High‐efficiency sodium storage of Co0.85Se/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 0.85 Se/WSe 2 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 0.85 Se/WSe 2 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 0.85 Se/WSe 2 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.