A systematic study of well-known electrolyte additives in LiCoO2/graphite pouch cells

The effectiveness of well-known electrolyte additives singly or in combination on LiCoO2/graphite pouch cells has been systematically investigated and compared using the ultra high precision charger (UHPC) at Dalhousie University and electrochemical impedance spectroscopy (EIS). UHPC studies are believed to identify the best electrolyte additives singly or in combination within a short time period (several weeks). Three parameters: 1) the coulombic efficiency (CE); 2) the charge endpoint capacity slippage (slippage) and 3) the charge transfer resistance (Rct), of LiCoO2/graphite pouch cells with different electrolyte additives singly or in combination were measured and the results for over 55 additive sets are compared. The experimental results suggest that a combination of electrolyte additives can be more effective than a single electrolyte additive. However, of all the additive sets tested, simply using 2 wt.% vinylene carbonate yielded cells very competitive in CE, slippage and Rct. It is hoped that this comprehensive report can be used as a guide and reference for the study of other electrolyte additives singly or in combination.