Effect of Carbon Content on Electrochemical Performance of LiFePO4/C Thin Film Cathodes

Submicron-sized hydrothermal-grown LiFePO4 particles were added into sucrose-water solution followed with annealing in 600 °C for 3 hours in nitrogen to form thin, binder-free and high energy LiFePO4/C composite film cathodes and the effects of carbon content on the microstructure and electrochemical properties of such films were investigated. Carbon from sucrose pyrolysis served as both conducting additive and adhesion binder. The structure characters of the LiFePO4/C films were analyzed by XRD, SEM, BET, etc. and the electrochemical properties of the films were studied. It was found that 23wt% carbon content could effectively improve the conductivity of the LiFePO4 material and keep the films intact. The coherent LiFePO4/C composite film cathode is capable of delivering lithium-ion intercalation capacity of 141 mAh g-1 and 131 mAh g-1 at current density of 85 mA g-1 [0.5 C] and 170 mA g-1 [1 C], respectively, with a good cyclic stability.