JPH0687425B2 - Organic electrolyte battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to an organic electrolyte battery. For more details,
Formula (I) LiXFn (I), wherein X is P, As, Sb or B, n is 6 when X is P, As or Sb, and 4 when X is B. The present invention relates to an organic charged battery in which the thermal stability of an organic electrolyte solution using a Lewis acid salt as a solute is enhanced and storage characteristics are improved.

[Conventional technology]

Recently, a Lewis acid salt represented by the general formula (I) as a solute of an electrolyte solution (hereinafter referred to as an electrolyte solution) of an organic electrolyte battery has good solubility in an organic solvent, high conductivity, and perchloric acid. It is attracting attention because it has higher stability than that of the system, and various proposals have been made in the past regarding this. For example, in US Pat. No. 3,607,020, LiP
F ₆ , LiASF ₆ and other synthetic methods have been proposed, and US Pat.
No. 977 proposes a synthesis method and a purification method of high-purity products of LiPF ₆ and LiAsF ₆ using CH ₃ CN. In U.S. Pat Li-A1 negative electrode / Cu ₂ S cell lines at the 3,639,174 Pat, LiPF ₆ / propylene carbonate, LiPF ₆ / dimethyl monkey Hoki cell system using a SID has been proposed as an electrolytic solution.

[Problems to be solved by the invention]

However, according to the experiments conducted by the present inventors, an electrolyte solution prepared by dissolving LiPF ₆ in an organic solvent such as propylene carbonate, 1,3-dioxolane, tetrahydrofuran, 4-methyl-1,3-dioxolane, and 1,2-dimethoxyethane. Although the lithium organic electrolyte battery using is excellent in battery characteristics at room temperature, when it is stored at 60 ° C, LiPF ₆ which is a solute is thermally decomposed to generate HF (hydrogen fluoride). There is a problem that the decomposition or polymerization of the solvent is caused to significantly deteriorate the battery characteristics. Like LiPF ₆ , Lewis acid salts such as LiSbF ₆ , LiAsF ₆ and LiBF ₄ represented by the general formula (I) also have the same problem of thermal stability as LiPF ₆ .
When it is stored at a high temperature, there is a problem that it is thermally decomposed to cause decomposition or polymerization of the solvent of the electrolytic solution to deteriorate the battery characteristics.

[Means for solving problems]

The present invention solves the above-mentioned problems of the prior art, in which at least one C = N bond and at least two rings are shared by the electrolyte containing the Lewis acid represented by the general formula (I) as a solute. The present invention provides an organic electrolyte battery in which the thermal stability of an electrolytic solution is improved by adding a nitrogen-containing bicyclic tertiary amine, and the deterioration of the battery performance during storage is small.

In the present invention, the bicyclic tertiary amine added to the electrolytic solution to enhance the thermal stability of the electrolytic solution is, for example, 1,8-
Examples thereof include diazabicyclo [5.4.0] undec-7-ene, 1,5-diazabicyclo [4.3.0] non-5-ene, and derivatives thereof.

1,8-diazabicyclo [5.4.0] undec-7-ene is a liquid substance, the structural formula of which is as follows: 1,5-diazabicyclo [4.3.0] non-5-ene is also a liquid substance, the structural formula of which is as follows: These have a C = N bond and a nitrogen shared by the two rings.

Then, the above 1,8-diazabicyclo [5.4.0] undeca-
Derivatives such as 7-ene and 1,5-diazabicyclo [4.3.0] non-5-ene are their substitution products and C = in the molecule.
For example, those having a C bond. For example, a compound having a double bond between the 3-position and 4-position of 1,8-diazabicyclo [5.4.0] undec-7-ene or between the 4-position and 5-position, 1,8-diazabicyclo [5.4. .0] having a methyl group, an ethyl group or a phenyl group at the 3-position, 4-position or 5-position of undec-7-ene or at the 8-position of 1,5-diazabicyclo [4.3.0] non-5-ene It is a compound.

The bicyclic tertiary amine, for example, forms a complex with Li ⁺ ion generated by ionization of LiPF _6, and suppresses the generation of LiF by the reaction with F ⁻ generated by the decomposition of PF _{6 −} ion, Stabilize the electrolyte. Since the above-mentioned bicyclic tertiary amine is a large molecule, it is difficult for it to enter the interlayer of titanium disulfide (TiS ₂ ) which is often used as a positive electrode active material when forming a secondary battery, and LiPF ₆ or the like decomposes. Since it has a basicity that neutralizes HF when HF is generated, it stabilizes the electrolytic solution even with a small amount of usage.

As the amount of this bicyclic tertiary amine increases, the effect of stabilizing the electrolytic solution increases, and from this aspect, it is preferable that the amount added is large. However, if the amount is too large, the conductivity at low temperature and the secondary battery are increased. Since the charge and discharge characteristics are deteriorated, the addition amount of the Lewis acid salt of the general formula (I) is 0.2 to
It is preferably doubled.

In the present invention, specific examples of the Lewis acid salt represented by the general formula (I) used as the solute of the electrolyte include LiPF ₆ (lithium hexafluorophosphate) in which X is P (phosphorus), and X is Sb.
(Antimony) LiPF ₆ (lithium hexafluoroantimonate), X is As (arsenic) LiAsF ₆ (lithium hexafluoroarsenate), X is B (boron) LiBF ₄ (boron tetrafluoride) Lithium acid). Then, the electrolytic solution contains the Lewis acid salt represented by the general formula (I) such as propylene carbonate, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1, 3-dioxolane,
It is dissolved in an organic solvent such as 4-methyl-1,3-dioxolane or a mixed solvent of two or more kinds, and the above bicyclic tertiary amine is added thereto, or the above bicyclic compound is added to the organic solvent. It is prepared by adding a tertiary amine and then dissolving the Lewis acid salt represented by the general formula (I) therein. What is essential is that the electrolyte solution contains the Lewis acid salt represented by the general formula (I) and the bicyclic tertiary amine as a stabilizer, and the bicyclic tertiary amine and the general formula (I) are contained. The order of addition with the Lewis acid salt is not limited. The amount of the Lewis acid salt represented by the general formula (I) in the electrolytic solution is usually 0.1 to ³ mol / dm ³ .

In the battery of the present invention, as the negative electrode active material, for example, lithium, lithium-aluminum, lithium-lead, lithium-indium, lithium-gallium-indium, lithium-magnesium, lithium-zinc, and other lithium alloys are used. Examples of the active material include titanium disulfide (TiS ₂ ) and molybdenum disulfide (Mo).
S ₂ ), molybdenum trisulfide (MoS ₃ ), zirconium sulfide (ZrS ₂ ), niobium disulfide (NbS ₂ ), nickel nickel trisulfide (NiPS ₃ ), vanadium selenide (VSe ₂ ), iron sulfide,
Copper oxide, fluorocarbon, etc. are used. In particular, when used as a secondary battery, titanium disulfide is preferably used because it has a layered structure and has a large lithium diffusion constant.

〔Example〕

Next, the present invention will be described in more detail with reference to examples.

Example 1 A mixture of 57% by volume of 4-methyl-1,3-dioxolane, 38% by volume of 1,2-dimethoxyethane and 5% by volume of 1,8-diazabicyclo [5.4.0] undec-7-ene as an electrolytic solution. An organic electrolyte solution in which LiPF ₆ was dissolved to a concentration of 1 mol / dm ³ was used as a solvent, and lithium was added to the negative electrode at a concentration of 40 at% lithium.
A lithium organic electrolyte battery as shown in FIG. 3 was assembled using an aluminum alloy and a molding compound containing titanium disulfide as a positive electrode active material for the positive electrode. In the above electrolyte solution, 1,8
-The amount of diazabicyclo [5.4.0] undec-7-ene is L
This corresponds to about 0.3 times mol of iPF ₆ .

In FIG. 3, reference numeral 1 is a negative electrode can, the negative electrode can 1 is made of stainless steel and the surface thereof is nickel plated, and 2 is a negative electrode side current collecting net made of stainless steel, which is spotted on the inner surface of the negative electrode can 1. It is welded. 3 is a negative electrode made of the above-mentioned lithium-aluminum alloy, and 4 is a separator made of a microporous polypropylene film. Reference numeral 5 is an electrolytic solution absorber made of polypropylene nonwoven fabric, 6 is a positive electrode formed by pressure-molding a mixture containing titanium disulfide as a positive electrode active material into pellets, and 7 is a positive electrode side current collecting net made of stainless steel. is there. Reference numeral 8 is a positive electrode can made of stainless steel and having a surface plated with nickel, and 9 is an annular gasket made of polypropylene. The theoretical electricity quantity of the negative electrode of this battery is about 30 mAh.
Therefore, the theoretical amount of electricity of the positive electrode is 13 mAh.

Example 2 58% by volume of 4-methyl-1,3 dioxolane as an electrolyte,
L in a mixed solvent consisting of 39% by volume of 1,2-dimethoxyethane and 4% by volume of 1,5-diazabicyclo [4.3.0] non-5-ene
A lithium organic electrolyte battery similar to that of Example 1 was assembled except that an organic electrolyte solution in which iPF ₆ was dissolved to 1 mol / dm ³ was used. In the above electrolyte, the amount of 1,5-diazabicyclo [4.3.0] non-5-ene was about 0.3 times mol of LiPF ₆ .

Comparative Example 4-Methyl-1,3-dioxolane 60% by volume as electrolyte
A lithium organic electrolyte battery was assembled in the same manner as in Example 1 except that an organic electrolyte solution prepared by dissolving LiPF ₆ at 1 mol / dm ^{3 in a} mixed solvent consisting of and 40% by volume of 1,2-dimethoxyethane was used.

The batteries of Examples 1 and 2 and the battery of Comparative Example were stored at 60 ° C., and the change in internal resistance with storage at 10 kHz and the change in closed circuit voltage after discharging for 300 Ω for 5 seconds were examined. The change in internal resistance at 10 kHz is shown in FIG. The internal resistance of 10 kHz depends on the electrolyte.

As shown in FIG. 1, in the battery of the comparative example which is a conventional battery, the internal resistance increased remarkably as the number of storage days increased, but in the batteries of Examples 1 and 2 of the present invention, such No large increase in internal resistance was observed.

Further, as shown in FIG. 2, the batteries of Examples 1 and 2 of the present invention showed less decrease in the closed circuit voltage due to storage and were excellent in storage characteristics, as compared with the batteries of Comparative Example.

In the examples, LiPF ₆ was used as the Lewis acid salt represented by the general formula (I), but the present invention is not limited to LiAsF.
It goes without saying that this also applies when using ₆ , LiSbF ₆ , LiBF _4, etc.

Also, in the examples, 1,8-diazabicyclo [5.4.0] undec-7-ene and 1,5 diazabicyclo [4.
3.0] The case where non-5-ene is added has been shown, but similar effects can be obtained when these derivatives, such as their substitution products and those having a C = C double bond in the molecule, are used. You can

〔The invention's effect〕

As described above, in the present invention, as a stabilizer, an electrolyte solution is prepared by adding a bicyclic tertiary amine having at least one C═N bond and at least one nitrogen shared by two rings. It was possible to obtain an organic electrolyte battery having good storage characteristics by increasing the thermal stability of.

[Brief description of drawings]

FIG. 1 is a diagram showing changes in internal resistance of a battery of Examples 1 and 2 of the present invention and a battery of a comparative example during storage at 10 kHz, and FIG. 2 is a battery of Examples 1 and 2 of the present invention and a comparative example. FIG. 6 is a diagram showing a change in closed circuit voltage due to storage of the battery of FIG. FIG. 3 is a sectional view showing an example of the organic electrolyte battery according to the present invention. 3 ... Negative electrode, 4 ... Separator, 6 ... Positive electrode

Claims (4)

[Claims] 1. A lithium-containing negative electrode and a positive electrode, wherein the solute has the general formula (I) LiXFn (I) (wherein X is P, As, Sb or B, and n is X, P, As or Sb is 6 and X is B is 4), the solvent is an organic solvent, and the stabilizer is at least one C═N bond and is shared by at least one two rings. An organic electrolyte battery using an organic electrolyte solution to which a bicyclic tertiary amine having nitrogen is added. 2. The bicyclic tertiary amine comprises 1,8-diazabicyclo [5.4.0] undec-7-ene, 1,5-diazabicyclo [4.3.0] non-5-ene and their derivatives. The organic electrolyte battery according to claim 1, which is at least one selected from the group. 3. A Lewis acid salt represented by the general formula (I) is LiPF 4.
The organic electrolyte battery according to claim 1 or 2, which is ₆ . 4. The organic electrolyte battery according to claim 1, 2, or 3, wherein the positive electrode active material is titanium disulfide.