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

Olivine-type LiMnPO 4 (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 LiFe x Mn 1-x PO 4 @carbon (LF x M 1-x P@C, x = 0, 0.25, 0.5, 0.75, 1) composites with different Fe doping amounts is investigated. Among the composites, LF 0.5 M 0.5 P@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 LF 0.5 M 0.5 P@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.