Rational Design of Graphene-Based Aerogels for High-Performance Supercapacitors

Recently, graphene (GN) aerogels with porous three-dimensional (3D) structures have attracted intensive attention because of their ultrahigh specific surface area, high conductivity and multiple electronic transport pathways. Up to date, a variety of strategies coupled with various chemical or physical cross-linkers, such as organic binders [1], ion linkages [2] and ion coordination [3], have been applied to fabricate 3D graphene gels. However, most of the cross-linkers (e.g. organic reagents and metal ions) used are environmentally harmful or expensive, and, more importantly, unexpected impurities and elements could be introduced in the resultants. On the other hand, although graphene electrode can fundamentally provide a specific capacitance up to 550 F/g [4], the specific capacity achieved so far is still far from the theoretical value, which is largely limited by the unexpected restacking of graphene sheets to greatly reduce its available surface. Various spacers, such as carbonaceous materials [5] and metal oxides [6], have been employed into the GN to inhibit the restacking and improve capacitive performance. However, graphene/metal oxide composites usually suffer a low rate performance and poor stability, and the performance of graphene/carbon was still unsatisfied due to the low specific capacity of spacers.

Herein, we have demonstrated a novel, simple, low-cost and green approach to produce graphene-based aerogels via the self-assembly of graphene oxide sheets in the alcohols. The as-prepared aerogles have shown special internal structures formed by self-assemble graphene sheets, whereby both macro- and mesopores for ionic transport have been achieved. In order to improve the electrochemical performance of the graphene aerogels, we have introduced ordered porous carbon (PC) with high specific capacity as an effective spacer to rationally design GN/PC aerogels [7]. The ordered porous carbon (PC) with high specific surface area and good capacitance was introduced as a spacer to efficiently inhibit the restacking of graphene (GN) sheets, which has significantly enhanced the specific surface area and facilitated the transmission of ions and electrons in the as-synthesized porous hybrid structure. The all-state-solid electrode fabricated by the as-prepared GN/PC aerogels  presented excellent flexibility, and exhibited high specific capacity and good rate performance in polyvinyl acetate/KOH gel electrolyte. Implication of the specific capacities of ~187 F g^-1 at 1 A g^-1 and 140 F g^-1 at 10 A g^-1 suggests that the GN/PC aerogels promised great potentials in the development of lightweight high-performance flexible energy storage devices.

References

[1] M.A. Worsley, P.J. Pauzauskie, T.Y. Olson, J. Biener, J.H. Satcher, Jr. and T.F. Baumann, J. Am. Chem. Soc., 132, 14067 (2010).

[2] Z.H. Tang, S.L. Shen, J. Zhuang and X. Wang, Angew. Chem., Int. Ed., 49, 4603 (2010).

[3] H. Bai, C. Li, X.L. Wang and G.Q. Shi, J. Phys. Chem. C 115, 5545 (2011).

[4] M.D. Stoller, S.J. Park, Y.W. Zhu, J.H. An and R.S. Ruoff, Nano Lett., 8, 3498 (2008).

[5] M. Beidaghi and C.L. Wang, Adv. Funct. Mater., 22, 4501 (2012).

[6] J.J. Liang, Y. Huang, J.Y. Oh, M. Kozlov, D. Sui1, S.L. Fang, R.H. Baughman, Y.F. Ma and Y.S. Chen, Adv. Funct. Mater., 21, 3778 (2011).

[7] L.Z. Fan, S.Y. Qiao, W.L. Song, M. Wu, X.B. He and X.H. Qu, Electrochim. Acta, 2013, 105, 299–304.