An electrolyte includes (a) a eutectic mixture of an alkoxy alkyl group-containing amide compound and an ionizable lithium salt; and (b) a carbonate-based compound. The electrolyte has excellent thermal and chemical stability and exhibits a low lowest limit of electrochemical window. Also, the electrolyte shows low viscosity and high ion conductivity, so it may be usefully applied as an electrolyte of electrochemical devices using various anode materials.