Abstract
The use of inorganic solid-ionic conductors with a metal electrode, has been proposed as a way to increase energy density, decrease capacity loss and prevent failure from metal propagation. Current observations of Li-metal electrodes causing cell shorting in solid-state systems have been identified as main obstacles limiting the development of this technology. However, many aspects of the involved phenomenon have not been fully addressed theoretically. In this work, we derive a mathematical model of electrodeposition-induced plastic flow in metal/inorganic solid-conductor systems. We use a semi-analytical solution to derive pressure increase expressions at metal protrusions and assess the possibility of fracture. The results give flow solutions analogous to laminar channel flow. The solutions also show how taking into account a boundary traction potential from built up pressure, leads to ionic redistribution and effectively screens isolated flaws, making local current focusing an incomplete explanation for observed electrolyte fracture. We show that the boundary traction potential sets a maximum value for the pressure increase that can occur from deposition at an isolated flaw. We derive conditions under which fracture can occur, and quantify the role of ionic conductivity and electrolyte fracture toughness in extending safe operating regimes of solid-state electrolytes with metal electrodes.
Highlights
To cite this article: Luis Barroso-Luque et al 2020 J
We present a continuum scale model for electrodeposition induced plastic flow in reactive metal electrode and solid ionic conductor systems, similar to what was done in work on molten Na and β-alumina
We show that when the effects of a boundary traction on deposition are neglected, and no other ionic redistribution methods are considered, the metal flow is exactly analogous to laminar and fully developed channel flow; and the pressure increase is spatially linear as given by Armstrong.[24]
Summary
To cite this article: Luis Barroso-Luque et al 2020 J. The use of solid inorganic ion conductors paired with a reactive metal electrode, such as Li or Na, is being increasingly studied as a promising path to increase energy density of current Li-ion battery technology. Understanding electrodeposition from a solid electrolyte to a reactive metal is a vital step toward resolving the underlying problems observed from cycling reactive metal solid state batteries (MSSB). Current research has suggested that conductor-metal interface contact, parasitic interface reactions, deposited metal nucleation and metal propagation through the solid conductor are the main challenges limiting current development in MSSBs.[3] These unresolved challenges stem from a limited understanding of solid state electrodeposition, where electrochemical and mechanical behavior can be strongly coupled. The mechanism is described by increased current densities at sharp defects and edges leading to high deposition rates which cause large
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