Abstract
We investigated the influence of water molecules on the diffusion, dynamics, and electrosorption of a room temperature ionic liquid (RTIL), [BMIm+][Tf2N-], confined in carbide-derived carbon with a bimodal nanoporosity. Water molecules in pores improved power densities and rate handling abilities of these materials in supercapacitor electrode configurations. We measured the water-dependent microscopic dynamics of the RTIL cations using quasielastic neutron scatting (QENS). The ionic liquid demonstrated greater mobility with increasing water uptake, facilitated by the nanoporous carbon environment, up to a well-defined saturation point. We concluded that water molecules displaced RTIL ions attached to the pore surfaces and improved the diffusivity of the displaced cations. This effect consequently increased capacitance and rate handling of the electrolyte in water-containing pores. Our findings suggest the possible effect of immiscible co-solvents on energy and power densities of energy storage devices, as well as the operating viability of nonaqueous supercapacitor electrolytes in humid environments.
| Original language | English |
|---|---|
| Article number | 035402 |
| Journal | Physical Review Materials |
| Volume | 1 |
| Issue number | 3 |
| DOIs | |
| State | Published - Aug 11 2017 |
Funding
This work was supported as part of the Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Work at ORNL's Spallation Neutron Source was supported by the U.S. Department of Energy, Office of Basic Energy Sciences. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for U.S. DOE under Contract No. DE-AC05-00OR22725. Experiments on HFBS at NIST Center for Neutron Research (NCNR) were supported in part by the National Science Foundation under Agreement No. DMR-1508249. Certain commercial material suppliers are identified in this paper to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose.