Graphene has become a very promising material for electrochemical supercapacitors that store electrical energy by polarization of the electrode (graphene) / electrolyte interface. The electrical energy storage performance of graphene-based electrochemical supercapacitors, however, remains limited by the low electronic density of states of graphene near the Fermi level.
Our work demonstrated that this limitation can be overcome by integrating carbon 60 (C60) fullerene and its monoadduct derivatives into graphene-based electrochemical supercapacitor electrodes. We developed a concept that allows the integration of the characteristic properties of C60 fullerene in three-dimensional (3D) graphene networks. In these composite materials, the graphene network provides high electrical conductivity and surface area while fullerenes add high electron affinity, thus boosting the electrical energy storage performance of the material. Guided by theory, we developed C60 monoadduct derivatives to optimize the graphene–fullerene interaction, specifically in the context of stability and charge transfer performance in an electrochemical environment. We demonstrated that the electrical energy storage capacity of the 3D graphene network is significantly improved upon by the addition of C60 and C60 monoadducts by providing additional acceptor states in the form of the low-lying lowest unoccupied molecular orbitals of C60 and its derivative. Using first-principles calculations, we studied the key factors that determine the electrical energy storage performance. We found that the graphene–fullerene hybrid electrode is a promising approach to overcoming the charge storage limitations of graphene-based supercapacitors.
The results of this project directly support Lawrence Livermore National Laboratory’s energy and climate mission focus area by providing a path forward to a new, all-carbon supercapacitor technology with lithium-ion battery-like charge storage performance and supercapacitor-like power performance by combining the high electrical conductivity of graphene with the high electron affinity of fullerene.
Cerón, M., et al. 2019. "Integration of Fullerenes as Electron Acceptors in 3D Graphene Networks: Enhanced Charge Transfer and Stability through Molecular Design." ACS Applied Materials & Interfaces 11 (32), 28818-28822. LLNL-JRNL-754189.
Zhan, C., et al. 2018. "Origins and Implications of Interfacial Capacitance Enhancements in C60-Modified Graphene Supercapacitors." ACS Applied Materials & Interfaces 10 (43), 36860-36865. LLNL-JRNL-754189.
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