Flexible Solid‐State Supercapacitor Based on Graphene‐based Hybrid Films

A flexible solid-state asymmetric supercapacitor based on bendable film electrodes with 3D expressway-like architecture of graphenes and “hard nano-spacer” is fabricated via an extended filtration assisted method. In the designed structure of the positive electrode, graphene sheets are densely packed, and Ni(OH)2 nanoplates are intercalated in between the densely stacked graphenes. The 3D expressway-like electrodes exhibit superior supercapacitive performance including high gravimetric capacitance (≈573 F g-1), high volumetric capacitance (≈655 F cm-3), excellent rate capability, and superior cycling stability. In addition, another hybrid film of graphene and carbon nanotubes (CNT) is fabricated as the negative electrodes for the designed asymmetric device. In the obtained graphene@CNT films, CNTs served as the hard spacer to prevent restacking of graphene sheets but also as a conductive and robust network to facilitate the electrons collection/transport in order to fulfill the demand of high-rate performance of the asymmetric supercapacitor. Based on these two hybrid electrode films, a solid-state flexible asymmetric supercapacitor device is assembled, which is able to deliver competitive volumetric capacitance of 58.5 F cm-3 and good rate capacity. There is no obvious degradation of the supercapacitor performance when the device is in bending configuration, suggesting the excellent flexibility of the device.