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

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 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 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. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

LiMnxFe1-xPO4 has competitive energy density and thermal stability, but its rate capability and capacity retention need to be improved. A hybrid layer of Li3VO4 and carbon was successfully coated on LMFP nanorods to enhance its performance. The modified LMFP shows excellent cycling stability and high discharge capacity even at high rates, providing a guideline for high-performance cathode materials.