Electrochemical impedance spectroscopy investigation on battery materials using a symmetrical cell

Various works have been carried out on lithium-ion batteries for improving the different conductivities of electrode materials. For this purpose, electrochemical impedance spectroscopy is a technique of choice to understand the elementary processes that take place during the charge/discharge steps and to quantify their respective contribution in total impedance. However, some materials, such as lithium iron phosphate (LFP), suffer from poor electronic conductivity and a high interfacial resistance when used with a standard aluminum current collector. In this article, the influence of both temperature and pressure on the LFP impedance response is reported in order to provide an accurate description of the interface and a detailed analysis of the time constants observed on the impedance response. This was made possible through the use of a carbon-coated Al current collector to decrease the contact impedance, and the development of a four-electrode symmetrical coin cell setup that allows the insertion mechanism to be studied as a function of the state of charge on a single battery, i.e., without the need to build a symmetrical battery for each SOC to be studied.