Electrolyte solution

Abstract

Disclosed is an electrolyte solution which does not cause phase separation at lower temperatures, which has excellent flame retardancy or non-flammability, in which an electrolyte salt is dissolved at a high solubility, which has a high discharge capacity, which is excellent in a charge-discharge cycling property, and which is suitable for an electrochemical device such as a lithium ion secondary battery. The electrolyte solution comprises: a solvent (I) for dissolving an electrolyte salt (II) therein, which comprises a fluorinated ether (A) represented by the formula: Rf1-O-Rf2 [wherein Rf1 and Rf2 are the same as or different from each other, Rf1 is a fluorinated alkyl group having 3 to 6 carbon atoms, and Rf2 is a fluorinated alkyl group having 2 to 6 carbon atoms], at least one fluorinated solvent (B) selected from the group consisting of a fluorinated cyclic carbonate (B1) and a fluorinated lactone (B2), and at least one non-fluorinated carbonate (C) selected from the group consisting of a non-fluorianted cyclic carbonate (C1) and a non-fluorinated linear carbonate (C2); and the electrolyte salt (II), wherein the solvent (I) comprises 20 to 60 vol% of the fluorinated ether (A), 0.5 to 30 vol% of the fluorinated solvent (B), and 5 to 40 vol% of the non-fluorinated cyclic carbonate (C1) and / or 10 to 74.5 vol% of the non-fluorinated linear carbonate (C2), all relative to the total volume of the solvent (I).

Description

technical field [0001] The present invention relates to an electrolyte suitable for electrochemical devices such as lithium ion secondary batteries. Background technique [0002] Carbonates such as ethylene carbonate, propylene carbonate, and dimethyl carbonate are widely used as solvents for dissolving electrolyte salts for lithium ion secondary batteries. However, these hydrocarbon carbonates have a low ignition point and high flammability, so there is a risk of fire or explosion due to overcharging or overheating, especially in large lithium-ion secondary batteries for hybrid vehicles or distributed power sources. Among them, it becomes an important issue in terms of ensuring safety. [0003] As a method for preventing the explosion of the electrolyte, it is proposed to mix fluoroalkanes, phosphoric acid esters, and phosphorus compounds in the electrolyte as additives (for example, refer to Japanese Patent Laid-Open No. 11-233141, Japanese Patent Laid-Open No. 11-283669,...

AI Technical Summary

Problems solved by technology

[0015] The present invention was invented to solve these conventional problems. The object of the present invention is to provide an electrolytic solution that does not undergo phase separation even at low temperatures, has excellent flame retardancy or incombustibility, and has an electrolyte salt High solubility, large discharge capacity, excellent charge-discharge cycle characteristics, suitable for electrochemical devices such as lithium-ion secondary batteries

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