Influence of Counteranion on the Properties of Polymerized Ionic Liquids/Ionic Liquids Proton-Exchange Membranes

Abstract

In this work, we developed a family of protonexchange membranes based on the composites of polymerized ionic liquids and protic ionic liquids using 1-methyl-imidazolium as the cation. The influence of anion groups on physical properties was investigated. Among three composites with bis-(trifluoromethanesulfonyl)imide (TFSI), triflate (OTf), and H 2 PO 4 anions, the composite with TFSI anion presents the best ion conductivity. A synergistic effect has been observed for the composite with both TFSI and OTf mixed anion, which showed significantly enhanced ionic conductivity compared to the composites with either anion alone, reaching 1.47 mS/cm at 120 °C. This work highlights the combination of TFSI and OTf anion as a facile and efficient strategy for improving ionic conductivity and shows a promising prospect of polyILs/protic ILs composites as proton-conducting membrane materials.

Single-Ion Conducting Polymeric Protective Interlayer for Stable Solid Lithium-Metal Batteries

“…The DIPPI shows a minor decrease in modulus corresponding to the melting of the PEO crystalline region from 20 to 50 °C. With suppressed crystallinity, the SIPPI still possesses superior mechanical stability over the DIPPI, which is related to the presence of aromatic LiSTFSI and consistent with the DSC spectra . To quantify the mechanical property of the SIPPI and DIPPI, rectangle-shaped films are fabricated for tensile tests.…”

“…With suppressed crystallinity, the SIPPI still possesses superior mechanical stability over the DIPPI, which is related to the presence of aromatic LiSTFSI and consistent with the DSC spectra. 42 To quantify the mechanical property of the SIPPI and DIPPI, rectangle-shaped films are fabricated for tensile tests. The ultimate tensile stress and Young's modulus of the SIPPI film are determined to be 2.7 and 7.3 MPa, respectively, higher than those of the DIPPI, i.e., 0.43 and 1.0 MPa, respectively, due to the addition of the rigid LiSTFSI unit as discussed ahead.…”

Study of Ion Transport in Novel Protic Polymerized Ionic Liquids and Composites

“…As shown in Figure 4, the mobile cations in all materials were found to move faster than the anions over the whole temperature range, consistent with several previous studies. [17,26] This feature is highly desirable for proton conducting materials as it leads to higher proton transport (we note that the proton here may be carried along with the IL cation). More importantly, the combination of protic IL and protic PolyIL appeared to be an effective approach to enhance cation/anion relative mobility, a similar concept to the transference number in electrochemistry.…”

“…In our recent work, a family of cationic PDADMA backbone based PolyILs and their ILs composites have been reported. [ 17 ] The PolyIL, coupled with the [TFSI] anion, displayed the best ionic conductivity compared to those with [OTf], [H 2 PO 4 ], and [HSO 4 ] anions. Moreover, ionic conductivity at 120 °C increases to 1.47 × 10 –4 S cm −1 for a composite (with 25 wt% [MIm][TFSI]) compared with 10 –6 S cm −1 for neat [PDADMA][TFSI], due to higher cation and anion mobility.…”

Effect of Fumed Silica on Ion Conduction in Proton-Conducting Nanocomposites

“…10,11 Poly(diallyldimethylammonium) (PDADMA) backbone-based cationic PolyILs were mixed with imidazolium-based PILs to prepare composite membranes with single-anion and bi-anion species, with the intention to explore the effect of the anion chemistry on proton conduction. 10 The composite with both [TFSI] and [OTf] anion showed greater ionic conductivity and cation/anion diffusivity than those with either anion alone. In the case of the composites based on the anionic protic PolyIL, poly( ionic conductivity of composites was enhanced as the PIL content increased, whereas the mechanical strength of composites was diminished due to the strong plasticization effect of the PIL.…”