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

Abstract

Abstract 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 LiFePO 4 /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.