Researchers from the Korea Advanced Institute of Science and Technology (KAIST) and SK Innovation have used urea-reduced graphene oxide (URGO) to build lithium ion capacitors (LICs) that deliver a specific energy density of approximately 106 Wh kgtotal−1 and a specific power density of approximately 4200 W kgtotal−1 with perfect capacity retention up to 1,000 cycles. These values are far superior to those of previously reported LICs and supercapacitors, they noted in a paper published in the journal ChemSusChem, and suggested that appropriately treated graphene can be a promising electrode material for LICs.
Lithium ion capacitors (LICs) have recently drawn considerable attention because they utilize the advantages of supercapacitors (high power) and lithium ion batteries (high energy). However, the energy densities of conventional LICs, which consist of a pair of graphite and activated carbon electrodes, are limited by the small capacities of the activated carbon cathodes. To overcome this limitation, we have engaged urea-reduced graphene oxide.
The amide functional groups generated during the urea reduction facilitate the enolization processes for reversible Li binding, which improves the specific capacity by 37% compared to those of conventional systems such as activated carbon and hydrazine-reduced graphene oxide.—Lee et al.
Lee, J. H., Shin, W. H., Ryou, M.-H., Jin, J. K., Kim, J. and Choi, J. W. (2012), Functionalized Graphene for High Performance Lithium Ion Capacitors. ChemSusChem. doi: 10.1002/cssc.201200549