Investigation of Lithium-ion battery parameters using pulses and EIS
Awais Chaudhry · Chalmers Publication Library (Chalmers University of Technology) · 2018
Purpose of this thesis was to acquire a better understanding of different methods in low frequency area when doing measurements on a lithium-ion battery cell.Also, to compare the methods chosen for the measurements to each other and show how they differ.The methods that were used in this thesis are Charge and Discharge, open circuit potential (OCP) relaxation, Pulse tests and Electrochemical Impedance spectroscopy (EIS).The measurements are done at room temperature, for most part in a temperature chamber with the temperature of 20°C and at current level of 0.25-30A and state of charge (SOC) level between 0-100%.Charge and Discharge measurements are used to help identify SOC of different voltage level of the battery cell, to obtain the data of the resistance at different SOC level and to give an idea of how the charge and discharge curve looks like for different current levels.Open circuit potential curves are used to confirm the resistance retrieved from the charge and discharge measurements and also to better understand the relaxation of the battery cell.Pulse tests are then done and with the data obtained from the charge and discharge measurements, resistance of the pulse tests is calculated.The resistance from the pulse tests is then compared with the resistance from EIS measurements.