Anisotropic Compositional Expansion and Chemical Potential for Amorphous Lithiated Silicon under Stress Tensor
نویسندگان
چکیده
Si is a promising anode material for Li-ion batteries, since it absorbs large amounts of Li. However, insertion of Li leads to 334% of volumetric expansion, huge stresses, and fracture; it can be suppressed by utilizing nanoscale anode structures. Continuum approaches to stress relaxation in LixSi, based on plasticity theory, are unrealistic, because the yield strength of LixSi is much higher than the generated stresses. Here, we suggest that stress relaxation is due to anisotropic (tensorial) compositional straining that occurs during insertion-extraction at any deviatoric stresses. Developed theory describes known experimental and atomistic simulation data. A method to reduce stresses is predicted and confirmed by known experiments. Chemical potential has an additional contribution due to deviatoric stresses, which leads to increases in the driving force both for insertion and extraction. The results have conceptual and general character and are applicable to any material systems.
منابع مشابه
Anisotropic compositional expansion in elastoplastic materials and corresponding chemical potential_ Large-strain formulation and application to amorphous lithiated silicon
A general large-strain thermodynamic approach with anisotropic (tensorial) compositional expansion/contraction in elastoplastic material under stress tensor is developed. The dissipation rate due to compositional expansion/contraction is introduced. Adapting and utilizing a previously formulated postulate of realizability, we derived a simple equation for the deviatoric part of the compositiona...
متن کاملOrientation-dependent interfacial mobility governs the anisotropic swelling in lithiated silicon nanowires.
Recent independent experiments demonstrated that the lithiation-induced volume expansion in silicon nanowires, nanopillars, and microslabs is highly anisotropic, with predominant expansion along the <110> direction but negligibly small expansion along the <111> direction. The origin of such anisotropic behavior remains elusive. Here, we develop a chemomechanical model to study the phase evoluti...
متن کاملKinetics of initial lithiation of crystalline silicon electrodes of lithium-ion batteries.
Electrochemical experiments were conducted on {100}, {110}, and {111} silicon wafers to characterize the kinetics of the initial lithiation of crystalline Si electrodes. Under constant current conditions, we observed constant cell potentials for all orientations, indicating the existence of a phase boundary that separates crystalline silicon from the amorphous lithiated phase. For a given poten...
متن کاملRobustness of amorphous silicon during the initial lithiation/delithiation cycle
Recent research on the electrochemical lithiation of amorphous silicon nanoparticles shows that amorphous silicon is more fracture resistant than crystalline silicon during lithiation. Nanoparticles of amorphous silicon can be lithiated and delithiated without any fracture at all. To fully exploit the potential of using amorphous silicon as electrodes for lithium ion batteries it is important t...
متن کاملReactive flow in silicon electrodes assisted by the insertion of lithium.
In the search for high-energy density materials for Li-ion batteries, silicon has emerged as a promising candidate for anodes due to its ability to absorb a large number of Li atoms. Lithiation of Si leads to large deformation and concurrent changes in its mechanical properties, from a brittle material in its pure form to a material that can sustain large inelastic deformation in the lithiated ...
متن کامل