Challenges in the reliable detection of lithium plating using dynamic electrochemical impedance spectroscopy

Fast charging of lithium-ion batteries is strongly limited by the risk of lithium plating, which accelerates aging and compromises safety. While electrochemical impedance spectroscopy has been widely explored for plating detection, significant challenges regarding its practical reliability and signal interpretation remain insufficiently addressed. Three commercially available 18650 lithium-ion cell types representing both high-energy and high-power designs are examined. Therefore, an experimental setup with single-sine and multi-sine excitation was developed to analyze the dynamic impedance under different excitation signals, C-rates, and temperatures. The evolution of impedance is evaluated in conjunction with voltage relaxation behavior to identify characteristic features associated with lithium plating. Additionally, post-mortem analysis of cells subjected to extended fast-charging indicates that unambiguous identification of lithium plating under extreme conditions remains challenging. Higher-order derivatives of the impedance are assessed as potential mathematical metrics for plating detection. However, a sensitivity analysis reveals that the accuracy of the metrics depends on signal quality and post-processing parameters, leading to shifts in the suspected plating onset or the introduction of artifacts. Consequently, robust signal post-processing is essential to ensure the reliability and accuracy of impedance-based plating detection.