Heterodimensional Superlattice with Electron Spin-Polarization and Se-Vacancies for Superior Sodium-Ion Storage

Transition metal dichalcogenides (TMDs) are remarkable in their high specific capacity, good electrical conductivity, and weak van der Waals force between adjacent layers in sodium-ion batteries (SIBs). However, TMD anodes are limited by sluggish reaction kinetics and significant volumetric change, which can lead to poor rate performance and cycle stability. Herein, we design a V 2 Se 9 /SnSe composite with a heterodimensional superlattice structure that offers contributions to reaction kinetics, electrical conductivity, and structural stability demonstrated by both experimental measurements and theoretical calculations. In addition, selenium vacancies (Se-vacancies) produce rich active sites, which can improve the specific capacity. Therefore, the as-prepared V 2 Se 9 /SnSe demonstrates an excellent rate capability of 648.5 mA h g –1 at 10 A g –1 and exceptional long-term cyclability of 653.2 mAh g –1 after 2200 cycles at 4 A g –1 .