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Results for “perfluoroether electrolyte”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Effects of Salt Aggregation in Perfluoroether Electrolytes

Electrolytes comprised of polymers mixed with salts have great potential for enabling the use of Li metal anodes in batteries for increased safety. Ionic conductivity is one of the key performance metrics of these polymer electrolytes and achieving high room-temperature conductivity remains a challenge to date. For a bottom-up design of the polymer electrolytes, we must first understand how the structure of polyelectrolytes on a molecular level determines their properties. Here, we use classical molecular dynamics to study the solvation structure and ion diffusion in electrolytes composed of a short-chain perfluoroether with LiFSI or LiTFSI salts. Density functional theory is also used to provide some insights into the structures and energies of the salt interactions with the perfluoroether. We observe the formation of aggregates of salts in the fluorinated systems even at low salt concentrations. The fluorine-fluorine attraction in the solvent is the governing factor for creating the salt aggregates. The aggregates’ size and lifetime change with concentration and anion. These simulations provide an insight into the structure and dynamics of perfluoroether based electrolytes that can be used to improve Li-ion batteries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Topological Considerations in Electrolyte Additives for Passivating Silicon Anodes with Hybrid Solid–Electrolyte Interphases

Unlike most anodes used in high energy density batteries, lithiated Si does not form long-lasting passivating solid-electrolyte interphases (SEI) during formation or on charge due to SEI delamination, reconstruction, or dissolution. As a result, electrolyte degradation is continuous and results in a permanent loss of the Li inventory, shortening the useful life of the battery. Here, in this study, we show that perfluoroether electrolyte additives featuring either sulfonyl fluorides or trifluorovinyl ethers, when introduced in prescribed amounts to locally superconcentrated electrolytes, exhibit preferential reactivity at Si during formation due to their higher reduction potential than salts and solvents, creating a hybrid SEI that is simultaneously enriched with LiF and organics tethered to the reactive functionality. While both reactive motifs are effective in creating a hybrid SEI, perfluoroether additives bearing sulfonyl fluorides show more substantial integration. More important, however, is the combined influence of additive topology on anchoring efficacy and tether flexibility between anchoring sites on SEI resiliency. Top-performing Si|LFP cells featuring ditopic additive-enriched SEI improve capacity retention by as much as 45% over 100 cycles when compared to additive-free cells.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Methods for manufacturing electrodes including fluoropolymer-based solid electrolyte interface layers

Methods for manufacturing electrodes include applying a fluoropolymer film to a lithium-based host material, defluorinating the fluoropolymer film by heating to produce a lithium electrode having a solid electrolyte interface (SEI) layer including defluorinated fluoropolymers and at least about 5 wt. % LiF. The fluoropolymers can include one or more of fluorinated ethylenepropylene, perfluoroalkoxy alkanes, vinylidenefluoride, and copolymers of perfluoromethylvinylether and tetrafluoroethylene. The fluoropolymers can include one or more fluorinated monomers, including hexafluoropropylene, tetrafluoroethylene, ethylene-tetrafluoroethylene, perfluoroethers, and vinylidene fluoride. The —CF 3 functional groups of the defluorinated fluoropolymers can be about 3 wt. % to about 10 wt. % of the SEI layer. The SEI layer can include about 30 wt. % to about 50 wt. % LiF. The method can include assembling a battery cell by disposing a battery separator between a cathode and the electrode, and disposing the battery separator, the cathode, and the electrode in an electrolyte.

Xiao, Xingcheng↗