Synthesis of LiFePO4 nanocrystals and their properties as cathodic material for lithium ion batteries (Short communication)

Abstract

The method of lithium iron phosphate (LiFePO₄) synthesis in a melt mixture of choline chloride and diethylene glycol (DEG) at 230 °C is proposed. Powders with lamellar morphology consisting of LiFePO₄ crystals (size ~30 nm) with olivine structure were synthesized. The size of crystals increased to ~60 nm during the annealing process carried out to obtain a carbon coating on the grain surface of LiFePO₄. The charge-discharge curves of the electrode pre­pared from these powders have a horizontal portion at the potential of 3.4 and 3.5 V, corresponding to the intercalation/deintercalation of lithium in the struc­ture of olivine. The specific discharge capacity of the LiFePO₄/C is 133 mA h g^-1 for a discharge current of 0.1C. The dependence of the anodic (cathodic) voltammetric current peaks, I_p, on the potential scan rate indicates the diffusion nature of the lithiating step. For the anodic and cath­odic processes the averaged diffusion coefficient values are 1.3´10^-10 and 1.5´10^-10 cm² s^-1,respectively.