An Analysis of Solid-State Electrodeposition-Induced Metal Plastic Flow and Predictions of Stress States in Solid Ionic Conductor Defects

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.

Promises and Challenges of Next-Generation “Beyond Li-ion” Batteries for Electric Vehicles and Grid Decarbonization

“…In addition, high ionic conductivity has been shown to limit pressure build up in the SE and may therefore favorably influence resistance against Li penetration. 217 More superionic conductors are likely to be discovered given the improved understanding of alkali-ion conductivity 218−223 and the large number of discovery projects going on worldwide. 224−229…”

“…287,288 The use of a Li metal anode results in additional issues of contact loss during plating/stripping, possible interfacial reactions, and Li propagation through the conductor. 214,215,217,289 Most of these mechanical and chemical interfacial instabilities increase the overpotential, resulting in lower energy density and capacity fade. Finally, practical cells will also require very thin SE separators that are easily processed and handled, and high cathode loading, which are issues that have only been partially addressed so far by the scientific community.…”

Synchrotron Imaging of Li Metal Anodes in Solid State Batteries Aided by Machine Learning

“…20 Finally, interface and surface roughness has also been identified as a crucial factor dictating filament nucleation and growth. 21 Recently, a few experimental studies have suggested that lithium filament growth is affected by stack pressure. 10,14,17 The latter result suggests that non-uniform contact upon electrochemical cycling may be a significant driver for filament growth.…”

Transitioning solid-state batteries from lab to market: Linking electro-chemo-mechanics with practical considerations

“…It is generally hypothesized that the ability of a Li filament to nucleate and propagate is dependent on the fracture toughness of the electrolyte. 11,[28][29][30] Additionally, the strains associated with cathode particle expansion or the strain associated with interphase formation have been shown to be sufficient to fracture the solid electrolyte. 7,8,31 The dynamic nature of the interface poses further restrictions on the mechanical properties of coatings and interlayers, which must also be sufficiently tough to avoid fracture.…”

“…Although earlier models for describing electro-chemo-mechanical phenomena in SSBs only considered the elastic response of the Li metal, the recent increase in experimental measurements have aided the development of models to account for the complexities of both elastic and plastic behavior, as illustrated by the examples in Figure 2. For example, a work by Barroso-Luque et al 30 developed a model to predict the magnitude of internal pressures generated by Li electrodeposition into a Griffith-like flaw. Barai et al 37 studied the impact of inhomogeneity (grain boundaries) on Li penetration in LLZO, accounting for both elastic and plastic deformation of the Li (Figure 2D).…”