Employing Na2CO3 and NaCl as sources of sodium in NaFePO4 cathode: A comparative study on structure and electrochemical properties

Encouraged by the tremendous success of lithium iron phosphate (LiFePO4), analogous NaFePO4 has been predicted to show identical properties as LiFePO4. Synthesis of NaFePO4 materials in the maricite phase has been carried out using the sol-gel method with variations of calcination temperature and starting materials as sources of sodium Na2CO3 and NaCl. The resulted NaFePO4 maricite phase with the purity between 40% and 85%, according to X-ray diffractometry (XRD) characterization was obtained. The morphology and grain size of the particles in samples, as observed by a scanning electron microscope (SEM), tend to enlarge upon calcination at higher temperatures. The increment of calcination temperature increases the NaFePO4 maricite phase content in the sample. The impedance data analysis shows that the diffusion coefficient of Na+ ions and the electrical conductivity of a sample using Na2CO3 is higher than that of NaCl. This comprehensive study provides a feasible method and opens new opportunities for the continuous study of Na-ion batteries.