High Surface Area Carbon Composite LiMn0.8Fe0.2PO4 as High-Power Electrodes for Lithium-Ion Batteries

Abstract LiMn0.8Fe0.2PO4 (LMFP) is projected to replace LiFePO4 cathode due to high voltage (4.1 V), long-term cyclability (> 90 % capacity retention after >1000 cycles), and safety for Lithium-ion batteries. The poor electronic conductivity (~ 10-10 S cm-1) and Li-ion diffusion (10-10-10-13 cm2 s-1), make it practically inferior. To address these challenges, a high surface area carbon (HSAC) and LMFP composite is developed in varying compositions, investigating the impact of HSAC content on the electrochemical performance of the LMFP composite. It demonstrates significant improvements (~2.43 times) in conductivity and Li-ion diffusion (~1 order) than pristine LMFP, leading to the enhanced overall performance of the cathode material. An optimum 6 wt.% HSAC composite delivers 140 mAh g-1 discharge capacity at 0.05 C and 118 mAh g-1 at 1 C with > 99% average coulombic efficiency and 93.7% retention after 1000 cycles. This work presents a promising approach for optimizing LMFP-based cathodes for Li-ion full cells with graphite anode, which delivers 119 mAh g-1 capacity at 0.1 C and 86 mAh g-1 at 1C rate (with respect to cathode active mass) with capacity retention of 65% and average coulombic efficiency of 99.5% over 200 cycles at 1 C rate.