In Situ Growth of δ-MnO2 Nanosheets on K+ Intercalation Nb2CT x MXene for Aqueous Zinc-Ion Battery Cathodes

Aqueous zinc-ion batteries (AZIBs) are regarded as a feasible option for large-scale energy storage, benefiting from intrinsic safety, resource availability, and cost-effectiveness. Nevertheless, their advancement is hindered by the sluggish ion-transport kinetics and poor structural stability of cathode materials during cycling. In this work, K+-intercalation Nb2CTx MXene was coupled with δ-MnO2 nanosheets via a mild water bath in situ growth strategy to prepare K-Nb2C@MnO2 heterojunction composite cathodes. Electrochemical evaluations revealed that the as-obtained composite delivers a high specific capacity of 367.51 mAh g−1 at 0.1 A g−1. Even under 3.0 A g−1, decent capacity retention can be obtained over 1000 continuous cycles, with the Coulombic efficiency stably kept above 96%. Electrochemical impedance spectroscopy measurements verified the dramatically decreased charge-transfer resistance and improved Zn2+ diffusion capability. Such improvements originate largely from the constructed heterointerfaces, which effectively modulate the overall electrochemical reaction kinetics. This work offers an effective pathway for engineering interlayer structures and enhancing interfacial activity, providing guidance for the design of niobium-based MXene composite cathodes in high-performance AZIBs.