Preparation and electrochemical properties of NiCo-layered double hydroxide supercapacitor.

• A series of NiCo-LDHs were prepared by a novel ammonia diffusion method at room temperature. • The NiCo-LDH0.6 exhibits excellent electrochemical properties due to its large surface area and perfect honeycomb structure. • The optimal honeycomb-like NiCo-LDH shows a high specific capacitance of 1463.2F·g−1 at 1 A·g−1. Layered double hydroxides (LDHs) are favorable pseudocapacitance electrodes due to their adjustable composition and low cost. Here, a series of NiCo-LDHs were prepared by a novel ammonia diffusion method at room temperature. Compared with other synthesis methods, this method is a simple, green, original and effective method. The morphology, structure, and elemental composition of NiCo-LDH electrode materials were characterized and their electrochemical properties were tested. The optimal honeycomb NiCo-LDH shows a specific capacitance (Cs) of 1463.2F·g−1 at 1 A·g−1, and the rate capacity is 75.2 % at 20 A·g−1. Particularly, the Cs is still 87.9 % after 2000 charge–discharge cycles at a high current density of 20 A·g−1. In addition, the hybrid supercapacitor with NiCo-LDH//activated carbon (AC) could show an energy density of 23.4 Wh·kg−1 at a power density of 900 W·kg−1, along with 73.4 % capacity retention after 5000 cycles. [ABSTRACT FROM AUTHOR]