Real-time monitoring of dynamic changes in Li-metal deposition and dissolution using a MHz impedance sensor

Abstract

Li-metal deposition represents a critical degradation pathway in Li-ion batteries, rendering real-time monitoring of this process essential for ensuring safe operation. In this study, Li-metal deposition and dissolution are monitored using a sensor that measures the real part of the impedance (Re(Z)) in the MHz range. The MHz-range Re(Z) is highly sensitive to Li-metal, enabling compact sensor implementation and rendering it well-suited for monitoring applications. Thus, a highly accurate sensor is developed to monitor Li-metal deposition and dissolution dynamics. For proof of principle, an operando cross-sectional observation cell with sensor monitoring is employed to validate the ability to capture Li-metal dynamics. It is also confirmed that this approach is effective for application in commercial 18 650 cells, and cycle testing demonstrates that deposition and dissolution evolve with degradation. This work provides a robust tool for investigating Li-metal dynamics and offers a pathway for real-time monitoring of safer and more reliable battery systems.