Electrolyte for an electrochemical cell, and an electrochemical cell including the electrolyte

An electrolyte for use as a molten salt electrolyte in an electrochemical cell, and which comprises:

• aluminium cations;
• alkali metal cations selected from the group consisting in lithium cations, a mixture of lithium and potassium cations and a mixture of sodium and potassium cations;
• and
• halide anions comprising a mixture of chloride and fluoride anions;
• the proportions of the constituents of the electrolyte being selected such that the relative quantities of said aluminium, alkali metal and halide ions conform substantially with the stoichiometric product:
• MAlX.sub.4
• wherein:
• M represents said alkali metal cations;
• and
• X represents said halide anions,
• the proportions of the alkali metal cations and the halide anions making up said stoichiometric product being such that the melting point of the electrolyte at atmospheric pressure is below 140.degree. C.