Studies on the Electrochemical Thermodynamics and Safety Behavior of Advanced Batteries and Their Materials

Layered oxides NMC (LiNi_xMn_yCo_zO₂) and spinel phases (LiMn₂O₄) are commercially most relevant cathode materials for lithium-ion battery design. However, there is still lack of fundamental knowledge on electrochemical-thermodynamic properties and related safety behavior of these materials and the batteries assembled thereof. The presented work focuses on the investigation of such properties to provide quantitative data for better understanding the performances of lithium-ion batteries in their regular and irregular operational use and during accidents. Experimental electrochemical, thermodynamic and safety studies are combined with computational methods (CALPHAD). We use various calorimetric methods (DSC, Tian-Calvet) for studies of the energetics of battery active materials as well as electrochemical cells. Such data are input for the thermodynamic modeling and calculation. The results are then used to derive fundamental electrochemical and thermal properties. Accelerating Rate Calorimetry (ARC) is used to quantitatively measure the thermal runaway behavior of self-made and commercial coin cells, cylindrical cells and pouch cells, respectively.