Effect of High and Low Storage Temperatures, Storage Duration and Varying Depth of Discharge on Coin Cell SOH Degradation

Portable consumer electronics devices continue to be one of electronics high-demand items, with rising interest in such products recently. Li-Ion batteries are the most popular power source choice of these products owing to a combination of high specific energy and specific power. In consumer electronics products, these batteries are generally employed in their coin form factor in biomedical devices, sensors, wireless earbuds, etc. These developments have boosted the research effort on Li-Ion power sources, and a major part of this effort is the prognostics of Li-Ion battery state of health (SOH) and predicting its remaining useful life. The ubiquitous use-parameters of batteries in modern consumer electronics devices are charging currents i.e. C-rates, operating temperatures, depths of charge, etc. Depth of discharge of the battery is another use parameter that has been explored in the current study. Two levels of depth of discharge have been tested and their SOH degradation profiles have been included in the SOH estimation dataset. Apart from this, calendar ageing of the battery due to storage at high and low temperatures for long durations is another common cause leading to battery SOH degradation. The storage scenario generally occurs during the manufacturing and retailing stage of the battery rather than at the end-usage stage. To study the degradation in state of health caused due to such calendar ageing, the coin cells in this study were subjected to storage at three temperatures (i.e., -10°C, 40°C, 60°C) for three durations (45 days, 120 days, 180 days). The pre-aging and post-aging capacities were measured and the difference between them was correlated with the harshness of the particular storage condition. In addition, after storage, the samples were subjected to accelerated life testing to evaluate the effect of storage on their SOH degradation rate. Thus, the SOH estimation models developed for two different coin cells in our previous study have been appended with the data generated during this study. Apart from this, calendar-ageing models have also been developed for the battery samples that were aged using different storage conditions.