Rational design of solid polymer electrolyte membranes based on poly(vinyl alcohol)/lithium salt plasticized with deep eutectic solvent

Abstract As a key component for the future high‐safety lithium batteries, solid polymer electrolyte (SPE) is gaining an attractive momentum toward large‐scale production due to their remarkable compatibility and processability with electrodes. Further, their excellent performance can be improved using the potential use of plasticizers. A deep eutectic solvent (DES) synthesized from choline chloride (ChCl) and citric acid monohydrate (CAM) demonstrates a promising plasticizer to design good SPE membranes along with poly (vinyl alcohol) (PVA). The changes in the surface chemistry of PVA‐based membranes, as determined by Fourier transform infrared (FTIR) spectroscopy, confirm the success of DES‐plasticizing effect, where detected by wavenumber shifting around main functional groups such as OH, CO, and COC. Following this, EIS characterization on electrical properties reveals the role of 30 wt% DES in improving the ionic conductivity, with the highest ionic conductivity equivalent to 4.66 × 10 −4 S cm −1 and the crystallinity index as high as 41.09%. The presence of LiClO 4 and DES significantly reduces mechanical performance, and glass transition of PVA‐based membranes, as characterized by tensile testing and differential thermal analysis/thermogravimetric analysis. Thus, the presence of DES in PVA and LiClO 4 matrices could open another window for designing SPE with novel physicochemical properties.