Effect of U-Flex-to-Install and Dynamic U-Flexing on Li-Ion Battery State of Health Degradation Subjected to Varying Fold Orientations, Folding Speeds, Depths of Charge, C-Rates, and Temperatures

Abstract

The demand for wearable consumer electronics, fitness accessories, and biomedical equipment has led to the growth research and development of thin flexible batteries. Wearable equipment and other asset monitoring applications require conformal installation of power sources on nonplanar surfaces. For power sources in wearable electronics, durability to sustain repetitive mechanical stresses induced by human body motion is paramount along with the usual desirable power source characteristics. Previous research documenting the reliability of statically and dynamically folded power sources is scarce and does not follow standardized test protocols. Particularly, the use of manual stressing for mechanical folding of the power sources instead of a mechanical test setup is a key shortcoming in existing literature. Data are lacking on battery life cycling and in situ mechanical stress-testing of the power sources including their impact of performance and reliability. This study aims to overcome these deficiencies by testing a commercial Li-ion power source under static as well as dynamic folding. Furthermore, the fold orientation and its fold speed are varied to evaluate the effect of different mechanical stress topologies on the power source. Finally, a regression model was developed to capture the effect of these use parameters on battery capacity degradation.