Self-restriction to form in-situ N, P co-doped carbon-coated LiFePO4 nanocomposites for high-performance lithium ion batteries

Olivine-type lithium iron phosphate LiFePO4 (LFP) is widely used as the cathode for lithium ion batteries in electric vehicles due to its excellent structural stability and low cost. Herein, LFP/C composites are prepared using expired beer as carbon source, which exhibits environmentally friendly benignity and provides a uniform N, P in-situ co-doped carbon layer. On one side, the polysaccharides and monosaccharides in beer has strong steric hindrance ability, which inhibits the growth of particles during sintering. On the other side, the uniform N, P co-doping tunes the electron cloud of the carbon layer, improving the electronic conductivity. As a result, the as-prepared LFP/C composite shows enhanced rate capabilities and structural stability. In detail, the material delivers the initial specific discharge capacity of 134 mAh•g−1 with capacity retention of 94.5% after 1000 cycles at a high rate of 5 C. Even at a higher rate of 10 C, it has a specific discharge capacity of 123 mAh•g−1. Besides, the LFP/C displays enhanced low-temperature performance compared to conventional carbon-coated LFP. Therefore, this work demonstrates the advantages of using expired beer as carbon source for LFP cathode material, which is also feasible for other carbon-coated cathode or anode materials, beneficial for increasing the power density of lithium ion batteries.