Mn-doped NaFeO₂ from a low purity-Fe precursor and its performance as cathode for Sodium-Ion Battery

Abstract

Research to produce Mn-doped NaFeO₂ was conducted from a low purity Fe-precursor aims to check the reliability for the inexpensive-mass production of the compound. The NaFeO₂ was prepared through the co-precipitation method from iron sand concentrate with Fe content of 86.72% consist of the hematite-ilmenite mixture. The reaction was conducted at 650 °C for 12 h under air argon atmosphere producing a mix of β-NaFeO₂ and α-NaFeO₂, which was then mixed with Mn₂O₃ to produce Na_1-x[Fe_1-xMn_x]O_2-δ (NFMO) at various x of 0.02; 0.05; and 0.07. The result shows that Mn doping changed the crystal structure from orthorhombic into a hexagonal, P63/mmc. FTIR spectra provides peaks attributed to Na-O, Na-Fe, Mn-O, and Fe-O. Voltammetry analysis to NFMO-0.02 and NFMO-0.05 provide peaks attributed to Na⁺/Na and Fe³⁺/Fe⁴⁺ redox reaction. Meanwhile, the NFMO-0.07 provides Na⁺/Na, Fe³⁺/Fe⁴⁺, and Mn³⁺/Mn²⁺. The NFMO-0.07 also shows the highest electrical conductivity of 1.372 x 10⁻⁴ Scm⁻¹. A split cell test developed with NFMO-0.07 as cathode produced an initial specific capacity of 50.57 mAhg⁻¹ and an initial discharge capacity of 36.29 mAhg⁻¹ correlate to 71.70% Columbic efficiency.

Keywords:

• Mn-doped NaFeO₂
• low purity Fe-precursor
• Sodium-Ion Battery
• cathode material

Additional information

Funding

This research is a part of Hibah Penelitian Dasar 2019, contract number: 719/UN.27.21/PN/2019, funded by The Ministry of Research, Technology, and Higher Education, Republic of Indonesia.