Synergistic Engineering of Se Vacancies and Heterointerfaces in Zinc-Cobalt Selenide Anode for Highly Efficient Na-Ion Batteries.

ABSTRACT

The exploitation of effective strategies to accelerate the Na+ diffusion kinetics and improve the structural stability in the electrode is extremely important for the development of high efficientcy sodium-ion batteries. Herein, Se vacancies and heterostructure engineering are utilized to improve the Na+ -storage performance of transition metal selenides anode prepared through a facile two-in-one route. The experimental results coupled with theoretical calculations reveal that the successful construction of the Se vacancies and heterostructure interfaces can effectively lower the Na+ diffusion barrier, accelerate the charge transfer efficiency, improve Na+ adsorption ability, and provide an abundance of active sites. Consequently, the batteries based on the constructed ZnSe/CoSe2 -CN anode manifest a high initial Coulombic efficiency (97.7%), remarkable specific capacities (547.1 mAh g-1 at 0.5 A g-1 ), superb rate capability (362.1 mAh g-1 at 20 A g-1 ), as well as ultrastable long-term stability (1000 cycles) with a satisfied specific capacity (535.6 mAh g-1 ) at 1 A g-1 . This work facilitates an in-depth understanding of the synergistic effect of vacancies and heterojunctions in improving the Na+ reaction kinetics, providing an effective strategy to the rational design of key materials for high efficiency rechargeable batteries.