Lithium-ion batteries in battery-electric vehicles must balance charging speed, degradation, and safety to ensure optimal performance. High charging speeds can lead to lithium plating, resulting in lithium inventory loss, solid electrolyte interphase (SEI) build-up, and dendrite formation. These phenomena contribute to capacity reduction, increased resistance, and potential safety risks. Controlling the charging current based on temperature and state-of-charge (SOC) can help mitigate these issues. The state-of-health (SOH) of the battery must also be considered as it influences the maximum charging current. Inhomogeneities within cells, such as variations in lithiation states, temperature, and current distributions, can exacerbate localized lithium plating.
Various techniques are employed to detect lithium plating, both in-operando and post-plating. Common in-operando methods include reference electrodes and impedance spectroscopy. Reference electrodes allow the measurement of the anode potential, providing insight into the onset of lithium plating (U_anode < 0V). However, their application requires modifications to the original cell, such as experimental cells with different electrolytes and separators, potentially introducing errors. Additionally, reference electrodes measure locally, disturb the processes in the cell, and cannot track inhomogeneities within the cell. The time-consuming assembly and disassembly of experimental cells further complicate their usage. The experimental validation of these technique's results is necessary. Impedance spectroscopy offers a less intrusive alternative by monitoring changes in cell impedance during charging. This method superimposes an impedance measurement to the applied charging current. When lithium plating occurs, part of the applied current contributes to plating rather than intercalation into the anode material, leading to a sudden decline in impedance. This phenomenon can be used to determine the maximum plating-free charging current for specific SOC, temperature, and SOH conditions. A stepwise increase in charging current helps identify the current thresholds, but the hypothesis of detectability behind impedance changes requires further validation, and its sensitivity needs to be thoroughly assessed. Post-plating techniques, such as voltage feature analysis, can detect lithium stripping, which only occurs after reversible lithium plating takes place. However, these methods are limited to identifying the reversible portion of plating, not the irreversible part of interest that significantly impacts performance and safety. Additionally, these techniques often require relaxation at a constant temperature, constant voltage (CV), or constant current (CC) conditions to observe indicative voltage features. Thus, they are unsuitable for directly determining maximum charging currents and are primarily diagnostic tools. Similarly, post-mortem analysis using imaging or material characterization can confirm the presence of metallic lithium on the anode surface after suspected plating events but provides only retrospective insights. Ageing studies are another approach, where cells are cycled using an anticipated plating-free charging curve to observe degradation behaviour over time. While this method validates charging curves, it is time-consuming and does not determine the conditions under which plating initiates. Instead, it serves as a tool to confirm the long-term impact of specific charging protocols. Thus, in-operando methods are of interest to accomplish fast results with little effort and resources. Most existing studies focus on individual detection techniques without cross-comparison or validation across multiple methods. This work addresses this gap by systematically comparing various detection techniques across multiple different cell types and chemistries. By evaluating their sensitivity, accuracy, and reliability, this study aims to enhance the mitigation and detectability of lithium plating, contributing to the development of safer and more efficient charging strategies for lithium-ion batteries.