3 years ago

Design of 3D Graphene-Oxide Spheres and Their Derived Hierarchical Porous Structures for High Performance Supercapacitors

Design of 3D Graphene-Oxide Spheres and Their Derived Hierarchical Porous Structures for High Performance Supercapacitors
Zhuangnan Li, Srinivas Gadipelli, Zhengxiao Guo, Yuchen Yang
Graphene-oxide (GO) based porous structures are highly desirable for supercapacitors, as the charge storage and transfer can be enhanced by advancement in the synthesis. An effective route is presented of, first, synthesis of three-dimensional (3D) assembly of GO sheets in a spherical architecture (GOS) by flash-freezing of GO dispersion, and then development of hierarchical porous graphene (HPG) networks by facile thermal-shock reduction of GOS. This leads to a superior gravimetric specific capacitance of ≈306 F g−1 at 1.0 A g−1, with a capacitance retention of 93% after 10 000 cycles. The values represent a significant capacitance enhancement by 30–50% compared with the GO powder equivalent, and are among the highest reported for GO-based structures from different chemical reduction routes. Furthermore, a solid-state flexible supercapacitor is fabricated by constructing the HPG with polymer gel electrolyte, exhibiting an excellent areal specific capacitance of ≈220 mF cm−2 at 1.0 mA cm−2 with exceptional cyclic stability. The work reveals a facile but efficient synthesis approach of GO-based materials to enhance the capacitive energy storage. Hierarchical porous graphene networks derived by facile thermal reduction of predesigned 3D graphene-oxide spheres lead to exceptional performance for supercapacitors. A gravimetric specific capacitance of 306 F g−1 at 1 A g−1 and excellent capacity retention of 93% after 10 000 cycles are readily achieved.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/smll.201702474

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