Abstract: An electrochemical element for use at a high temperature has a cathode comprising an intercalation material as active material, an anode and an electrolyte arranged between the cathode and anode, which electrolyte comprises an ionic liquid with an anion and a cation, which cation comprises a pyrrolidinium ring structure comprising four Carbon atoms and one Nitrogen atom. Experiments revealed that rechargeable batteries comprising N—R1—N—R2-pyrrolidinium, wherein R1 and R2 are alkyl groups and R1 may be methyl and R2 may be butyl or hexyl, are particularly suitable for use at a temperature of up to about 150 degrees Celsius and may be used in oil and/or gas production wells.