SnSe2/NiSe2@N‐Doped Carbon Yolk‐Shell Heterostructure Construction and Selenium Vacancies Engineering for Ultrastable Sodium‐Ion Storage

Abstract Tin diselenide, a promising anode material for sodium ion batteries (SIBs), still faces sluggish Na + diffusion kinetics and severe volume change, resulting in undesirable cycling stability and rate capability. Heterostructure construction is an effective strategy for boosting Na + storage of SnSe 2 . Herein, an appealing yolk‐shell nanostructure of SnSe 2 /NiSe 2 heterointerface with rich Se vacancies embedded into N‐doped carbon (SnSe 2 /NiSe 2 @NC) is precisely designed through a facile hydrothermal process followed by a selenization strategy. The experimental studies coupled with theoretical calculations results verify that the heterostructure interfaces and Se vacancies accelerate the charge and Na + transfer efficiency, improve Na + adsorption energy and supply ample active sites. The yolk‐shell nanostructure and N‐doped carbon buffer the volume variation and improve the structural stability of the electrode material during sodium storage processes. The SnSe 2 /NiSe 2 @NC delivers ultra‐long term cycling stability (322.7 mAh g −1 after 7500 cycles at 3 A g −1 ) and exceptional rate capability (314.6 mAh g −1 at 10 A g −1 ). The Na‐ion storage mechanism of SnSe 2 /NiSe 2 @NC is explored through in situ X‐ray diffraction and ex situ high‐resolution transmission electron microscopy analysis. The present work provides an effective avenue to the rational design of heterostructure anode materials for high efficiency SIBs.