posted on 2024-02-24, 00:03authored byAlexandros
J. Tsamopoulos, Zhen-Gang Wang
We construct a coarse-grained
molecular dynamics model based on
poly(ethylene oxide) and lithium bis(trifluoromethane)sulfonimide
salt to examine the combined effects of temperature and salt concentration
on the transport properties. Salt doping notably slows the dynamics
of polymer chains and reduces ion diffusivity, resulting in a glass
transition temperature increase proportional to the salt concentration.
The polymer diffusion is shown to be well represented by a modified
Vogel–Fulcher–Tamman (M-VFT) equation that accounts
for both the temperature and salt concentration dependence. Furthermore,
we find that, at any temperature, the concentration dependence of
the conductivity is well described by the product of its infinite
dilution value and a correction factor accounting for the reduced
segmental mobility with increasing salt concentration. These results
highlight the important role of polymer segmental mobility in the
salt concentration dependence of ion conductivity for temperatures
near and above the glass transition.