Improving the mechanical performance of green starch/glycerol/Li+ conductive films through cross-linking with Ca2

This study uses calcium chloride to induce cross-linking of starch chains in order to enhance the mechanical response of starch-based solid electrolytes. The films are prepared at five different CaCl2 contents (0, 0.125, 0.250, 0.50, 1.0 g) using a fixed amount of glycerol (1.5 g), LiCl (1.5 g) and starch (3 g) dispersed in 100 g of water. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and cyclic voltammetry are used to characterize the composites. An effective cross-linking of starch chains by calcium ions is revealed by FTIR, while the amorphous features of the film microstructure is exhibited by XRD. The estimated relative crystallinity in the absence of calcium is not higher than 6.5%, while the CaCl2 addition reduces this parameter as low as 3.0%. In connection with the above parameters, the ionic conductivity of calcium-free film is ~3.0 × 10−5 S cm−1, while it presents an increase with CaCl2 incorporation (~7.0 × 10−5 S cm−1) due to the presence of free Ca2+ remaining from the maximum cross-linking capacity. The electrical capacitance (~0.032 mF·cm−2) is slightly affected by calcium-mediated cross-linking. However, the mechanical response is greatly improved as revealed by the elongation-at-break parameter, increasing from ~90% for calcium-free film to ~160% for films containing these ions. This indicates the enhancement of film elasticity, yielding 3D networks with robust mechanical stability. •CaCl2 induces the cross-linking of starch chains in starch/glycerol/Li+ films.•CaCl2 incorporation in the films reduces relative crystallinity.•Ionic conductivity of films depends on free Ca2+ remaining from cross-linking.•3D networks with robust mechanical stability are generated by CaCl2 addition.•Electrical capacitance is slightly affected by calcium-mediated cross-linking.