Effect of Shallow Cycling on Flexible Power-Source Survivability under Bending Loads and Operating Temperatures Representative of Stresses of Daily Motion

Flexible batteries in wearable applications can serve a diverse array of functions including logic, control, memory and biometric sensing. The power sources may be operate under sustained exposure to human body temperature superimposed on ambient temperature extremes, mechanical loads under stresses of daily motion, and various depths of charge-discharge cycles. There are significant technical challenges in meeting the power-needs of wearable electronics including maximizing capacity in thinner form-factors, flexibility and robustness under the operating and usage environment. In this research study, the combined effects of deep-charge, shallow-charge, distinct bending load(s) and operating temperatures have been characterized for Li-Ion batteries. Thin flexible battery cells were cycled through multiple charge-discharge cycles under simultaneous bending loads plus thermal stresses. Output parameters such as efficiency, power, capacity and charge-discharge time have been analyzed for battery state assessment. The sensitivity of capacity degradation to a number of charge-discharge parameters is quantified with a regression model.