MnO₂ Nanoflower Intercalation on Ti₃C₂T_x MXene With Expanded Interlayer Spacing for Flexible Asymmetric Supercapacitors

ABSTRACT Supercapacitors are promising energy storage solutions known for their high‐power density, fast charge–discharge rates, and long cycle life. Recently, Ti 3 C 2 T x MXene, a member of the 2D MXene family, has emerged as a potential electrode material for supercapacitors. However, its limited interlayer spacing hinders broader applications. In this study, we introduce a novel δ‐MnO 2 @MXene heterostructure with expanded interlayer spacing, synthesized using a hydrothermal approach. This design enhances charge transfer efficiency and improves the contact between the components, significantly boosting supercapacitor performance. The unique nanoflower‐like structure of δ‐MnO 2 combined with MXene substantially improves capacitance retention and ion diffusion, surpassing the performance of each individual material. The sponge‐like architecture of δ‐MnO 2 increases accessible charge storage sites and widens the interlayer gaps in MXene, facilitating better ion migration. As a result, the δ‐MnO 2 @MXene electrode exhibits a capacitance 54 times greater than MXene alone (2.0 F g⁻¹), an impressive rate capability of 67.3% (after a 20‐fold increase in current density), and exceptional cycling stability, maintaining 93% of its capacity after 10,000 cycles. This novel δ‐MnO 2 @MXene heterostructure significantly enhances electrochemical performance, making it a promising candidate for advanced energy storage applications.