High Dielectric Poly(vinylidene fluoride)‐Based Polymer Enables Uniform Lithium‐Ion Transport in Solid‐State Ionogel Electrolytes

Ionic liquids (ILs)‐incorporated solid‐state polymer electrolytes (iono‐SPEs) have high ionic conductivities but show non‐uniform Li+ transport in different phases. This work greatly promotes Li+ transport in polymer phases by employing a poly (vinylidene fluoride‐trifluoroethylene‐chlorotrifluoroethylene) [P(VDF‐TrFE‐CTFE), PTC] as the framework of ILs to prepare iono‐SPEs. Unlike PVDF, PTC with suitable polarity shows weaker adsorption energy on IL cations, reducing their possibility of occupying Li+‐hopping sites. The significantly higher dielectric constant of PTC than PVDF facilitates the dissociation of Li‐anions clusters. These two factors motivate Li+ transport along PTC chains, narrowing the difference in Li+ transport among varied phases. The LiFePO4/PTC iono‐SPE/Li cells cycle steadily with capacity retention of 91.5 % after 1000 cycles at 1 C and 25 °C. This work paves a new way to induce uniform Li+ flux in iono‐SPEs through polarity and dielectric design of polymer matrix. The P(VDF‐TrFE‐CTFE) shows lower adsorption energy on Pyr13+ from ionic liquids (ILs) than PVDF, which reduces the chance for Pyr13+ to occupy transport sites of Li+ and lower the Li+ migration barrier. In consequence, the Li+ transport in polymer phases is promoted, which narrows the gap of Li+ mobility between polymer phases with ILs and polymer‐ILs interfaces, contributing to uniform Li+ flux to inhibit the lithium dendrites’ growth.