PVDF-based composite microporous gel polymer electrolytes containing a novelsingle ionic conductor SiO2(Li+)

In this paper, a novel silica sol conductor SiO2(Li+) was synthesized from tetraethylorthosilicate (TEOS) and γ-(2,3-epoxypropoxy) propyltrimethoxysilane via sol-gel hydrolysis followed by neutralized with lithium hydroxide. The prepared SiO2(Li+) were incorporated into poly(vinylidene fluoride) (PVdF) by standard solution-casting technique coupled with phase inversion process to fabricate a composite microporous membrane. Then the resultant composite microporous gel polymer electrolyte (CMGPE) was obtained by simply immersing the dried composite microporous membrane into liquid electrolyte and being gelled. The physicochemical properties of the CMGPEs were characterized by FTIR, DSC, XRD, TG, stress-strain response and electrochemical measurements. They exhibit a higher porosity and a higher electrolyte uptake with a proper addition of SiO2(Li+), while, the degree of crystallization of composite microporous membranes decrease with it. In addition, the ionic conductivity of CMGPEs can also be enhanced by vast amount of Li+ ions on the added SiO2(Li+). When the content of SiO2(Li+) was 5 wt%, ionic conductivity of the CMGPEs reached to 10−3 S cm−1 order of magnitudeat at room temperature and its electrochemical stability window was 5.2 V. A proper content of SiO2(Li+) in PVdF-based membrane makes it a potential candidate for application as polymer electrolyte in devices.