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 Re is a C1-C5 linear or branched alkyl group optionally containing an ether bond; Rf is a C1-C5 linear or branched alkyl group optionally containing an ether bond; and at least one of Re or Rf contains 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.