A combined thermo-electric resistance degradation model for nickel manganese cobalt oxide based lithium-ion cells

This paper presents a novel effort in combining an electro-thermal internal resistance model for Nickel Manganese Cobalt Oxide (NMC) cathode and graphite anode based cells, designed for predictive analysis for automotive applications. This unique approach provides insight in the degradation rate of the internal resistance with respect to the Depth of Discharge, Current rate, cycle number, storage State of Charge and storage time. The data used for the model development is courtesy of a huge test-campaign, spanning the course of 2.5 years, and provides a good insight in the behavior of what is considered to be a very promising battery cell technology for automotive applications. Experimental results show that the internal resistance evolution is strongly dependent on Depth of Discharge and temperature, while high storage State of Charges and high storage temperatures increase the degradation rate during calendaring aging. The combined electric and thermal models make it possible to estimate the influence of the current rate on the degradation of the internal resistance. The developed lifetime model is capable of correctly estimating the degradation and temperature behavior of static load profiles, while also providing insight in the evolution of the temperature profile and other cell characteristics.