posted on 2020-09-01, 16:06authored byHuan Qin, Matthew J. Panzer
A series of zwitterionic
(ZI) copolymers, including both binary,
fully-ZI and ternary, partially-ZI copolymer variations, have been
successfully employed as scaffolds to support mechanically robust
ionic liquid-based gel (ionogel) electrolytes containing sodium bis(trifluoromethylsulfonyl)imide
salt. All of the synthesized ionogels, which were optically transparent
and freestanding without any covalent cross-links, contained 15 mol
% copolymer and displayed room-temperature ionic conductivities above
1 mS cm–1 while also exhibiting high compressive
elastic modulus values (0.7–11 MPa). The activation energy
of ionic conductivity of an ionogel with a fully-ZI copolymer scaffold
(18 kJ mol–1) was found to be noticeably lower than
that of the ionic liquid electrolyte solution itself (23 kJ mol–1), highlighting the positive role that ZI moieties
may play in aiding ion transport. NMR chemical shift analysis revealed
favorable interactions between sodium cations and both types of ZI
motifs employed here (sulfobetaine and phosphorylcholine). In addition,
the sodium-ion transference number value of a ternary copolymer-supported
ionogel electrolyte was determined to be larger compared to that of
the ionic liquid solution (0.19 vs 0.10, respectively).