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

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 surface chemistry of PVA-based membranes, as determined by FTIR spectroscopy, confirms 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 x 10(-4) S cm(-1) and the crystallinity index as high as 41.09%. The presence of LiClO4 and DES and 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 LiClO4 matrices could open another window for designing SPE with novel physicochemical properties.