Dynamic Impedance Spectrum: A Novel Metric for Lithium-Ion Batteries Overcharging Diagnosis

Diagnosis of overcharging in lithium-ion batteries (LIBs) is crucial to guaranteeing the long-term thermal stability and operational lifespan of a battery system. Compared with conventional diagnosis methods that rely on cell temperature and voltage measurements, the dynamic impedance spectrum (DIS) provides novel insights into assessing battery charging and overcharging processes. In this article, the perturbation signals are superimposed onto the charging current for the real-time monitoring of the dynamic impedance variation. A quantitative analysis is conducted to examine the applicability of the characteristic parameters, which are extracted by fitting the DIS with an equivalent circuit model (ECM), in assessing the overcharging in LIBs. Experimental investigations confirm the validity of the DIS measurements by performing the Kramers-Kronig (K-K) tests, where the maximum absolute residuals are lower than 0.5%. The proposed method is capable of reliably warning the battery overcharge when the batteries are charged up to 98% state of charge (SOC).