Thermal and Electrochemical Properties of Solid Biopolymer Electrolytes From Starch of Different Botanical Origin

Abstract

Background: Solid biopolymer electrolytes are a type of material with high technological potential used in the development of solar cells, batteries, fuel cells, among others, due to their biodegradable nature and low environmental impact. Aim: This study aimed to evaluate the effect of the botanical origin of the starch used to prepare solid biopolymeric electrolyte films on its electrochemical and thermal properties and to establish the variations in thermal decomposition temperatures and redox potentials depending on the botanical origin of the starch used. Methods: Films of solid biopolymer electrolyte were made by thermochemical synthesis processes using corn starch, cassava starch, potato starch, glycerol, polyethylene glycol, and glutaraldehyde as plasticizers and lithium perchlorate salt. The synthesis solutions were taken to an oven at 70 °C for 48 hours. The films were characterized electrochemically by cyclic voltammetry using a dry electrochemical cell and thermally by differential scanning calorimetry and thermogravimetric analysis. Results and Discussion: The results showed that the electrochemical behavior of the films was similar in terms of registered redox processes. However, the potential values of the oxidation and reduction were different, as are the stability and intensity of the processes. On the other hand, the thermal analysis allowed establishing two decomposition processes in each of the films studied; the first process was due to dehydration and depolymerization phenomena in the films. The temperatures recorded were 59.0 °C, 58.9 °C, and 89.9 °C for potato starch, cassava starch, and corn starch films. The second process evidenced the thermal decomposition at different temperatures, 267.7 °C in potato starch films, 280.6 °C in corn starch films, and 287.1 °C in cassava starch films. Conclusions: It could be concluded that the botanical origin of the starch used in the synthesis of solid biopolymer electrolyte films affects its behavior and electrochemical and thermal stability.

Effect of Lithium Salts on the Properties of Cassava Starch Solid Biopolymer Electrolytes

“…Starch has been used in the preparation of SBPEs in their pure form or mixed with some compounds [17]. The synthesis of starch SBPEs of different botanical origins was reported and the effect of this factor on its properties was studied [18], the synthesis of starch SBPEs using potato starch doped with glutaraldehyde and polyethylene glycol as plasticizers and NaI as lithium salt [19], tamarind seed starch was used with CF 3 LiSO 3 salt [20], and rice starch with different iodine salts (NH 4 I, LiI, and NaI) [21], among others. Additionally, the combination of starch with other compounds has been reported to improve the properties of the resulting SBPEs, for example, the combination of starch with chitosan [22], cellulose [23], polyaniline [24], polypyrrole [25], poly(vinyl alcohol) [26], etc.…”