Optimizing Reversible Phase-Transformation of FeS₂ Anode via Atomic-Interface Engineering Toward Fast-Charging Sodium...

Sodium-storage performance of pyrite FeS₂ is greatly improved by constructing various FeS₂-based nanostructures to optimize its ion-transport kinetics and structural stability. However, less attention has been paid to rapid capacity degradation and electrode failure caused by the irreversible phase-transition of intermediate Na_xFeS₂ to FeS₂ and polysulfides dissolution upon cycling. Under the guidance of theoretical calculations, coupling FeS₂ nanoparticles with honeycomb-like nitrogen-doped carbon (NC) nanosheet supported single-atom manganese (SAs Mn) catalyst (FeS₂/SAs Mn@NC) via atomic-interface engineering is proposed to address above challenge. Systematic electrochemical analyses and theoretical results unveil that the functional integration of such two type components can significantly enhance ionic conductivity, accelerate charge transfer efficiency, and improve Na⁺-adsorption capability. Particularly, SAs Mn@NC with Mn-N_x coordination center can reduce the decomposition barrier of Na₂S and Na_xFeS₂ to further accelerate reversible phase transformation of Fe/Na₂S→NaFeS₂→FeS₂ and polysulfides decomposition. As predicted, such FeS₂/SAs Mn@NC showcases outstanding rate capability and fascinating cyclic durability. A sequence of kinetic studies and ex situ characterizations provide the comprehensive understanding for ion-transport kinetics and phase-transformation process. Its practical use is further demonstrated in sodium-ion full cell and capacitor with impressive electrochemical capability and excellent energy-density output.