JPH11111333A - Electrolyte for lithium or lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the use of an electrolyte, especially in a lithium or lithium ion secondary battery by dissolving the lithium salt as an electrolyte salt in a bis (2-cyanoethyl) ether as a solvent. SOLUTION: As a lithium salt for electrolyte, LiClO4 or the like is used. Content thereof is usually set in a range of 1-20 wt.% in relation to the total quantity of the electrolyte. As the electrolyte, besides bis (2-cyanoethyl) ether, other non-proton group polar solvents such as diethyl carbonate can be used together. In this case, bis (2-cyanoethyl) ether is set at 10 wt.% or more with respect to the total quantity with other aprotic group polar solvent. Specifically, electrolyte is manufactured by the following method: LiBF4 0.5 g is dissolved in 5 g of bis (2-cyanoethyl) ether and 5 g of ethylene carbonate, followed dehydration with a molecular sieve. An electrolyte having 2.1×10<-3> S.cm<-1> of conductivity at 1 kHz is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrolyte for a lithium or lithium ion secondary battery, and more particularly to an electrolyte using a specific low molecular cyanoethyl compound as an electrolyte solvent.

[0002]

The electrolytic solution of the present invention is characterized in that bis (2-cyanoethyl) ether is dissolved in bis (2-cyanoethyl) ether as an electrolyte solvent and a lithium salt is dissolved as an electrolyte salt. Useful for use in

[0003] The above bis (2-cyanoethyl) ether is
Formula: NCCH ₂ CH ₂ OCH ₂ CH ₂ CN, for example, in 2-cyanoethanol or water,
Acrylonitrile, a reaction catalyst (preferably lithium hydroxide (including hydrates); lithium metal; lithium alkoxides (lithium methyl alcoholate, lithium ethyl alcoholate, ethylene glycol lithium bis alcoholate, etc.); lithium and an active methylene compound (acetylacetone, (Eg, lithium malonate, ethyl acetoacetate, and malonate dinitrile), for example, lithium acetylacetonate] at room temperature to about 60 ° C. for cyanoethylation.

As the lithium salt, for example, LiCl
_{O 4, LiSCN, LiBF 4,} LiAsF 6, LiCF 3 S
O ₃ , LiPF _{6 and the} like.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrolytic solution according to the present invention comprises
It is composed of a system in which a lithium salt is dissolved in (2-cyanoethyl) ether. Here, the content of the lithium salt is usually selected in a range of about 1 to 20% (% by weight, hereinafter the same) based on the total amount of the electrolyte. Good. Further, in addition to the bis (2-cyanoethyl) ether, other conventionally used aprotic polar solvents (for example, diethyl carbonate, ethylene carbonate, propylene carbonate, N-methylpyrrolidone, γ-butyrolactone, dimethyl sulfoxide, Sulfolane, N, N'-tetramethylurea, ethyl cyanoacetate, acetonitrile,
Propionitrile, succinonitrile, dioxane, trioxane, tetrahydrofuran, dimethoxyethane,
Diethoxyethane, triacetin, triethyl phosphate,
Nitromethane, nitroethane, nitropropane, etc.). In this case, bis (2-cyanoethyl) ether may be selected in a range of 10% or more based on the total amount of other aprotic polar solvents. If it is less than 10%, the effect of using bis (2-cyanoethyl) ether tends to be not exhibited.

[0006]

Next, the present invention will be described more specifically with reference to production examples and examples. Production Example 1 A four-necked flask was charged with 144 g (2 mol) of 2-cyanoethanol and 0.5 g of lithium hydroxide (LiOH.H ₂ O), and heated and stirred at 60 ° C. until the LiOH.H ₂ O was dissolved. Then, while maintaining the temperature at 40 to 50 ° C, 117 g (2.2 mol) of acrylonitrile is added dropwise over 2 hours. After completion of the dropwise addition, stirring is continued for 3 hours at the same temperature, 250 g of methylene chloride and 500 ml of ion-exchanged water are added, and the mixture is stirred for several minutes. When stirring is stopped and left to stand, it separates into two layers.
The upper aqueous layer is separated, discarded, washed twice with ion-exchanged water in the same manner, dried using a vacuum pump, and low-volatile components are removed to obtain bis (2-cyanoethyl) ether.

Example 1 LiBF _{4 (} 0.5 g) was dissolved in bis (2-cyanoethyl) ether (5 g) obtained in Production Example 1 and ethylene carbonate (5 g), followed by dehydration with a molecular sieve (3 Å). Was measured by an LCZ meter and found to be 2.1 × 10 ⁻³ S · cm ⁻¹ .

Claims (3)

[Claims] 1. A lithium or lithium ion 2 solution comprising bis (2-cyanoethyl) ether as an electrolyte solvent and a lithium salt as an electrolyte salt.
Electrolyte for secondary battery. 2. The electrolytic solution according to claim 1, wherein bis (2-cyanoethyl) ether and another aprotic polar solvent are used in combination. 3. The electrolytic solution according to claim 2, wherein bis (2-cyanoethyl) ether is used in an amount of 10% by weight or more based on the total amount of other aprotic polar solvents.