Se‐p Orbitals Induced “Strong d–d Orbitals Interaction” Enable High Reversibility of Se‐Rich ZnSe/MnSe@C Electrode as Excellent Host for Sodium‐Ion Storage

Abstract

AbstractThe heterostructure of transition‐metal chalcogenides is a promising approach to boost alkali ion storage due to fast charge kinetics and reduction of activation energy. However, cycling performance is a paramount challenge that is suffering from poor reversibility. Herein, it is reported that Se‐rich particles can chemically interact with local hexagonal ZnSe/MnSe@C heterostructure environment, leading to effective ions insertion/extraction, enabling high reversibility. Enlightened by theoretical understanding, Se‐rich particles endow high intrinsic conductivities in term of low energy barriers (1.32 eV) compared with those without Se‐rich particles (1.50 eV) toward the sodiation process. Moreover, p orbitals of Se‐rich particles may actively participate and further increase the electronegativity that pushes the Mn d orbitals (dxy and dx2‐y2) and donate their electrons to dxz and dyz orbitals, manifesting strong d–d orbitals interaction between ZnSe and MnSe. Such fundamental interaction will adopt a well‐stable conducive electronic bridge, eventually, charges are easily transferred from ZnSe to MnSe in the heterostructure during sodiation/desodiation. Therefore, the optimized Se‐rich ZnSe/MnSe@C electrode delivered high capacity of 576 mAh g−1 at 0.1 A g−1 after 100 cycles and 384 mAh g−1 at 1 A g−1 after 2500 cycles, respectively. In situ and ex situ measurements further indicate the integrity and reversibility of the electrode materials upon charging/discharging.