Triethylene glycol assisted synthesis of pure tavorite LiFeSO₄F cathode material for Li-ion battery

Pure tavorite-structured lithium iron fluorosulphate (LFSF: LiFeSO ₄F) cathode material was successfully synthesized using newly prepared sub-micro sized lithium fluoride (LiF) and ferrous sulfate monohydrate (FeSO₄ · H₂O) as the precursors in triethylene glycol (TEG) medium. Experimental parameters, such as reaction temperature and time, polyol media, and different size of LiF, were investigated to see their influences on the phase formation of the t-LFSF. XRD and SEM were used to characterize the as-prepared precursors and t-LFSF. The product exhibited a capacity of 92 mA h g^-1 at 0.05 C rate (1 C corresponding to 151 mA g^-1 of current rate) and a capacity retention of 60% in reference to the initial capacity 34.5 mA h g^-1 after 100 cycles at 0.2 C. The apparent lithium diffusion coefficient of the t-LFSF was firstly calculated to be about 4.99 × 10^-13 cm² s^-1 by cyclic voltammetry (CV) method.