Exploring the effects of aging, temperature and hysteresis on the entropy variation of lithium-ion batteries

The entropy variation Δ S poses a fundamental characteristic of lithium-ion batteries due to its influence on their thermal behavior. This study presents an extensive open source dataset containing potentiometric entropy variation measurements on two commercially available cell types. The experimental campaign includes 20 temperature steps over 9 different states of charge (SoC) approached in charging and discharging direction. Further measurements on half cell level were conducted in order to investigate the electrodes’ contribution to the full cell entropy. In addition, a reduced testing regime was applied to 6 degraded cells aged via various aging regimes. The measurements were analyzed to quantify the influence of SoC, non-linearity, hysteresis, temperature-path-dependency and aging on the entropy variation. Comparing the results to literature, the expected influence of both SoC and load-history-dependent hysteresis were confirmed. Regarding the influence of non-linearity, no significant effect was determined for the given dataset. The effects temperature-path-dependency observed in literature were successfully reproduced. However, the proposed loop-like relationship resembling common hysteresis phenomena could not be verified. The reconstruction of the full cell entropy variation curve from half cell measurements was successfully conducted for cells in pristine condition, while its application on aged specimens proved difficult likely due to challenges during determination of the electrode balancing. • Open-source dataset with entropy variation measurements for two cell types. • Electrode entropy measurements and reconstruction of full cell entropy variation. • Analysis of aging, temperature and hysteresis effects on the entropy variation.