NaSICON-type materials with the general formula Na3MM’(PO4)3 (i.e., M, M’: transition metals) have shown tremendous interest thanks to their good electrochemical properties, high ionic conductivity, and high structural/ thermal stabilities. Nevertheless, NaSICONs suffer from low electronic conductivity. which is generally mitigated by doping with conductive elements, carbon-coating, and reduction of particle size.
In this study, we report for the first time novel NCFP material as cathode for SIBs. NCFP was synthesized using sol-gel method followed by a calcination at 600 °C under Ar atmosphere. The electrochemical properties of the NCFP were studied in a half-cell configuration. The 1.0 – 4.6 V voltage range and 1M NaPF6 in EC: DEC (50: 50, by vol.) electrolyte were recognized as the optimal. NCFP demonstrated high-rate performance at increasing C-rates. Charge/discharge capacities of 146 mAh g-1/ 116 mAh g-1, 123 mAh g-1/ 103 mAh g-1, 98 mAh g-1/ 86 mAh g-1, 81 mAh g-1/ 71 mAh g-1, and 73 mAh g-1/ 69 mAh g-1 were obtained at C/10, C/5, C/2, 1C, and 2C, respectively. Furthermore, the sodiation/de-sodiation mechanism of NCFP was investigated using Operando diffraction of synchrotron radiation and the X-ray absorption fine structure.
Keywords: NaSICON ; cathode ; sodium-ion batteries ; Operando diffraction of synchrotron radiation ; X-ray absorption fine structure