Facile assembly of 2D Ni-based coordination polymer nanosheets as battery-type electrodes for high-performance supercapacitors.

Large-scale Ni-based nano-sized coordination polymers (Ni-nCPs) are facilely constructed by a self-assembled approach at room temperature and atmosphere pressure. In this strategy, we use only the environmentally friendly solvents of water and ethanol, and the synthesis of 2D Ni-nCPs via a self-assembly route appears close to the "green chemistry" concept. In addition, the morphologies of the Ni-nCPs can be easily adjusted by the water/ethanol ratio. Owing to its unique 2D ultrathin nature and large specific surface area, Ni-nCPs-1 achieves a great number of channels for the transport of electrons and ions and electrochemically redox active sites for a faradaic reaction. Therefore, battery-type Ni-nCPs-1 electrodes have a bright prospect in energy storage, and can reach an outstanding specific capacitance value as high as 1066.9 F g-1 at 1 A g-1. Additionally, the asymmetric supercapacitor (Ni-nCPs-1//active carbon) displays a high energy density of 47.9 W h kg-1 at a power density of 440 W kg-1 and an excellent long-term cycle stability. This work may open up a new path in advanced electrode materials for efficient and real-time energy storge applications.