Wu Xianming

Characterization and electrochemical properties of LiMn2O4 thin films prepared by solution deposition

LiMn2O4 thin films were prepared by solution deposition using lithium acetate and manganese acetate as raw materials. The phase constitution and surface morphology were observed by X-ray diffraction and scanning electron microscopy. The electrochemical properties of the thin films were studied by cyclic voltammetry, charge-discharge experiments and impedance spectroscopy in 1 mol·L−1 LiPE6/EC-DMC solution using lithium metal as both the counter and reference electrodes. The films prepared by this method are of spinel phase. The lattice parameter increases with the annealing temperature and annealing time. The film annealed at 750°C for 30 minutes has the highest capacity of 34.5 μAh·cm−2·μm−1, and its capacity loss per cycle is 0.05% after being cycled 100 times.

Preparation and characterization of LiMn1.8Co0.2O3.95F0.05 by the combustion-assisted soft route

LiMn1.8Co0.2O3.95F0.05 powder was prepared by heating the ignited LiMn1.8 Co0.2 O3.95 F0.05 precursor gel using lithium acetate, magnesium acetate, cobalt acetate, lithium fluoride, citric acid and glycol as raw materials. The influence of the calcination temperature on the structural and electrochemical properties of LiMn1.8 Co0.2 O3.95 F0.05 was investigated by X-ray diffraction, scanning electron microscopy, and galvanostatic charge-discharge experiments. The powders prepared under different conditions are of good crystallinity. The discharge capacity of LiMn1.8 Co0.2 O3.95 F0.05 powder increased from 92 mAh/g to 105 mAh/g as the calcination temperature increased from 750 °C to 850 °C. The capacity of LiMn1.8 Co0.2 O3.95 F0.05 heated at 750 °C, 800 °C, 850 °C for 4 hours remained at 95.2%, 97%, 94.2%, respectively, after being cycled 20 times, suggesting that the multiple substitution of Co and F for Mn and O results in a good cycling behavior.