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

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 SnSe2. Herein, an appealing yolk‐shell nanostructure of SnSe2/NiSe2 heterointerface with rich Se vacancies embedded into N‐doped carbon (SnSe2/NiSe2@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 SnSe2/NiSe2@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 SnSe2/NiSe2@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. A SnSe2/NiSe2@NC yolk‐shell nanostructure with heterogeneous interfaces and Se vacancies is constructed, which delivers ultra‐stable cycling life (7500 cycles) for sodium ion batteries. The experimental results, in situ detections and DFT calculations reveal the heterointerfaces can accelerate charge transfer efficiency and improve Na+ adsorption energy, and the yolk‐shell structure buffers the volume variations.