High rate capability and cycle performance of Ce-doped LiMnPO4/C via an efficient solvothermal synthesis in water/diethylene glycol system

LiMn1 1.5xCexPO4/C (x = 0, 0.01, 0.03, 0.05) are synthesized by an efficient solvothermal synthesis in water/diethylene glycol system. The structures and morphologies of all samples are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) results suggest that trivalent Ce3+ doping has no influence on the valence state of Mn2+ in LiMnPO4/C. The Ce-doped LiMn1 1.5xCexPO4/C (x not equal 0) materials show better cycling stability and high rate capability than the pristine LiMnPO4/C (LCe0). The Ce3+ doping content has an obvious influence on the electrochemical performances of LiMn1 1.5xCexPO4/C. After 50 cycles at 0.1 C, the LiMn0.955Ce0.03PO4/C (LCe3) exhibits the highest discharge capacity of 132.3 mAh g (1) (95.4 % of its initial discharge capacity), while LCe0 delivers only 115.1 mAh g (1) (85.5 % capacity retention). And LCe3 also has the best high rate capability, which can still deliver 78.2 mAh g (1) at 10 C in comparison with 49.6 mAh g (1) of LCe0. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements suggest that Ce3+ doping not only improves the electronic conductivity of LiMnPO4/C, but also facilitates the diffusion of lithium ion in bulk materials. (C) 2015 Elsevier Ltd. All rights reserved.