Connectivity, ionic interactions, and migration in a fast-ion-conducting polymer-in-salt electrolyte based on poly(acrylonitrile) and LiCF3SO3

The ionic conductivity of a polymeric fast-ion-conductor based on ${\mathrm{LiCF}}_{\mathrm{3}}{\mathrm{SO}}_{\mathrm{3}}$ salt and poly(acrylonitrile), ${\mathrm{[CH}}_{\mathrm{2}}{\mathrm{CH(CN)]}}_n\mathrm{),}$ is enhanced by ∼5 orders of magnitude when the composition approaches the “polymer-in-salt” regime; i.e., when the salt content increases from N:Li=12:1 to 1.2:1 (or ∼70 wt % of salt). This is in contrast to common salt-in-polymer electrolytes where a conductivity maximum typically is encountered at intermediate compositions. We suggest that connectivity effects in a microscopically phase segregated material may influence the long-range migration of charge carriers. Conductivity data are augmented with Raman spectroscopic investigations, thus probing microscopic details regarding the state of the dissolved salt.