Identification and quantification of ageing mechanisms in Lithium-ion batteries using the EIS technique

Ageing diagnosis in Lithium-ion batteries is essential to ensure their reliability and optimum performance over time. The Battery Management System (BMS) usually monitors battery ageing with the aid of two metrics: capacity and power fade. However, these metrics do not identify the main root causes of battery ageing. Using the Electrochemical Impedance Spectroscopy technique, this work proposes a novel method to identify and quantify ageing mechanisms over time. The method is applied to four parallelised Lithium-ion cells cycled with a constant driving profile for 500 cycles. As a result, Loss of Active Material (LAM) and Loss of Lithium Ions (LLI) were found to be the most pertinent ageing mechanisms over time for the four cells. Identification and quantification of ageing mechanisms will support novel battery lifetime control strategies within the BMS, so that potential failures during normal operation are prevented.