Fault Diagnosis of Electrolyte Lithium Concentration in Lithium-Ion Batteries

Faults in lithium-ion batteries can diminish performance and shorten lifespan. One notable electrochemical fault arises from the loss of lithium concentration in the electrolyte, which can lead to degradation over time. This paper studies the detection and estimation of electrolyte lithium concentration degradation fault in battery cells. The proposed model-based fault detection scheme consists of two cascaded closed-loop Partial Differential Equation (PDE) observers. The first observer, state observer, estimates the distributed lithium concentration in the electrolyte. The second observer, fault estimator, utilizes the concentration estimated by the first observer to detect and estimate the electrolyte lithium concentration fault. The scheme is validated through simulations conducted on a LiFePO4 battery cell under an Urban Dynamometer Driving Schedule (UDDS) current profile.