Heterointerface Seeding Accelerates Bi⁰/Bi³⁺ Phase Conversion for Ultrafast Aqueous Alkaline Batteries

Ultrafast aqueous alkaline batteries (AABs) require anodes capable of sustaining rapid multielectron redox kinetics under extreme current densities. Although bismuth oxides offer high theoretical capacities, their high-rate performance is constrained by the large nucleation barrier during phase transitions. This kinetic barrier remains unresolved by conventional charge-transport engineering. Herein, one-dimensional heterointerface-seeded Bi/Bi₂O₃@C nanowires are developed to regulate the phase-transition pathway. Ex situ/operando characterizations and theoretical analyses reveal that persistently retained Bi/Bi₂O₃ heterointerfaces serve as pre-existing nucleation sites, enabling bidirectional Bi⁰/Bi³⁺ conversion via interfacial regrowth rather than repeated homogeneous nucleation. This seeded conversion pathway substantially reduces phase-transition polarization, while the nitrogen-doped carbon shell provides continuous electron/OH^- transport pathways and suppresses structural degradation. Consequently, the Bi/Bi₂O₃@C anode delivers a specific capacity of 295.7 mAh g^-1 at 1 A g^-1 and maintains 123.1 mAh g^-1 even at 150 A g^-1, alongside a capacity retention of 82.4% after 1000 cycles at 100 A g^-1. This robust rate capability is preserved even at a high mass loading of 12.4 mg cm^-2. Full AAB cells paired with a CoOOH/Co(OH)₂/CoO cathode further demonstrate the device-level feasibility of the proposed architecture. This heterointerface-seeding strategy offers a general design principle for high-capacity electrode materials operating under ultrafast-charging conditions.