A high temperature rechargeable electrochemical cell which comprises a cell housing divided by a separator into an anode compartment and a cathode compartment. The anode compartment contains an active anode substance which is a molten alkali metal M, the separator being capable of conducting ions of the alkali metal of the anode therethrough. The cathode compartment contains a cathode comprising an electronically conductive electrolyte-permeable porous matrix having, dispersed therein, a solid active cathode substance the matrix being impregnated with a molten salt electrolyte. The cathode comprises also, in contact with the matrix, a porous, electrolyte-permeable reservoir of material which is electrochemically and chemically inert in the cathode environment, said reservoir having an ability to wick the molten salt electrolyte at the operating temperature of the cell which ability is less than the ability of the matrix to wick said molten salt electrolyte.