Uncover Transport, Mechanics and Failure in Solid Electrolytes Through Atomic and Dynamic Visualization

Solid electrolytes with superior ionic conductivity, fast interfacial kinetics, and high mechanical strength are promising for renewable energy storage and conversion systems such as batteries and fuel cells. However, fundamental mechanisms of charge transport and the related electro-chemo-mechanics are not well understood. In this talk, I will highlight my recent work on two types of solid electrolytes: an oxygen-ion conductor CeO₂ for fuel cells, and a Li-ion conductor Li₇La₃Zr₂O₁₂ for solid-state batteries. First, I will present a unique approach to study the charge transport at grain boundaries in polycrystalline CeO₂: a combination of electron holography and atom probe tomography. The atomic visualization of electric fields and chemical species reveals the chemical origins of resistive grain boundaries. These insights suggest chemical tunability of grain boundary transport properties which can potentially benefit the design of low temperature solid-oxide fuel cells, solid-state batteries and sensors. Second, I will discuss the Li intrusion phenomena in Li₇La₃Zr₂O₁₂, a failure mechanism in solid-state batteries involving both electrochemistry and mechanics. Using <i>operando</i> electron microscopy and statistical analysis, I will discuss the mechanical origins of Li intrusion and highlight the mechanical tunability of electrochemical plating reactions in brittle solid electrolytes. I will also show how surface engineering with ultra-thin 3 nm metallic coatings can significantly toughen solid electrolytes and reduce detrimental lithium intrusions.