Lawrence Livermore National Laboratory

November 30, 2018

A snapshot of the simulation model representing the C60/graphene electrode in an aqueous electrolyte. The charging behavior of the hybrid electrode is also shown in comparison with that of graphene.

Understanding and controlling the electrical response at a complex electrode–electrolyte interface is key to the development of next-generation supercapacitors and other electrochemical devices. While it is largely acknowledged that the capacitive performance of these devices is governed by both the quantum capacitance of the electrode and the electric double layer capacitance (EDL) of the electrolyte, the fundamental nature of the relationship between these two contributions remains enigmatic.

In a recent study, researchers from LLNL, UC Riverside, and Japan’s National Institute of Advanced Industrial Science and Technology explored the role of EDL formation and its interplay with quantum capacitance in graphene-based supercapacitors. In addition to pristine graphene, the researchers investigated a novel C60-modified graphene supercapacitor material, which promises higher charge-storage capacity. Beyond the expected enhancement in the quantum capacitance, they found that the introduction of C60 molecules significantly alters the EDL response. They traced these changes in EDL to the unique surface morphology and charge localization character of the hybrid electrode, which in turn improves and dominates the overall capacitive performance of the device. This study highlights the complex interplay among surface morphology, electronic structure, and interfacial capacitance, suggesting general improvement strategies for optimizing carbon-based supercapacitor materials.

The study was funded by the Laboratory Research and Development Program (17-ERD-017).

[C. Zhan, T.A. Pham, M.R. CerĂ³n, P.G. Campbell, V. Vedharathinam, M. Otani, D. Jiang, J. Biener, B.C. Wood, and M. Biener, Origins and Implications of Interfacial Capacitance Enhancements in C60-Modified Graphene Supercapacitors, ACS Appl. Mater. Interfaces, available online on October 8, 2018, doi: 10.1021/acsami.8b10349.]