Pseudocapacitive Transparent/Flexible Supercapacitor based on Graphene wrapped Ni(OH)2 Nanosheet Transparent Film Produced using Scalable Bio-inspired Methods

High specific-capacity pseudocapacitive transition-metal-hydroxide (TMH) materials are desirable for future high performance transparent supercapacitors, but have been rarely reported previously. The successful synthesis of TMH materials with desired nanostructures is a key factor for their transparency. Here, Ni(OH)2 nanosheet transparent film (NNS-TF) was developed simply through a gas-liquid diffusion method. The nanostructures were enwrapped in graphene shells (NNS@Gr-TF) for using as transparent electrodes. The unique encapsulation structures build up rapid three-dimensional electron and ion transport pathways together with the underlying ITO layer. The specific areal capacitance (18.9 mF/cm2 at 0.1 mA/cm2) was greatly improved, at least a thousand times higher than the reported value for transparent devices based on planer CVD graphene, and ten times as that for 3D micro-structured graphene membrane.