LiFePO 4 /C thin films have been deposited on Ti-coated Si and stainless-steel substrates by radio frequency magnetron sputtering. Negative electric bias ͑0,−50,−80 V͒ and postdeposition vacuum annealing ͑150-650°C͒ was applied to modify the film properties. Suitable substrate bias resulted in films with finer grains and pure olivine phase. The films deposited with Ti underlayers exhibited enhanced crystallization, grain sizes, and conductivity, as compared with films deposited without Ti underlayers. Composition depth profiles showed interdiffusion at the film/underlayer interfaces after annealing. Charge-discharge and cyclic voltammetry curves revealed the different electrochemical characteristics of the films. The films with Ti underlayers displayed lower initial capacity than those without underlayers due to heavy doping of Ti. However, the cycling stability is greatly improved, which was attributed to the enhanced adhesion property of the Ti underlayers to the substrates and films.

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