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

Abstract 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‐Sb 0.6 Bi 0.4 anode exhibits high‐capacity and ultra‐stable potassium and lithium storage performance. Particularly, the 2D‐Sb 0.6 Bi 0.4 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.