Lawrence Berkeley National Laboratory

Ion-exchange (IX) is frequently used in the manufacturing of glasses to increase their fracture resistance. Using IX to introduce surface layer compressive stress in a solid electrolyte like lithium lanthanum zirconium tantalum oxide (LLZTO) has the potential to improve electrochemical performance by delaying lithium (Li) filament penetration through the solid electrolyte (SE). Computational work has proven the feasibility of ion-exchange between lithium ions and larger ions in LLZTO depending on the precursor used [1]. This experimental work explores several salt chemistries and heat treatments to evaluate the impact of IX on LLZTO. A multi-beam optical stress sensor (MOSS) was used to measure changes in curvature from IX induced stress. Scanning electron microscope (SEM) and electron-dispersive X-ray spectroscopy (EDS) were used to characterize the composition of samples. Symmetric Li/Li cells were used to measure critical current density (CCD) and for long-term cycling tests to benchmark improvements in electrochemical performance. Results show controlled IX with LLZTO can introduce stress in the near surface layer, increase CCDs, and improve long-term cycling performance in a symmetric Li/Li cell. [1] Tradeoff between the Ion Exchange-Induced Residual Stress and Ion Transport in Solid Electrolytes. Harsh D. Jagad, Stephen J. Harris, Brian W. Sheldon, and Yue Qi. Chemistry of Materials 2022 34 (19), 8694-8704. DOI: 10.1021/acs.chemmater.2c01806