Plasma Induced Low Temperature Crystallization of Lithium Transition-Metal Oxide Thin Films for Lithium Microbatteries

The choices of substrates for lithium microbatteries or thin-film batteries have been limited by the high annealing temperatures, which are generally required in the fabrication of polycrystalline thin-film cathodes. In this paper, a plasma-assisted technique was developed for the low temperature fabrication of polycrystalline lithium transition-metal oxides as thin-film cathodes. The thin films were deposited by magnetron sputtering, followed by thermal annealing, and plasma treatments. By applying the plasma treatments, polycrystalline films of LiCoO(2), LiMn(2)O(4), and LiFePO(4) were obtained under relatively lower annealing temperatures (< 400 degrees C). The low temperature prepared films with/without plasma treatments were compared in terms of morphologies, crystal structures, and electrochemical performances. The plasma treatments lifted the discharge voltages and increased the capacity of the low temperature prepared films. The results demonstrated the feasibility of fabricating thin-film batteries on polymers or glass substrates, which generally can only endure temperatures lower than 400 degrees C.