IN SITU VOLUME STUDIES OF LI-ION POUCH CELLS

Abstract

The lifetime of Li-ion cells can increase more than tenfold when a few weight percent of additives is added to the electrolyte of the cells. A principal challenge in understanding how these additives work is how they affect films formed on both the negative and positive electrodes. Using Archimedes’ principle, it is possible to measure the change in volume of flexible Li-ion pouch cells during charge and discharge by using equipment described in the present work. Quantitative knowledge of gases produced during the first charge, or formation, of cells can allow insight into film-forming chemical pathways. In this work, DFT (density functional theory) with a solvation model was used in the Gaussian quantum chemistry software package to further understand such pathways. The additives studied were prop-1-ene-1,3-sultone (PES) and vinylene carbonate (VC), where the control electrolyte was a mix of linear and cyclic carbonates with a conductive salt.