A continuum study of the role of coupled electrochemistry and stress on the morphological evolution of Li-anode

We present a continuum-level electro-chemo-mechanical framework that captures the coupled influence of stress and electrochemistry on the morphological evolution of viscoplastic Li-metal anodes and solid electrolyte interphase (SEI) layers in liquid-electrolyte Li-metal batteries. Our model incorporates a two-way coupling between mechanical deformation and electrochemical transport, including stress-modulated Li-ion migration across the SEI, large deformation viscoplasticity of the Li-anode during plating/stripping cycles, and surface energy effects at the anode interface. This multiphysics approach enables a systematic investigation of how electrochemical (e.g., diffusivity, conductivity), mechanical (e.g., modulus, residual stress), and geometric (e.g., thickness) properties of the SEI affect interfacial stability. Through numerical simulations, we generate design maps that quantify the roles of SEI geometry, material properties, and current density in either suppressing or amplifying surface instabilities. Crucially, our results highlight the dominant role of Li-metal viscoplasticity in driving surface roughening – even under homogeneous SEI conditions – a factor often overlooked in earlier linear stability or decoupled studies. We also explore the performance of composite and bi-layer SEIs, offering insights into optimal combinations of mechanical stiffness and interfacial energy to block protrusion growth. Together, this work offers a predictive modeling tool and design guidance for engineering artificial SEIs to suppress dendrite formation and enable fast, stable cycling of Li-metal batteries. • Li-anode instability studied considering the coupling between stress and electrochemistry. • Li-viscoplasticity is modeled and has a destabilizing effect on the Li-anode SEI. • SEI stability maps with safe current densities to avoid instability are provided as guidelines. • A soft inner-hard outer bilayer SEI is mechanically better at suppressing instability.