The Effects of Electric Field Distribution on the Interface Stability in Solid Electrolytes

Abstract

Ceramic electrolytes could potentially enable Li metal anodes, leading to safer and more energy dense solid-state batteries. However, it has been hypothesized that electric field amplification at electrode edges can destabilize the interface and lead to short circuiting during charging. By comparing models of the electric field distribution at the electrode/electrolyte interface for varying electrode geometries with experimental solid-electrolyte systems, we show that areas of high electric field can localize at sharp corners, which may facilitate Li metal penetration at these locations. Symmetric Li/ Li6.5La3Zr1.5Ta0.5O12 (LLZO) cells were cycled until failure and the spatial distribution of the degradation was analyzed using electron microscopy. We report a decrease in nominal critical current density (CCD) from 1.48 to 1.26 mA cm−2 due to a 15% increase in electric field from edge effects. Moreover, when considering the CCD locally at spots of high electric field amplification, we find current densities of at least 4 mA cm−2 can still be sustained. Non-uniform electric field distributions at the Li/LLZO interface could play a major role in determining cycling capabilities and failure modes of solid-state batteries and may also have important implications for the manufacturing of Li metal battery electrodes.