Tailoring Adaptive van der Waals Gap Evolution in Bi2Se3 via Weakly Coupled Copper Intercalation for Nondestructive Aqueous Potassium-Ion Storage

Aqueous potassium-ion batteries (APIBs) are promising for sustainable energy storage owing to their intrinsic safety, low cost, and environmental benignity. However, their practical application is hindered by sluggish K+ diffusion and unstable electrode structures. Herein, a weakly coupled copper-ion (Cu+) intercalation-enabled van der Waals gap modulation strategy is proposed to optimize the potassium storage performance of Bi2Se3. Distinct from conventional doping, Cu+ ions are preferentially inserted into the van der Waals gaps of Bi2Se3, enabling nondestructive interlayer regulation without significantly disturbing the intrinsic Bi–Se framework. Such weakly coupled intercalation effectively modulates interlayer interactions and the local electronic environment, thereby broadening K+ transport pathways and improving reaction kinetics. The optimized Cu0.108Bi2Se3 cathode delivers a high capacity of 124.6 mAh g–1 at a high current density of 10 A g–1, demonstrating competitive rate capability among reported Bi-based cathodes. The electrode achieves a capacity retention of 66.3% after 100 cycles at 2 A g–1. In addition, a full battery assembled with a Zn anode exhibits a capacity of 315.9 mAh g–1 at 100 mA g–1, demonstrating promising practical applicability. This work provides an effective strategy for interlayer modulation and offers new insights into designing safe, sustainable aqueous energy storage systems.