Preparation of core–shell structural single ionic conductor SiO2-Li+ and its application in PVDF–HFP-based composite polymer electrolyte

Graphical abstract: Cycle stability and coulombic efficiency curves of Li/PE/LiCoO2 cell at different rates, (A): Pure PVDF–HFP GPE; (B): SiO2 doped PVDF–HFP-based CPE; (C): SiO2-Li+ doped PVDF–HFP-based CPE. Highlights: ► SiO2-Li+ was successfully was synthesized by polymerization and ion exchange. ► SiO2-Li+ doped PVDF–HFP based polymer electrolyte was fabricated by phase inversion method. ► Mechanism of ionic conductivity follows Arrhenius relation. ► SiO2-Li+ modified membrane showed excellent physicochemical and electrochemical properties. ► The fabricated Li/As-prepared electrolyte/LiCoO2 (graphite) cell shows excellent rate and cyclic performances. - Abstract: Core–shell structural single ionic conductor SiO2-Li+ was successfully synthesized from vinyltriethoxysilane, sodium p-styrenesulfonate and LiOH·H2O by hydrolysis, polymerization and ion exchange and confirmed by TEM and FT-IR. The poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP)-based composite polymer electrolyte (CPE) membrane doped with SiO2-Li+ was prepared by phase inversion method and the desirable CPE was obtained after being activated in liquid electrolyte. The physicochemical properties of the CPE were characterized by SEM, XRD, TG, and electrochemical measurements. The results show that the CPE membrane presents uniform surface with abundant interconnected micro-pores and possesses excellent mechanical performance with high decomposition temperature about 450 °C; and adding SiO2-Li+ into matrix remarkably decreases the crystallinity but enhances ionic conductivity of the CPE membrane; the ionic conductivity and lithium ion transference number at room temperature are up to 3.885 mS cm−1 and 0.4374, respectively, and the reciprocal temperature dependence of ionic conductivity of as-prepared CPEs follows Vogel–Tamman–Fulcher relation. The battery properties of the assembled cells using CPE doped with SiO2-Li+ as electrolyte show excellent rate and cycle performance, which is partly attributed to the improved interfacial performance between the electrolyte and electrodes and partly to enhanced electrochemical working window and lithium ion transference number.