Xuewu Liu

Supercritical-hydrothermal accelerated solid state reaction route for synthesis of LiMn2O4 cathode material for high-power Li-ion batteries

Abstract Synthesis of the spinel structure lithium manganese oxide (LiMn2O4) by supercritical hydrothermal (SH) accelerated solid state reaction (SSR) route was studied. The impacts of the reaction pressure, reaction temperature and reaction time of SH route, and the calcination temperature of SSR route on the purity, particle morphology and electrochemical properties of the prepared LiMn2O4 materials were studied. The experimental results show that after 15 min reaction in SH route at 400 °C and 30 MPa, the reaction time of SSR could be significantly decreased, e.g. down to 3 h with the formation temperature of 800 °C, compared with the conventional solid state reaction method. The prepared LiMn2O4 material exhibits good crystallinity, uniform size distribution and good electrochemical performance, and has an initial specific capacity of 120 mA·h/g at a rate of 0.1C (1C=148 mA/g) and a good rate capability at high rates, even up to 50C.

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

LiFexMn1−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 LiFexMn1−xPO4/C was investigated. The experimental results show that the Fe2+ substitution for Mn2+ will lead to crystal lattice shrinkage of LiFexMn1−xPO4/C particles due to the smaller ionic radii of Fe2+. In the investigated Fe doping range (x = 0 to 0.7), LiFexMn1−xPO4/C (x = 0.4) composites exhibited a maximum discharge capacity of 148.8 mAh/g at 0.1 C while LiFexMn1−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 LiFexMn1−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.