ELECTROLYTE SOLUTION, ELECTROCHEMICAL DEVICE, LITHIUM ION SECONDARY BATTERY AND MODULE

An electrolyte solution including a solvent, the solvent containing a compound (1a) represented by the following formula (1a); and a compound (2) represented by the following formula (2): wherein Ris a C1-C5 linear or branched alkyl group optionally containing an ether bond; Ris a C1-C5 linear or branched alkyl group optionally containing an ether bond; and at least one of Ror Rcontains a fluorine atom. Also disclosed is an electrochemical device including the electrolyte solution, a lithium-ion secondary battery including the electrolyte solution, and a module including the electrochemical device or the lithium-ion secondary battery.