Electrochemical Impedance Spectroscopy (EIS) is a technique used to study the electrical properties of materials and electrochemical systems. It involves applying a small alternating current (AC) signal to a system and measuring the resulting voltage response. By analyzing the relationship between voltage and current over a range of frequencies, researchers can gain insights into the system's resistance, capacitance, and other characteristics. EIS is widely used in various fields, including battery research, corrosion studies, and fuel cell development. It helps in understanding reaction mechanisms, assessing material performance, and diagnosing issues in electrochemical devices, making it a valuable tool in both academic and industrial settings.