JPH0532867B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to improvements in nonaqueous solvent batteries. [Technical Background of the Invention] Nonaqueous solvent batteries using lithium and sodium as negative electrode active materials have high energy density, excellent storage characteristics, and a wide operating temperature range, making them useful for backup of calculators, watches, and memories. It is widely used as a power source. Among these, so-called lithium-thionyl chloride batteries, which use lithium for the negative electrode and thionyl chloride (SOCl ₂ ) as the main positive electrode active material, are attracting attention because of their particularly high energy density. Such batteries have a positive electrode made of a porous carbon body and a metal current collector, and generally use thionyl chloride (SOCl ₂ ) in which lithium chloride (LiCl) and aluminum chloride (AlCl ₃ ) are dissolved as an electrolyte. Therefore, thionyl chloride serves both as a positive electrode active material and as an electrolyte. By the way, the above-mentioned lithium-thionyl chloride battery has conventionally been known as having the structure shown in FIG.
Reference numeral 1 in the figure indicates a stainless steel outer can that is one of the constituent members of the can body, and this outer can 1 also serves as a negative electrode terminal. Further, a cylindrical negative electrode 2 made of metallic lithium is crimped onto the inner peripheral surface of the outer can 1 except for the upper part. A positive electrode 3 is housed in the outer can 1 inside the negative electrode 2 via separators 4 ₁ and 4 ₂ made of nonwoven fabric made of glass fiber, for example, which are arranged inside the negative electrode 2 and near the bottom of the outer can 1. . This positive electrode 3
is made by winding a band-shaped body in which a porous carbon layer 6 is crimped around a metal current collector 5. Further, in the outer can 1 above the positive electrode 3 , an insulating paper 7 having a hole in the center is disposed and supported by the separator ₄₁ . A metal top 8, which is the other component of the can body, is sealed to the upper opening of the outer can 1 by laser welding or the like. A hole 9 is opened in the center of this metal top 8. A pipe-shaped metal terminal 10 is inserted into the hole 9 and electrically insulated from the metal top 8 via a metal-glass sealing material 11. The lower end of this positive electrode terminal 10 is connected to the metal current collector 5 of the positive electrode 3 via a lead wire 12. Furthermore, an electrolytic solution 13 containing SOCl ₂ as a main component is injected from the pipe-shaped positive electrode terminal 10 into the outer can 1 . A needle body 14 made of stainless steel, for example, is inserted into the pipe-shaped positive electrode terminal 10, and the tip of the terminal 10 and the inserted needle body 14 are sealed by laser welding. [Problems with Background Art] However, the conventional battery shown in FIG. 1 has a drawback that capacity deterioration occurs during storage. Another drawback is that when discharging a large current after long-term storage at high temperatures or discharging large currents at low temperatures, a significant voltage drop occurs as soon as discharge begins, and it takes a considerable amount of time to recover to the desired voltage. It was hot. [Object of the Invention] The present invention aims to provide a non-aqueous solvent battery that exhibits less capacity deterioration due to storage and less voltage drop at the initial stage of large current discharge. [Summary of the Invention] As a result of various studies by the present inventors regarding the causes of capacity deterioration during storage in the conventional non-aqueous solvent battery shown in FIG _.
Also serves as the positive electrode active material, and the inner surface of the outer can and metal top, which serve as negative electrode terminals, are not completely covered with metallic lithium, which is the negative electrode, and are partially exposed. can body)
When the electrolyte comes into contact with the inner surface of the can,
We found that the reduction reaction of SOCl ₂ is caused by a so-called parasitic cell reaction, in which Li oxidation reaction occurs at the Li negative electrode. Furthermore, in general, in a lithium-thionyl chloride battery, the positive electrode active material SOCl ₂ is in direct contact with the negative electrode Li, so that a LiCl film, which is a reaction product, is generated on the Li surface. This LiCl film is composed of negative electrode Li and SOCl ₂
It has the function of preventing direct contact with the battery and prevents deterioration of battery capacity during storage, but during discharging it acts as a resistive component and causes a voltage drop in the early stages of discharge. It is thought that the growth of such a LiCl film is further promoted by the above-mentioned parasitic cell reaction, thereby making the voltage drop even larger at the beginning of a large current discharge. For this reason, the present inventors have attempted to avoid or suppress the parasitic battery reaction by covering part or the entire surface of the can with a passivation film or an insulating film, excluding the inner surface covered with the negative electrode. We have discovered a non-aqueous solvent battery that has low capacity deterioration and low voltage drop at the initial stage of large current discharge. [Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIG. Reference numeral 1 in the figure indicates a stainless steel outer can that is one of the constituent members of the can body, and this outer can 1 also serves as a negative electrode terminal. A cylindrical negative electrode 2 made of metallic lithium is crimped onto the inner peripheral surface of the outer can 1 except for the upper part. Further, the exposed inner surface of the outer can 1 other than the inner surface covered with the negative electrode 2, that is, the upper and bottom surfaces of the inner peripheral surface, is coated with, for example, a polypropylene film 15. A positive electrode 3 is housed in the outer can 1 inside the negative electrode 2 through separators 4 ₁ and 4 ₂ made of nonwoven fabric made of glass fiber, for example, which are arranged inside the negative electrode 2 and near the bottom of the outer can 1. . This positive electrode 3 is made by, for example, mixing a commercially available polytetrafluoroethylene emulsion with acetylene black at a ratio of 10 wt%, adding water and ethyl alcohol, stirring at room temperature for about 2 hours, kneading and forming into a sheet made of stainless steel. Crimp-bonded to a metal current collector 5 made of a mesh body,
The sheet is dried under vacuum at 150° C. to form a strip having a porous carbon layer 6, and this is produced by winding the strip. Further, in the outer can 1 above the positive electrode 3, an insulating paper 7 having a hole in the center and supported by the separator ₄₁ is disposed. A metal top 8, which is another component of the can body, is sealed to the upper opening of the outer can 1 by laser welding or the like. For example, the inner surface of the metal top 8 is coated with a polypropylene film 1.
5 is covered, and a hole 9 is opened in the center thereof. A pipe-shaped positive electrode terminal 10 is inserted into the hole 9 through a metal-glass sealing material 11 so as to be insulated from the metal top 8. The lower end of this positive electrode terminal 10 is connected to the metal current collector 5 of the positive electrode 3 via a lead wire 12. The outer can 1 accommodates an electrolytic solution 13 injected from the pipe-shaped positive electrode terminal 10. This electrolytic solution 13 has a composition in which aluminum chloride (AlCl ₃ ) and lithium chloride (LiCl) are each dissolved at a concentration of 1.8 mol in distilled thionyl chloride (SOCl ₂ ), for example. A needle body 14 made of stainless steel, for example, is inserted into the pipe-shaped positive electrode terminal 10, and the positive electrode terminal 10 is sealed by laser welding the tip of the terminal 10 and the inserted needle body 14. With this configuration, the exposed inner surface of the outer can 1 and the inner surface of the metal top 8 are coated with the polypropylene film 15, so that the electrolyte 13 is applied to both the exposed inner surface of the can and the Li negative electrode 2. Contact can be prevented, and the so-called parasitic cell reaction, in which a reduction reaction of SOCl ₂ occurs on the exposed inner surface of the can body and an oxidation reaction of Li on the Li negative electrode 2, can be prevented. Therefore, capacity deterioration due to storage can be suppressed, and the acceleration of the growth of the LiCl film on the surface of the Li negative electrode 2, which is thought to be caused by the parasitic cell reaction, can be suppressed, thereby reducing the significant voltage at the initial stage of large current discharge. You can improve your descent. In fact, the battery of the present invention shown in FIG.
The conventional battery shown in the figure was stored at 60°C for three months after assembly, and the relationship between load resistance and discharge capacity was investigated, and the characteristic diagram shown in Figure 3 was obtained. In addition,
In FIG. 3, A is a characteristic line of load resistance versus discharge capacity for the battery of the present invention, and B is the same characteristic line for a conventional battery. As is clear from FIG. 3, the battery of the present invention can reduce capacity deterioration due to storage compared to conventional batteries. Moreover, regarding the battery of the present invention and the conventional battery,
After assembly, the battery was stored at 25°C for one week, and discharged with a constant resistance of 8Ω to examine the voltage drop at the initial stage of discharge. The result was that while conventional batteries could drop to 1.2V,
It was found that the present invention has excellent initial discharge characteristics, with the voltage dropping to only 2.5V. In addition, in the above example, when covering the exposed inner surface of the can body with an insulating film, a polypropylene film was used.
It is not limited to this. For example, any insulating film that does not react with battery materials such as electrolyte can be used, such as a polyethylene film, a fluororesin film, or a polyamide resin film. Furthermore, if the outer can or metal top is made of a material such as stainless steel that can form a passivation film through strong acid treatment, a passivation film may be formed on the exposed inner surface of the can instead of the insulating film. . [Effects of the Invention] As detailed above, according to the present invention, it is possible to provide a non-aqueous solvent battery that exhibits less capacity deterioration due to storage and less voltage drop at the initial stage of large current discharge.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a conventional lithium-thionyl chloride battery, Fig. 2 is a cross-sectional view of a lithium-thionyl chloride battery showing an embodiment of the present invention, and Fig. 3 shows the relationship between load resistance and discharge capacity of the battery. It is a characteristic diagram showing a relationship. 1...Outer can, 2...Negative electrode, 3 ...Positive electrode, 4 ₁ ,
4 ₂ ... Separator, 5 ... Metal current collector, 6 ...
Porous carbon layer, 8... Metal top, 10... Pipe-shaped positive electrode terminal, 13... Electrolyte, 15... Polypropylene film.

Claims (1)

[Claims] 1 A negative electrode made of light metals such as lithium, sodium, and aluminum is provided on the inner surface of the can, and a positive electrode mainly composed of porous carbon is housed in the can inside the negative electrode via a separator, and oxyhalogen is In a non-aqueous solvent battery containing an electrolyte containing a compound as a main component and serving as a positive electrode active material, a passivation film or an insulating film is applied to a part or the entire exposed surface of the can excluding the inner surface covered with the negative electrode. A non-aqueous solvent battery characterized by being covered with.