Vacancy-Defect Ternary Topological Insulators Bi 2 Se 2 Te Encapsulated in Mesoporous Carbon Spheres for High Performance Sodium Ion Batteries and Hybrid Capacitors.

Ternary topological insulators have attracted worldwide attention because of their broad application prospects in fields such as magnetism, optics, electronics, and quantum computing. However, their potential and electrochemical mechanisms in sodium ion batteries (SIBs) and hybrid capacitors (SIHCs) have not been fully studied. Herein, a composite material comprising vacancy-defects ternary topological insulator Bi 2 Se 2 Te encapsulated in mesoporous carbon spheres (Bi 2 Se 2 Te@C) is designed. Bi 2 Se 2 Te with ample vacancy-defects has a wide interlayer spacing to enable frequent insertion/extraction of Na + and boost reaction kinetics within the electrode. Meanwhile, the Bi 2 Se 2 Te@C with optimized yolk-shell structure can buffer the volume variation without breaking the outer protective carbon shell, ensuring structural stability and integrity. As expected, the Bi 2 Se 2 Te@C electrode delivers high reversible capacity and excellent rate capability in half SIB cells. Various electrochemical analyses and theoretical calculations manifest that Bi 2 Se 2 Te@C anode confirms the synergistic effect of ternary chalcogenide systems and suitable void space yolk-shell structure. Consequently, the full cells of SIB and SIHC coupled with Bi 2 Se 2 Te@C anode exhibit good performance and high energy/power density, indicating its widespread practical applications. This design is expected to offer a reliable strategy for further exploring advanced topological insulators in Na + -based storage systems.