JPH02260368A - Organic electrolyte battery - Google Patents

Abstract

PURPOSE:To increase the storage stability of a battery by containing a specific N-dialkylamide in an organic electrolyte containing LiPF6. CONSTITUTION:In a battery having an organic electrolyte prepared by dissolving electrolytes containing LiPF6 in a nonaqueous solvent, N-dialkylamide represented by the general formula (a) (Wherein R1 and R2 are a saturated hydrocarbon group which may contain oxygen atom or nitrogen atom, R3 is hydrogen atom or the same saturated hydrocarbon group as R1 and R2, and two of R1-R3 may be linked together circularly.) is contained in the electrolyte. Good storage stability is obtained. The content of the N-dialkylamide in the electrolyte is generally 0.1-20vol.%, preferably 1-10vol.%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a battery using an organic electrolyte, such as a lithium battery.

[Conventional technology]

As an organic electrolyte used in this type of battery, one in which an electrolyte consisting of a lithium salt is dissolved in a nonaqueous solvent such as propylene carbonate, γ-butyrolactone, dimethoxyethane, or dioxolane is well known.

The above lithium salts include L i Cl 04 , L
iAsF, , LiPF6, etc. are commonly used, but among these, LiCIO4 has safety problems such as ignition when over-discharged, and LiAsF6 contains As, so it is not popular in Japan. It is difficult for consumers to accept it due to its toxicity. For this reason, LiPF, which does not have such safety and toxicity problems, is practically used as the most preferable material.

[Problem to be solved by the invention]

However, organic electrolyte batteries that use LiPF6 as an electrolyte have poor thermal stability and lose Li when stored at high temperatures.
There was a problem in that the electrolyte solution was colored due to decomposition of PF, and battery performance was significantly deteriorated.

Therefore, in order to avoid such problems, bexamethylphosphoric triamide (hereinafter referred to as HM) was added to the organic electrolyte.
PA) and tetramethylethylenediamine (hereinafter referred to as PA) and tetramethylethylenediamine (hereinafter referred to as
Attempts have been made to add additives such as TMEDA, but these additives do not have sufficient effects, especially when
Since MPA and the like may react with the negative electrode Li, it was not possible to expect much improvement in storage stability.

In view of the above-mentioned circumstances, this invention significantly improves the storage stability of an organic electrolyte battery using LiPF6 as an electrolyte by including a specific additive with low reactivity with negative electrode Li in the organic electrolyte. The aim is to improve.

[Means to solve the problem]

As a result of intensive studies to achieve the above object, the inventors found that a specific N
- It was found that the storage stability of the battery was significantly improved when a dialkylamide compound was included, and this invention was completed.

That is, in this invention, the electrolyte is in a non-aqueous solvent with l, i
In a battery made of an organic electrolyte in which an electrolyte containing PF is dissolved, the general formula (a) in the above electrolyte is: (where RI and Rz contain an oxygen atom or a nitrogen atom in the carbon chain) R1 is a hydrogen atom or a saturated hydrocarbon group similar to the above RI, Rz, and two of R1-R3 may be connected to each other in a cyclic form) - An organic electrolyte battery characterized by containing a dialkylamide compound.

[Structure and operation of the invention]

As mentioned above, the organic electrolyte of the battery of this invention is LiP
A specific N-dialkylamide compound represented by the general formula (a) is contained in a non-aqueous solvent in which an electrolyte containing F is dissolved, and this provides particularly good storage stability. The reasons for this are not necessarily clear at present. It is speculated that because the nitrogen atom part has a strong L+ ion attracting property, it has a strong stabilizing effect on unstable ions such as L i P F b.
This is presumed to be due to the fact that the reactivity with the Li electrode is not so strong.

The above N-dialkylamide compound used in the present invention is a compound represented by the general formula (al), in which R, R, may contain an oxygen atom or a nitrogen atom in the carbon chain. A certain number of carbon atoms is usually 1 to 10, particularly preferably 1
~3 saturated hydrocarbon groups, and R3 is a hydrogen atom or a saturated hydrocarbon group similar to the above RI, Rz, and R
Two of 1-R3 may be connected to each other in a ring. Note that, for example, when R and R1 are connected to each other, the number of carbon atoms may be twice the number of carbon atoms described above.

Specific examples of such N-dialkylamide compounds include 1-methyl-2-piperidone, 1-methyl-2-pyrrolidinone, 1-ethyl-2-pyrrolidinone, N-N-
Dimethylacetamide, N・N-diethylacetamide, N-N-dimethylformamide, N-N-dimethylpropionamide, ■・5-dimethyl-2-pyrrolidinone, 1,3-dimethyl-3,4,5,6-titrahydro 2(IH)-pyrimidinone, 4-formylmorpholine, l-formylpiperidine, 1-(3-methyl-butyryl)pyrrolidine, N-methylcaprolactam, bispentamethyleneurea, 1-cyclohexyl-2-pyrrolidinone, N -N-dimethyldodecanamide, N·N-diethylformamide, N-N-diethylpropionamide, 1,3-dimethyl-2-imidazolidinone, and the like.

The content of this N-dialkylamide compound in the electrolytic solution is generally 0.1-b, preferably 1-b. If this content is too small, the desired effect cannot be obtained, and if it is too large, there is a risk of impairing battery performance. Both are undesirable.

Non-aqueous solvents used in the electrolyte include propylene carbonate, γ-butyrolactone, dimethyl sulfoxide, ethylene carbonate, 1,2-dimethoxyethane,
Examples include tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 2-methyltetrahydrofuran, other aliphatic monoethers and polyethers.

In addition, as an electrolyte, LiPF can be used alone, or it can be used with other electrolytes, such as LiPF.
! 04 , L I CF 3 S O:l , L I
B F a, LiCFsCO□, LiAsF6, Li
B (C.

H5)4, Li5bl”, etc. When using the other electrolytes mentioned above, these other electrolytes should be used within an appropriate amount range that does not pose any problems in terms of safety or toxicity. The appropriate range should be determined individually depending on each electrolyte.

In addition, the total amount of electrolyte used is generally determined by the type of electrolyte from a range of 0.2 to 1.5 mol/l so that the electrical conductivity of the electrolyte at 25°C is usually 3 ms/a++ or more. It is preferable to select the optimum usage amount depending on the situation.

The battery of the present invention uses an organic electrolyte solution obtained by dissolving an electrolyte containing LiPF6 in the above-mentioned non-aqueous solvent and further containing an N-dialkylamide compound represented by the above-mentioned general formula (a). It includes various primary batteries and secondary batteries constructed by combinations of active materials used for positive and negative electrodes.

As the positive electrode active material, MnO□, ■201, MO03%
Pb30a, Bi:+Os, CO:+04,
Ti0z, Cr+Os, Cr, O,, LiCoO
Metal oxides such as 2 and their composite oxides, T
Examples include metal sulfides such as iS z , Cu S s Fe S, and mixtures thereof. Among these, MnO□ is suitable because it has a high single-electrode potential and a high voltage of about 3V can be obtained in a battery using lithium as the negative electrode active material. High quality MnO□ has the advantage of providing excellent cycle characteristics.

On the other hand, examples of the negative electrode active material include light metals such as lithium, potassium, sodium, calcium, and magnesium, as well as lithium alloys, and among these, lithium is particularly preferred.

FIG. 1 shows an example of the configuration of a spiral cylindrical battery to which the present invention is applied. In this figure, l is a positive electrode, 2 is a negative electrode, 3 is a bag-shaped separator that encloses the positive electrode 1, 4 is an organic electrolyte having the above structure, and both electrodes 1.2 are formed by overlapping strips and winding them in a spiral shape. In this state, it is loaded into a cylindrical stainless steel battery case 5 that forms a negative electrode can, and the entire battery case is immersed in an electrolytic solution 4.

Note that the present invention is applicable to various battery forms, such as various cylindrical batteries other than the illustrated spiral type, and thin batteries such as button-shaped and coin-shaped batteries.

〔Effect of the invention〕

The organic electrolyte battery of this invention uses LiPFh as the electrolyte.
By incorporating a specific N-dialkylamide compound into the organic electrolyte containing the organic electrolyte, there is no problem of safety or toxicity, and there is an advantage of excellent storage stability.

〔Example〕

EXAMPLES Below, examples of the present invention will be described in more detail.

Example 1 Inside a stainless steel battery case with an outer diameter of 15 m, a battery with a thickness of 0
．． A strip-shaped negative electrode made of lithium with a width of 17 W and a width of 30 mm and a strip-shaped positive electrode made of a MnO□ mixture with a thickness of 0.4+n and a width of 30 mm wrapped in a bag-shaped separator made of microporous polypropylene are stacked and swirled. The lead body of both positive and negative poles was attached and loaded in a wound state, and 0.6 mol/l was added to a mixed solvent of propylene carbonate, tetrahydrofuran, and 1,2-dimethoxyethane in a weight ratio of 1:1:1. An organic electrolyte having a water content of 50 ppm or less was injected into the tank by dissolving LiPFb as an electrolyte and adding 5% by volume of 1-methyl-2-piperidone after removing water.

Next, the battery is sealed, stabilized, and aged.
A spiral cylindrical battery having the structure shown in FIG. 1 was manufactured.

Comparative Example I A spiral cylindrical battery was produced in the same manner as in Example 1, except that 5% by volume of 1-methyl-2-piperidone, which is an additive for the electrolytic solution, was not used.

Comparative Example 2 A spiral cylindrical cell was prepared in the same manner as in Example 1, except that 5% by volume of HMPA was used as an additive for the electrolytic solution instead of 5% by volume of 1-methyl-2-piperidone. A battery was created.

Regarding the batteries of Example 1 and Comparative Examples 1 and 2, 6
Stored at 0°C for 20 days, 3A orally.

The results of examining the closed circuit voltage after 0.5 seconds were as shown in Figure 2. In Figure 0, curve -a is Example 1, curve -
b is the test result of each battery of Comparative Example 1, and curve -0 is Comparative Example 2. Further, the following stabilization test was conducted on the organic electrolyte used in each of the above batteries, and the results were as shown in Table 1 below.

<Stabilization test> 1 Qml of organic electrolyte is placed in a vial with the same capacity, a Li piece of 1 cm x 4 cm is placed in the vial, the vial is covered with a polyethylene stopper, and the vial is sealed with an aluminum cap. 8
After being stored at 0°C for 10 days, it was opened and the color of the electrolyte was examined.

Table 1 As is clear from Table 1 and Figure 2 above, the battery of Example 1 in which 1-methyl-2-piperidone was added to the electrolyte had a stabilizing effect of the additive on LtPF It can be seen that it exhibits very good storage stability because it has good properties and has a property of not easily reacting with Li electrodes.

On the other hand, in the battery of Comparative Example 2 using the conventionally known HMPA as an additive, although the stabilizing effect of L i P F h was good, there was a problem of reactivity with the Li electrode, etc. , it can be seen that the effect of improving the storage stability of the battery is inferior.

Examples 2 to 4 Three types of spiral cylindrical batteries were produced in the same manner as in Example 1, except that the additives listed in Table 2 were used as additives for the electrolytic solution.

Table 2 shows excellent stability. The results of the stabilization test similar to the above were also listed in Table 2 above.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing an example of the structure of an organic electrolyte battery of the present invention, and FIG. 2 is a characteristic diagram showing the storage stability test results of each battery of Example 1 and Comparative Example 1.2. Patent Applicant: Hitachi Maxell Co., Ltd. When the storage stability of each of the above batteries was examined in the same manner as above, all of them were found to be in good condition, same as in Example 1.

Claims (1)

[Claims] (1) In a battery where the electrolyte is an organic electrolyte in which an electrolyte containing LiPF_6 is dissolved in a non-aqueous solvent, the above electrolyte contains the following general formula (a); ▲ mathematical formula, chemical formula, table, etc. ▼ (In the formula, R_1 and R_2 are saturated hydrocarbon groups that may contain an oxygen or nitrogen atom in the carbon chain, R_3 is a hydrogen atom or a saturated hydrocarbon group similar to R_1 and R_2 above, and R_1 An organic electrolyte battery comprising an N-dialkylamide compound represented by R_3, two of which may be connected to each other in a ring.