Ion-Exchange in LLZTO to Induce Compressive Stress and Improve Electrochemical Performance

This experimental study builds on a computational model that analyzed the feasibility of ion-exchange (IX) in the solid electrolyte (SE) lithium lanthanum zirconium tantalum oxide (LLZTO) [1]. IX is commonly used to increase the fracture resistance of glasses. Employing IX to induce compressive stress in a solid electrolyte like LLZTO also has the potential to improve electrochemical performance by delaying lithium (Li) filament penetration through the SE. To explore this, various salt chemistries and heat treatments were employed. A multi-beam optical stress sensor (MOSS) was used to measure curvature due to the IX induced stress. Scanning electron microscope (SEM) and electron-dispersive X-ray spectroscopy (EDS) were used to further characterize samples. Electrochemical tests with symmetric Li/Li cells, including long-term cycling tests and critical current density (CCD) measurements were used to benchmark improvements in electrochemical performance compared to baseline values. Results demonstrate that carefully 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.<br/> <br/> <br/>[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