High Capacitance and Cycling Stability of Flexible-Asymmetric-Supercapacitor Based on Hierarchical Mxene@Nial-Layered Double Hydroxides Electrodes

To address the limitations of flexible asymmetric supercapacitor (FASC) with poor stability and low capacitance, highly electrochemically active materials and rational structural design are urgently needed. Herein, a  heterostructure of NiAlP/NiAl-LDHs@MXene composite electrode with high capacitance and cycling stability was fabricated by hydrothermal reaction and electrostatic assembly. As a result, the NiAlP/NiAl-LDHs@MXene hybrid electrode delivers a high specific capacitance of 3.88 F cm-2(2589.3 F g-1) and excellent cycling stability (91.1% capacity retention after 8000 cycles) at 1.0 mA cm-2. In addition, the fabricated NiAlP/NiAl-LDHs@MXene//AC FASC exhibits a higher power density of 1800 W kg-1 at the energy density of 81.1 Wh kg-1. It is worth noting that FASC still exhibits good structural integrity and outstanding stability (96.9% capacity retention after 10000 cycles) after being folded at different angles. Comparative experiments and density functional theory (DFT) reveal that the synergistic effect of NiAlP@NiAl-LDHs and Ti3C2Cl2 MXene can provides a large number of hierarchical channels and generates more active sites, which accelerates the rapid migration of electrons and ions during charge-discharge. This work not only provides a promising electrode material for energy storage, but also opens a new idea for the selection of electrode materials for flexible wearable electronic devices.