Plate-type LiFePO4 nanocrystals by low temperature polyol-assisted solvothermal reaction and its electrochemical properties

Highly nanocrystalline LiFePO4 was synthesized by a solvothermal process in a polyol medium namely, diethylene glycol (DEG) without any heat-treatment as a post procedure. The synchrotron powder XRD pattern of the LiFePO4 was indexed well to a pure orthorhombic system of olivine structure (space group: Pnma) with no undesirable impurities and refined fit parameters were obtained by the Rietveld refinement method using the FULLPROF program. XPS analysis revealed the divalent state of iron (Fe(II)) in the prepared sample thereby further confirming the formation of a pure olivine phase. The synthesized LiFePO4 nanocrystals exhibited well dispersed plate morphologies with average length, width and thickness of 250, 200 and 20 nm, respectively. Nanoplate LiFePO4 indicated initial discharge capacity of 138 mA h/g and exhibited stable capacity retention until 50 electrochemical cycles. It also appeared to reveal considerably better rate performance at enhanced C-rates because of the contribution from nano-dimensional particles when compared to that of LiFePO4 synthesized by solid state method.