Synthesis and performance of LiFe x Mn 1− x PO 4 /C as cathode material for lithium ion batteries

LiFe x Mn 1− x PO 4 /C composites were synthesized by a solid-state reaction route using phenolic resin as both reducing agent and carbon source. The effect of Fe doping on the crystallinity and electrochemical performance of LiFe x Mn 1− x PO 4 /C was investigated. The experimental results show that the Fe 2+ substitution for Mn 2+ will lead to crystal lattice shrinkage of LiFe x Mn 1− x PO 4 /C particles due to the smaller ionic radii of Fe 2+ . In the investigated Fe doping range ( x = 0 to 0.7), LiFe x Mn 1− x PO 4 /C ( x = 0.4) composites exhibited a maximum discharge capacity of 148.8 mAh/g at 0.1 C while LiFe x Mn 1− x PO 4 /C ( x = 0.7) composite showed the best cycle capability with a capacity retention ratio of 99.0% after 30 cycles at 0.2 C. On the contrary, the LiFe x Mn 1− x PO 4 /C ( x = 0.5) composite performed better trade-off on discharge capacity and capacity retention ratio, 127.2 mAh/g and 94.7% after the first 30 cycles at 0.2 C, respectively, which is more preferred for practical applications.