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Until now, few sp2 carbon materials simultaneously exhibit superior performance for specific surface area (SSA) and electrical conductivity at bulk state. Thus, it is extremely important to make such materials at bulk scale with those two outstanding properties combined together. Here, we present a simple and green but very efficient approach using two standard and simple industry steps to make such three-dimensional graphene-based porous materials at the bulk scale, with ultrahigh SSA (3523 m2/g) and excellent bulk conductivity. We conclude that these materials consist of mainly defected/wrinkled single layer graphene sheets in the dimensional size of a few nanometers, with at least some covalent bond between each other. The outstanding properties of these materials are demonstrated by their superior supercapacitor performance in ionic liquid with specific capacitance and energy density of 231 F/g and 98 Wh/kg, respectively, so far the best reported capacitance performance for all bulk carbon materials.

Because of advantages such as excellent electronic conductivity, high theoretical specific surface area, and good mechanical flexibility, graphene is receiving increasing attention as an additive to improve the conductivity of sulfur cathodes in lithium-sulfur (Li-S) batteries. However, graphene is not an effective substrate material to confine the polysulfides in cathodes and stable the cycling. Here, we designed and synthesized a graphene-based layered porous carbon material for the impregnation of sulfur as cathode for Li-S battery. In this composite, a thin layer of porous carbon uniformly covers both surfaces of the graphene and sulfur is highly dispersed in its pores. The high specific surface area and pore volume of the porous carbon layers not only can achieve a high sulfur loading in highly dispersed amorphous state, but also can act as polysulfide reservoirs to alleviate the shuttle effect. When used as the cathode material in Li-S batteries, with the help of the thin porous carbon layers, the as-prepared materials demonstrate a better electrochemical performance and cycle stability compared with those of graphene/sulfur composites.

A high‐performance graphene oxide (GO)‐doped ion gel (P(VDF‐HFP)‐EMIMBF4‐GO gel) is prepared by exploiting copolymer (poly(vinylidene fluoride‐hexafluoro propylene), P(VDF‐HFP)) as the polymer matrix, ionic liquid (1‐ethyl‐3‐methylimidazolium tetrafluoroborate, EMIMBF4) as the supporting electrolyte, and GO as the ionic conducting promoter. This GO‐doped ion gel demonstrates significantly improved ionic conductivity compared with that of pure ion gel without the addition of GO, due to the homogeneously distributed GO as a 3D network throughout the GO‐doped ion gel by acting like a ion “highway” to facilitate the ion transport. With the incorporation of only a small amount of GO (1 wt%) in ion gel, there has been a dramatic improvement in ionic conductivity of about 260% compared with that of pure ion gel. In addition, the all‐solid‐state supercapacitor is fabricated and measured at room temperature using the GO‐doped ion gel as gel polymer electrolyte, which demonstrates more superior electrochemical performance than the all‐solid‐state supercapacitor with pure ion gel and the conventional supercapacitor with neat EMIMBF4, in the aspect of smaller internal resistance, higher capacitance performance, and better cycle stability. These excellent performances are due to the high ionic conductivity, excellent compatibility with carbon electrodes, and long‐term stability of the GO‐doped ion gel.

Aiming at preventing restacking of individual graphene sheets by using a simple green hydrothermal route, we have introduced carbon nanotubes to act as the spacer in fabricating a three-dimensional (3-D) hierarchical structure with graphene sheets. These 3-D hierarchical structure materials have been used to fabricate supercapacitor devices, and a high specific capacitance of 318 F/g for graphene with an energy density of 11.1 (W h)/ kg has been achieved.

A series of sp(2) carbon materials with different specific surface area (SSA) and controlled pore size distribution (PSD) were synthesized at large scale through a facile and low-cost method. The SSA and PSD of these carbon materials were controlled by using different carbon sources and preparation methods. With different total and effective SSA (E-SSA) and PSD, the impacts on their capacitance performance were investigated thoroughly, which demonstrated that both E-SSA and PSD played the most important roles in their capacitance performance. Furthermore, theoretical modeling was performed, and the results are in agreement with the experimental results for the influence of E-SSA and PSD on their capacitance performance. Based on these, a general model using the slit/cylindrical NL-DFT approach is proposed for the estimation of the specific capacitance of sp(2) carbon materials, which offers a simple but reliable method to predict the capacitance performance of these materials, thus speeding up the design and screening of the materials for high-performance supercapacitor and other surface area related devices.

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