface. The battery reaction proceeds.
Among them, lithium is used for the negative electrode, and thionyl chloride (SOCl
So-called lithium-thionyl chloride batteries using ₂ ) as the main positive electrode active material have attracted attention because of their particularly high energy density.

Generally, in a cylindrical lithium-thionyl chloride non-aqueous solvent battery, a lithium negative electrode is provided on the inner surface of the can, and a metal current collector such as a wire net is placed inside the negative electrode via a separator. While accommodating a positive electrode made of an internal porous carbon body, the positive electrode contains thionyl chloride as a main component,
It has a structure in which an electrolytic solution that also serves as a positive electrode active material is impregnated. In a battery having such a structure, the battery discharge characteristics are greatly affected by the characteristics of the positive electrode, and the catalytic activity for the electrochemical reaction of the positive electrode active material, the porosity electrical conductivity, etc. are important factors.

By the way, as the porous carbon body of the positive electrode of the above-mentioned cylindrical battery, polytetrafluoroethylene is conventionally added to carbon black such as acetylene black as a binder, and the mixture is kneaded and then molded into a predetermined shape. What has been done is being used. Microscopically, the porous carbon body of such a positive electrode has carbon black particles assisted in the polytetrafluoroethylene being formed into a cobweb-like fiber, and the discharge accompanying the positive electrode reaction Since it has the function of smoothly and uniformly absorbing the volume expansion of the positive electrode that occurs when the product is deposited between carbon black particles, it contributes to the improvement of the utilization rate of the positive electrode. Such a bonding mode by cobweb-like fiberization is the greatest feature of the polytetrafluoroethylene binder and cannot be realized by other binders. Also,
Polytetrafluoroethylene is also extremely excellent in durability against liquid oxyhalides.

[0006]

However, carbon black bound with polytetrafluoroethylene is
It is not a solid solid but a clay-like semi-solid, and the porous carbon body obtained by molding this into a predetermined shape by press molding or the like is easy to collapse. Therefore, in assembling a battery in which a metal current collector is internally provided in the porous carbon body and is loaded into the can body as a positive electrode, the porous carbon body causes defects such as cracking and chipping, and a machine after battery assembly. Separation from the metal current collector due to static impact, or deterioration of adhesion with the separator. As a result, in a battery having such a positive electrode, the discharge voltage may drop irregularly or, in the worst case, an internal short circuit may occur.

The present invention is intended to provide a non-aqueous solvent battery which eliminates the battery failure caused by the weak mechanical strength of the porous carbon body of the positive electrode, and has excellent discharge voltage stability and heavy load characteristics. Is.

[0008]

According to the present invention, an alkali metal such as lithium or sodium is used as a negative electrode active material, and a positive electrode having a porous carbon body as a main constituent, and an oxyhalide as a main component are also used as a positive electrode active material. A non-aqueous solvent battery comprising an electrolytic solution, wherein carbon fibers are added and mixed to the porous carbon body of the positive electrode. In the present invention, the mixing ratio of the carbon fiber is preferably 5 to 20% by weight with respect to the porous carbon.

[0009]

[Function] A porous carbon body formed of a binder mixed with such carbon fibers is used in a discharge reaction after battery assembly,
It is considered that the intermediate reaction product and the discharge reaction product are accumulated in the positive electrode made of the porous carbon body and are electrically insulated. With respect to this electrical insulation, the carbon fiber can maintain electrical continuity and provide the positive electrode with electrical conductivity, thereby improving the stability of the discharge voltage of the battery and improving the voltage during heavy load discharge. Further, since the porous carbon body can be solidified solidly, it becomes easy to handle it during the manufacturing process of the positive electrode and the battery assembly.

The carbon fiber has a fiber diameter of 8 to 25.
It is effective to have a carbon content of 96% by weight or more and a fiber length of 0.5 to 7 mm. The mixing ratio is preferably in the range of 5 to 20% by weight with respect to the porous carbon body. The reason for this is that if the mixing ratio is less than 5% by weight, the shape retention and strength of the porous carbon body become insufficient, and if it exceeds 20% by weight, the porosity of the porous carbon body is reduced and discharge performance is deteriorated. May have an adverse effect.

[0011]

EXAMPLE An example in which the present invention is applied to an AA size lithium thionyl chloride battery will be described below with reference to FIG. Reference numeral 1 in the figure is a bottomed cylindrical can body made of, for example, stainless steel, the upper surface of which also serves as a negative electrode terminal is opened. The inner surface of the can body 1 has a cylindrical negative electrode 2 made of metallic lithium.
Is crimped. Inside the negative electrode 2, a positive electrode 3 is provided via a separator 4 made of a glass fiber nonwoven fabric arranged on the inner surface of the negative electrode 2.

A bottom paper 5 made of the same glass fiber non-woven fabric as the separator 4 is also interposed between the positive electrode 3 and the bottom surface of the can body 1. The positive electrode 3 has a tubular porous carbon body 6,
The porous carbon body 6 is composed of a metal current collector 7 made of a cylindrical wire mesh and arranged on the inner surface of the hollow portion. The positive electrode 3 was obtained by adding 10% by weight of polytetrafluoroethylene to carbon black, and corresponding to 10% by weight of the mixture, the fiber diameter was 8 to 25 μm, and the fiber length was 0.5 to 7.0 m.
m, carbon fibers having a carbon content of 95% by weight or more were mixed, and ethyl alcohol was added and kneaded, and then press-formed into a tubular shape, and a tubular metal current collector made of nickel mesh was inserted into the hollow portion and pressure-welded. And further dried and solidified under vacuum at 150 ° C.

In the can body 1 above the positive electrode 3,
An insulating paper 8 having a hole in the center thereof is arranged to be supported by the separator 4. A metal top 9 is capped at the upper opening of the can body 1 by laser welding or the like. A hole 10 is opened at the center of the metal top 9.
A pipe-shaped positive electrode terminal 11 is fixed to the metal top 9 by a glass sealing material 12 in an electrically insulated state. The positive electrode terminal 11 is connected to the metal current collector 7 of the positive electrode 3 via a lead wire 13 attached to the lower end thereof. Further, the pipe-shaped positive electrode terminal 1 is provided in the can body 1.
The electrolytic solution 14 injected from 1 is contained. The electrolytic solution 14 is lithium aluminum tetrachloride (LiAlC).
l ₄₎ made of, for example, 1.2 mol 1 liter dissolved thionyl chloride (SOCl _2). It should be noted that the pipe-shaped positive electrode terminal 11 is inserted with, for example, a stainless steel flanged plug body 15, and the hole of the positive electrode terminal 11 is sealed by laser welding the tip of the terminal 11 and the inserted plug body 15. There is.

Comparative Example Polytetrafluoroethylene was added to carbon black in an amount of 10
% By weight, and ethyl alcohol is added to this mixture and kneaded. In addition, carbon fiber is not mixed with this mixture. After that, it was formed into a tubular shape in the same manner as in the example, and a tubular metal current collector was inserted into the hollow portion of the formed body under pressure contact, dried under a vacuum of 150 ° C. and solidified to produce a positive electrode. A comparative battery having the same structure as that of the example was assembled except that such a positive electrode was used.

Here, the battery A of this example and the battery B of comparative example
Regarding the number of defective occurrences such as cracking and chipping of the porous carbon body of the positive electrode in the assembling process such as loading the positive electrode into the can body, as shown in FIG. 2, and a good discharge curve at 300Ω load,
The number of defective batteries, such as non-defective products, which do not maintain a flat voltage until the end of discharge, was examined. The results are shown in the table below.

[0016]

[Table 1]

The heavy load discharge characteristics of the batteries of this example and comparative example were examined. The results are shown in FIG. In the figure, A is the characteristic line of the battery of the embodiment of the present invention,
B shows the characteristic lines of the battery of the comparative example, respectively. As is clear from Table 1 and FIG. 3, the battery of the present invention has significantly less cracking and chipping of the porous carbon body of the positive electrode, stability of discharge voltage, and heavy load characteristics, as compared with the conventional comparative battery. You can see that it is also excellent.

The diameter of the carbon fiber is set to 8 to 25 μm because when the diameter is less than 8 μm, the carbon fiber is cut off during mixing.
This is because if it exceeds 25 μm, uniform mixing cannot be achieved. Further, the length of the carbon fiber is set to 0.5 to 7.0 mm, because the conductive net is cut by the discharge reaction product when the length is less than 0.5 mm, and the porous when the length exceeds 7.0 mm. This is because there is no point in making the carbonaceous material cut when it is formed and making it long.

[0019]

As described in detail above, by mixing the carbon fiber of the present invention, it is possible to improve the mechanical strength of the porous carbon body of the positive electrode and eliminate the battery failure due to the brittleness of the carbon body. A non-aqueous solvent battery having excellent discharge voltage stability and heavy load characteristics can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a lithium thionyl chloride battery of an example of the present invention.

FIG. 2 is a comparison diagram of discharge curves of non-defective and defective lithium thionyl chloride batteries.

FIG. 3 is a characteristic diagram of a discharge voltage at heavy load resistances of the inventive battery A and the comparative battery B of the present invention.

[Explanation of symbols]

 1 Can body 2 Negative electrode 3 Positive electrode 6 Porous carbon body 7 Metal current collector 9 Metal top 11 Positive electrode terminal 14 Electrolyte

Claims (2)

[Claims] 1. A positive electrode containing an alkali metal such as lithium or sodium as a negative electrode active material and a porous carbon body as a main component, and an electrolytic solution containing oxyhalide as a main component and also serving as a positive electrode active material. In the non-aqueous solvent battery, carbon fiber is added and mixed to the porous carbon body of the positive electrode. 2. The mixing ratio of the carbon fibers is 5 to 20% by weight with respect to the porous carbon.
The non-aqueous solvent battery described.