Alloying-type anodes show capacity and density advantages for sodium/potassium-ion batteries (SIBs/PIBs), but they encounter serious structural degradation upon cycling, which cannot be resolved through conventional nanostructuring techniques. Herein, we present an in-depth study to reveal the intrinsic reason for the pulverization of bismuth (Bi) materials upon (de)alloying and report a novel particle-in-bulk architecture with Bi nanospheres inlaid in the bulk carbon (BiNC) to achieve durable Na/K storage. We simulate the volume-expansion-resistant mechanism of Bi during the (de)alloying reaction and unveil that the irreversible phase transition upon (de)alloying underlies the fundamental origin for the structural degradation of Bi anode, while a proper compressive stress (~10%) raised by the bulk carbon can trigger a "domino-like" Bi crystal recovering. Consequently, the as obtained BiNC exhibits a record high volumetric capacity (823.1 mAh cm-3 for SIBs, 848.1 mAh cm-3 for PIBs) and initial coulombic efficiency (95.3% for SIBs, 96.4% for PIBs), and unprecedented cycling stability (15000 cycles for SIBs with only 0.0015% degradation per cycle), outperforming the state-of-the-art literature. This work provides new insights on the undesirable structural evolution and proposes basic guidelines for design of the anti-degradation structure for alloy-type electrode materials.
Keywords: bismuth anode, domino-like phase recovering, sodium/potassium ion batteries, cycling stability.
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