Interlayer engineering of MXene nanosheets with polypyrrole-coated manganese dioxide for high-performance asymmetric supercapacitors

To address the challenges of poor cycling stability in manganese dioxide (MnO₂) and the tendency of MXene nanosheets to aggregate, this study designed and synthesized a ternary MXene/MnO₂@polypyrrole (PPy) composite for high-performance supercapacitor electrodes. Initially, conductive PPy was uniformly coated onto MnO₂ nanotubes through in situ polymerization, forming a core–shell structure. This coating effectively buffers the volumetric variations during electrochemical cycling. Subsequently, these MnO₂@PPy nanotubes were integrated with MXene nanosheets to construct a three-dimensional heterostructure. This architecture not only prevents the restacking of MXene but also establishes continuous conductive pathways throughout the electrode. Detailed material characterization confirms the formation of the target composite and demonstrates strong interfacial interactions between its components. The MXene/MnO₂@PPy electrode exhibits superior electrochemical performance, achieving a remarkable specific capacitance of 466.9 F g −1 when evaluated at a slow scan rate of 1 mV s −1 . This value is approximately double that of a pure MXene electrode. Furthermore, an asymmetric supercapacitor was assembled, employing this composite as the cathode and activated carbon as the anode. The assembled device delivers a notable energy density of 23.5 Wh kg −1 while demonstrating superior cycling durability. The electrode maintains a high capacitance retention ratio of 88.6% following 5000 consecutive galvanostatic charge-discharge cycles. This work demonstrates a rational material design strategy that successfully integrates multiple functional components, offering a synergistic effect for advanced energy storage applications.