Electrochemical device

Abstract

The invention provides an electrochemical device having an electrolyte solution comprising: (I) a solvent for dissolving an electrolyte salt, which comprises (A) a fluorinated ether represented by the formula (1), (B) a cyclic carbonate and (C) a linear carbonate compatible with both the fluronated ether (A) and the cyclic carbonate (B); and (II) the electrolyte salt, wherein the solvent (I) contains the fluorinated ether (A) in an amount of 30 to 60% by volume, the cyclic carbonate (B) in an amount of 3 to 40% by volume and the linear carbonate (C) in an amount of 10 to 67% by volume relative to the total volume of the solvent (I). Rf-O-Rf (1) wherein Rf and Rf2 independently represent a fluorinated alkyl group having 3 to 6 carbon atoms. The electrochemical device hardly causes phase-separation even at lower temperatures, and has excellent flame retardancy and heat resistance, can highly dissolve an electrolyte salt, has a high discharge capacity, and is excellent in charge / discharge cycle property.

Description

technical field [0001] The present invention relates to an electrochemical device having an electrolytic solution containing a specific fluorine-containing ether, which is stable at low temperatures and has excellent flame retardancy. Background technique [0002] Carbonates such as ethylene carbonate, propylene carbonate, and dimethyl carbonate are commonly used as solvents for dissolving electrolyte salts for lithium secondary batteries. However, due to the low flash point and high flammability of these hydrocarbon carbonates, there is a danger of sparks and explosions caused by overcharging and overheating. Secondary batteries, in order to ensure safety, this is an important issue. [0003] As an explosion-preventing means of the electrolytic solution, it has been proposed to mix fluoroalkanes, phosphoric acid esters, phosphides, etc. as additives in the electrolytic solution (Japanese Patent Laid-Open Publication No. 11-233141, Japanese Patent Laid-Open Publication No. ...

AI Technical Summary

Problems solved by technology

However, the solubility of the electrolyte salt in this mixed solvent system is low, and LiPF, which is commonly used as a high-quality electrolyte salt, cannot be dissolved. 6 and LiBF 4 , as the electrolyte salt, the metal corrosive LiN(O 2 SCF 3 ) 2

Also, poor retardation characteristics due to high viscosity

[0013] In this way, the current situation is that there is no development of an electrolyte solution for lithium secondary batteries that is excellent in incombustibility and flame retardancy, and has sufficient battery characteristics (charge-discharge cycle characteristics, discharge capacity, etc.)

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