Employing Na<sub>2</sub>CO<sub>3</sub> and NaCl as sources of sodium in NaFePO<sub>4</sub> cathode: A comparative study on structure and electrochemical properties

Abstract

<abstract> <p>Encouraged by the tremendous success of lithium iron phosphate (LiFePO<sub>4</sub>), analogous NaFePO<sub>4</sub> has been predicted to show identical properties as LiFePO<sub>4</sub>. Synthesis of NaFePO<sub>4</sub> 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 Na<sub>2</sub>CO<sub>3</sub> and NaCl. The resulted NaFePO<sub>4</sub> 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 NaFePO<sub>4</sub> maricite phase content in the sample. The impedance data analysis shows that the diffusion coefficient of Na<sup>+</sup> ions and the electrical conductivity of a sample using Na<sub>2</sub>CO<sub>3</sub> 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.</p> </abstract>