High-performance cobalt carbonate hydroxide nano-dot/NiCo(CO3)(OH)2 electrode for asymmetric supercapacitors

Highlights: • By adding cobalt compound, NiCo(CO)₃(OH)₂ nanowires are separately grown without agglomeration. • The nano-scale Co₂(CO₃)(OH)₂ is distributed in NiCo(CO₃)(OH)₂ nanowire arrays. • The NiCo(CO)₃(OH)₂ electrode shows a great specific capacity of 1288.2 mAh g⁻¹ at a current density of 3 A g⁻¹. Binder-free mesoporous NiCo(CO₃)(OH)₂ nanowire arrays were grown using a facile hydrothermal technique. The Co₂(CO₃)(OH)₂ in NiCo(CO₃)(OH)₂ nanowire arrays was well-decorated as nano-dot scale (a few nanometer). In addition, increasing cobalt content in nickel compound matrix, NiCo(CO₃)(OH)₂ nanowire arrays were separately uniformly grown without agglomeration on Ni foam, providing a high specific surface area to help electrolyte access and ion transfer. The enticing composition and morphology of the NiCo(CO₃)(OH)₂ nanowire exhibit a superior specific capacity of 1288.2 mAh g⁻¹ at a current density of 3 A g⁻¹ and excellent cycling stability with the capacity retention of 80.7% after 10,000 cycles. Furthermore, an asymmetric supercapacitor composed of the NiCo(CO₃)(OH)₂ composite as a positive electrode and the graphene as a negative electrode presented a high energy density of 35.5 W h kg⁻¹ at a power density of 2555.6 W kg⁻¹ and satisfactory cycling stability with 71.3% capacity retention after 10,000 cycles. The great combination of the active nano-dot Co₂(CO₃)(OH)₂ and the individually grown NiCo(CO₃)(OH)₂ nanowires made it a promising electrode material for asymmetric supercapacitors. A well-developed nanoarchitecture of the nano-dot Co₂(CO₃)(OH)₂ decorated NiCo(CO₃)(OH)₂ composite could pave the way for an excellent electrode design for high-performance supercapacitors.