A critical barrier to overcome in the development of solid‐state electrolytes for lithium batteries is the trade‐off between sacrificing ionic conductivity for enhancement of mechanical stiffness. Here, a physically cross‐linked, polymer‐supported gel electrolyte consisting of a lithium salt/ionic liquid solution featuring a fully zwitterionic (ZI) copolymer network is introduced for rechargeable lithium‐based batteries. The ZI scaffold is synthesized using a 3:1 molar ratio of 2‐methacryloyloxyethyl phosphorylcholine and sulfobetaine vinylimidazole, and the total polymer content is varied between 1.1 and 12.5 wt%. Room‐temperature ionic conductivity values comparable to the base liquid electrolyte (≈1 mS cm−1) are achieved in ZI copolymer‐supported gels that display compressive elastic moduli as large as 14.3 MPa due to ZI dipole–dipole cross‐links. Spectroscopic characterization suggests a change in the Li+coordination shell upon addition of the zwitterions, indicative of strong Li+···ZI group interactions. Li+transference number measurements reveal an increase in Li+conductivity within a ZI gel electrolyte (
Recent experimental results have demonstrated that zwitterionic ionogel comprised of polyzwitterion (polyZI)-supported lithium salt-doped ionic liquid exhibits improved conductivities and lithium transference numbers than the salt-doped base ionic liquid electrolyte (ILE). However, the underlying mechanisms of such observations remain unresolved. In this work, we pursued a systematic investigation to understand the impact of the polyZI content and salt concentration on the structural and dynamic properties of the poly(MPC) ionogel of our model polyZI ionogel, poly(2-methacryloyloxyethyl phosphorylcholine) [poly(MPC)] supported LiTFSI/N-butyl-N-methylpyrrolidinium TFSI base ionic liquid electrolyte. Our structural analyses show strong lithium–ZI interaction consistent with the physical network characteristic observed in the experiments. An increase in polyZI content leads to an increased fraction of Li+ ions coordinated with the polyZI. In contrast, an increase in salt concentration leads to a decreased fraction of Li+ ions coordinated with the polyZI. The diffusivities of the mobile ions in the poly(MPC) ionogel were found to be lower than the base ILE in agreement with experiments at T > 300 K. Analysis of ion transport mechanisms shows that lithium ions within the poly(MPC) ionogel travel via a combination of structural, vehicular diffusion, as well as hopping mechanism. Finally, the conductivity trend crossover between the poly(MPC) ionogel and the base ILE was rationalized via a temperature study that showed that the base ILE ions are influenced more by the variation of temperature when compared to the poly(MPC) ions.
more » « less- Award ID(s):
- 2225167
- PAR ID:
- 10534980
- Publisher / Repository:
- AIP
- Date Published:
- Journal Name:
- The Journal of Chemical Physics
- Volume:
- 160
- Issue:
- 2
- ISSN:
- 0021-9606
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract nearly doubles). ZI gels display enhanced stability against Li metal, dendrite suppression, and suitable charge–discharge performance in a graphite|lithium nickel cobalt manganese oxide cell. Fully ZI polymer networks in nonvolatile, ionic liquid‐based electrolytes represent a promising approach toward realizing highly conductive, mechanically rigid gels for lithium battery technologies. -
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1063/5.0176149
