Design and fracture mechanics of lithium-ion batteries

Fracture mechanics plays a crucial role among the mechanisms causing damage, meant as capacity fade, in lithium-ion batteries. Mechanical stresses arise in the electrode active material particles because of the interaction of lithium ions with electrode microstructure during battery operation. The stresses lead to fractures growth in the electrode, which accelerates detrimental chemical reactions. In this work, a modelling approach is presented to assess the fracture level in the electrode microstructure, evaluating the influence of the current delivered by the battery, and electrode design characteristics, such as the electrode thickness, the electrode active material fraction and the size of the electrode micro-particles. The results show that stress intensity factor linearly increase with the current delivered by the battery. Furthermore, thicker electrodes, greater active material fraction and greater electrode micro-particles represent a more detrimental condition from the fracture mechanics point of view. The results provide a practical electrode design guideline for electrode manufacturing, especially for choosing the right particle size in the electrode powder, the electrode thickness and its composition to limit fracture according to the current expected to be delivered by the battery.