Preparation of core-shell structural single ionic conductor SiO_2@Li~+ and its application in PVDF-HFP-based composite polymer electrolyte

摘要

Core-shell structural single ionic conductor SiO_2@Li~+ was successfully synthesized from vinyltriethoxysilane, sodium p-styrenesulfonate and LiOH·H_2O 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 SiO_2@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 micropores and possesses excellent mechanical performance with high decomposition temperature about 450℃; and adding SiO_2@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 SiO_2@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.