Fluorine based additives have a tremendously beneficial effect on the performance of lithium ion batteries, yet the origin of this phenomenon is unclear. In this paper we show that the formation of a solid electrolyte interphase (SEI) on the anode surface in the first 5 charge / discharge cycles is affected by the stereochemistry of the electrolyte molecules on the anode surface starting at open circuit potential. We have studied an anode specific model system, the reduction of 1,2-diethoxy ethane with LiTFSI, lithium Bis(trifluoromethane)sulfonimide, as salt on amorphous silicon anode and compared the electrochemical response and SEI formation to its fluorinated version BTFEOE, Bis(2,2,2-trifluoroethoxy) ethane by sum frequency generation (SFG) vibrational spectroscopy under reaction conditions. Our SFG results suggest that the -CF3 end groups of the linear ether BTFEOE change its adsorption orientation on the a-Si surface at open circuit potential, leading to a better protective layer. Supporting evidence from ex situ scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) depth profiling measurements show that the fluorinated ether, BTFEOE, yields a smooth SEI on the a-Si surface and enables lithium ion to intercalate deeper into the a-Si bulk.
High-throughput and combinatorial approaches have been applied to the discovery of catalysts for selective low temperature CO oxidation/VOC removal using mixed CO/propylene feeds, and for the water-gas shift (WGS) reaction using real post-reformer feeds containing CO, CO 2 , H 2 O and H 2 . The screening approach was based on a hierarchy of qualitative and semi-quantitative primary screens for the discovery of hits, and quantitative secondary screens for hit confirmation, lead optimization and scale-up. For WGS, primary screening was carried out using scanning mass spectrometry. For CO oxidation and VOC removal, parallel IR thermography was the primary screen. Multi-channel fixed bed reactors equipped with imaging reflection FTIR spectroscopy or GC were used for secondary screening. Novel RuCoCe compositions were discovered and optimized for CO oxidation/VOC removal and the effect of doping was investigated for supported and bulk mixed oxide catalysts. For WGS, noble metal-free and Pt-doped CoFeRu mixed oxides as well as Pt on CeO 2 and Pt on CeO 2 /ZrO 2 were investigated and a new synergistic PtFeCe ternary composition was discovered. In these cases oxygen vacancies in the ceria lattice are believed to play a key role in the strong and synergistic Pt-Ce interaction. Alkaline metal doping was found to enhance the selectivity towards WGS by suppressing the unselective methanation side reaction and to increase the low temperature catalytic activity.
High-throughput approaches were applied to the discovery of more efficient catalysts for various applications in emissions control. The screening approach was based on a hierarchy of qualitative or semi-quantitative primary screens for discovery of hits and quantitative secondary screens for confirmation and scale-up of leads. In this work, primary screening was carried out by fast scanning mass spectrometry (SMS) for NO(x) abatement, low temperature CO oxidation, VOC removal, CO(x) methanation and the water gas shift (WGS) reaction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.