Preparation of NaFeO2 from iron sand as a raw material for cathode of sodium-ion battery

Abstract

Sodium-Ion Battery (SIB) is now gaining attention instead of Lithium-Ion Battery (LIB) due to a high sodium abundance compare to lithium. Na-iron oxide compound mostly studied as raw material for SIB cathode. The abundance of iron source on earth is an advantage to develop SIB. Therefore, this research aims to prepare Fe2O3 from Indonesian iron sand through co-precipitation method, and then react the Fe2O3 with Na2O2 to produce NaFeO2. The reaction was conducted at 650 °C for 12 h. XRD analysis equipped with Le Bail refinement found that the prepared Fe2O3 has diffraction pattern similar to Fe2O3 ICSD#15840, trigonal structure and space group of R-3CH. Meanwhile, the prepared NaFeO2 has a diffraction pattern similar to standard diffraction ICSD#75588. The crystal structure is trigonal / rhombohedral with a space group of R-3MH. Test of NaFeO2 as a potential host for Mn2+ ions was conducted by doped 0.1 mol% Mn into NaFeO2. Cyclic voltammetry analysis of a half cell Na | NaFeO2 | Al and Na | Mn doped-NaFeO2 | Al shows an active electrochemical reduction-oxidation of Fe2+/Fe3+ at 1.776 V vs Na+/Na. Meanwhile a potential peak at 0.808 V released by NaFeO2 half-cell confirms the electrochemical activity of Na+ ions to leach out and be inserted back into NaFeO2 cathode.