Facile synthesis of NiAl-LDH/MnO2 and NiFe-LDH/MnO2 composites for high-performance asymmetric supercapacitors

In this work, NiAl-LDH/MnO2 and NiFe-LDH/MnO2 composites are synthesized via a facile hydrothemal method, followed by loading of MnO2 through a redox reaction. MnO2 particles are loaded on the surface of LDH nanosheets, leading to the high electrochemical performance of the composites. The as-prepared NiAl-LDH/MnO2-6 exhibits a specific capacitance of 1092 F g−1 at 1 A g−1 and rate retention of 43.2% at 20 A g−1, which are higher than those of pure NiAl-LDH. Meanwhile, an asymmetric supercapacitor (ASC) with NiAl-LDH/MnO2-6 as a positive electrode and activated carbon (AC) as the negative electrode is assembled. It shows high capacitance (87.6 F g−1 at 1 A g−1), rate capability (58.4% at 10 A g−1), high energy density (30.4 Wh Kg−1) and excellent cyclic stability (90.1% after 10000 cycles at 10 A g−1). The other electrode material NiFe-LDH/MnO2-16 exhibits a specific capacitance of 1127 F g−1 at 1 A g−1, and remains 69.8% at 20 A g−1. Meanwhile, NiFe-LDH/MnO2-16//AC ASC also shows high capacitance (81.7 F g−1 at 1 A g−1), rate capability (57.5% at 10 A g−1), energy density (27.3 Wh Kg−1) and excellent cyclic stability (80.5% over 10000 cycles at 10 A g−1). These results indicate that the NiAl-LDH/MnO2 and NiFe-LDH/MnO2 hybrid electrodes could offer great promise in energy storage applications.