Quantitative Diagnosis of Li Plating Morphology by Analyzing Response of Electrochemical Impedance Spectroscopy in Working Li Batteries

Lithium (Li) plating, a major cause of capacity degradation and safety risks in Li-ion batteries (LIBs), remains a critical challenge in LIBs. Li plating with distinct morphologies exhibits fundamental differences in dendrite growth kinetics, interfacial stability, and "dead Li" formation─factors that directly determine a battery's safety threshold and degradation rate, yet the ability to predict deposition morphology has remained elusive. This study develops an in situ, nondestructive diagnostic method for Li deposition morphology through quantitative analysis of charge transfer resistance (Rct) evolution. We systematically controlled deposition morphology through different electrolytes and current densities. Dynamic distribution of relaxation times (DRT) analysis revealed a strong correlation between Rct decay rates and deposition morphology, quantified through the exponential parameter b in the fitting equation y = axb. Based on the distinct decreasing rates of Rct, we defined the Li Growth Factor (LGF) as a quantitative indicator for characterizing deposition morphology. Dendritic deposits exhibited rapid Rct reduction (LGF > 2.0) due to their large electrochemically active surface area (ECSA), while compact spherical or nodule-like Li showed gradual changes (LGF < 1.7). The established methodology provides both fundamental insights into Li deposition processes and a practical tool for battery safety monitoring, offering significant potential for optimizing fast-charging protocols and improving battery management systems.