In Situ Formed Amorphous Bismuth Sulfide Cathodes with a Self‐Controlled Conversion Storage Mechanism for High Performance Hybrid Ion Batteries

Abstract Conversion‐type electrodes offer a promising multielectron transfer alternative to intercalation hosts with potentially high‐capacity release in batteries. However, the poor cycle stability severely hinders their application, especially in aqueous multivalence‐ion systems, which can fundamentally impute to anisotropic ion diffusion channel collapse in pristine crystals and irreversible bond fracture during repeated conversion. Here, an amorphous bismuth sulfide (a‐BS) formed in situ with unprecedentedly self‐controlled moderate conversion Cu²⁺ storage is proposed to comprehensively regulate the isotropic ion diffusion channels and highly reversible bond evolution. Operando synchrotron X‐ray diffraction and substantive verification tests reveal that the total destruction of the Bi─S bond and unsustainable deep alloying are fully restrained. The amorphous structure with robust ion diffusion channels, unique self‐controlled moderate conversion, and high electrical conductivity discharge products synergistically boosts the capacity (326.7 mAh g⁻¹ at 1 A g⁻¹), rate performance (194.5 mAh g⁻¹ at 10 A g⁻¹), and long‐lifespan stability (over 8000 cycles with a decay rate of only 0.02 ‰ per cycle). Moreover, the a‐BS Cu²⁺‖Zn²⁺ hybrid ion battery can well supply a stable energy density of 238.6 Wh kg⁻¹ at 9760 W kg⁻¹. The intrinsically high‐stability conversion mechanism explored on amorphous electrodes provides a new opportunity for advanced aqueous storage.