Enhanced Ionic Conductivity through Chemical Modification: From 1,2,3-Triazole to 1,2,3-Triazolium Salt in Solid Polymer Electrolytes

Poly(ionic liquid)s (PILs) that combine the advantages of both polymers and ILs are promising solid polymer electrolytes (SPEs) for overcoming the drawbacks of liquid electrolytes. In this study, we report the synthesis and ionic conduction properties of two cross-linked polymer electrolytes (TR-P and TL-P) based on 1,2,3-triazole and 1,2,3-triazolium salt linkage groups, respectively. The unique approach in this study is the chemical modification from triazole to triazolium salt to increase ionic conduction. Through photopolymerization, both SPEs can be obtained as free-standing films. Notably, the electrochemical analysis demonstrates that the ionic conductivity of TL-P is 5.5 times greater than that of TR-P. This considerable increase in ionic conductivity arises from differences in the interaction between Li+ and the two linkage groups. For TR-P, the nitrogen atoms of the triazole group can tightly bind Li+, thus retarding ion conduction. In contrast, the modification into a triazolium salt in TL-P repels Li+, facilitating ion conduction. This experimental result is further supported by energy simulations, where attractive and repulsive interactions with Li+ are dominant in TR-P and TL-P, respectively. Consequently, simple chemical modification is strongly suggested as a way to improve the ionic conductivity of SPEs.