Vanadium-doping of LiFePO4/carbon composite cathode materials synthesized with organophosphorus source

Abstract A series of V-doped LiFePO 4 /C composites are synthesized through a quasi-sol–gel method using organophosphorus source. Amino tris(methylene phosphonic acid) is utilized as phosphorus and carbon co-precursor, sucrose as assisted carbon source, and NH 4 VO 3 as dopant. The effect of vanadium doping on the structural property and electrochemical performance of LiFePO 4 /C cathode material is systematically investigated. Carbon is coated uniformly on the LiFePO 4 nanoparticles and vanadium (+4) is incorporated into LiFePO 4 /C without altering the olivine structure. The appropriate V-doping refined LiFePO 4 particle size, induced the lattice distortion and weakened the Li O bonds, leading to the enhancement of Li + diffusion and electronic conductivity, and hence resulting in the improvement of the electrochemical performance of LiFePO 4 /C composites. A high rate discharge capacity of 140.2 mAh g −1 at 5 C, 120.4 mAh g −1 at 10 C, and 105.8 mAh g −1 at 20 C is obtained for LiFe 0.97 V 0.03 PO 4 /C. It is demonstrated that the simple and green synthesis process of the quasi-sol–gel route with organophosphonic acid as precursor is efficient to fabricate V-doped LiFePO 4 /C composite cathode materials for high-power lithium-ion batteries.