ELECTROLYTE, ELECTROLYTIC SOLUTION FOR LITHIUM ION SECONDARY BATTERY COMPRISING THE ELECTROLYTE, AND LITHIUM ION SECONDARY BATTERY USING THE ELECTROLYTIC SOLUTION

摘要

Disclosed is an electrolytic solution for use in a lithium ion secondary battery, which comprises a tetralkylphosphonium salt and which can improve the cycle properties and safety of a lithium ion battery. Also disclosed is a lithium ion secondary battery which utilizes the electrolytic solution. Specifically disclosed is an electrolyte which comprises a tetraalkylphosphonium salt represented by the general formula (1): (1) wherein R₁ represents a linear, branched or alicyclic alkyl group having 2 to 6 carbon atoms; R₂ represents a linear, branched or alicyclic alkyl group having 1 to 14 carbon atoms, provided that R₁ and R₂ are different from each other and the total number of carbon atoms in the phosphonium cation is 20 or less; and X represents an anion.