Analysis of ionic migration behavior of the electrodes for lithium-ion batteries through electrochemical impedance spectroscopy

Abstract

Lithium-ion batteries (LIBs) are widely used as energy storage devices for portable electronic devices (PED), electric vehicles (EVs), and energy storage systems (ESS) due to their high-energy density, high-power density, and prolonged cycling lifespan. By the United States Department of Energy (DOE) target, LIBs for powering EVs need to be reduced to 15 minutes or less in their charging time to promote the EV market supply. Many studies reported that to achieve quick chargeable LIBs, improving the kinetic of storing lithium (Li) ions in the anode is effective because it acts as a rate-limiting step of the electrochemical charging process. Especially, improving the ionic migration kinetic by modifying the electrode structure is known as one of the most feasible strategies to upgrade the kinetic in the anode. However, few studies have conducted electrochemical analysis on electrodes to understand the ionic migration and capacitive behavior. Therefore, in this study, various types of graphite (Gr) electrodes that have different morphological factors (such as electrode thickness, and compositions) are fabricated and the ionic migration and capacitive behavior are investigated by electrochemical impedance spectroscopy (EIS) and complex capacitance analysis. Additionally, the electrochemically active surface area (ECSA) analysis tool was introduced and quantitatively analyzed by complex capacitance analysis. As a result, the relationship between the morphological factor of the electrode and the ECSA was clarified.