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The need for the longer mileage of electric vehicles has pushed the energy density of lithium ion batteries (LIBs) to their limits. However, enhancing the energy density of LIBs usually causes poor wetting of an anode electrode and its higher ionic resistance (R ion ), resulting in lithium (Li) plating. Therefore, it is highly crucial to monitor the anode R ion influenced by wetting condition of the anode during formation process. Here, we introduce the electrochemical indicator to estimate the R ion of the silicon (Si)/graphite (Gr) blended anode in 21700 cylindrical cells depending on its wetting condition, which can be utilized as a screening tool for manufactured cells. It is attributed to the better rate capability of Si compared to Gr in the blended electrode, and their overpotential difference enables the appearance of the diagnostic signal on differential voltage profiles. In practice, we confirm that the proposed indicator has a strong correlation with the overpotential of the Si/Gr anode, and further is related to the cycle performance and whether Li plating occurs or not. Therefore, the indicator can be utilized as a diagnostic tool for inspecting wetting condition of manufactured cells, which can ensure the safety of LIBs. • A new indicator diagnoses wetting condition of the silicon/graphite anode in cells. • An indicator assesses the overpotential of the individual anode in a full-cell. • A diagnostic tool for anode wetting condition is proved by 21700 cylindrical cells. • A tool is simple enough to perform a full inspection of cells at manufacturing step.
Kim et al. (Tue,) studied this question.