Simultaneous Electrochemical Impedance Spectroscopy and Adiabatic Calorimetric Measurements (ARC) of Lithium-Ion Batteries

Kurzfassung

In order to study the thermal characteristics of commercial cylindrical lithium-ion batteries (type 18650) simultaneous measurements with an accelerated rate calorimeter (ARC) and electrochemical impedance spectroscopy (EIS) were performed. The thermal runaway analysis of two different types of intercalation cathode materials was investigated: LiFeO4 and LiCoO2. The cells were tested at different state of charges (SOCs) at the initial state and after aging. The thermal deterioration was determined by recording each 10 minutes an impedance spectrum in the frequency range from 100 mHz to 3 kHz at open circuit voltage as a function of time and temperature respectively. The EIS were evaluated with an equivalent circuit consisting of a serial ohmic resistance, representing the electrolyte resistance of the cell, two parallel RC-elements and a Warburg impedance element in series.