On the effects of hydrostatic stress on Li diffusion kinetics and stresses in spherical active particles of Li-ion battery electrodes

The main process in lithium-ion batteries is insertion/extraction of lithium into/from active electrode particles. Some active material of lithium-ion battery electrodes experiences a large volume change due to changes in lithium concentration. Since the failure of the electrode might be caused by large stresses, the mechanical phenomena in the electrode which are associated with the insertion and extraction of lithium, are of particular importance. This paper establishes an integrated framework of balance laws and thermodynamically consistent equations which couples lithium diffusion with a small elastic deformation. We investigate the effect of hydrostatic stress on lithium diffusion and stresses in the processes of potentiostatic and galvanostatic lithiation. In addition, we consider this effect for different current densities and various sizes of spherical electrode particles. Results show that the hydrostatic stress can lead to acceleration and enhancement in lithium diffusion as well as a larger state of charge (a representative for the percentage of full capacity). The results provide a strong basis for evaluating the effect of material properties on stresses and battery damage and could be basis for selecting electrode materials and proper strategy for charging and discharging with minimum stresses in Li-ion battery electrodes.