(219c) Kasim A. Adewuyi Poster

This poster presents a new optimal charging methodology called Constant Gradient Constant Voltage (CGCV), which limits mechanical crack propagation at the surface of the particles in electrodes by regulating the current to maintain a constant lithium gradient at the surface. One important cause of battery degradation is the stress that is developed due to the concentration gradient inside active particles. The proposed new charging protocol actively controls the concentration gradient by utilizing the fact that the lithium diffusivity is strongly state-of-charge (SOC) dependent. Here, the diffusivity is not on-time measurable, so a modeling-based approach is incorporated, in which the charging protocol is guided based on the concentration gradient predicted from the modeling results. The upper limit of the concentration gradient is defined based on the maximum stress during the conventional Constant Current Constant Voltage (CCCV) charging. Then, two values (72.42% and 57.26% of the maximum gradient in CCCV for high and low CGCV, respectively) are considered for the demonstration of the proposed algorithm. The experimental results under three charging scenarios of high CGCV, low CGCV, and standard CCCV show similar degradation rates with a 25% or 17% reduction in charging time from the two CGCV methods compared to CCCV charging. This is a new protocol considering battery physics on particle level and has great potential to address the key challenge of regulating battery degradation during fast charging of Electric Vehicles (EVs).