Disclosed is an electrolyte for batteries, which comprises: (a) an electrolyte salt; (b) an electrolyte solvent; and (c) a sulfonate-based compound containing at least one electron withdrawing group (EWG) selected from the group consisting of a cyano group (—CN), an isocyanate group (—NCO), a thiocyanate group (—SCN) and an isothiocyanate group (—NCS). An electrode comprising the sulfonate-based compound or a chemical reaction product thereof, partially or totally formed on the surface thereof, and an electrochemical device comprising the electrolyte and/or the electrode are also disclosed. The electrochemical device using the sulfonate-based compound containing a cyano group, an isocyanate group, a thiocyanate group and/or an isothiocyanate group as an additive for electrolytes can provide significantly improved high-temperature lifespan characteristics.