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.