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

Restricted by the poor ability of polymers to dissociate lithium salts and transport ions, solid-state polymer electrolytes (SPEs) show extremely low ionic conductivities (approximate to 10(-7)-10(-5) S cm(-1)) and transference number of lithium ions (t(Li+) approximate to 0.2-0.4) at 25 degrees C. Here, a novel polymer matrix of SPEs that simultaneously promotes lithium salt dissociation and ion transportation based on a high dielectric 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 -CH2CF2 polar groups; then, brings a strong electronegative end that dissociates Li+ from lithium salts. The all-trans conformation assures all fluorine atoms locate on one side of the chain, constructing ion hopping highways. As a result, the TerP/CoP (TC) SPE exhibits a high ionic conductivity (2.37 x 10(-4) S cm(-1)) and a quite large t(Li)(+) of 0.61 at 25 degrees C. The Li/TC SPE/Li symmetric cells cycle stably for more than half a year (>4500 h) and the LiNi0.8Co0.1Mn0.1O2/TC SPE/Li cell cycles steadily for 1000 and 600 cycles at 1 C and 2 C at 25 degrees C, respectively. This work paves a new way to prepare high-performance SPEs by simultaneously modulating dielectric constants and conformation of polymers.

Automated summary

A novel solid-state polymer electrolyte (SPE) is developed based on a high dielectric poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (TerP) and an all-trans conformational poly(vinylidene fluoride-trifluoroethylene) (CoP), which promotes the dissociation of lithium salts and ion transportation. The TerP/CoP (TC) SPE exhibits high ionic conductivity and lithium ion transference number at 25 degrees C, making it a promising candidate for high-performance SPEs.