Provided herein is an electrochemical cell for a secondary battery, which includes a positive electrode having an active intercalation cathode material of treated bentonite; a negative electrode material having an active anode material containing one of magnesium and sodium; an electrolyte positioned in contact with at least one of the positive electrode and the negative electrode; wherein, when the active anode material contains magnesium, the electrolyte is a solid gel polymeric electrolyte; and wherein, when the active anode material is sodium, the electrolyte is a salt electrolyte, both the anode material and the electrolyte are molten at the operating temperature of the battery, and the cell further comprises a beta alumina solid electrolyte separator between the negative electrode and the electrolyte.