Fluorine-doped carbon coating of LiFe0.5Mn0.5PO4 enabling high-rate and long-lifespan cathode for lithium-ion batteries

Abstract

The limited electron and ionic conductivity, along with the sluggish kinetics caused by the Jahn-Teller effect of Mn³⁺, impose constraints on the electrochemical performance of LiFe_xMn_1-xPO₄. Herein, the surface of LiFe_0.5Mn_0.5PO₄ (LFMP) is modified with a F-doped carbon using the solvothermal and calcination methods. The incorporation of F-doped carbon coating, along with the formation of interfacial F-Li, F-Fe and F-Mn bonds between the carbon layer and LFMP nanoparticles, significantly mitigates charge transfer resistance, facilitates rapid electron transfer, as well as enhances Li⁺ diffusion kinetics. The LFMP@C-F2 cathode prepared in this study exhibits an unexceptionable capacity retention of 90.5 % after 300 cycles at a low rate of 0.2C and a capacity retention of 78.8 % over 1000 cycles at a high rate of 1C. When incorporated into the solid battery configuration (Li/PEO-LATP CSE/LFMP@C-F2), it exhibits an initial discharge specific capacity of 148 mAh g⁻¹ and maintains a capacity retention of 85.8 % after 60 cycles at 0.1C, thereby offering an innovative approach to enhance the performance of LFMP in terms of cycling stability and rate capacity in lithium-ion batteries, as well as to apply LFMP into solid-state lithium batteries.