Investigation of lithium-ion battery nonlinear degradation by experiments and model-based simulation

Understanding the lithium-ion battery (LIB) nonlinear degradation is essential for battery full-lifespan usage and management. In this study, LIBs are cycled under conditions of low-temperature and high-current charging respectively. By designing a multi-battery parallel aging experiment, the evolution process and changing regu-lation of lithium ions (Li-ions) loss are quantified. The amount of irreversible lithium loss caused by two side reactions, i.e., the side reaction of SEI film growth and irreversible lithium plating, within the full lifespan of LIBs is measured and analyzed, which reveals that irreversible lithium plating is the dominant reason causing the battery nonlinear degradation. With the quantitative results above, an electrochemical aging coupled model is established, which agrees well with the experimental nonlinear aging. Furthermore, a simulation of the battery secondary capacity diving is conducted, and the formation of the nonlinear aging mechanism is revealed. A porosity reduction theory is proposed, in which the capacity diving of the battery is caused by the exponential growth of irreversible lithium plating, while the exponential growth phenomenon is due to the positive feedback loop formed by the porosity reduction of the negative electrode and the irreversible lithium plating.