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Chemo-mechanics of Li-ion intercalation of Silicon-based anodes

Claudio Di Leo (MIT), Lallit Anand (MIT)

Lithium ion batteries: When Chemistry meets Mechanics

Tue 2:40 - 4:00

Salomon 003

Silicon-based anodes show substantial potential for application in the next generation Li-ion batteries because of their enhanced capacity for storing Li-ions. During first lithiation, crystalline silicon (c-Si) undergoes an irreversible phase transformation to amorphous silicon (a-Si), which is accompanied by a substantial volume increase. Further, experiments in the literature have clearly shown that the swelling during amorphization of the silicon is highly anisotropic. In order to better design Li-ion battery systems that utilize silicon-based anodes, a theory and an accompanying numerical implementation must be developed to model all the intricate phenomena that occur in crystalline silicon during first lithiation. To this end, we have developed a large deformation thermodynamically-consistent chemo- mechanical theory, which accounts for diffusion of Li-ions, large anisotropic swelling due to lithiation, transformation of crystalline silicon to amorphous silicon, and concurrent elastic-plastic deformations. The highly nonlinear coupled equations of the resulting theory have been numerically implemented in the finite element program Abaqus by programming custom user-elements (UELs). Using the numerical capability we study several characteristic problems related to the lithiation of silicon.