Novel Ultra‐Stable 2D SbBi Alloy Structure with Precise Regulation Ratio Enables Long‐Stable Potassium/Lithium‐Ion Storage

The inferior cycling stabilities or low capacities of 2D Sb or Bi limit their applications in high‐capacity and long‐stability potassium/lithium‐ion batteries (PIBs/LIBs). Therefore, integrating the synergy of high‐capacity Sb and high‐stability Bi to fabricate 2D binary alloys is an intriguing and challenging endeavor. Herein, a series of novel 2D binary SbBi alloys with different atomic ratios are fabricated using a simple one‐step co‐replacement method. Among these fabricated alloys, the 2D‐Sb0.6Bi0.4 anode exhibits high‐capacity and ultra‐stable potassium and lithium storage performance. Particularly, the 2D‐Sb0.6Bi0.4 anode has a high‐stability capacity of 381.1 mAh g−1 after 500 cycles at 0.2 A g−1 (≈87.8% retention) and an ultra‐long‐cycling stability of 1000 cycles (0.037% decay per cycle) at 1.0 A g−1 in PIBs. Besides, the superior lithium and potassium storage mechanism is revealed by kinetic analysis, in‐situ/ex‐situ characterization techniques, and theoretical calculations. This mainly originates from the ultra‐stable structure and synergistic interaction within the 2D‐binary alloy, which significantly alleviates the volume expansion, enhances K+ adsorption energy, and decreases the K+ diffusion energy barrier compared to individual 2D‐Bi or 2D‐Sb. This study verifies a new scalable design strategy for creating 2D binary (even ternary) alloys, offering valuable insights into their fundamental mechanisms in rechargeable batteries. A novel 2D thin‐layer binary SbBi alloy is designed, which displays superior 2D structural stability, highly reversible alloying/dealloying, fast K/Li storage kinetics, and ultra‐long‐cycle stability in potassium/lithium‐ion batteries (PIBs/LIBs).