Flexible and ITO-free asymmetric energy storage devices based on graphene/Ni(OH)2 nanocomposites

Abstract

Asymmetric energy storage devices were developed using thin films of reduced graphene oxide (rGO) and Ni(OH)2 nanocomposite as cathode, and activated carbon (AC) as anode. The films were prepared using the liquid/liquid interfacial route and were fully characterized by spectroscopic, microscopic and electrochemical techniques. The rGO/Ni(OH)2 nanocomposite thin film exhibited thickness of 112 ± 20 nm, while the AC films were presented in the micrometric range. Rigid and flexible devices were developed using indium-doped thin oxide (ITO)/glass or single-walled carbon nanotubes thin film/plastic as transparent electrodes, respectively. The rigid devices showed high capacities (e.g. 168 mA h g−1 at 4.94 A g−1) and high charge-discharge stability after 2000 cycles (75% of the initial capacity at 8.24 A g−1). The flexible device exhibited a lower capacity, corresponding to 25% of the capacity of the rigid device at 0.82 A g−1, which could be improved to 54% when the plastic electrode was previously treated with the deposition of metallic contacts over it.