A model for crack initiation in the Li-ion battery electrodes

• This work presents a theoretical formulation that predicts crack formation at an electrode surface under a lithiation cycle.
• The research provides the critical parameters required to improve the life of the Li-ion batteries.
• These research findings can be used to modify the surface structure to minimize crack formation.
• The predictions from the model show a reasonable agreement with the experiments.
• None of the theoretical literature so far has addressed the crack formation problem addressed in this paper.

The development of high energy density Lithium-ion batteries is of intense interest due to their application in the electric car and consumer electronics industry. The primary limiter in using high energy density battery electrodes is the cracking of the electrode material due to the severe strain caused by the charging–discharging cycles. In this paper, a linear perturbation model is used to describe the evolution of the electrode surface under stress. The driving force for the surface undulation formation is the reduction in the electrode strain energy. The kinetics of mass transport is described by the surface and volume diffusion. The model predicts that the Si electrode will develop surface undulations of the order of sub-1 μm length scale on the electrode surface, showing a reasonable agreement with experimental results reported in literature. Such surface undulations roughen the anode surface and can form notches that can act as crack initiation sites. It is also shown that this model is applicable when the temperature of the system is not constant and the system is not isolated. The limitations of the model are also discussed.