High rate performance of LiF modified LiFePO sub(4)/C cathode material

Nonstoichiometric LiF modified F-LiFePO sub(4)/C cathode material is successfully synthesized by solid-state-reaction using LiF as the additive and FePO sub(4) and Li sub(2)CO sub(3) as precursors. The synthesized F-LiFePO sub(4)/C powders are characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscope (TEM), Raman spectrum, X-ray photoelectron emission microscopy (XPS) and potentiostatic intermittent titration technique (PITT). The XRD results show that the LiF additive modification can improve the crystallinity of LiFePO sub(4) without introducing any impurities. LiF modification has little influence on LiFePO sub(4) crystal structure based on lattice parameters, calculated by MDI Jade 6. The DSC curve shows that a LiF additive can lower the LiFePO sub(4) formation temperature by about 100 [degrees]C F1s signal and a C - F bond have been discovered on the surface of the modified sample via XPS analysis, indicating that LiF has an influence on the chemical reaction. The final particle size varied with LiF additive content based on SEM and HRTEM images. F-LiFePO sub(4)/C samples have better and clearer crystal fringes than the untreated LiFePO sub(4)/C sample from HRTEM, which suggests that LiF modification can improve the crystallinity of LiFePO sub(4). Charge-discharge curves indicate that the F-LiFePO sub(4)/C sample has excellent capacities at high discharge rates: 130.0 mAh g super(-1) at 5 C. PITT indicates that the F-LiFePO sub(4)/C sample has a higher Li+ ion diffusion coefficient than the LiFePO sub(4)/C sample.