Controllable synthesis of aluminum doped peony-like α-Ni(OH) with ultrahigh rate capability for asymmetric supercapacitors.

Ion substitution and micromorphology control are two efficient strategies to ameliorate the electrochemical performance of supercapacitors electrode materials. Here, Al doped α-Ni(OH) with peony-like morphology and porous structure has been successfully synthesized through a facile one-pot hydrothermal process. The Al doped α-Ni(OH) electrode shows an ultrahigh specific capacitance of 1750 F g at 1 A g, and an outstanding electrochemical stability of 72% after running 2000 cycles. In addition, the Al doped α-Ni(OH) electrode demonstrates an excellent rate capability (92% retention at 10 A g). Furthermore, by using this unique Al doped α-Ni(OH) as the positive electrode and a hierarchical porous carbon (HPC) as the negative electrode, the assembled asymmetric supercapacitor can demonstrate a high energy/power density (49.6 W h kg and 14 kW kg). This work proves that synthesizing an Al doped structure is an effective means to improve the electrochemical properties of α-Ni(OH). This scheme could be extended to other transition metal hydroxides to enhance their electrochemical performance.