Improved cycle performance of LiMn2O4 cathode material for aqueous rechargeable lithium battery by LaF3 coating

Abstract

LaF3-coated LiMn2O4 composites were prepared by a simple co-precipitation method using pristine LiMn2O4, La(NO3)3·6H2O, NH4F and polyvinyl pyrrolidone (PVP) as raw materials and the physical and electrochemical properties of the composites were investigated. The results indicate that LaF3 coating is beneficial to improving the electrochemical performance of LiMn2O4 used as a cathode material for aqueous rechargeable lithium battery (ARLB) in 1 mol/L LiNO3 solution. The optimal LaF3-coated LiMn2O4 composite (L-3-LMO) containing 3 wt% LaF3 exhibits much improved electrochemical performance as compared with the pristine LiMn2O4. When galvanostatically charged and discharged at 2 C (296 mA g-1), L-3-LMO displays initial discharge capacity of 118.4 mAh g-1 and capacity retention of 99.7% after 50 cycles, while the pristine LiMn2O4 presents initial discharge capacity of 109.2 mAh g-1 and capacity retention of 89.4%. Even at high current density of 10 C, L-3-LMO delivers discharge capacity of 109.5 mAh g-1 and the capacity remains 107.9 mAh g-1 after 100 cycles, while the highest discharge capacity of pristine LiMn2O4 is only 101.6 mAh g-1 and the capacity is as low as 86.3 mAh g-1 after 100 cycles. The effects of LaF3 coating on Li+ diffusion coefficient, dissolution of manganese ion of electroactive materials are also investigated.