Lithium Salt Tuned Biopolymer–Gelatin–PVA-Based Membrane Electrolytes: Electrochemical Insights for Solid-State Lithium-Ion Battery

A polymer composite electrolyte membrane of Polyvinyl alcohol, Gelatin and Lithium bis(trifluoromethanesulfonyl)imide were prepared via solution casting technique. They were investigated for its electrochemical behavior at both room and higher temperatures up to 80°C and structural properties at room temperature. Lithium bis(trifluoromethanesulfonyl)imide of various concentrations ranging from 0.25 to 1.5 g were added to investigate how salt concentration affects the membrane properties. The conductive behavior of membrane electrolyte was determined using nyquist plots and linear sweep potentiometry and the highest ionic conductivity of 1.07 × 10−6 S cm−1 was found in the electrolyte membrane with the composition of polyvinylalcohol-Gelatin with 10 wt % of Lithium bis(trifluoromethanesulfonyl)imide. The interaction between polymer, gelatin and lithium salt is confirmed by the FT-IR spectroscopy. X-ray diffraction studies were employed for the structural determination of the electrolyte membrane and it was found to be amorphous in nature. In addition, surface roughness (1.1 µm), skewness (–1.57 to –0.86), kurtosis (2.9 to 6.8) values were calculated using 3-D optical profilometry and this suggests that the polymer membrane was neither porous nor rough but it is good enough for uniform ionic conduction between electrodes. Thermal stability was analysed using thermogravimetric analysis and observed that synthesized polyvinyalalcholo-Gelatin with 10 wt % of Lithium bis(trifluoromethanesulfonyl)imide electrolyte membrane is thermally stable upto 350°C. Therefore, the polymer membrane with 10 wt % LiTFSI content shows the most optimal performance in lithium-ion battery applications.