Electrochemical cell

Claim 1

A high temperature rechargeable electrochemical power storage cell comprising (i) an anode compartment containing, at the operating temperature of the cell and when the cell is in the charged state, a molten alkali metal anode; (ii) a cathode compartment containing, at said operating temperature and in said charged state, an alkali metal aluminum halide molten salt electrolyte which is also molten at the operating temperature of the cell, and having the formula MAlHal 4 , wherein R is the alkali metal of the anode and Hal is a halide, the cathode compartment also containing in said charged state, a cathode which comprises an electronically conductive electrolyte-permeable porous matrix which has dispersed therein an active cathode substance THal 2 in which Hal is the halide of the electrolyte and T is a transition metal selected from the group of transition metals consisting of Fe, Hi, Co, Cr, Mn and mixtures thereof, the matrix being impregnated with said molten electrolyte (iii) a separator separating the anode compartment from the electrolyte, the separator comprising a solid conductor of the ions of the alkali metal of the anode or a micromolecular sieve which contains said alkali metal sorbed therein; and (iv) a current collector assembly comprising a current collecting member and at least one bimetallic current collector, in at least one of the cell compartments, the bimetallic current collector being composed of abutting layers of first and second metals respectively, with the metals having different co-efficients of thermal expansion and the layers being bonded together, and with a first portion of the bimetallic current collector being attached to the current collecting member so that, when the cell is at ambient temperature, the bimetallic current collector is in a first non-deformed configuration, and, when the cell is at its normal operating temperature, the bimetallic current collector is in a second deformed configuration in which a second portion thereof is spaced further from the current collecting member than in the first configuration, with the deformation of the bimetallic current collector resulting from the difference in co-efficients of thermal expansion of the metals making up the bimetallic current collector, and the second portion of the current collector, in the second configuration of the current collector bearing against the separator, thereby to make electrical contact with the separator.