Facile synthesis of fluorine doped single crystal Ni-rich cathode material for lithium-ion batteries

Fluorine doped single crystal Ni-rich cathode material with excellent electrochemical properties were successfully synthesized. X-ray diffraction (XRD) revealed that the fluorine substitution process did not change the hexagonal layer structure, but it promoted the unit cell expanded along the c-direction which was conductive to improving the kinetic of Li+ transmission. Energy dispersive X-ray Spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) further proved the fluorine doped into the cathode material, which simultaneously triggered partial Ni3+ reduction to Ni2+. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrated that fluorine substitution can effectively decrease polarization and suppress migration resistance of lithium ions. The lithium ions diffusion rate (DLi+) indicated that lithium ions migrated more smoothly in fluoride doped sample. Both the substitution effects of fluorine and short migration path way for lithium ions in single crystal particles account for excellent electrochemical performance of the Ni-rich lithium cathode material. This study provided some new thought into synthesis of high performance fluorine doped single crystal Ni-rich lithium cathode materials.