 The metals used were cobalt, nickel, copper, and iron, which proved to have capacities of 700 mA h/g and maintain full capacity for 100 cycles.The materials operate by reduction of the metal cation to either metal nanoparticles or to a lower oxidation state oxide.These promising results show that transition-metal oxides may be useful in ensuring the integrity of the lithium-ion battery over many discharge-recharge cycles.