Optimization of LiFePO4 cathode material based on phosphorus doped graphite network structure for lithium ion batteries

Abstract

Lithium iron phosphate (LiFePO4) has been recommended as a hopeful cathode material for lithium ion batteries (LIBs) in the future due to its lots of advantages, such as stable operating voltage, excellent cycle performance, controllable cost, and environmental protection. However, pure LiFePO4 (LFP) shows bad reversible capacity and charge/discharge performance at high rate. Many methods including decrease of particle size, optimization of coating carbon, introduction of conductive polymer, and doping of metal or non-metallic element have been developed to improve the electrochemical performance of LFP cathode material. In this study, LFP/C-P composite cathodes were prepared successfully by a facile sol-gel approach that graphite was used to generate a carbon network structure and triphenylphosphine was used to greatly facilitate generation of a network connecting passage. Electrochemical test results show that LFP/C-P composite cathode has achieved a remarkable improvement in capacity and apparent ascension in rate performance. Compared with LFP, LFP/C, and LFP-P cathode, LFP/C-P composite material shows the best electrochemical performance with a discharge capacity of 168.8 mAh g−1 and a remarkable retention rate of 98.8% over 100 cycles at 0.1 C.