High capacitance and cycling stability of flexible-asymmetric-supercapacitor based on hierarchical NiAlP/NiAl-LDHs@MXene electrodes

Abstract

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 lamellar interwoven 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 and 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.