Physical and electrochemical properties of LiFePO4/C thin films deposited by direct current and radiofrequency magnetron sputtering

In this study, LiFePO4/C thin films with various contents of carbon were prepared by direct current (DC), radiofrequency (RF) and combined (DC/RF) magnetron sputtering methods. Influences of the composition, morphology and microstructure on the electrochemical properties of LiFePO4/C thin films are investigated by studying charge–discharge curves, cyclic voltammetry and electrochemical impedance spectroscopy. Cyclic voltammogram of the LiFePO4/C thin film showed the typical redox reaction peaks characterizing the electrochemical lithium insertion/extraction reactions in LiFePO4. Obtained LiFePO4/C thin films have relatively high charge capacities (127 mAh g− 1). It was found that optimal magnetron sputtering conditions use a combined CD/RF process to obtain LiFePO4/C thin films with the best electrochemical performance.

Research highlights
► LiFePO4/C thin films as cathode material for lithium ion batteries.
► Optimal magnetron sputtering conditions use a combined CD/RF process to obtain films with the best electrochemical performance.
► Obtained films have relatively high charge capacity.
► Under the polarization conditions the Li+ ion diffusion is not the limiting stage in thin film LiFePO4/C.
► The minimal value of charge transfer resistance is acquired in discharged state.