Room Temperature Synthesis of Vertically Aligned Amorphous Ultrathin NiCo‐LDH Nanosheets Bifunctional Flexible Supercapacitor Electrodes

Developing a simple scalable method to fabricate electrodes with high capacity and wide voltage range is desired for the real use of electrochemical supercapacitors. Herein, we synthesized amorphous NiCo‐LDH nanosheets vertically aligned on activated carbon cloth substrate, which was in situ transformed from Co‐metal–organic framework materials nano‐columns by a simple ion exchange process at room temperature. Due to the amorphous and vertically aligned ultrathin structure of NiCo‐LDH, the NiCo‐LDH/activated carbon cloth composites present high areal capacities of 3770 and 1480 mF cm−2 as cathode and anode at 2 mA cm−2, and 79.5% and 80% capacity have been preserved at 50 mA cm−2. In the meantime, they all showed excellent cycling performance with negligible change after >10 000 cycles. By fabricating them into an asymmetric supercapacitor, the device achieves high energy densities (5.61 mWh cm−2 and 0.352 mW cm−3). This work provides an innovative strategy for simplifying the design of supercapacitors as well as providing a new understanding of improving the rate capabilities/cycling stability of NiCo‐LDH materials. A simple scalable method involving the transformation of cobalt–metal–organic framework materials precursors has been adopted to produce vertically aligned NiCo‐LDH on activated carbon cloths. The designed electrode composed of amorphous ultrathin nanosheets serves as a bifunctional electrode for high voltage and high energy density aqueous supercapacitors.