Improving electrochemical performance of LiMn0.5Fe0.5PO4 cathode by hybrid coating of Li3VO4 and carbon

Highlights: • A hybrid layer composed of LVO and C was successfully coated on LMFP. • LVO content influences the electrochemical behavior of LMFP/C-LVO. • LMFP/C-3LVO exhibits optimal cycling stability and superb rate performance. • The enhanced kinetics of LMFP/C-3LVO were confirmed by EIS and GITT. • LMFP/C-3LVO can run smoothly over 120 cycles at 1 C in full cells. -- Abstract: LiMn_xFe_1-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 capacity retention during long cycles remain to be further improved. Herein, a hybrid layer composed of Li₃VO₄ (LVO) and carbon was designed and successfully coated on LiMn_0.5Fe_0.5PO₄ (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.