Asymmetric reaction pathway of Na+-ion during fast cycling in α- and γ-Fe2O3 thin film anode for sodium-ion battery.

This study aims to evaluate various polymorphs of Fe₂O₃ (γ- and α-types) as anode material for sodium-ion batteries and their conversion mechanisms. In this work, pulsed laser deposition (PLD) was used to successfully fabricate Fe₂O₃ (both γ- and α-types) thin film followed by the electrochemical investigation as anode material for a sodium-ion battery. The γ-Fe₂O₃ shows high reversibility than α-Fe₂O₃ while discharging at a deep discharge voltage of 0.01 V. The α-Fe₂O₃ changes to Fe₃O₄ during sodium extraction, while the γ-Fe₂O₃ remains unaltered upon cycling. The γ-Fe₂O₃ shows high electrochemical performance regarding cycle life and discharge capacity than α-Fe₂O₃ (considering up to 80 cycles). The discharge capacity of γ-Fe₂O₃ is 335.2 mAh g⁻¹ and of α-Fe₂O₃ is 248.7 mAh g⁻¹ for the 1st cycle at a current rate of 475 mA g⁻¹. The achieved superior performance of γ-Fe₂O₃ is credited to the reversible reaction path and binder-free nature of the thin film. [ABSTRACT FROM AUTHOR]