Pseudo Electrochemical Impedance Spectroscopy Method for In-Situ Performance and Safety Assessment of Lithium-Ion Battery Energy Storage Systems for Grid-Scale Applications

Battery energy storage system (BESS) is a key enabler of the modern renewable- and inverter-heavy electric grid. It is generally expected [1] that the BESS will see a more demanding duty in the modern grid as it delivers a multitude of ancillary services dispatched simultaneously (stacked duty) and sequentially (mixed duty). Such harsher duty will entail larger operating envelope of timescale, power, and state-of-charge (SOC), and further elevate the issues of BESS performance and safety. Lithium plating (lithium deposition in general) is widely reported as a significant aging and failure mechanism when charging the BESS at high current and high SOC [2], [3]. In this work we describe an extension to the so-called pseudo electrochemical impedance spectroscopy (EIS) method to detect and quantify general degradation in performance and specifically to detect lithium plating. The pseudo-EIS protocol is amenable to implementation in a battery management system (BMS) for real-time assessment of performance and safety. In particular, it enables proactive management of current profile during (fast) charging to trade-off performance and safety. Further, it can also be used offline to gauge state-of-health (SOH) of second-life batteries before redeployment.