Ultralong Cycle Life for Deep Potassium Storage Enabled by BiOCl/MXene van der Waals Heterostructures

Abstract Conversion/alloying‐type anodes are drawing attention due to their high theoretical capacities, but inferior reversibility, especially under low current densities, has hampered potential applications. Conventional strategies mainly focus on conversion/alloying processes, whereas the intercalation process is rarely analyzed. Herein, the intercalation process is correlated with conversion/alloying processes by ion dispersion states. BiOCl/Ti₃C₂T_x MXene van der Waals heterostructure is selected as a proof‐of‐concept system. Multifunctional MXenes not only contribute to atomic dispersion and boosted ion diffusion at the first cycle by constructing a novel heterostructure but serve as supporting frameworks to sustain long‐term structural stability. Consequently, a cell with BiOCl/MXene anode delivers an ultralong cycle‐life of running over ten months, maintaining a high capacity of 225 mAh g⁻¹ over 1300 cycles at 100 mA g⁻¹ and a retention of 81.3%. These findings verify that enhanced initial intercalation can facilitate higher reversibility and shed light on developing high‐performance conversion/alloying‐type anodes.