Dr. Sergiy Kalnaus
Computational Sciences and Engineering Division
Oak Ridge National Laboratory

Does Mechanical Behavior of Invert Glasses Make Them Ideal Solid State Electrolytes?

ABSTRACT: Inorganic electrolytes for solid state batteries with lithium metallic anodes must combine properties such as high ionic conductivity, chemical stability, and resistance to failure due to propagation of Li dendrites. Abundance of experimental evidence suggests that cracking of the solid electrolytes due to pressure exerted by lithium plating into the material defects is the primary source of failure. This is due to inherent brittleness of the ceramic ionic conductors, i.e., their inability to reduce stress by means other than fracture. Unlike ceramics, plastic deformation in glass can be achieved via shear and/or by densification. Both mechanisms can be operational in glasses with reduced content of glass formers relative to the content of glass modifiers – i.e., invert glasses. Using the example of lithium phosphorus oxynitride (LiPON), this talk will demonstrate how these two mechanisms are capable of accommodating applied stress while avoiding creation of new surfaces by cracking. Dr. Kalnaus will investigate the resistance to fracture in LiPON-like glasses and the underlying connection to their composition via instrumented nano-indentation, Raman spectroscopy, and numerical simulations. Enhancement of isochoric shear with increase of lithium content, similarly to the reports of increased plasticity in sodium aluminoborate glasses with high alkali content will be observed. Nano-indentation demonstrates that LiPON is extremely resistant to fracture, compared to other inorganic solid electrolytes.

BIOGRAPHY: Sergiy Kalnaus is a senior staff scientist at Oak Ridge National Laboratory (ORNL) in the Multiphysics Modeling and Flows Group. He joined ORNL’s Materials Science and Technology Division in 2009. His interests are in mechanics of materials and numerical simulations of mass and charge transport in energy storage devices to improve their performance and safety. He has over 140 papers, holds 7 patents, and he is a recipient of a Research & Development 100 Award for the development of impact resistant electrolyte for lithium-ion batteries. He received his Bachelor of Science and Master of Science degrees from Kharkiv Polytechnic University in Ukraine and Ph.D. from the University of Nevada.