ИСТИНА

Na2FePO4F fluorophosphate represent a perspective type of the compounds for the use in cathode materials of lithium- and sodium-ion batteries because of three reasons: its layered structure allows relatively fast diffusion of lithium and sodium ions; it is more thermally stable towards electrolyte in comparison with oxide materials; and finally – total absence of expensive or hazardous chemical elements in the case of a sodium cell. Moreover, the presence of two alkali cations in the formula unit gives theoretical possibility of the existence of multi-electron transition for the Fe cations which leads to higher values of the theoretical capacity (124 mAh/g per 1 Na+/Li+). In the present work we performed hydro- and solvothermal synthesis of the Na2FePO4F and studied its morphology and electrochemical properties depending on synthetic conditions. A novel scalable synthetic procedure of carbon-coated nanoparticles Na2FePO4F is proposed. Obtained Na2FePO4F materials demonstrate more than 90% of the theoretical capacity for one alkaline metal ion at the C/10 rate and more than 40% of theoretical capacity at 10C rate in Li-ion cell. Chemical diffusion coefficients as well as the contribution of single-phase and two-phase mechanisms of Li(Na) (de)intercalation are calculated using PITT experiments.