Electrodeposition of polyaniline on three-dimensional graphene hydrogel as a binder-free supercapacitor electrode with high power and energy densities

The construction of a 3D graphene-based hybrid electrode with an optimized porous structure remains an attractive topic. Herein, we used the highly conductive graphene hydrogel (GH) with a well-defined 3D macroporous structure as a support to electrodeposite polyaniline (PANI), aimed to improve the energy density of GH-based capacitor electrode without deteriorating its high power capability. The as-prepared GH/PANI heterostructure with thin PANI layer conformally coated on the GH framework totally retains the native hydrogel pore structure and its high surface area, which facilitates the effective electron and ion transport within the electrode and thus endows GH/PANI composite electrode with excellent electrochemical properties such as a specific capacitance of 710 F g(-1) at 2 A g(-1) and 73% capacitance retention upon a current increase to 100 A g(-1). Moreover, the assembled symmetric supercapacitor device based on GH/PANI heterostructure electrode delivers a maximum energy density and power density of 24 W h kg(-1) and 30 kW kg(-1,) respectively, and also exhibits a good cycling stability with 86% capacitance retention after 1000 cycles. These findings demonstrate the importance and great potential of GH-based heterostructure in the development of high-performance energy-storage systems.