An electrochemical element for use at a high temperature has an anode, a cathode comprising an intercalation material having an upper reversible potential-limit of at most 4 V versus Li/Li+ as active material, and an electrolyte arranged between the cathode and anode, which electrolyte comprises an ionic liquid with an anion and a cation a pyrrolidinium ring structure having four Carbon atoms and one Nitrogen atom. Experiments revealed that rechargeable batteries comprising such an intercalation material and 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.