In operando detection of Lithium plating via electrochemical impedance spectroscopy for automotive batteries

Reducing the charging time is one of the main goals towards increasing the acceptance of electric vehicles. One of the limits of fast charging lithium-ion batteries with graphite-based anodes is lithium plating, a process which occurs mainly at high charging rates, low temperatures and high state of charge. Detecting the onset of lithium plating during a charging procedure is essential in order to optimize fast-charging profiles. This paper introduces a new method that allows the detection of the onset of lithium plating in automotive lithium -ion batteries using on-line electrochemical impedance spectroscopy. Compared to similar approaches, the measurement itself does not result in a significant increase in the charging time. The detection is based on observing the real part of the impedance across the state of charge during the charging procedure. The onset of lithium plating can be detected by a deviation from the nominal behavior in the form of a drop towards lower impedance. The behavior is both explained theoretically using electrochemical equivalent circuits and shown experimentally. The impedance measurements are carried out using an integrated small-scale device to allow on-line impedance analysis in an automotive environment and an integration into future battery management systems.