Cation-Trapping Engineering Tailors Bismuth Selenide to Enable Superior Multivalent Ion Storage via an Optimized Synergistic Dual-Reaction Mechanism

Aqueous multivalent-ion batteries have garnered considerable attention as a promising alternative to lithium-ion batteries, offering advantages such as low cost, high specific capacity, enhanced safety, and environmental sustainability. However, the development of efficient cathodes remains challenging, constrained by sluggish multivalent-ion diffusion and pronounced structural degradation. Here, we introduce cation-trapping engineering to tailor the topological insulator Bi₂Se₃ (Zn_xBi₂Se₃), enhancing the electrochemical performance by activating additional active sites and expanding the interlayer spacing. Furthermore, comprehensive experimental characterizations reveal that Zn_xBi₂Se₃ stores Cu²⁺ via a "synergistic dual-reaction mechanism", attaining rapid reaction kinetics and high capacity. Accordingly, an excellent rate performance (350 mAh g^-1 at 1.0 A g^-1 and 241.3 mAh g^-1 at 10 A g^-1) and a long cycling life (10,000 cycles at 10 A g^-1) are obtained. Moreover, the prepared quasi-solid-state flexible pouch battery demonstrates superior performance and the ability to operate under various destructive conditions, offering potential utilization in flexible electronic devices.