Self‐Adaptive Bismuth Composite Anode for High‐Performance Potassium‐Ion Batteries

Abstract Bismuth (Bi)‐based anode materials have gained significant attention in potassium‐ion batteries (PIBs) due to their promising theoretical gravimetric and volumetric capacity. However, Bi‐based anode suffers from significant volumetric expansion during potassiation/depotassiation, bringing stress/strain accumulation and the resultant pulverization. In this work, a stable Bi‐based anode material is designed by embedding Bi nanoparticles in red phosphorus via ball‐milling. Amorphous BiPO₄ is formed uniformly in situ, which induces self‐adaptive expansion and contraction behavior during potassiation/depotassiation and therefore effectively buffers the volume change and assures the particle integrity. Molecular dynamics (MD) calculation reveals that the incorporation of BiPO₄ enhances the electron affinity of Bi@P@BiPO₄@C with the electrolyte, promoting the formation of a homogeneous solid electrolyte interphase (SEI). Moreover, the presence of BiPO₄ enhances electron accumulation in the bonding region between Bi@BiPO₄ and the TEP electrolyte, leading to stronger adsorption and improved interfacial stability of Bi@P@BiPO₄@C in the TEP electrolyte compared to Bi@P@C. As a result, the designed Bi‐based anode exhibits a high capacity retention of 95.9% after 1700 cycles at 0.5 A g⁻¹. In a full‐cell configuration, a stable cycling performance is also achieved. This study presents a straightforward and effective strategy for enhancing Bi utilization as high‐performance anodes in PIBs.