Experimental and Theoretical Insights on Interface Engineered FeS/rGO as Anode for Fast-Charging Lithium- and...

Interface engineering facilitates the development of stable energy storage devices that can endure the severe changes encountered during operation. In the context of fast-charging anodes for lithium- and sodium-ion batteries (LIBs and SIBs), the interface needs to promote charge/ion transfer processes, enhance Li-/Na-ion storage capacity, and ensure good reversibility in order to function efficiently at high rates. Herein, a simple synthetic strategy is reported to design interfaces between transition metal sulfides and carbonaceous supports to generate high-performance fast-charging anodes. FeS/rGO nanostructures are synthesized via a simple solid-state annealing method by employing FeOOH/rGO, a metastable precursor, which is annealed at 600 °C in the presence of H₂S gas. Interface engineering between FeS and rGO significantly improved the electrochemical performance, particularly demonstrated by stable capacities at high rates (625 mAh g⁻¹ at 5 A g⁻¹ for LIBs and 708 mAh g⁻¹ at 10 A g⁻¹ for SIBs). The high-rate charge storage is primarily governed by capacitive processes. Density functional theory (DFT) calculations attributed the enhanced performance of the FeS/rGO anode to a lower diffusion energy barrier for Li- and Na-ion diffusion at the interface along with the presence of a built-in electric field at the heterointerface.