Li-Ion battery degradation

Lithium-ion batteries are at the forefront of the effort to reduce global CO2 emissions. For example, the transition from the fossil fuel-based internal combustion engine to the electrical vehicle (EV) is growing at an increasingly rapid rate, a transition in which Li-Ion batteries play a pivotal role. However, Li-Ion batteries suffer from capacity fade during their lifetime. One of the main degradation mechanisms is the fracture of electrode particles, which is caused by the stresses associated with the inhomogeneous swelling and shrinkage of electrode materials that occurs when lithium-ions are inserted and extracted. The resulting cracks in the electrode particles lead to two negative effects on the battery performance: loss of electronic contact between particles, which decreases the amount of active material in a cell, and additional parasitic side reactions that occur on fresh crack surfaces, e.g. the formation and growth of the solid electrolyte interphase (SEI), which leads to lithium inventory loss.

We have tried to develop a new class of mechanistic, computational tools that resolve the physical process involved in Li-Ion battery degradation, providing the following pioneering contributions:

▪ Developing the first finite element model for predicting cracking in electrode particles exposed to cyclic damage.

▪ Developing a new class of image-based coupled finite element models to predict electrode particle cracking at both the particle and electrode levels.

▪ Gaining insight into the cracking of electrode particles at the microstructural level through the combination of modelling and experiments.

In addition, we have also tried to contribute to the develop of all-solid-state batteries. All-solid-state batteries are the most promising development in energy storage technology. However, commercialisation is hindered by the formation of voids and dendrites at the interface between the Li metal anode and the solid electrolyte. We recently developed the first mechanistic electro-chemo-mechanics model capable of predicting the evolution of voids and the emergence of local current ‘hot spots’, which act as precursors for dendrite formation and cell death. The model can be a game-changer as it enables: identifying safe regimes of operation, mapping the conditions that lead to dendrite formation, and assessing the viability of new materials and cell/interface designs; effectively enabling an all-solid-state battery breakthrough. We also recently demonstrated that the model could be used to rationalise accelerated short-circuiting in anode-free solid-state batteries.

A recent talk on this topic is given below: