Synthesis and performance of LiFe _xMn_1−xPO₄/C as cathode material for lithium ion batteries

Abstract

LiFe _xMn_1−xPO₄/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 _xMn_1−xPO₄/C was investigated. The experimental results show that the Fe²⁺ substitution for Mn²⁺ will lead to crystal lattice shrinkage of LiFe _xMn_1−xPO₄/C particles due to the smaller ionic radii of Fe²⁺. In the investigated Fe doping range (x = 0 to 0.7), LiFe _xMn_1−xPO₄/C (x = 0.4) composites exhibited a maximum discharge capacity of 148.8 mAh/g at 0.1 C while LiFe _xMn_1−xPO₄/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 _xMn_1−xPO₄/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.

Keywords

LiMnPO₄ / Fe doping / solid-state reaction route / phenolic resin

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