Converting a metal-coordinating polymer to a polymerized ionic liquid improves Li+ transport

Solid polymer electrolytes (SPEs) with mechanical strength and reduced
flammability may also enable next-generation Li+ batteries with higher
energy densities. However, conventional SPEs have fundamental limitations
in terms of Li+ conductivity. While an imidazole functionalized polymer
(PMS-Im) has been previously shown to have ionic conductivity related to
the imidazole-Li+ coordination, herein we demonstrate that quaternization
of this polymer to form an analogous imidazolium functionalized polymer
(PMS-Im+) more efficiently solvates lithium salts and plasticizes the
polymer. In addition, inverse Haven ratios as high as 10 indicate
positively correlated Li+ transport, possibly due to percolation of
nanochannels that significantly improve battery-relevant conductivity.
From these combined effects, Li+ conductivity in PMS-Im+ (2.1*10-5 S/cm)
is over an order of magnitude greater than in PMS-Im at 90 °C (1.6*10-6
S/cm).