Murata 362 (SR721SW) - formerly Sony - Silver Oxide 0%Hg Mercury Free 1.55 volts batteries. Silver oxide batteries are primary cells that have a high energy/weight ratio. Silver oxide is used as the positive electrode (cathode) while zinc is used as the negative electrode (anode) with an alkaline electrolyte. Murata silver oxide batteries provide an extremely high quality, compact battery for the high performance devices today.