Study On The Solvent Effect And Application In Lithium Sulfur Battery Of Poly Sorbitol Acetal Derivatives As Gelator

In this work, sorbitol acetal derivatives 2,4-(3,4-dichlorobenzylidene)-D-sorbitol(DCBS) and 2,4-(3,4-dimethylbenzylidene)-D-sorbitol(DMBS) as low molecular weight gelators were synthesized.Mixed solvent effect on the gelation ability of one-component gelator(DCBS) was evaluated. DCBS was soluble in pure ethanol, but it formed stable gels in a certain volume ratio ethanol-methylcyclohexane mixtures. SEM studies showed that the solvent system changed the morphologies of the aggregates, which was in agreement with the different macroscopic gelation behaviors. According to the FT-IR and XRD, intermolecular hydrogen bonding was the main driving force for the gel formation, and the packing mode also depended on the composition of the solvents. The Flory-Huggins parameter was used to further illustrate the interactions between the gelator and solvents. According to the values of Flory-Huggins parameter and the gelation behaviors of DCBS in other solvent mixtures, a gelation model was established to predict the gelation behavior of DCBS in some untested solvents, which broadened the application of Flory-Huggins parameter.The DMBS was used as a low molecular weight gelator for the gelation of 1.0mol/L LITFSI/DME:DOL(1:1,v/v) solution. The gel electrolyte was stable as the gel-to-sol phase transition temperature was above the normal use temperature of the lithium sulfur battery. The electrochemical measurements indicated that the gel electrolyte and the solution electrolyte had the similar electrochemical behavior. To some extent, the gel electrolyte could slow down the solubility of reductive polysulfides in liquid organic electrolyte and effectively inhibit the corrosion of the lithium electrode, which helped to improve the utilization of sulfur material and the charge and discharge cycle performance of the lithium sulfur battery.