Flexible Solid-State Supercapacitors with Enhanced Performance from Hierarchically Graphene Nanocomposite Electrodes and Ionic Liquid Incorporated Gel Polymer Electrolyte

High energy density, durability, and flexibility of supercapacitors are required urgently for the next generation of wearable and portable electronic devices. Herein, a novel strategy is introduced to boost the energy density of flexible soild-state supercapacitors via rational design of hierarchically graphene nano-composite (GNC) electrode material and employing an ionic liquid gel polymer electrolyte. The hierarchical graphene nanocomposite consisting of graphene and polyaniline-derived carbon is synthesized as an electrode material via a scalable process. The meso/microporous graphene nanocomposites exhibit a high specific capacitance of 176 F g(-1) at 0.5 A g-(1) in the ionic liquid 1-ethyl-3- methylimidazolium tetrafluoroborate (EMIBF4) with a wide voltage window of 3.5 V, good rate capability of 80.7% in the range of 0.5-10 A g(-1) and excellent stability over 10 000 cycles, which is attributed to the superior conductivity (7246 S m(-1)), and quite large specific surface area (2416 m(2) g(-1)) as well as hierarchical meso/micropores distribution of the electrode materials. Furthermore, flexible solid-state supercapacitor devices based on the GNC electrodes and gel polymer electrolyte film are assembled, which offer high specific capacitance of 180 F g(-1) at 1 A g(-1), large energy density of 75 Wh Kg(-1), and remarkable flexible performance under consecutive bending conditions.