The Technology

Supercapacitors are an energy storage technology rapidly gaining traction in a variety of applications (e.g., transportation and renewable energy) due to their high-power density, ability to charge/discharge rapidly, and extreme durability. The choice of electrode material greatly affects the supercapacitor's electrochemical performance. For optimal performance, supercapacitor electrode materials need to have high porosity with a mixture of micro- and meso-pores, high electrical conductivity, and high density. While most carbon materials possess only one or two of these characteristics, NETL’s 3DG meets all of these requirements.

NETL’s invention entails powder comprised of 3DG and synthetic fluoropolymer polytetrafluoroethylene (PTFE)  compressed (4 tons/cm²) into free-standing electrode pellets with varying mass loadings (i.e., amount of active material per unit area). Electron microscopy showed that the compression used to fabricate NETL’s 3DG into electrodes did not adversely affect the structure or porosity, relative to unprocessed 3DG. The 150–770 micron-thick electrodes retained the hierarchical, interconnected, network of graphene sheets, as well as the macro- and meso-porosity of the original graphene.

When used as a supercapacitor electrode at commercial level mass loadings (e.g. > 10 mg/cm²), NETL’s 3DG exhibited an increase of specific capacitance, areal capacitance, and gravimetric energy density by 46-53% over the standard commercial material.  Finally, NETL’s 3DG retained ∼80% of its capacitance after 20,000 cycles of operation.