Electrochemical study comparing liquid and gel electrolytes for lithium-ion batteries based on LiTDI or LiPF6

Abstract

Liquid and gel electrolytes based on common commercial and recently commercialized salts for application in lithium-ion (Li-ion) batteries are presented herein. Various solvent mixtures and electrolytes based on them are presented. Selected organic carbonates’ mixtures are chosen as the base for these electrolytes. LiTDI (lithium 4,5-dicyano-2-(trifluoromethyl)-imidazolide) and LiPF₆ (lithium hexafluorophosphate) are chosen to compare the behavior and the electrochemical properties of the investigated systems. The limited optimizations of electrolytes are presented for LiTDI salt. Results for LiPF₆ electrolytes are presented as a benchmark. The detailed comparison of lithium transference numbers is presented. All liquid electrolytes present quite high values of conductivity at room temperature and in some cases reach above 6 mS cm⁻¹ for LiTDI solutions. The base for gel electrolytes is PVdF-HFP co-polymer (poly(vinylidene difluoride-co-hexafluoropropylene)). The conductivity of gel electrolytes exceeds 1 mS cm⁻¹ in case of the LiTDI system. All presented electrolytes show relatively high stability vs. Li/Li⁺, up to 4.7 V in both liquid and gel systems.

Graphical abstract