期刊
CARBON
卷 129, 期 -, 页码 104-118出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.carbon.2017.12.001
关键词
Energy storage; Carbide-derived carbon; Ionic liquid; Neutron scattering; Self-diffusion; Supercapacitor; Pair distribution function; Surface chemistry; Molecular dynamics; Interface
资金
- Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center - U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences
- DOE Office of Science Graduate Student Research Fellowship (SCGSR)
We investigate the aggregation, diffusion, and resulting electrochemical behavior of ionic liquids inside carbon electrodes with complex pore architectures and surface chemistries. Carbide-derived carbons (CDCs) with bimodal porosities and defunctionalized or oxidized electrode surfaces served as model electrode materials. Our goal was to obtain a fundamental understanding of room-temperature ionic liquid ion orientation, mobility, and electrosorption behavior. Neat 1-octyl-3-methylimidazolium bis(-trifluoromethylsulfonyl) imide confined in CDCs was studied using an integrated experimental and modeling approach, consisting of quasielastic neutron scattering, small-angle neutron scattering, X-ray pair distribution function analysis, and electrochemical measurements, which were combined with molecular dynamics simulations. Our analysis shows that surface oxygen groups increase the diffusion of confined electrolytes. Consequently, the ions become more than twice as mobile in oxygen-rich pores. Although greater self-diffusion of ions translates into higher electrochemical mobilities in oxidized pores, bulk-like behavior of ions dominates in the larger mesopores and increases the overall capacitance in defunctionalized pores. Experimental results highlight strong confinement and surface effects of carbon electrodes on electrolyte behavior, and molecular dynamics simulations yield insight into diffusion and capacitance differences in specific pore regions. We demonstrate the significance of surface defects on electrosorption dynamics of complex electrolytes in hierarchical pore architectures of supercapacitor electrodes. (C) 2017 Elsevier Ltd. All rights reserved.
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