Dual-ion (K+/Cu2+) Intercalated δ-MnO2 as an Advanced Cathode Material for High Performance Aqueous Zinc-Ion Batteries

Manganese dioxide (MnO 2 ) is widely recognized as a potential cathode candidate for aqueous zinc-ion batteries (AZIBs) owing to its high theoretical capacity and suitable operating potential. However, its widespread application is restricted by intrinsic issues, including low electrical conductivity and slow Zn 2+ diffusion kinetics. Herein, a Cu 2+ /K + co-intercalated δ-MnO 2 cathode (denoted as KCu-MO) is synthesized via a simple one-step hydrothermal method. The as-prepared material features a three-dimensional hierarchical porous nanoflower architecture composed of interconnected ultrathin nanosheets, which provides rich active sites and alleviates volume variation upon repeated ion insertion/extraction processes. Meanwhile, the introduction of Cu 2+ and K + serves as interlayer pillars to strengthen structural integrity. Benefiting from dual-ion co-intercalation, the KCu-MO cathode delivers a specific capacity of 182 mA h g -1 at 1 A g -1 and exhibits outstanding long-term cycling stability with 84% capacity retention over 5000 cycles. Theory calculations suggest that the enhanced electrochemical performance stems from the improved electron conductivity and the reduced Zn diffusion kinetic barrier, which is consistent with the experimental observations. Furthermore, the related characterizations validate a reversible Zn 2+ /H + co-intercalation/deintercalation energy storage mechanism. This work provides an effective intercalation strategy for the design of MnO 2 cathodes toward high-performance AZIBs.