The present invention relates to a high capacity electrochemical cell (18) including a cathode (24) that can contain an oxide of copper as an active material, an anode (26), an electrolyte, and a separator (32) disposed between the anode and the cathode. The oxide can have surface area greater than 0.5 m2/g, and the cathode can include an additive that increases the discharge voltage of the cell. In some cases the additive has a lower voltage than the oxide alone. The additive can have a surface area within the range defined by a lower limit of 0.5 m2/g and an upper limit of 100 m2/g. The anode can include a quantity of mercury below .025%.