Improving Electrochemical Performance of LiMn0.5Fe0.5PO4 Cathode by Hybrid Coating of Li3VO4 and Carbon

Abstract LiMnxFe1-xPO4(0.5≤x≤1) has been regarded as a promising cathode material for lithium-ion batteries due to its competitive energy density and excellent thermal stability, yet its rate capability and insufficient capacity retention during long cycles still remain to be further improved. Herein, a hybrid layer composed of Li3VO4 (LVO) and carbon was designed and successfully coated on LiMn0.5Fe0.5PO4 (LMFP) nanorods via a wet ball-milling method combined with the heat treatment. This layer performs as not only a protector to maintain the structural integrity of LMFP but also a conductor to induce the fast transport of both Li-ions and electrons. LMFP modified with the hybrid layer of carbon and 3 wt% LVO (LMFP/C-3LVO) exhibits super long cycling stability over 1000 cycles at 5 C, with considerable capacity retention of 91.5%. Even at a high rate of 10 C, LMFP/C-3LVO can also deliver a substantial discharge capacity of 125 mAh•g−1. The favorable kinetics of the modified composite were confirmed in detail by EIS and GITT measurement. When paired with the modified Li4Ti5O12/C anode, LMFP/C-3LVO shows a stabilized discharge capacity of 107 mAh•g−1 over 120 cycles at 1 C. Our strategy on ionic/electronic dual-conductive hybrid layer provides a guideline on the synthesis and modification of high-performance cathode materials.