Synthesis of vanadium doped LiMnPO4 by an improved solid-state method

A series of LiMn1-xVxPO4/C (0 <= x <= 0.075) samples are synthesized via an improved solid-state method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. XRD, XPS and cyclic voltammetry (CV) tests reveal that olivine phase is observed exclusively in LiMn1-xVxPO4/C (0 <= x <= 0.05) samples and the valence of the doped V is +3, whereas a minor amount of Li3V2(PO4)(3) is additionally detected in the LiMn1-xVxPO4/C at x=0.075. SEM observation shows that much smaller crystals of V-doped LiMnPat can be obtained at relatively high temperatures by our synthesis method and consequently more vanadium can be incorporated into the lattice of LiMnPO4. Electrochemical test demonstrates that a proper amount of V doping on the Mn-site in LiMnPO4 can effectively enhance its electrochemical performance due to the reduced resistance of charge transfer, and the LiMn1-xVxPO4/C at x=0.025 exhibits the best rate performance. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.