The EMPIR-Project LiB4SecUse (Lithium Batteries for Second Use) develops impedance spectroscopy based techniques for the prediction of the state-of-health (SOH) of Lithium-Ion Batteries to asses their usability in second life applications. The Distribution of relaxation times (DRT) technique allows detailled interpretation of the spectra of Lithium-Ion batteries and is there-fore a promissing approach for fast characterisation of aged cells and modules.
In a first approach 18650 type Lithium-Ion batteries were cycled until the SOH fell below 80 % – meanwhile impedance spectra were recorded. By means of DRT, the changes taking place in the cell can be monitored in detail. The vertical plot clearly shows the different degrees to which the individual electrochemical loss processes contribute to aging of the cell. Thereby parameters for SOH prediction can be derived.