JPS58163176A - Organic electrolytic battery - Google Patents

Abstract

PURPOSE:To restrict the increase of internal resistance and prevent the deterioration of discharge capacity during storage by using an electrolyte obtained by dissolving the compound indicated by a specific chemical formula in 1,3-dioxolane or a mixed solvent containg 1,3-dioxolane. CONSTITUTION:An electrolyte is obtained by dissolving a compound indicated by general formula (I) (where, m is a positive number of 1-4) in 1,3-dioxolane or a mixed solvent containing 1,3-dioxolane. In this case, the concentration of the compound indicated by general formula (I) should be 0.5-3.5mol/l. Besides, since the compound indicated by general formula (I) has slightly a property of non-ring-opening polymerization to 1,3-dioxolane, an amine compound should previously be dissolved in 1,3-dioxolane or a mixd solvent containing 1,3-dioxolane to suppress this phenomenon. The compound indicated by general formula (I) is obtained by dissolving LiPE6 in 1,2-dimethoxyethane, filtering it, then cooling and crystallizing the filtrate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a compound represented by the general formula (1) (% formula %) () (in the formula, m is a positive number from 1 to 4) as an electrolyte, and uses this as an electrolyte. The present invention relates to an organic electrolyte battery using an electrolyte solution dissolved in a mixed solvent containing dioxolane or 1,8-dioxolane.

Recently, LiPF6 has attracted much attention as an electrolyte for organic electrolyte batteries because it has good solubility in organic solvents, high conductivity, and is safer than perchlorate-based ones. .

However, this compound is very unstable and easily decomposes in the presence of moisture and heat, and commonly available commercial products contain considerable impurities, and these impurities and decomposition products become active materials in batteries. The reaction causes a decrease in discharge capacity, gas generation, and an increase in internal resistance.

In particular, when a cyclic ether organic solvent such as 1,8-dioxolane is used as a solvent for the electrolyte, the impurities and decomposition products cause ring-opening polymerization of the cyclic ether organic solvent, and the conductivity of the electrolyte increases. becomes extremely low and becomes unusable.

However, 1,8-dioxolane has properties that are highly desirable as an electrolyte solvent for organic electrolyte batteries, such as high electrolyte solubility and high conductivity.
There is a request to use this by all means.

The present inventors have conducted various studies in view of the above circumstances, and have found that LiPF6 is dissolved in 1,2-dimethoxyethane, and after filtration, the filtrate is cooled and crystallized. When preparing an electrolytic solution by obtaining a compound represented by general formula (I) which is a solvate of 1,8-dioxolane or a mixed solvent containing 1,8-dioxolane, during storage, We have discovered that an organic electrolyte battery can be obtained with little increase in internal resistance or decrease in discharge capacity, and which takes advantage of the advantages of LiPF6 as an electrolyte and the advantages of 1,8-dioxolane as an electrolyte solvent. He completed his invention.

That is, the compound represented by general formula (I) is more stable than its starting material L i P F6, and L
Since the impurities contained in LiPF6 are removed during the transformation from iPF6 to the compound represented by the general formula (I), an organic electrolyte battery with less increase in internal resistance and less decrease in discharge capacity during storage can be obtained. It will be done. However, LiPF
The excellent properties of 6 as an electrolyte, such as good solubility in organic solvents and high electrical conductivity, are not lost even when it is converted into a compound represented by general formula (I), and therefore it has very characteristic properties. You can get a good battery.

The compound represented by the general formula (I) can be obtained by dissolving L i P F6 in 1,2-dimethoxyethane, filtering it, and then cooling the filtrate to crystallize it.

When LiPF6 is dissolved in 1,2-dimethoxyethane, heat is generated and LiPF6 is solvated with 1,2-dimethoxyethane and changes into a compound represented by general formula (I). In order to avoid decomposition of the compound represented by general formula (I), the dissolution is preferably carried out at 70°C or lower, and the temperature of the solution is kept at 50°C or lower from the time of dissolution until the end of filtration.
Preferably, the temperature is maintained at 70°C. By this dissolution and filtration, impurities contained in LiPF6 that do not dissolve in 1,2-dimethoxyethane are removed. Cooling for crystallization is usually carried out at a temperature below 25°C and above the freezing point of 1,2-dimethoxyethane. At this time, L i P
Impurities contained in F6 dissolved in 1,2-dimethoxyethane do not crystallize and remain in the solution, and are removed by filtration. After filtration, 1,2-dimethoxyethane adhering to the crystals is removed by drying at 0 to 6°C under reduced pressure. The value of m in general formula (I) can be adjusted by appropriately adjusting the degree of reduced pressure, temperature, time, etc. during this drying.

The electrolytic solution is obtained by dissolving the compound represented by the general formula (I) in a mixed solvent containing 1,8-dioxolane or 1,8-dioxolane. At that time, the general formula (I
) is preferably 0.5 to 8.5 mol/l.

The compound represented by the general formula (I) itself has a 1°8
-Since dioxolane has a slight tendency to cause ring-opening polymerization, in order to suppress this, 1,8-dioxolane or 1,8-dioxolane or
It is desirable to dissolve the amine compound in advance in a mixed solvent containing , 8-dioxolane.

Examples of such amine compounds include 1t8-bis(dimethylamino)naphthalene, 2,2.6°6-titramethylpiperidine, N, N, N', N'-tetramethyl-1,8-propanediamine, 2.8.5.
6-tetramethyl-p-phenylenediamine, N, N,
N5N1-tetramethylbenzidine, N, N, N'
, N'-tetramethyl-1,4-butanesiaquine, N
, N, N', N'-tetramethylethylenecyamine, etc. are used.

If the amount of these amine compounds is too large, the battery performance will deteriorate, so it is preferable that the amount of these amine compounds is 0.1 to 5% by weight (wt%, the same applies hereinafter) to the solvent.

When 1.8-dioxolane is mixed with other organic solvents, examples of the other organic solvents include propylene carbonate, T-butyrolactone, 1,2-dimethoxyethane, dimethylformacide, dimethylacetoacide, dimethylsulfoxide, and nitromethane. , N-methyl-
2-oxazolidone, diglyme, triglyme, etc. are used.

The above electrolyte can be applied to all organic electrolyte batteries regardless of the type of active material, but a preferred example is when the negative electrode active material is lithium or a lithium-based alloy such as lithium-aluminum or lithium-zinc; This is a battery in which the positive electrode active material is a metal sulfide such as titanium disulfide, iron sulfide, or copper sulfide.

Next, the present invention will be explained with reference to Examples.

Example 1 LiP F6 was added to a mixed solvent of 1,8-dioxolane and 1,2-dimethoxyethane in a volume ratio of 91:9.
・An electrolytic solution was prepared by dissolving 1.5 mol/l of 8 (CH30CH2CH20CH5).

Using this electrolyte, a battery with a hermetic seal structure was manufactured using lithium as a negative electrode active material and titanium disulfide as a positive electrode active material.

The electrodes of the above battery consist of a negative electrode plate with a stainless steel welded mesh crimped onto one side of a lithium plate, and a positive electrode mixture containing titanium disulfide as the positive electrode active material in the form of a plate with a stainless steel welded mesh as the core material. A positive electrode plate that has been molded and covered with a separator is stacked one on top of the other, and this is spirally wound around a stainless steel pipe provided in the center of the sealing lid. The separator is made of a stack of microporous polypropylene film and polypropylene nonwoven fabric, and the sealing lid is made of an insulating part made of glass around a stainless steel pipe and a part of the body made of stainless steel formed around it. After forming the spiral electrode, put it into a stainless steel battery case together with the spiral electrode, weld the opening of the battery case and the outer periphery of the sealing lid, and then inject the electrolyte through the pipe. After injection of
A thin stainless steel rod is inserted into the pipe, and its head is welded to the pipe to seal the inside of the battery.

Example 2 N+ N+ N'+ N in a mixed solvent with a volume ratio of 91:9 of 1.8-dioxolane and 1,2-dimethoxyethane
After adding and mixing 1.0 g of '-tetramethylethylenediamine, 1.0 g of LiPF6.8 (CH30CH2CH20CH3) was added.
．． An electrolytic solution was prepared by dissolving 5 mol/l, and a battery was manufactured in the same manner as in Example 1 except that this electrolytic solution was used.

Comparative Example 1 N・N, N', N' in a mixed solvent of 1.8-dioxolane and 1,2-dimethoxyethane with a volume ratio of 91:9
- After adding and dissolving 1.0 g of tetramethylethylenediamine, 1.5 g of commercially available LiPF6 (purity 98 g) was added.
An electrolytic solution was prepared by dissolving mol/l, and a battery was manufactured in the same manner as in Example 1 except that this electrolytic solution was used.

Table 1 shows the results of measuring the initial internal resistance and the internal resistance after storage at 60° C. for 10 days of the batteries of Examples 1 and 2 and the battery of Comparative Example 1 manufactured as described above.

Table 1 As shown in Table 1, the battery of the present invention shows less increase in internal resistance due to storage than the battery of Comparative Example 1.

Claims (1)

[Claims] 1. A compound represented by the general formula (1) % formula % (in the formula, m is a positive number from 1 to 4) is 1,8-dioxolane or 1.8
- An organic electrolyte battery characterized by using an electrolyte solution dissolved in a mixed solvent containing dioxolane. 2. The organic electrolyte battery according to claim 1, wherein the mixed solvent containing 1.8-dioxolane or 1,8-dioxolane is one in which an amine compound is dissolved in advance. 8. The organic electrolyte battery according to claim 1 or 2, wherein the negative electrode active material is lithium or a lithium-based alloy. 4. The organic electrolyte battery according to claim 1, 2 or 8, wherein the positive electrode active material is titanium disulfide.