Synergistic Vacancy and Amorphization Engineering in BiOCl Heterostructures Enable Ultrafast Potassium‐Ion Storage

Abstract Slow diffusion kinetics and structural stability have hindered the development of anode materials employed in potassium ion batteries. In this work, the oxygen vacancy (O V ) concentration in BiOCl is modulated by varying the solvothermal time to improve the anode material properties. Specifically, O V ‐rich BiOCl synthesized with a reaction time of 10 hours (BiOCl‐10 h) exhibit expanded interlayer spacing and the presence of amorphous regions. These structural features synergistically improve both electron/ion transport kinetics and electrode stability. Ex situ transmission electron microscopy and in situ X‐ray diffraction reveal a dual reaction mechanism: an irreversible conversion of BiOCl to Bi, followed by a reversible Bi‐K alloying process. This unique structural configuration effectively disperses the K insertion‐induced stresses and promotes the formation of Bi intermediates for sustained alloying reactions, achieving a high initial Coulombic efficiency (78.2%). Remarkably, BiOCl‐10 h delivers 285.2 mAh g −1 at 50 A g −1 while maintaining 82.5% versus 1 A g −1 , exhibiting notable high‐rate behavior compared to recently reported works. Long‐term cycle at 20 A g −1 retains 205 mAh g −1 after 1500 cycles, highlighting structural robustness. Practical application is demonstrated through a fully battery‐powered LED screen and continuous light emission from light strips. This research provides novel concepts for the study of layered anode materials.