Controllable synthesis of aluminum doped peony-like α-Ni(OH)2 with ultrahigh rate capability for asymmetric supercapacitors

Abstract

Ion substitution and micromorphology control are two efficient strategies to ameliorate the electrochemical performance of supercapacitors electrode materials. Here, Al³⁺ doped α-Ni(OH)₂ with peony-like morphology and porous structure has been successfully synthesized through a facile one-pot hydrothermal process. The Al³⁺ doped α-Ni(OH)₂ electrode shows an ultrahigh specific capacitance of 1750 F g⁻¹ at 1 A g⁻¹, and an outstanding electrochemical stability of 72% after running 2000 cycles. In addition, the Al³⁺ doped α-Ni(OH)₂ electrode demonstrates an excellent rate capability (92% retention at 10 A g⁻¹). Furthermore, by using this unique Al³⁺ doped α-Ni(OH)₂ 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⁻¹ and 14 kW kg⁻¹). This work proves that synthesizing an Al³⁺ doped structure is an effective means to improve the electrochemical properties of α-Ni(OH)₂. This scheme could be extended to other transition metal hydroxides to enhance their electrochemical performance.