Investigation of Lithium-Ion Battery Interface Degradation Mechanism through EIS Analysis Under Various Cycling Conditions

Lithium-ion batteries have attracted enormous attention in the past decade both in the academia and in the industry due to their extreme high energy and power density compared with the conventional battery systems. Stepping into 2019, the lithium-ion battery industry unprecedentedly focuses on the fast charging and diagnosis solutions, especially for the dynamic battery systems. However, the complicated environmental conditions, such as vibration, extreme temperature change, overcharging or overdischraging, fast charging, various testing techniques, combined with insufficient understanding of the State of Health (SOH) of the commercial batteries lead to thermal runaway, aging and explosion issues to the batteries. Stemmed from that fact, EIS (Electrochemical Impedance Spectroscopy) technique has been proposed to accurately determine the SOH of the commercial batteries. EIS has been proved to be an effective approach to investigate the electrochemical, structual and dynamical properties of the electrochemical systems, especially the interfaces. The study focuses on the effects of one of the most concerning technique "fast charging" and one testing technique, GITT (Galvanostatic Intermittent Titration Technique). Under pre-design conditions, EIS with pre-built equivalent circuit is then implemented at specific conditions to further gather the electrochemical and structural properties of the interfaces inside the battery at proper voltages. Finally, the electrochemical and structual degradation mechanism especially of the interfaces under various conditions is achieved, which inspires further investigation on the comprehensive analysis and determination of the SOH of the lithium-ion batteries. The proposed approach has shown better accuracy and more in-depth analysis compared with the existing techniques.