Investigation of the Electrochemical Properties of Polymer–LiX–Ionic Liquid Ternary Systems

Abstract

The electrochemical properties of ternary systems that consist of a polymer, a lithium salt, and an ionic liquid that shares the same anion (TFSI, bis(trifluoromethansulfonyl)imide) are reported and compared. The investigation involved two different polymers (PVdF-HFP and PTFE) that were selected because of their common use in lithium-based electrochemical devices. It was found that PVdF-HFP swelled by the ionic liquid used in the work while porous PTFE remained inert. The ternary electrolytes showed interesting ionic conductivities. However, the presence of fluorinated polymers resulted in poor interfacial properties with lithium metal electrodes.

New high-throughput methods of investigating polymer electrolytes

“…Although the "soft gels" formed free standing films, they suffered from liquid release or "sweating" under pressure, a problem that has been noted in the case of methylpyrrolidinium-TFSI in PVdF-HFP. [19] The conductivity results showed trends in composition that were generally in accordance with those found by Jiang et al using conventional methods, i.e. the conductivity decreased at high polymer content due to the viscosity increase.…”

Safer Electrolytes for Lithium‐Ion Batteries: State of the Art and Perspectives

“…Following the first approach, further studies showedv ery promising resultsfor such electrolyte systems by using avariety of ILs and replacing the PEO matrix, for instance, with "inactive" PVdF-HFP, [240][241][242][243][244][245][246][247] poly(urethane acrylate), [248] cross-linked polymers, [248][249][250][251][252] polymer blends, [253,254] or polymerici onic liquids (PILs). [255][256][257][258][259] Concerning the utilization of "inactive" polymerm atrices, such as PVdF-HFP, the enhanced conductivity for ac ontrolled amount of added IL was assigned to the increased number of chargec arriers, as supported by the presence of strong electron-withdrawing functionalg roups,s uch as ÀCÀF( and their high dielectric constant, e = 8.4);t his leads to extendedl ithium salt dissolution, and thus, compensates for decreased ion mobility due to increased viscosity.…”

(Invited) Long-Term Cyclability of Lithium Metal Electrodes in Ionic Liquid-Based Electrolytes at Room Temperature

“…These issues support for an excellent long-term stability of the interface formed between the lithium metal electrode and the electrolyte based on PYR 14 FSI, even at medium-high temperatures (80°C). It is to note that the 0.1LiFSI-0.9PYR 14 FSI electrolyte exhibited at 20°C one of the lowest and, at the same time, of the most time-stable interfacial resistance values ever reported for any kind of room temperature highly conductive electrolyte (13,16,(47)(48)(49)(50).…”