Studies of the Effect of Varying Prop-1-ene-1,3-sultone Content in Lithium Ion Pouch Cells

Li[Ni1/3Mn1/3Co1/3]O2 (NMC111)/graphite pouch cells made with varying concentrations of the electrolyte additive prop-1-ene-1,3-sultone (PES), were studied using high precision coulometry and storage experiments as well as gas evolution and electrochemical impedance spectroscopy (EIS) measurements. In addition, the performance of PES at high temperature was studied and compared to vinylene carbonate (VC). Adding increased concentrations of PES (up to 6% by weight) to the control electrolyte led to larger charge transfer resistance after formation, but reduced gas evolution. Ultra high precision charger (UHPC) cycling showed that cells containing 2% PES were comparable to 2% VC, and that 4 and 6% PES were superior, but at the expense of higher charge transfer impedance. During 60°C storage experiments, PES-containing cells produced 90% less gas than VC-containing cells, and additions of Li-TFSI (LiN[SO2CF3]2) were found to be beneficial as far as gas production and self-discharge were concerned.