Fast Charging of Lithium-Ion Batteries While Accounting for Degradation and Cell-to-Cell Variability

Abstract

Safety and maintaining high performance are key considerations during the operation of lithium-ion batteries. Battery degradation, in particular lithium plating and loss of active material, is often accelerated by fast charging. This study explores a strategy for the design of fast charging protocols that takes into account the influence of the variability between battery cells on factors that can impact degradation. We employ a non-intrusive polynomial chaos expansion to identify the key parameters for each degradation condition. We explore the reduction of battery degradation by adjusting constraints such as the maximum C-rate and voltage. Tight control of the key adjustable parameters contributes significantly to reducing the confidence interval of the degradation factors, allowing reduced charging time with minimal degradation. The application of our approach to two state-dependent fast charging protocols for a LiC6/LiCoO2 battery indicates the value in explicitly accounting for uncertainties when designing charging protocols that minimize degradation. Highlights A novel optimal charging strategy is proposed for reducing battery degradation The strategy explicitly takes probabilistic uncertainties into account The uncertainties are addressed by using a polynomial chaos expansion The strategy is used to design fast charging protocols for lithium-ion batteries The key parameters contributing to battery degradation are identified