This student-run monthly series spotlights the latest research from Stanford, presented by PhD candidates and postdocs. Registration is required, and is free and open to the public.

This month's speakers:

Samuel Lee, Ph.D. Candidate, Stanford University
"Heterogeneous Doping via Nanoscale Coating Impacts the Mechanics of Li Intrusion in Brittle Solid Electrolytes"

Talk Abstract: Lithium dendrite intrusion in solid-state batteries limits fast charging and causes short-circuiting, yet the underlying regulating mechanisms are not well-understood. Here we discover that heterogeneous Ag⁺ doping dramatically affects lithium intrusion into Li6.6La3Zr1.6Ta0.4O12 (LLZO), a brittle solid electrolyte. Nanoscale Ag⁺ doping is achieved by thermally annealing a 3-nm-thick metallic coating on LLZO, inducing Ag–Li ion exchange and Ag diffusion into grains and grain boundaries. Density functional theory calculations and experimental characterization show negligible impact on the electronic properties and surface wettability from Ag⁺ incorporation. Mechanically, nanoindentation experiments show a fivefold increase in the mechanical force required to fracture the surface Ag+-doped LLZO, indicating substantial doping-induced surface toughening. Operando microprobe scanning electron microscopy experiments show that the Ag⁺-doped LLZO surface exhibits improved lithium plating at >250 mA cm−2 and an electroplating diameter that is expanded by over fourfold, even under an extreme indentation stress of 3 GPa. This demonstrates enhanced defect tolerance in LLZO, rather than electronic or adhesion effects. Our study reveals a chemo-mechanical mechanism via surface heterogeneous doping, complementing present bulk design rules to minimize mechanical failures in solid-state batteries.

Speaker's Bio: 

Samuel Lee is a 4th-year Ph.D. candidate, co-advised by Prof. Will Chueh in Materials Science & Engineering and Prof. Wendy Gu in Mechanical Engineering at Stanford University. His research focuses on understanding the failure mechanisms in solid-state batteries, especially the lithium dendrite growth in solid electrolytes during fast-charging conditions. Previously, he received his B.S. from The University of Texas at Austin in Austin, Texas in 2021, graduating with an Honors in Mechanical Engineering.