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 (MnO 2 ), i.e., NiMn-LDH@MnO 2 , assembled by NiMn-LDH nanoparticles and MnO 2 nanosheets was developed on nickel foam by facile electrodeposition and the subsequent hydrothermal reaction . The optimized NiMn-LDH@MnO 2 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@MnO 2 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.