Assessment of State of Health in Multi-Batch Retired Lithium Batteries Using an Equivalent Circuit Model

To meet the demand of retired lithium batteries to obtain their state of health (SOH) when recycling, traditional lithium battery SOH estimation algorithms often need to charge/discharge test to extract time domain features, which leads to a long test cycle and makes it difficult to cope with the estimation demand of large batches of retired batteries, for this reason, electrochemical impedance spectroscopy (EIS) is used in this paper to improve the speed of data acquisition. This study develops a frequency-domain equivalent circuit model (ECM) that is applicable to lithium-ion cells in various aging states, identify the ECM parameters using Zsimpwin software, and filter SOH features by combining correlation analysis to establish a SOH estimation model for retired lithium batteries based on the parameters of the ECM. The experimental results show that compared with the traditional SOH method relying on time-domain features, This paper introduces a novel method can complete the SOH estimation within 5 minutes and keep the mean absolute error (MAE) within 2.5%.