Conformational Regulation of Dielectric Poly(Vinylidene Fluoride)-Based Solid-State Electrolytes for Efficient Lithium Salt Dissociation and Lithium-Ion Transportation

摘要

Restricted by the poor ability of polymers to dissociate lithium salts and transportions, solid-state polymer electrolytes (SPEs) show extremely low ionicconductivities (≈10~（?7）–10~（?5） S cm~（?1）) and transference number of lithium ions(tLi+ ≈0.2–0.4) at 25 ℃. Here, a novel polymer matrix of SPEs that simultaneouslypromotes lithium salt dissociation and ion transportation based on a highdielectric poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (TerP)and an all-trans conformational poly(vinylidene fluoride-trifluoroethylene) (CoP),is developed. The high dielectric constant increases the polarity of -CH_2CF_2polar groups; then, brings a strong electronegative end that dissociates Li+ fromlithium salts. The all-trans conformation assures all fluorine atoms locate on oneside of the chain, constructing ion hopping highways. As a result, the TerP/CoP(TC) SPE exhibits a high ionic conductivity (2.37 × 10~(?4) S cm~(?1)) and a quite largetLi+ of 0.61 at 25 ℃. The Li/TC SPE/Li symmetric cells cycle stably for more thanhalf a year (>4500 h) and the LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2/TC SPE/Li cell cycles steadilyfor 1000 and 600 cycles at 1 C and 2 C at 25 ℃, respectively. This work pavesa new way to prepare high-performance SPEs by simultaneously modulatingdielectric constants and conformation of polymers.