Beneficial effect of incorporating particle nanocrystalline and V3+ doping into high-energy-density LiMn0.8Fe0.2PO4 for lithium-ion batteries

Olivine-structured LiMnPO4-based cathode materials have been considered upgrades to LiFePO4 due to their higher energy density and highly stable polyanionic Li+ storage structure. However, the high electronic and ionic insulation has severely limited their popularization and application. In this work, the reversible specific capacity and the rate performance of LiMn0.8Fe0.2PO4@C (LMFP@C) have been promoted by incorporating particle nanocrystalline and V3+ doping. The mechanical liquid phase activation technique ensures the uniform mixing of the raw materials and reduces their particle size to nanometer scale. Based on this typical synthetic strategy, about 1 at.% of V3+ can be doped into the LMFP lattice to form a uniform solid solution, while most of the V3+ ions tend to enrich on the surface of the particles as the introducing amount is >2 at.%. Optimally, 1 at.% of V3+ doping improves the electrochemical performance of LMFP@C significantly, but >2 at.% of V3+ introduction is detrimental. The optimized material exhibits high discharge capacities of 155.4 and 115.9 mAh·g−1 at 0.1 and 5.0C, respectively, and a high capacity retention of 93.4% after 100 cycles at 1.0C rate.