Performance assessment and classification of retired lithium ion battery from electric vehicles for energy storage

The external and internal characteristics of retired lithium-ion batteries from electric vehicles are evaluated using observational check, battery capacity measurement, pulse characteristic curve and electrochemical impedance spectroscopy. Non-parametric statistical tests have been introduced to assess the correlation between battery capacity and impedance. The results show that observational check and capacity measurement are only preliminary ways to screening and classification of retired batteries from electric vehicles. The voltage of pulse discharge is an important indicator for evaluating consistency among retired batteries. Of all factors influencing on battery capacity loss from the point of view of impedance, Warburg impedance is principal and charge transfer resistance is second. There is no correlation between capacity loss and ohmic resistance. Performance assessments and consistency sectionalization of retired batteries need synthetic judgment by their different performance parameters. Of all 60 retired batteries investigated in this work, 20 batteries in good appearance are divided into three groups in the light of synthetic classifications of capacity, voltage of pulse discharge, charge transfer resistance and lithium ion diffusion coefficient while other 40 batteries disqualified in appearance are fundamentally taken no account of reuse.