 Electrochemical impedance spectroscopy, EIS, is a powerful tool for monitoring the health of lithium ion batteries. It measures the impedance of the battery over a wide frequency range, allowing researchers to detect changes in the internal structure of the battery as it ages. EIS is able to provide more accurate information than traditional methods such as voltage and current measurements, making it ideal for monitoring the health of lithium ion batteries. This article was authored by Ming Zhang, Yan Zhuolu, Dijili, and others.