Modeling and half-cell-resolved measurement of the influence of cell degradation on the anode potential of high-energy lithium-ion cells

Understanding and modeling lithium-ion battery degradation is essential for optimized use but remains a significant challenge, with various aging mechanisms proposed in recent years. Towards a holistic, physics-based model description, the complex interrelationships among aging mechanisms, parameter identification, and experimental validation are highly active research areas. This work presents findings from a one-year, 1000-cycle aging study using multi-reference electrode single-layer pouch cells with NMC-811/graphite. These were utilized to validate a physics-based degradation model based on the Doyle-Fuller-Newman framework, leveraging half-cell-resolved measurement data in a pre-plating regime. The validated model is applied to investigate the influence of different aging mechanisms on the anode’s surface potential, a key parameter for avoiding lithium plating during charging. Additionally, the effects of degradation on anode-potential limited fast charging capability are discussed. Loss of active material is identified as a key mechanism which, if not considered, results in overestimation of the anode potential. Additionally, a significant resistance increase in the cathode material, which alters cell performance during aging, was identified and empirically captured in the model. Without reference electrodes, this resistance increase could not be accurately detected and, as suggested in the literature, would likely have been misattributed to the anode in the aging model. • Single-layer pouch cells with reference electrodes underwent over 1000 cycles. • A physicochemical aging model is validated, revealing critical aging parameters. • The validated aging-sensitive model is then analyzed for the anode potential. • Key degradation mechanisms are identified and discussed for the anode potential.