Synthesis of LiFePO4/C using ionic liquid as carbon source for lithium ion batteries

LiFePO4/C (LFP/C) materials are synthesized by a hydrothermal method with ionic liquid 1-vinyl-3-ethylimidazolium bis(trifluoromethylsulfony)imide ([VEIm]NTf2) as carbon source. Carbon films of 5-10 nm are successfully coated on the surface of LiFePO4 (LFP) particles and serve as the protective layers of LFP particles during cycling. The carbon materials also fill the gap between LFP particles, which creates electron transfer paths. Due to the integrated carbon materials, the LFP/C exhibits significantly improved reversibility, cycle stability, rate performance, and charge and discharge capacity. These results demonstrate a simple and scalable application of ionic liquid [VEIm]NTf2 as carbon source toward electrochemical energy storage.