Dielectric properties of sulfonated poly(ether ether ketone) (SPEEK) electrolytes with 1-ethyl-3-methylimidazolium tetrafluoroborate salt: Ionic liquid-based conduction pathways

Abstract This article relates to the synthesis, characterization and dielectric measurements of solid polymer electrolytes, derived from the ionic interaction of sulfonated poly(ether ether ketone) (sPEEK) and a Brønsted acidic ionic liquid (1-methylimidazolium tetrafluoroborate, [Hmim][BF4]), for electrochemical applications. The efficiency of the interaction was examined by incorporating different amounts of ionic liquid (IL) with the sulfonated polymer matrices having three different degrees of sulfonation (DS). The composite electrolytes were systematically characterized with FT-IR, SEM, TGA and DMA analysis. Anhydrous proton conductivity and dielectric measurements were studied in detail as a function of temperature. The presented analyzes revealed that sPEEK1.0-2 sample (2.50–3.51×10− 1 Sm-1 at 380–450 K) exhibited maximum proton conductivity and thermomechanical stability under anhydrous environment. Furthermore, sPEEK1.0-2 composite membrane exhibited higher glass transition temperature and reasonable storage modulus value (Tg = 157 ℃; E' = 0.22 GPa) compared to IL doped sPEEK membranes presented in the literature. The work herein opens new prospects for the as-synthesized materials to use as a solid polymer electrolyte for electrochemical applications such as high temperature proton exchange membrane fuel cells (HT-PEMFC) in a wide temperature range.

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Sulfonated Poly(ether ether ketone) Doped with Ammonium Ionic Liquids and Nano-Silicon Dioxide for Polymer Electrolyte Membranes

Polymers ◽

10.3390/polym11010007 ◽

2018 ◽

Vol 11 (1) ◽

pp. 7 ◽

Cited By ~ 8

Author(s):

Shuguo Qu ◽

Minhui Li ◽

Chenchen Zhang ◽

Yuanyuan Sun ◽

Jihai Duan ◽

...

Keyword(s):

Ionic Liquid ◽

Silicon Dioxide ◽

Proton Conductivity ◽

Composite Membranes ◽

Nano Sio2 ◽

Ether Ether Ketone ◽

Poly Ether Ether Ketone ◽

Ether Ketone ◽

Nano Silicon ◽

Sulfonated Poly

Nano-silicon dioxide (SiO2) was incorporated into the matrix of sulfonated poly(ether ether ketone) (SPEEK)/ammonium ionic liquid (AIL) membranes by solution casting, with the aim of reducing ionic liquid leaching and any consequent decrease in proton conductivity. Fourier transform infrared (FTIR) spectra results indicate incorporation of the SPEEK matrix with AIL and nano-SiO2. Scanning electron microscopy (SEM) and X–ray diffraction (XRD) images revealed that incorporation of nano-SiO2 make the ternary composite membranes more flexible. The maximum ion exchange capacity (IEC) value was 3.25 meq/g, and the net structure formed by the nano-SiO2 not only retarded AIL leaching, but also increased the proton conductivity of the composite membranes. AIL leaching from the membranes was between 20% and 30%, which was lower than that of the SPEEK/AIL membrane. The maximum proton conductivity for the SPEEK/AIL/SiO2 membranes reached 10.73 mS/cm at 393 K.

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