MnO2 Nanoflower Intercalation on Ti3C2Tx 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, Ti₃C₂T_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-MnO₂@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-MnO₂ combined with MXene substantially improves capacitance retention and ion diffusion, surpassing the performance of each individual material. The sponge-like architecture of δ-MnO₂ increases accessible charge storage sites and widens the interlayer gaps in MXene, facilitating better ion migration. As a result, the δ-MnO₂@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-MnO₂@MXene heterostructure significantly enhances electrochemical performance, making it a promising candidate for advanced energy storage applications.