S, Se-Codoped Dual Carbon Coating and Se Substitution in Co-Alkoxide-Derived CoS2 Through SeS2 Triggered Selenization for High-Performance Sodium-Ion Batteries

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The development of metal sulfides as anodes for sodium-ion batteries (SIBs) is significantly obstructed by the slow kinetics of the electrochemical reactions and the substantial volume changes on the cycling. Herein, we introduce a selenium-substituted cobalt disulfide embedded within a dual carbon–graphene framework (Se-CoS2/C@rGO) for high-performance SIBs. The Se-CoS2/C@rGO was prepared via a synchronous sulfurization/selenization strategy using Co-alkoxide as the precursor and SeS2 as the source of selenium and sulfur, during which the EG anions are converted in situ to a S, Se codoped carbon scaffold. The dual carbon–graphene matrix not only improves the electronic conductivity but also stabilizes the electrode material effectively. In addition, the Se substitution within the CoS2 lattice further improves the electrical conductivity and promotes the Na+ reaction kinetics. The enhanced intrinsic electronic/ionic conductivity and reinforced structural stability endow the Se-CoS2/C@rGO anode with a high reversible capacity (558.2 mAh g−1 at 0.2 A g−1), superior rate performance (351 mAh g−1 at 20 A g−1), and long cycle life (93.5% capacity retention after 2100 cycles at 1 A g−1). This work provides new insights into the development of stable and reversible anode materials through Se substitution and dual carbon encapsulation.