Rational design and synthesis of nickel-cobalt-manganese trimetallic hydroxides with micro-flower like for high-performance asymmetric supercapacitors

The construction of high energy density and porous micro-nano structure is suitable for fast electron/ion transport, which motivates us to design electrode materials with hierarchical structures. However, the synthesis route of multi-metal hydroxides is still restricted due to the complexity and high cost. Herein, we use a rational design constructing nickel-cobalt-manganese hydroxides (Ni–Co–Mn–OH) micro-flower structure by using the one-pot hydrothermal. The Ni–Co–Mn–OH is consisting of ultrathin stacking nanosheets with a three-dimensional multi-order micro-flower structure. And its internal nanoporous channels can stimulate electron/ion transfer. Toward the application in supercapacitor, when the molar ratio of Ni and Mn is 9.69:1, the prepared electrode presented superior capacitance performance (1135 F g−1 at 1 A g−1) and excellent rate performance 97% retention at 20 A g−1) in the three electrode system. Moreover, the asymmetric supercapacitor was also fabricated, exhibiting excellent capacitance of 115 F g−1 at 1 A g−1, high energy density of 54.375 Wh·kg−1 at a power density of 0.3758 kW kg−1. And the maximum power density could reach 7.5 kW kg−1 and the energy density at this time was 12.08 Wh·kg−1. [Display omitted] •The pore size of H-6 mainly distributed in mesoporous structure at around 3.0 and 30 nm.•H-6 displayed 1135 F g−1 high specific capacitance as the electrode for supercapacitor at the current density of 1 A g−1.•The excellent cycling stability of H-6 only decreased 3% after 5000 cycles.•An asymmetric supercapacitor displayed an excellent energy density of 54.375 Wh·kg−1 at the power density of 0.3758 kW kg−1.