Electrochemical impedance spectroscopy as a non-destructive tool to investigate lithium ion battery aging

Kurzfassung

In order to run lithium ion batteries in a secure and lifetime optimized way, it is essential to understand the cell degradation behavior due to load cycling and calendar aging. Thereby, cell degradation is associated with an increasing cell resistance. For automotive applications battery cells will usually be replaced when the cell capacity drops under 80% or the internal ohmic resistance is doubled in comparison to the new state. A very useful and non-destructive method to detect increasing cell resistances during cell operation is electrochemical impedance spectroscopy (EIS). One main reason for increasing ohmic resistances during load cycling is attributed to a growing solid electrolyte interface (SEI) located at the phase boundary between graphite anode and electrolyte. In this work we present first results of EIS measurements as a function of different operating parameters. In this context, a useful tool to interpret EIS spectra is the use of suitable equivalent circuits to simulate battery components, chemical reactions and mass transfer limitations. All experiments are performed with different electrode materials assembled in self-build coin cells (LIR2032 body).