Analysis of energy storage battery degradation under different electrical stress levels

Exploring the aging characteristics of batteries and investigating their degradation mechanisms are crucial for optimizing battery usage and developing reliable energy storage systems. In this work, we utilize an equivalent circuit model to analyze the input and output data of the battery, identifying changes in the battery's internal parameters during the aging process. The results indicate that aging cycle tests conducted using three discharge modes—1C, 3C, and over-discharge—show capacity retention rates with linear, sub-linear, and super-linear evolutionary trajectories, respectively. During cyclic testing at 1C discharge, structural changes in the graphite anode due to prolonged cycling lead to decreased charge transfer efficiency, which is the primary cause of performance degradation. Under 3C discharge conditions, high currents result in the formation and growth of the solid electrolyte interphase (SEI) film, electrolyte decomposition, and structural changes in the electrode materials, all of which accelerate the rate of battery aging. In over-discharge mode, the main cause of aging is attributed to current collector corrosion and the decomposition of electrolyte components. Furthermore, under 3C discharge conditions, the battery performance exhibits the fastest degradation rate, with heat generation power increasing nearly threefold compared to the initial test, while the power decay rate is approximately 0.7.