Effect of over and undercharging on intercalation induced stress in lithium nickel–manganese–cobalt electrode

Abstract Cathode materials in lithium-ion batteries are prone to delamination under over-voltage and fast charging conditions. This causes loss of active materials, reduction of battery capacity, and cycle life. This work develops a physics-based model to simulate the effect of over and undercharging of different cathode particle sizes in a composite electrode. A chemo-mechanical model is designed to simulate the non-linear volumetric expansion of a range of electrode particle sizes encapsulated in a binder, under different voltage conditions. The cathode fracture is modeled under fast charging conditions due to fatigue loading caused by (de)lithiation of lithium-ions during electrochemical cycling of nickel–manganese–cobalt (NMC) cathode in a half-cell arrangement. Two modes of degradation are considered, i.e. particle surface is free, and particle surface is fixed. Paris’ law is used to model the growth of fatigue cracks. The variation of tangential and radial stress in the particle and film are presented for the charging rate (1C–4C). The results predict crack growth and conditions of failure in the electrode during electrochemical cycling under various charging rates. Finally, an intuitive capacity loss model is developed to predict the cycle life and active material losses due to film delamination and particle fracture.