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Abstract

The invention provides a method of making an electrochemical cell. The method comprises loading, into the cathode compartment of the cell an alkali metal aluminium halide molten salt electrolyte having the formula MAlHal.sub.4 wherein M is the alkali metal of the separator and Hal is a halide; an alkali metal halide MHal wherein M and Hal are respectively the same alkali metal and halide as in the molten salt electrolyte; aluminium; and an active cathode substance which includes a transition metal T selected from the group conprising Fe, Ni, Co, Cr, Mn and mixtures thereof. An electrochemical cell precursor is thereby made. When the precursor is subjected to charging at a temperature at which the molten salt electrolyte and alkali metal M are molten, aluminium reacts with the alkali metal halide MHal to produce further said molten salt electrolyte and to form said alkali metal M, the alkali metal M passing through the separator into the anode compartment. After all the aluminium has reacted with the alkali metal halide to provide a cell in a discharged state, the active cathode substance is halogenated, with further alkali metal M being produced and passing through the separator into the anode compartment, the proportions of alkali metal halide MHal, molten salt electrolyte and aluminium loaded into the cathode compartment being selected so that when the cell is fully charged and all the available active cathode substances has been halogenated, the proportion of alkali metal ions and aluminium ions in the electrolyte being selected such that the solubility of the active cathode substance in the molten electrolyte is at or near its minimum.

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First Claim