VS2/Bi2S3 Spring‐Type Heterointerfaces Hollow Microspheres with Spatial Confinement and Vacancy Defects for Fast‐Charging and Ampere‐Hour Scale Pouch Sodium‐Ion Hybrid Capacitors

This work reports a VS₂/Bi₂S₃ spring-type heterointerfaces hollow microspheres with spatial confinement and sulfur vacancies defects. Benefiting from the unique spring-type heterointerfaces design and vacancy effect mitigates volume expansion, improves charge transfer and pseudocapacitive storage, the assembled pouch SIHC exhibits a high specific energy of 120 Wh kg⁻¹ with fast-charging at 10 C, and 95.5% capacity retention after 1000 cycles.

Abstract

Optimizing electrochemical kinetics by regulation ion/charge transfer efficiency and stabilizing the electrode structure of electrode materials is crucial to maximize the rapid charging and long cycling sodium-ion storage. Herein, VS₂/Bi₂S₃ spring-type heterointerfaces hollow microspheres with spatial confinement and sulfur vacancy defects are synthesized as a fast-charging anode for sodium-ion hybrid capacitors (SIHCs). The experimental studies coupled with density functional theory calculations verify that the strong coupling between VS₂ and Bi₂S₃ induces a stable built-in electric field, largely promoting the charge and sodium-ion transfer efficiency. Sulfur vacancy defects at the heterointerfaces produce additional sodium-ion pseudocapacitive storage, which improves the reversible capacity and large-rate fast charge performance of the VS₂/Bi₂S₃ electrode. Finite element analysis and in situ expansion test confirm that the spring-type heterostructured hollow microspheres formed by flat-morphology VS₂ and zigzag-morphology Bi₂S₃ stacking mitigate the lattice expansion and contraction during sodium-ion insertion/extraction, accommodate the mechanical stresses, and maintain the integrity of the heterojunction interface. When employed in coin SIHC, it achieves a high energy/power density of 135 Wh kg⁻¹/22 kW kg⁻¹, and an ultralong life of 50 000 cycles; the assembled pouch SIHC (1 Ah) demonstrates a high specific energy of 120 Wh kg⁻¹ with fast-charging at 10 C, and 95.5% capacity retention after 1000 cycles.