An electrochemical cell assembly comprising: at least one electrochemical cell or cells comprising—a cathode comprising an electrochemically active material, wherein alkali metal is present in the cathode;—an anode comprising a current collector comprising an electronically conducting, inert metal or non-metal; and said anode further comprising a protection layer containing a first layer and a second layer; wherein the first layer comprises a metal and/or non-metal that alloys with an alkali metal and is formed on the current collecting layer, and an second layer deposited on the first layer, wherein the second layer is an Tonically conducting layer having an electronic conductivity of less than 10−5 S cm−1; wherein the cell assembly further comprises a means of applying pressure to the at least one electromechanical cell or cells.