Optimization of Synthesis Process for Carbon-Mixed LiFePO4 Composite Thin-Film Cathodes Deposited by Bias Sputtering

Abstract

Thin films of carbon-mixed were deposited on Si and stainless steel substrates by radio-frequency magnetron sputtering. The goal of this study was to optimize the conditions of sputter deposition for thin films to obtain a film with pure phase. Negative electric bias was applied on the substrates during deposition to modify the film properties. After deposition, the films were annealed at different temperatures ranging from without leaving the vacuum deposition chamber. Suitable bias was found to purify the olivine phase and reduce the grain size. Too high a substrate bias and anneal temperature resulted in undesired second phases. Carbon mixing effectively lowered the resistivity of the films to the order of . Charge-discharge and cyclic voltammetry curves revealed the different electrochemical characteristics of these films, which were attributed to the modified crystallography and morphology. The films deposited under substrate bias of and anneal temperature of exhibited a capacity of with a plateau.