Investigation of lithium-ion battery degradation by corrected differential voltage analysis based on reference electrode

Differential voltage analysis (DVA) is a non-destructive method for analyzing the degradation mechanisms of lithium-ion batteries and is widely used. The capacity variations between the peaks on the differential voltage curves are considered to reflect different degradation mechanisms of the batteries. However, DVA of batteries is the coupling of cathodes and anodes, and is based on idealized assumptions that still require experimental validation and correction. Due to the challenges in fabricating long-term and reliable reference electrodes for commercial batteries, it is hard to decouple the cathode and anode over the battery entire lifespan. In this study, four types of three-electrode batteries are fabricated. The cycling aging experiments are conducted on the three-electrode batteries, decoupling the voltages of the cathode and anode over the entire battery lifespan. The DVA method is validated and corrected. The corrected DVA, combined with electrochemical impedance spectroscopy based on reference electrodes, is used to analyze and quantify the battery degradation mechanisms. The degradation mechanisms of 36.3 % loss of lithium inventory, 7.8 % loss of active material (LAM) for anode, and severe LAM for cathode are identified. Finally, the degradation mechanisms are validated by post-mortem analysis. This study provides valuable insights and guidance for the use of DVA and the future commercial three-electrode batteries in battery diagnosis and prognosis.