Synergistic Regulation of Polyselenide Dissolution and Na-Ion Diffusion of Se-Vacancy-Rich Bismuth Selenide toward Ultrafast and Durable Sodium-Ion Batteries

Abstract

Metal selenides (MSes) have great potential as candidate anode materials in high-specific-energy sodium-ion batteries (SIBs) but are plagued by rapid capacity degradation and slow kinetics. Here, it is reveal that the Bi₂Se₃ anode discharge process involves multiple-types of sodium polyselenides (Na-pSe_x) which suffer from terrible dissolution and shuttling properties. Based on these observations, a nanoflower-like composite of dual carbon-confined Bi₂Se_3−x crystallites is designed via facile defect chemistry. The robust dual N-doped carbon layer suppresses the precipitation and aggregation of Bi₂Se₃, significantly alleviating the dissolution and shuttle effect of Na-pSe_x. Theoretical calculations indicate that the pyridine/pyrrole nitrogen sites exhibit strong van der Waals resistance and chemisorption properties against Na₂Se₄ and Na₂Se₂. Furthermore, the abundant Se vacancies improve the inherent conductivity of Bi₂Se₃, reduce the diffusion barrier of Na⁺, and accelerate the reaction kinetics. Consequently, the resulting Bi₂Se_3−x@DNC electrode exhibits extraordinary durability (over 2000 cycles at 10.0 A g⁻¹) and high-rate capability (354.4 mAh g⁻¹ at 75.0 A g⁻¹), propelling the battery performance to new heights. Encouragingly, the assembled hybrid capacitor displays competitive rate performance and an ultra-long lifespan exceeding 40 000 cycles, making the Bi₂Se_3−x@DNC electrode a promising candidate for SIBs.