Effects of cycling ranges on stress and capacity fade in lithium-ion pouch cells

The coupling between mechanics and electrochemistry can be a useful tool in identifying battery aging. Here we investigate the relationship between stress and capacity fade in different types of commercial batteries under various cycling ranges. We identify individual contributions from stress-increasing mechanisms, such as film growth, and non-linear stress relaxation mechanisms. Different cycling ranges affect the average stress level inside the batteries, leading to varying levels of stress relaxation, which dominates the overall stress behavior initially, but gradually is overtaken by linear stress-increasing mechanisms at higher cycle number. The slopes of the linear film growth vary with cycling range and battery type, and we correlate these effects with both mechanical and electrochemical phenomena. Commercial batteries with different compositions exhibit qualitatively similar results on stress vs. state of health (SOH), but vary quantitatively due to differences in their mechanical properties, which can be identified through mechanical tests.