Abstract
Dendrite-induced short circuits threaten the deployment of solid-state batteries with metal anodes. Whether dendrites grow by internal chemical reduction of lithium or because of mechanical stresses has been a topic of debate. For both oxide and electrolyte electrolytes, we address this question by conducting operando microscopy to observe mechanical and electrochemical phenomena underlying dendrite growth. Here, we build upon the method from Athanasiou-Fincher et al. to observe stress-optic couplings around dendrite tips in thin oxide electrolytes[1]. Specifically, operando measurements of dendrite-induced stress fields are measured as a function of applied potential, and then the images are quantitatively analyzed to measure the mechanical driving forces underlying failure (i.e., the energy release rate). These operando measurements demonstrate a complex interplay between electrochemistry and mechanics. We develop a mechanistic framework to describe the observed behavior, discussed in juxtaposition with stress-corrosion cracking and linear elastic fracture mechanics. The resulting implications for electrolyte testing and design are discussed. Lastly, we assess whether mechanical stresses in electrolytes can be used to "steer" the dendrite growth directory. By dynamically applying mechanical loads to growing dendrites in LLZTO, we show that dendrite growth trajectory can be deflected to avoid short-circuit failures in oxide electrolytes[2]. Together, these results demonstrate a complex relationship between electrochemical and mechanical driving forces. Despite the observed complexity, processing-induced residual stresses can deflect dendrites and avert short circuits.
[1] CE Athanasiou=, CD Fincher=, C Gilgenbach, WC Carter, H Gao, YM Chiang, BW Sheldon. Manuscript in preparation. "On the Use of Photoelasticity for Operando Dendrite-Induced Stress Quantification in Ceramic Electrolytes," 2022 Materials Research Society Fall Conference; manuscript in preparation.
[2] CD Fincher, CE Athansiou, C Gilgenbach, MJ Wang, BW Sheldon, WC Carter, YM Chiang, "Controlling dendrite propagation in solid-state batteries with engineered stress," Joule, in press. DOIs: 10.1016/j.joule.2022.10.011