Stress-Dependent Chemo-Mechanical Performance of Amorphous Si Anodes for Li-Ion Batteries upon Lithiation

MC Wang and H Ye and CX Zhai and G Yang, ACS APPLIED ENERGY MATERIALS (2021).

DOI: 10.1021/acsaem.1c03394

Alloying-type anodes are significantly governed by their chemo- mechanical performance during the electrochemical cycling. The reaction- induced huge volumetric change of these anodes may cause material degradation and failure under mechanical constraints. Here, we investigate the stress-dependent lithiation behavior of amorphous Si (a-Si) anodes using molecular dynamics simulations. It is indicated that a-Si anodes can sustain higher hydrostatic stress than biaxial/uniaxial ones without the occurrence of mechanical failure. Thermodynamic and electrochemical calculations demonstrate that although the lithiation procedure also affects the thermodynamic stability of a-Si anodes, it is mainly dominated by the external mean stresses. Compressive stress is confirmed to destabilize a-Si anodes and further trigger their capacity fading. Compared with our atomistic simulations, previous continuum models underestimate the open-cell potentials of a-Si anodes, due to their ignored large volumetric deformation at higher stresses and Li concentrations. This computational study provides the intensive atomic- level understanding of the stress-dependent lithiation behavior of a-Si anodes.

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