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Decoupling the Ionic Conductivity and Elastic Modulus of Gel Electrolytes: Fully Zwitterionic Copolymer Scaffolds in Lithium Salt/Ionic Liquid Solutions
Author(s) -
D'Angelo Anthony J.,
Panzer Matthew J.
Publication year - 2018
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201801646
Subject(s) - materials science , ionic conductivity , electrolyte , lithium (medication) , chemical engineering , copolymer , ionic liquid , elastic modulus , conductivity , polymer , inorganic chemistry , polymer chemistry , composite material , organic chemistry , chemistry , electrode , catalysis , engineering , endocrinology , medicine
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 ( t L i +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.