An electrolyte solution proposed for double layer capacitors contains at least one conducting salt comprising a cation having a maximum diameter<9.20 which additionally comprises substituents on the central atom which are not all the same and further contains at least one solvent comprising a functional group selected from lactones and nitrites. Such electrolyte solutions are superior to conventional electrolyte solutions at low temperatures when acetonitrile is the solvent, so that double layer capacitors provided with electrolyte solutions according to the invention have improved electrical properties at low temperatures.