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Concurrent reaction and plasticity during initial lithiation of crystalline silicon in lithium-ion batteries

Kejie Zhao's picture

In an electrochemical cell, crystalline silicon and lithium react at room temperature, forming an amorphous phase of lithiated silicon.  The reaction front—the phase boundary between the crystalline silicon and the lithiated silicon—is atomically sharp.  Evidence has accumulated recently that the velocity of the reaction front is limited by the rate of the reaction at the front, rather than by the diffusion of lithium through the amorphous phase.  This paper presents a model of concurrent reaction and plasticity.  We identify the driving force for the movement of the reaction front, and accommodate the reaction-induced volumetric expansion by plastic deformation of the lithiated silicon.  The model is illustrated by an analytical solution of the co-evolving reaction and plasticity in a spherical particle.  We derive the conditions under which the lithiation-induced stress stalls the reaction.  We show that fracture is averted if the particle is small and the yield strength of lithiated silicon is low.  Furthermore, we show that the model accounts for recently observed lithiated silicon of anisotropic morphologies. 

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Dibakar Datta's picture

 Congrats Kejie .. Great Work ...

Regards,
Dibakar Datta
Email : dibakar_datta@brown.edu
PhD Student ; Major : Solid Mechanics
Shenoy Research Group
Brown University
Providence 02912 , USA

Kejie Zhao's picture

Thank you Dibakar,  hope you can find it interesting.    -Kejie

Dibakar Datta's picture

 Kejie,

You have mentioned in the introduction section that the phase boundary between the crystalline silicon and the lithiated silicon has a thickness of ~1 nm as observed in experiment . However, in your model, you have not considered phase boundary. You have considered only LixSi zone . Any explanation ?

I am trying to do some work related to your work. Thanks . 

Regards,
Dibakar Datta
Email : dibakar_datta@brown.edu
PhD Student ; Major : Solid Mechanics
Shenoy Research Group
Brown University
Providence 02912 , USA

Kejie Zhao's picture

Hi Dibakar, 

Thanks for the questions. We considered the amorphous lithiated silicon shell and crystalline silicon core is seperated by a sharp phase boundary,  without more experimental evidence, we didn't describe details of such boundary, for example, how lithium assiste the reconstruction of the structure, if a small amount of lithium is dissolved in the crystalline silicon lattice ahead of reaction front, etc. There are still quite a bit open questions to make the picture clearer.   Please let me know if I answered your concerns. 

 -Kejie

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