Modelling ageing of NCA-type Li-ion batteries: From half cells to complete batteries

Summary:

With the increasing applications of Li-ion batteries (LIB) in electrical vehicles, the state-of-health (SoH) awareness nowadays is of great significance and plays an important role in avoiding safety issues. Mathematical models are considerably used in this aspect due to their real-time response, high accuracy and low cost. In the present poster, a pseudo-two-dimensional (P2D) model is adopted to simulate the ageing of cylindrical NCA/graphite-silicon batteries, providing SoH status of these batteries. A simulation procedure from half cells to full cells is fundamentally applied to analyze the relations between the model parameters and the (electro)chemical and physical properties of the electrodes and electrolyte. Firstly, the NCA/graphite-silicon batteries have been dismantled in a glovebox to acquire pieces of the NCA cathode and graphite-silicon anode. Subsequently, NCA/Li and graphite-silicon/Li half cells are assembled in a glovebox and then tested in a temperature-controlled chamber to obtain (dis)charge voltage profiles. The experimental voltage curves of half cells are compared with the simulation voltage curves. Some of the optimized parameters from half cells are used for the commercial NCA/graphite-silicon batteries. By regulating electrolyte parameters, a good agreement can be found between the experimental and simulated voltage curves for the commercial NCA/graphite-silicon batteries. These optimized parameters are treated as the ones for pristine batteries. The different degradation mechanism including Li inventory loss (SEI formation and evolution, Li plating) and active material loss are related to the corresponding parameters. Through adjusting the responsible parameters, the voltage responses are analyzed for the batteries with a individual or combined degradation.