Selenium-induced anion vacancy and active site migration stimulating remarkable sulfide Na-Ion storage

Heterojunctions and controllable anionic vacancies are perceived to be powerful means of ameliorating the performance of sodium-ion batteries assignable to their unique physical and chemical properties. However, the mechanism by which heterojunction and vacancy structures affect sodium-ion battery storage remains to be systemically explored. In this study, the Se doped CoS₂@CoS_1.035@Carbon (Se-CoS₂@CoS_1.035@C) heterostructure with anion vacancy was synthesized by a one-step calcination. These heterostructures with lower metal oxidation states and anionic vacancies exhibit exceptional Na⁺ storage performance (554.3 mA h g^-1 after 1500 cycles at 5.0 A g^-1). Both electrochemical tests and theoretical calculations demonstrate excellent pseudocapacitive behavior and enhanced Na⁺ adsorption during discharge because of anionic vacancies and Se doping. Additionally, introducing weaker Co-Se bonds and extending Co-S and Co-Se bonds reduce binding energies, which effectively accelerates the conversion reaction. Our findings provide a feasible way to rationally design and facilely prepare heterostructured anode materials with rich anionic vacancies for sodium-ion batteries.