Structural evolution and electrochemical performance of LiFePO4/C thin films deposited by ionized magnetron sputtering

Thin films of carbon mixed LiFePO4 were prepared by ionized magnetron sputter deposition (IMSD) and post anneal. The IMSD technique uses a built-in radio frequency coil to generate an inductively coupled plasma (ICP) confined close to the substrate. Therefore, the films were deposited under concurrent ion bombardment, which resulted in an atomic-peening effect during film growth. The evolution of film structures and surface morphologies under different ICP plasma conditions was investigated. The deposited LiFePO4/C thin films were tested as cathodes for lithium ion batteries. The performances of these thin film cathodes can be related to the modified film structures and surface morphologies. All the films showed a typical discharge voltage of LiFePO4 at 3.5-3.4 V, except for the 600 °C annealed films. The thin film cathodes deposited under suitable ICP plasma powers exhibited higher specific capacity.