High‐efficiency sodium storage of Co_0.85Se/WSe₂ encapsulated in N‐doped carbon polyhedron via vacancy and heterojunction engineering

Abstract With the advantage of fast charge transfer, heterojunction engineering is identified as a viable method to reinforce the anodes' sodium storage performance. Also, vacancies can effectively strengthen the Na⁺ adsorption ability and provide extra active sites for Na⁺ adsorption. However, their synchronous engineering is rarely reported. Herein, a hybrid of Co_0.85Se/WSe₂ heterostructure with Se vacancies and N‐doped carbon polyhedron (CoWSe/NCP) has been fabricated for the first time via a hydrothermal and subsequent selenization strategy. Spherical aberration‐corrected transmission electron microscopy confirms the phase interface of the Co_0.85Se/WSe₂ heterostructure and the existence of Se vacancies. Density functional theory simulations reveal the accelerated charge transfer and enhanced Na⁺ adsorption ability, which are contributed by the Co_0.85Se/WSe₂ heterostructure and Se vacancies, respectively. As expected, the CoWSe/NCP anode in sodium‐ion battery achieves outstanding rate capability (339.6 mAh g⁻¹ at 20 A g⁻¹), outperforming almost all Co/W‐based selenides.