Electrochemical Impedance Spectroscopy Study with a Blocking Symmetric Cell: Qualitative Analysis for Interface of Electrode-Electrolyte

Abstract

Li-ion transport which is the fundamental driving force affects to lithium-ion batteries performance thermodynamically and kinetically. A facile and accurate tool is needed to analyze Li-ion transport affected by the electrode structure and electrolyte. Electrochemical impedance spectroscopy (EIS) is a well-known tool to evaluate a battery system. The actual interface of electrode-electrolyte and Li-ion transport can be confirmed quantitatively by analyzing low frequency region of EIS.Herein, symmetric cells with SOC 0 state electrodes are analyzed with complex capacitance. In low frequency, Li-ion is accumulated along the electrode surface in the symmetric cell assembled with SOC 0 state electrodes (SC-SOC 0). Therefore, the interface of electrode-electrolyte can be investigated using this cell configuration. The accumulated amount of Li-ion is expressed as a real capacitance (C') (Figure 1a). In addition, the time constant (τ) is the value representing double-layer formation time related with the transport of Li-ion (Figure 1b). This approach can be used as a fundamental tool to understand Li-ion batteries performance by studying the interface of electrode-electrolyte (Figure 1c). Figure 1