JPH09245775A - Non-aqueous solvent battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the mechanical strength of a porous carbon body and obtain a battery with its superior discharge voltage stability and heavy load characteristics by adding and mixing a glass fiber of specific diameter to the porous carbon body of a positive electrode main constituent in a non-aqueous solvent battery. SOLUTION: A non-aqueous solvent battery is composed of a positive electrode having an alkali metal as a negative electrode active material and a porous carbon body as a main constituent and an electrolyte having an oxy- halide as a main component serving as a positive electrode active material. A glass fiber of 5 to 13μm in diameter is added to and mixed with a porous carbon body by 1 to 8wt.%. Since the porous carbon body can be solidified rigidly by molding a binding agent, handling during manufacturing process of the positive electrode and during battery assembling is facilitated. In addition, the adhesive property to or shape holing characteristics of a metal aggregate can be improved, the internal resistance of the battery is not varied at the end of discharging, the voltage is stabilized, and the battery characteristics are improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an improvement of 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 An alkali metal such as lithium or sodium is used as a negative electrode active material, and an oxyhalide such as thionyl chloride or sulfuryl chloride is used as a solvent for an electrolytic solution and a positive electrode active material. A non-aqueous solvent battery, whose main material is a positive electrode, has a large energy density, excellent storage characteristics, and a wide operating temperature range, and is widely used as a backup power source for calculators, watches, and memories. There is.

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
_The so-called lithium-thionyl chloride battery using ₂ ) as the main positive electrode active material has attracted attention because of its 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, porosity, electrical conductivity, etc. of the positive electrode active material for the electrochemical reaction are important factors.

By the way, as a porous carbon body for the positive electrode of the above-mentioned cylindrical battery, polytetrafluoroethylene has been conventionally added to a carbon black such as acetylene black as a binder and kneaded, and then formed into a predetermined shape. Are used. Such a porous carbon body is microscopically viewed. Carbon black particles are trapped in polytetrafluoroethylene formed into a cobweb-like fiber, and the positive electrode volume expansion that occurs when the discharge product accompanying the positive electrode reaction is deposited between the carbon black particles can be performed smoothly. Since it has the function of absorbing uniformly, it contributes to the improvement of the utilization factor of the positive electrode. Such a binding mode by cobweb-like fiberization is the greatest feature of the polytetrafluoroethylene binder, and cannot be realized by other binders. Polytetrafluoroethylene is also extremely excellent in durability against liquid oxyhalides.

[0006]

However, the 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 contained in the porous carbon body and is loaded into the can body as a positive electrode, defects such as cracks and chips are generated in the porous carbon body, and a machine after the battery is assembled. The porous carbon body is separated from the metal current collector by static impact,
Adhesion with the separator may deteriorate. 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 solves the problems of the conventional battery of the same kind, that is, the battery failure caused by the weak mechanical strength of the porous carbon body of the positive electrode, and the stability of the discharge voltage and the heavy load characteristics. To provide an excellent non-aqueous solvent battery.

[0008]

Means for Solving the Problems The present invention comprises a positive electrode having an alkali metal as a negative electrode active material and a porous carbon body as a main constituent, and an electrolytic solution having an oxyhalide as a main component and also serving as a positive electrode active material. In the non-aqueous solvent battery comprising the above, the positive electrode is characterized in that glass fibers having a diameter of 5 to 13 μm are added and mixed to the porous carbon body in an amount of 1 to 8% by weight.

A porous carbon body molded with a binder mixed with such glass fibers strengthens the porous carbon body as compared with the case where the porous carbon body is composed of only polytetrafluoroethylene. Since it can be solidified, it not only facilitates the handling during the positive electrode manufacturing process or during electrical assembly, but also improves the adhesion to the metal current collector and shape retention characteristics, which in turn prevents the internal resistance of the battery from fluctuating at the end of discharge. , The voltage is stable and the characteristics are improved.

As the above-mentioned glass fibers, those having a fiber length of 0.5 to 9 mm are effective. The addition / mixing ratio is in the range of 1 to 8% by weight with respect to the porous carbon body, preferably 7 to 8% by weight, and more preferably 4%.
-6% by weight, particularly preferably 1-3% by weight. The reason is that if the addition / mixing ratio is less than 1% by weight, the shape retention and strength of the porous carbon body become insufficient, and if it exceeds 8% by weight, the porosity of the porous carbon body decreases. This is because the discharge performance may be adversely affected.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to an example applied to an AA size lithium thionyl chloride battery (see FIG. 1).

[Example] 1 in the drawing is a bottomed cylindrical can body made of, for example, stainless steel, which has an open upper surface which also serves as a negative electrode terminal. A cylindrical negative electrode 2 made of metallic lithium is pressure-bonded to the inner surface of the can body 1. 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.

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 is a cylindrical porous carbon body 6
And a metal current collector 7 made of a cylindrical wire mesh disposed on the inner surface of the hollow portion of the porous carbon body 6. The positive electrode 3 was obtained by adding 10% by weight of polytetrafluoroethylene to carbon black and adding 3% by weight to the mixture.
Fiber diameter of 7.5 μm and fiber length of 0.5-9.
After blending 0 mm glass fiber, adding ethyl alcohol and kneading, press-molding it into a tubular shape, insert a tubular metal current collector made of nickel mesh into the hollow part, press it, and
It was produced by drying and solidifying under vacuum at 50 ° C.

Further, in the can body 1 above the positive electrode 3, an insulating paper 8 supported by the separator 4 and having a hole in the center is disposed. 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, and a pipe-shaped positive electrode terminal 11 is fixed to the hole 10 by a glass sealing material 12 while being electrically insulated from the metal top. . 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 of the positive electrode terminal 11. Further, the electrolytic solution 14 injected from the pipe-shaped positive electrode terminal 11 is contained in the can body 1.
The electrolytic solution 14 is lithium aluminum tetrachloride (Li
It consists of thionyl chloride (SOCl ₂ ) in which 1.2 mol / liter of AlCl ₄ ) is dissolved. The pipe-shaped positive electrode terminal 11
For example, a plug 15 made of stainless steel with a collar is inserted, and the hole of the positive electrode terminal 11 is sealed by laser welding the tip of the terminal and the inserted plug 15.

Comparative Example-1 10% by weight of polytetrafluoroethylene was added to carbon black, and ethyl alcohol was added to this mixture and kneaded. It should be noted that glass 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 was assembled in the same manner as the example except that such a positive electrode was used.

[Comparative Example 2] 10% by weight of polytetrafluoroethylene was added to carbon black, and glass fiber having a fiber diameter of 3 μm and a fiber length of 0.5 to 9.0 mm corresponding to 10% by weight of the mixture. And knead by adding ethyl alcohol. 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 was assembled in the same manner as the example except that such a positive electrode was used.

Comparative Example 3 10% by weight of polytetrafluoroethylene was added to carbon black, and a glass fiber having a fiber diameter of 15 μm and a fiber length of 0.5 to 9.0 mm, which corresponds to 10% by weight of the mixture. And knead by adding ethyl alcohol. 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 was assembled in the same manner as the example except that such a positive electrode was used.

Here, the battery A of this embodiment, the battery B of Comparative Example-1 and the battery C of Comparative Example-2 and the battery D of Comparative Example-3 are as follows.
The number of good products and defective products was examined. The results are shown in Table 1. Here, the defective product is a product in which a porous carbon body that is a positive electrode is cracked or chipped in an assembly process such as loading the positive electrode into a can body, or a discharge curve under a load of 300Ω (see FIG. 2). In Fig. 2, a flat voltage could not be maintained until the end of discharge (b in Fig. 2), while a good product refers to a product showing the characteristics as shown in Fig. 2a.

[0019]

[Table 1]

The heavy load discharge characteristics of the batteries of this example and each comparative example were examined. The results are shown in FIG. Here, A in the drawing is the characteristic line of the battery of the example of the present invention, and B, C, and D are the characteristic lines of the batteries of Comparative Examples-1, -2, and -3.

As is clear from Table 1 and FIG. 3, the battery of the present invention has very few cracks and cracks in the porous carbon body of the positive electrode and the stability of the discharge voltage as compared with the conventional comparative battery.
It can be seen that it is also excellent in terms of heavy load characteristics.

The reason why the diameter of the glass fiber is 5 to 13 μm is that if the diameter is less than 5 μm, the glass fiber is cut during the mixing, and if it exceeds 13 μm, the uniform mixing cannot be achieved. The length of the glass fiber is 0.5 to 9.0 mm. The reason is that if the length is less than 0.5 mm, the discharge reaction product may cut the conductive network, and if it exceeds 9.0 mm, the porosity may increase. This is because there is no point in making the carbonaceous material cut when it is formed and making it long.

[0023]

As described above, according to the present invention, the mechanical strength of the porous carbon body of the positive electrode can be improved, the battery failure due to the brittleness of the porous carbon body can be eliminated, and the discharge voltage can be stabilized. It is possible to provide a non-aqueous solvent battery having excellent properties and heavy load characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of a battery of the present invention.

FIG. 2 is a diagram showing an example of a determination pattern of a non-defective product and a defective product.
Discharge curve at 0Ω load.

FIG. 3 is a diagram showing heavy load discharge characteristics.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Can body 2 ... Negative electrode 3 ... Positive electrode 6 ... Porous carbon body 7 ... Metal current collector 9 ... Metal top 11 ... Pipe-shaped positive electrode terminal 14 ... Electrolyte

Claims (1)

[Claims] 1. A non-aqueous solvent battery comprising a positive electrode containing an alkali metal as a negative electrode active material and a porous carbon body as a main constituent, and an electrolytic solution containing oxyhalide as a main component and also serving as a positive electrode active material. In, the positive electrode has a diameter of 5 to 13 μm.
A non-aqueous solvent battery, wherein the glass fiber of 1. is added and mixed in an amount of 1 to 8% by weight with respect to the porous carbon body.