Sundararajan Natarajan

Abstract:

In this paper, we study the fracture behaviour and associated crack patterns that develop in Si thin film anodes of lithium ion batteries. In order to account for the ~300% volume expansions that the Li-ion exchange results in, a coupled deformation-diffusion problem is considered. The non-linear equations are solved using the extended finite element method, allowing for numerical simulations that are in good agreement with the experimentally observed crack patterns. In the simulations, the derived stress and strain fields are obtained independently of the mesh within the framework of the extended finite element method and linear elastic fracture mechanics. The advancing front is represented by the level sets with the stress distribution and the fracture parameters being estimated to assess damage development during lithiation. The fracture is simulated based on the maximum principal stress criterion. The stress fields ahead of the crack tip are modelled by a semi-analytical approach, which facilitates the computation of the fracture parameters, i.e., the stress intensity factors and the T-stress. The numerical results are compared with available experimental observations. The proposed framework will provide guidelines for designing crack free thin-film electrodes. The influence of the particle size and shape on the fracture parameters and the stress distribution is also investigated.