Future technology requires electrical energy storage systems to have much larger storage capability, rapid charge/discharge cycling and improved endurance. Research at the U.S. Department of Energy's Lawrence Livermore National Laboratory (LLNL) shows that electrical charge-induced changes in the structure and bonding of graphitic carbon electrodes may one day improve batteries, supercapacitors and other storage systems needed to meet the burgeoning demands of consumer, industrial and green technologies.

Because these complex processes can change significantly as the system is charged and discharged, researchers have increasingly focused on how to look inside an operating energy storage system, from atomic through micron-length scales.

Graphitic supercapacitors may be ideal model systems to probe interfacial phenomena because they are relatively stable chemically, extensively characterized experimentally and theoretically, and are interesting technologically. The LLNL research team used its recently developed 3D nanographene (3D-NG) bulk electrode material as a model graphitic material.

"Our newly developed X-ray adsorption spectroscopy capability allowed us to detect the complex, electric-field induced changes in electronic structure that graphene-based supercapacitor electrodes undergo during operation. Analysis of these changes provided information on how the structure and bonding of the electrodes evolve during charging and discharging," says Jonathan Lee, a LLNL scientist and corresponding author of a paper scheduled to appear in the March 4 edition of the journal, Advanced Materials. This opens a window toward more efficient electrochemical energy storage systems.