A phase field electro-chemo-mechanical formulation for predicting void evolution at the Li-electrolyte interface in all-solid-state batteries
All-solid-state batteries are arguably the most promising development in energy storage technology. However, commercialisation is hindered by the formation of voids and dendrites at the interface between the Li metal anode and the solid electrolyte.
In this work, a mechanistic electro-chemo-mechanics model is developed to predict the evolution of voids and current hot spots in all-solid-state batteries. A phase field formulation is developed to model vacancy annihilation and nucleation, and to enable the tracking of the void-Li metal interface. This is coupled with a viscoplastic description of Li deformation, to capture creep effects, and a mass transfer formulation accounting for substitutional (bulk and surface) Li diffusion and current-driven flux. Moreover, we incorporate the interaction between the electrode and the solid electrolyte, resolving the coupled electro-chemical-mechanical problem in both domains. This enables predicting the electrolyte current distribution and thus the emergence of local current ‘hot spots’, which act as precursors for dendrite formation and cell death.
For both plating and stripping, insight is gained into the interplay between bulk diffusion, Li dissolution and deposition, creep, and the nucleation and annihilation of vacancies. The model is shown to capture the main experimental observations, including not only key features of electrolyte current and void morphology but also the sensitivity to the applied current, the role of pressure in increasing the electrode-electrolyte contact area, and the dominance of creep over vacancy diffusion. The model can be used to: (i) identify safe regimes of operation, mapping the conditions that lead to dendrite formation, and (ii) assess the viability of new materials and cell/interface designs; effectively enabling an all-solid-state battery breakthrough.
Authors: Ying Zhao, Runzi Wang, Emilio Martínez-Pañeda