3D Porous Graphene Nanostructure from a Simple, Fast, Scalable Process for High Performance Flexible Gel-Type Supercapacitors

A simple, fast, and scalable mix-and-heat process was developed for production of three-dimensional (3D) porous graphene nanostructure. The process involves only mixing and heating of starch and a graphene oxide (GO) suspension at 90 °C for 10 min to form 3D graphene monoliths, from which a three-dimensionally well-connected porous graphene nanostructure, starch/RGO, possessing a high specific surface area of 1519 m² g^–1 was obtained. The starch/RGO material was used as the electrode material to fabricate flexible, gel-type symmetric supercapacitors of outstanding capacitive performances, delivering a high energy density of 19.8 Wh kg^–1 at the power density of 0.5 kW kg^–1 and exhibiting an excellent high rate capability of a high power density of 9.9 kW kg^–1 at the energy density of 9.6 Wh kg^–1, among the highest for pristine carbon material based gel-type, symmetric supercapacitors. The cycling stability of the starch/RGO based supercapacitor was excellent, with a high specific capacitance retention rate of 80% after 8000 cycles at 10 A g^–1. The starch/RGO based supercapacitor exhibited outstanding mechanical stability with a retention rate of 90% in both energy and power densities at a large bending angle of 138° and functioned well in a wide temperature range environment

Catalytic Self-Limited Assembly at Hard Templates: A Mesoscale Approach to Graphene Nanoshells for Lithium–Sulfur Batteries

Hollow nanostructures afford intriguing structural features ranging from large surface area and fully exposed active sites to kinetically favorable mass transportation and tunable surface permeability. The unique properties and potential applications of graphene nanoshells with well-defined small cavities and delicately designed graphene shells are strongly considered. Herein, a mesoscale approach to fabricate graphene nanoshells with a single or few graphene layers and quite small diameters through a catalytic self-limited assembly of nanographene on <i>in situ</i> formed nanoparticles was proposed. The graphene nanoshells with a diameter of ca. 10–30 nm and a pore volume of 1.98 cm³ g^–1 were employed as hosts to accommodate the sulfur for high-rate lithium–sulfur batteries. A very high initial discharge capacity of 1520 mAh g^–1, corresponding to 91% sulfur utilization rate at 0.1 C, was achieved on a graphene nanoshell/sulfur composite with 62 wt % loading. A very high retention of 70% was maintained when the current density increased from 0.1 C to 2.0 C, and an ultraslow decay rate of 0.06% per cycle during 1000 cycles was detected