Facilely prepared nickel‑manganese layered double hydroxide-supported manganese dioxide on nickel foam for aqueous asymmetric supercapacitors with high performance

In order to achieve high-performance and long-lifespan supercapacitors, highly electrochemically active materials and rational structural design of are highly desirable. Herein, a hierarchical electrode structure of nickel (Ni)‑manganese (Mn) layered double hydroxide (NiMn-LDH)-supported manganese dioxide (MnO2), i.e., NiMn-LDH@MnO2, assembled by NiMn-LDH nanoparticles and MnO2 nanosheets was developed on nickel foam by facile electrodeposition and the subsequent hydrothermal reaction. The optimized NiMn-LDH@MnO2 electrode shows a high capacitance (~ 4336.8 F g−1 at 1.0 A g−1), good rate performance (~ 860 F g−1 at 60 A g−1) and long cycle stability (~ 83.2 % initial capacitance retention after 10,000 cycles at 20 A g−1). Furthermore, the aqueous asymmetric supercapacitors using the optimized NiMn-LDH@MnO2 cathode and activated carbon anode demonstrate a desirable energy density of ~104.51 W h kg−1 at 800.00 W kg−1, and good cycle stability with 86.8 % initial capacitance retention and about 100 % Coulomb efficiency after 22,000 cycles at 5.0 A g−1. The above results indicate that this study offers a meaningful exploration for manufacturing the energy storage devices with high comprehensive performance.