Ion Dynamics of Monomeric Ionic Liquids Polymerized In Situ within Silica Nanopores

Abstract

Polymerized ionic liquids are a promising class of versatile solid-state electrolytes for applications ranging from electrochemical energy storage to flexible smart materials that remain limited by their relatively low ionic conductivities compared to conventional electrolytes. Here, we show that the in situ polymerization of the vinyl cationic monomer, 1-ethyl-3vinylimidazolium with the bis(trifluoromethanesulfonyl)imide counteranion, under nanoconfinement within 7.5 ± 1.0 nm diameter nanopores results in a nearly 1000-fold enhancement in the ionic conductivity compared to the material polymerized in bulk. Using insights from broadband dielectric and Raman spectroscopic techniques, we attribute these results to the role of confinement on molecular conformations, ion coordination, and subsequently the ionic conductivity in the polymerized ionic liquid. These results contribute to the understanding of the dynamics of nanoconfined molecules and show that in situ polymerization under nanoscale geometric confinement is a promising path toward enhancing ion conductivity in polymer electrolytes.

Ultra-stable all-solid-state sodium-metal batteries enabled by perfluoropolyether-based electrolytes

“…We ascribe the relatively lower Tg to confinement effects on the dynamics of the EO-Na + complex, which is in good agreement with previously reported hybrid electrolyte systems. 38,39 As shown in Figure 1c, the introduction of the PFPE block into PEG leads 9 to the formation of self-assembled body-centered cubic (BCC) microstructures. The 10 presence of confinement in the microstructures allows the physical properties of 11 polymer electrolyte materials such as Tg, mobile diffusivity and molecular packing density to be modulated.…”

Ultra-stable all-solid-state sodium-metal batteries enabled by perfluoropolyether-based electrolytes

“…1b) which facilitates the ion transport. 38 Another bene t of introducing PFPE into the polymer backbone is seen by the increased Na + transference number (t Na+ ). As shown in Fig.…”

“…We ascribe the relatively lower T g to con nement effects on the dynamics of the EO-Na + complex, which is in good agreement with previously reported hybrid electrolyte systems. 38,39 As shown in Fig. 1c, the introduction of the PFPE block into PEG leads to the formation of self-assembled bodycentered cubic (BCC) microstructures.…”

“…[40][41][42][43] For instance, a larger free volume and separated phase with enhanced dynamics are suggested in con ned silica nano pores. 38,44 Similarly, when NaFSI is added into EO10-PFPE, the EO-Na + complex will be mainly located in the PEG domains, therefore the con nement effects in self-assembled structures will provide more free volume, resulting in a lower T g . 38 Meanwhile the selfassembled BCC structures of EO10-PFPE electrolyte are maintained at higher temperatures with an orderdisorder transition temperature (T ODT ) at 100°C, as determined by dynamic mechanical thermal analysis (DMTA, Figure S4).…”

“…38,44 Similarly, when NaFSI is added into EO10-PFPE, the EO-Na + complex will be mainly located in the PEG domains, therefore the con nement effects in self-assembled structures will provide more free volume, resulting in a lower T g . 38 Meanwhile the selfassembled BCC structures of EO10-PFPE electrolyte are maintained at higher temperatures with an orderdisorder transition temperature (T ODT ) at 100°C, as determined by dynamic mechanical thermal analysis (DMTA, Figure S4). Figure 1d shows the frequency sweep storage (G') and loss modulus (G") of EO10-PFPE electrolytes at 80 o C. G' is distinctly greater than G" in the full frequency window (10 − 2 -10 2 Hz), implying a solid-like behavior of the EO10-PFPE electrolyte even at 80 o C. In addition, the storage modulus G' is closer to the loss modulus G" at lower frequencies, indicating the soft behavior of the electrolyte, potentially allowing the PFPE electrolyte to adapt and achieve good contact with the electrodes, even with the unpredictable volume changes that may occur during cycling.…”