Encapsulation of Cu2S with a nitrogen-doped carbon boosts Na+ storage with a reversible Na2S conversion reaction

The high reversibility of a conversion-anode material enables high reversible capacity and maintains its cyclability. In this work, we report copper sulfide microspheres encapsulated by nitrogen-doped carbon (Cu2[email protected]) prepared via a conventional polyol process (CPP) and demonstrate their potential use as anode materials for sodium-ion batteries (SIBs). Nitrogen-doped carbon stimulates a reversible conversion reaction of Cu2S + Na ↔ Na2S + Cu while corroborating the phase stability, leading to excellent Na+ storage properties of the Cu2[email protected] Thus, the Cu2[email protected] anode demonstrates an excellent cyclability of 284.99 mA h g-1 at a higher current at 5000 mA g-1. Operando X-ray diffraction and density functional theory (DFT) calculations are combined to verify the electrochemical Na+ storage mechanism of the Cu2[email protected]