Fe-doped LiMnPO4@C nanofibers with high Li-ion diffusion coefficient

Olivine-type LiMnPO4 (LMP) cathodes have gained enormous attraction for Li-ion batteries (LIBs) due to high discharge platform, theoretical capacity and thermal stability. However, it is still challenging to achieve encouraging Li-storage behavior owing to the low electronic conductivity and slow Li-ion diffusion rate of LMP. Here, the electrochemical behavior of fibrous LiFexMn1-xPO4@carbon (LFxM1-xP@C, x = 0, 0.25, 0.5, 0.75, 1) composites with different Fe doping amounts is investigated. Among the composites, LF0.5M0.5P@C demonstrates a superior cell performance due to a higher Li-ion diffusion coefficient (D-Li), resulting from a proper Fe doping ratio and a more uniform morphology. At a current rate of 0.2 C (1 C = 170 mA g(-1)), the LF0.5M0.5P@C cathode delivers a specific capacity of 150 mAh g(-1) up to 500 cycles with a capacity retention of 119%. A longer-term cycling at 5 C for 2000 cycles can be maintained with a reversible capacity exceeding 102 mAh g(-1). The fundamental study provides an insightful guidance for future design of cathode materials with high performance. (C) 2019 Elsevier Ltd. All rights reserved.