The idea behind FE in this context is to formulate the lithiation process using physical models which provide results consistent with experimental observations. The model is based on the understanding that in SnO2 nanowire a slip plane is created due to non-perfect contact of the source or defects and the stress at the slip planes leads to significantly higher diffusion coefficient.1
The developed constitutive model which has been implemented in FE, captures the formation of striped diffusion regime and corresponding electrode’s expansion during the lithiation of SnO2. In particular, the model incorporates the formation of stripes by using a variable nonlinear diffusivity coefficient which is a function of the concentration-dependent stress. The structural changes associated with the Li diffusion/intercalation in the electrode geometry are modeled using a 2D plane strain assumption and linear elastic material. The results from the model show a clear formation of striped diffusion regime due to the induced stresses, at low concentrations of Li. This results in a small strain of 10% within the nanowire and is followed by a bulk diffusion and expansion at higher concentrations. Thus, the simulations allow for the spatiotemporally resolved prediction and analysis of Li diffusion/intercalation and its influence on the electrode performance under the realistic operation conditions.
1. A. Nie, L. Y. Gan, Y. Cheng, H. Asayesh-Ardakani, Q. Li, C. Dong, R. Tao, F. Mashayek, H. T. Wang, U. Schwingenschlgl, R. F. Klie, and R. S. Yassar, ACS Nano, 7, 6203–6211 (2013).
2. L. Q. Zhang, X. H. Liu, Y. C. Perng, J. Cho, J. P. Chang, S. X. Mao, Z. Z. Ye, and J. Y. Huang, Micron, 43, 1127–1133 (2012).
3. J. Y. Huang, L. Zhong, C. M. Wang, J. P. Sullivan, W. Xu, L. Q. Zhang, S. X. Mao, N. S. Hudak, X. H. Liu, A. Subramanian, H. Fan, L. Qi, A. Kushima, and J. Li, 330, 1515 LP – 1520 (2010).