JPH0570268B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for producing an electrolyte for a non-aqueous battery.

[Technical background of the invention and its problems]

Nonaqueous solvent batteries that use lithium or sodium as negative electrode active materials have high energy density, excellent storage characteristics, and a wide operating temperature range, and are often used as backup power sources for calculators, watches, and memories.

Among the batteries mentioned above, lithium is used for the negative electrode,
BACKGROUND ART Batteries using sulfur or phosphorus oxyhalides such as thionyl chloride (SOCl ₂ ), sulfuryl chloride (SO ₂ Cl ₂ ), and phosphoryl chloride (POCl ₃ ) have attracted attention in recent years because of their particularly high energy density. These batteries have a positive electrode consisting of a carbon and metal current collector, and are generally made of a Lewis acid such as aluminum chloride (AlCl ₃ ), aluminum bromide (AlBr ₃ ) and lithium chloride (LiCl), lithium bromide (LiBr), etc. A sulfur or phosphorus oxyhalide in which Lewis base is dissolved is used as an electrolyte. Therefore, the oxyhalide serves both as a positive electrode active material and as an electrolyte, and by using a positive electrode with an appropriate shape, a battery with excellent high rate discharge characteristics can be expected.

By the way, in the above battery system, since the sulfur or phosphorus oxyhalide, which is the positive electrode active material, is in direct contact with the negative electrode lithium, a LiCl film, which is the main reaction product, is formed on the surface of the negative electrode lithium. This generated LiCl film has the function of preventing direct contact between the negative electrode lithium and the oxyhalide, and plays a role in preventing battery capacity deterioration during storage.
During discharge, it acts as a resistance component and causes a voltage drop at the beginning of discharge. The degree of this voltage drop is negligible when the discharge current is on the order of microamperes, but it cannot be ignored when the discharge current is large, especially when stored at high temperatures for long periods of time.
After a considerable amount of film growth has occurred or during discharge at low temperatures, there is a drawback that a significant voltage drop occurs at the start of discharge, and it takes a considerable amount of time to recover to a predetermined voltage.

[Purpose of the invention]

The present invention aims to provide a method for producing an electrolyte solution for a nonaqueous solvent battery that prevents voltage drop even in the initial stage of large current discharge and has excellent initial discharge characteristics.

[Summary of the invention]

As a result of extensive investigation into the cause of the voltage drop at the initial stage of discharge, the present inventors found that the neutralization reaction between Lewis acid and Lewis base in the electrolytic solution is incomplete, and in particular, an excessive amount of unreacted Lewis acid remains. We found out what happens due to this.

As a result of extensive research into the excessive residual unreacted Lewis acid, the present inventors found that a Lewis base was added to the Lewis acid dissolved in a solution of sulfur or phosphorus oxyhalide (positive electrode active material). The neutralization reaction takes an extremely long time, and
It has been found that in the past, a theoretical reaction equivalent of a Lewis base was added to a Lewis acid, so the neutralization reaction was not completed sufficiently and the Lewis acid remained.

Therefore, in the present invention, by adding an excess of Lewis base to Lewis acid in an amount of 1.2 times or more of the theoretical reaction equivalent,
It is possible to prepare an electrolytic solution with no residual unreacted Lewis acid, and by using this electrolytic solution, a large voltage drop can be suppressed even in the early stages of discharge, making it possible to obtain a non-aqueous solvent battery with excellent initial discharge characteristics. I discovered that.

Examples of the Lewis acid include AlF ₃ , AlCl ₃ ,
AlBr ₃ , SbCl ₅ , PCl ₃ , BF ₃ , BCl ₃ , BBr ₃ and the like can be used. In addition, examples of the Lewis base include LiF, LiCl, LiBr, NaF, NaCl,
KF, KCl, KBr, etc. can be used. As the positive electrode active material that constitutes the electrolyte together with Lewis acids and Lewis bases, that is, sulfur oxyhalides, thionyl chloride, sulfuryl chloride, etc. can be used, and as phosphorus oxyhalides, phosphoryl chloride, etc. can be used. can.

The reason for limiting the amount of Lewis base added to the Lewis acid is that if the amount of Lewis base is less than 1.2 times the theoretical reaction equivalent with Lewis acid, unreacted Lewis will remain even after a fairly long period of neutralization reaction. This is because the acid remains in the electrolytic solution, making it impossible to obtain an electrolytic solution suitable for a nonaqueous solvent battery that is highly effective in suppressing voltage drop at the initial stage of discharge.

Note that, as described above, after adding an excess of Lewis base to Lewis acid, the Lewis base that is not consumed in the reaction with Lewis acid remains in the prepared solution, but Lewis base is usually difficult to dissolve in oxyhalides. For this purpose, either filter the prepared solution to remove the Lewis base, or remove the supernatant of the prepared solution.
By either method, an electrolytic solution in which no Lewis base remains can be obtained.

[Embodiments of the invention]

Examples of the present invention will be described below.

Prepare four commercially available 100 ml volumetric flasks, add 13.3 g of aluminum chloride (AlCl ₃ ) and 80 ml of thionyl chloride (SOCl ₂ ) to each, and stir and dissolve.
Lithium chloride (LiCl) in an amount of 1.0 times, 1.1 times, 1.2 times, and 1.5 times the theoretical reaction equivalent with AlCl ₃ , respectively;
That is, add 4.24 g, 4.66 g, 5.09 g, and 6.36 g, stir, filter excess LiCl, and then add SOCl ₂ .
Four kinds of 100 ml of LiCl-AlCl ₃ /SOCl _2- based electrolytes were prepared.

Next, using these electrolytes, four types of R6 type lithium-thionyl chloride batteries as shown in FIG. 1 were fabricated.

In the figure, reference numeral 1 denotes a stainless steel can which also serves as a negative electrode terminal with an open top, and a cylindrical negative electrode 2 made of metallic lithium is crimped onto the inner surface of this can. Inside the can body 1 inside the negative electrode 2, there is a positive electrode 5, which has a structure in which a cylindrical porous carbon layer 4 is crimped onto the outside of a metal current collector 3 made of a cylindrical stainless steel net, and a cage-shaped cathode 5 made of glass fiber nonwoven fabric. are provided through a separator 6. The positive electrode 5 is made by mixing commercially available acetylene black and polytetrafluoroethylene, and molding the mixture together with a metal current collector 3 made of stainless steel in a cylindrical shape with the current collector 3 on the inside. After molding, the porous carbon layer 4 is produced by drying the kneaded material under vacuum at 150°C.

Further, a metal top 7 is sealed to the upper opening of the can body 1 by laser welding or the like, and a pipe-shaped positive electrode terminal 9 is connected to a hole 8 in the center of the metal top 7 through a sealing material 10 made of glass. electrically insulated and fixed. The lower end of the positive electrode terminal 9 is connected to the metal current collector 3 of the positive electrode 5 via a lead wire 11. Furthermore, four types of electrolytic solutions have already been prepared and injected into the can body 1 through the injection port 12 of the pipe-shaped positive electrode terminal 9, respectively. Note that after injection, the injection port 12 is sealed by laser welding or the like.

After the four types of R6 type lithium-thionyl chloride batteries were fabricated, they were stored at 45°C for 10 days, and then discharged at a constant resistance of 30Ω to examine the voltage change at the initial stage of discharge. I got it. In addition, A in Figure 2 indicates that when the amount of LiCl is 1.0 times the theoretical reaction equivalent with AlCl ₃ , B is 1.1 times, C is 1.2 times, and D is 1.5.
This is a discharge characteristic curve in the case of double the amount. As is clear from FIG. 2, when the amount of LiCl is 1.0 times, a significant voltage drop appears in A, and when the amount of LiCl is 1.1 times, there is still a significant voltage drop in B. On the other hand, compared to those
When the LiCl amount is 1.2 times C and 1.5 times D, almost no initial voltage drop occurs. This is because the neutralization of AlCl ₃ by LiCl is insufficient when LiCl is added at 1.0 times or 1.1 times the theoretical reaction equivalent of AlCl ₃ .
This is thought to be because complete neutralization occurs only when LiCl is added in an amount of 1.2 times or more.

In the above embodiments, a cylindrical structure in which a porous carbon layer was crimped to the outside of a metal current collector was used as the positive electrode, but the present invention is not limited to this. It is also possible to use a belt-shaped body which is wound spirally to form a positive electrode.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide a method for producing an electrolyte solution for a non-aqueous solvent battery that prevents voltage drop even in the initial stage of large current discharge and has excellent initial discharge characteristics.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one form of a non-aqueous solvent battery;
FIG. 2 is a diagram showing the discharge characteristics of the battery of this example at the initial stage of large current discharge. 1...Can body, 2...Negative electrode, 3...Metal current collector,
4... Porous carbon layer, 5 ... Positive electrode, 6... Separator, 7... Metal top, 9... Pipe-shaped positive electrode terminal, 10... Sealing material, 11... Lead wire, 1
2... Inlet.

Claims (1)

[Claims] 1. In the production of an electrolytic solution for non-aqueous batteries by dissolving a Lewis acid and a Lewis base in a sulfur or phosphorus oxyhalide, the amount of the Lewis base is 1.2 times the theoretical reaction equivalent with the Lewis acid. A method for producing an electrolytic solution for a non-aqueous battery, characterized in that a solution is prepared by adding the above amount in excess.