Ugata, Yosuke
Department of Chemistry and Life Science, Yokohama National University & Advanced Chemical Energy Research Center (ACERC), Institute of Advanced Sciences, Yokohama National University
Kazuhide, Ueno
Department of Chemistry and Life Science, Yokohama National University & Advanced Chemical Energy Research Center (ACERC), Institute of Advanced Sciences, Yokohama National University
Dokko, Kaoru
Department of Chemistry and Life Science, Yokohama National University & Advanced Chemical Energy Research Center (ACERC), Institute of Advanced Sciences, Yokohama National University
Certain highly concentrated electrolytes (HCEs) enhance the charge-transfer reaction rate at the electrode/electrolyte interface in Li-ion batteries. The solvation structure of Li+ in HCEs significantly affects the electrochemical interfacial reaction kinetics. However, the effects of different anions on these kinetics have not yet been fully understood. Therefore, in this study, we investigated the effects of anionic species on the liquid structure and electrochemical reactions of HCEs composed of various Li salts and propylene carbonate (PC). Raman spectra revealed that both PC and anions were coordinated to Li+ ions in HCEs and that the concentration of uncoordinated (free) PC changed depending on the anionic species. Consequently, the activity of Li+ in the electrolyte changed depending on the anionic species. The use of Li salts with weakly Lewis basic anions increased the activity of Li+ and decreased the concentration of free PC in HCEs. The activity of Li+ in the electrolyte significantly affected the Li+ intercalation/deintercalation reaction rate of the LiCoO2 thin-film electrode. Electrochemical impedance spectroscopy revealed that the interfacial reaction rate of LiCoO2 was enhanced in the HCEs with anions having weaker Lewis basicity owing to the higher Li+ ion activity.
Draft_PC_Anion_revised_final_black.pdf (1.0 MB)
