Hierarchical carbon-coated LiFePO4 nano-grain microspheres with high electrochemical performance as cathode for lithium ion batteries

The hierarchical carbon-coated LiFePO4 nano-grain microspheres are prepared by a chemical co-precipitation method. The microstructure and electrochemical properties of LiFePO4/C composites treated at 950-1025 K are intensively investigated. The rate discharge capability has been obviously enhanced when sample is treated at 1025 K. This attributes to its improved electric conductivity of 0.09 S cm−1 due to the in-situ formation of Fe2P phase. The cycling stabilities are excellent until 300 cycles for all the samples at the rate 1C in discharge, which is very difficult to reach for nano-grains with large specific surface area and high reaction activity. Our samples with hierarchical microstructures exhibit high Li-ion diffusion rate (10−9-10−13 cm2 S−1) with enhanced tap density (1.30 g cm−3). It is considered in our paper that the rate capacities increased by Li-ion diffusion rate are not as obvious as electric conductivity. Therefore, the LiFePO4/FePO4 reaction is a non-diffusional controlled process.