EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Recently, potassium-ion batteries (KIB) have been considered as a potential alternative of Li-ion batteries due to the cost effectiveness and the variety of electrode materials. Graphite – the well-known anode in LIB – has gained numerous attention from KIB scientists owing to its ability of intercalating K+ ion to form KC8 with high theoretical capacity (278 mAh/g) and good cycling retention. KFSI in DME has been considered as a promising electrolyte for KIB due to its compatibility with not only K metal but also the electrode materials. However, the electrolyte concentration strongly affects the electrochemistry of graphite. A change in the intercalant as increasing the salt concentration, from [K(DME)x]+ (1M) to bare K+ ions (5 M), was confirmed by galvanostatic profiles and operando XRD. Additionally, Raman spectroscopy combined with quantum chemistry provided an insightful understanding on the solvation of K+ ions in DME in terms of conformational complexation. TGT – one among the five existent conformers of liquid DME - was found to form stable bidentate complexes, based on the binding energies of DME with K+ ions. Conformational vibration recorded on Raman spectra are well-defined thanks to the calculated Raman frequencies and activities. A statistical combination between computational and experimental data was applied to calculate the solvation number. At low concentration, the solvation number is 2.7, while it is lower than two in highly concentrated solutions. This difference provides a convincing explanation for the (co)-intercalation mechanisms mentioned above.