SUMMARY

Electric energy storage is an ever increasing area of demand in our modern world. Rechargeable batteries have thus become essential for a wide range of applications. This is due to the increase in demand for portable electronics and electric vehicles: These applications specifically require high-density batteries, as the weight and size of the battery is a limiting factor in many designs.

One method for solving the problem of energy density is by utilizing novel higher capacity anode materials in alkali-ion batteries (AIBs). But, the most promising high-capacity anode materials for these applications suffer from large volumetric expansions which if unheeded quickly lead to their fracture and failure, resulting in very poor cyclability. Thus, understanding of their mechanical properties is a lynchpin in their applicability.

In addition to the desire for higher capacity, another factor of gasoline combustion engines that must be competed with is their ability to last for decades, while the batteries in our phones and laptops degrade massively in just the span of a few years, and there have even been examples of batteries in electric vehicles experiencing thermal runaway and combusting catastrophically. Greatly increasing reliability, cyclability, and safety are essential traits desired for any battery system.

For this aim, there has been interest in solid electrolytes (SEs), which would immediately reduce the risk of combustion due to their higher stability and lower flammability. Recently there have been new chemistries which were shown to have high conductivities comparable to those of liquid electrolytes. But very little is known about the mechanical properties of these materials, which are relevant to SEs’ potential role in suppression of dendritic growth and their resistance to fracture if they are bonded to an electrode with large volumetric change.

For this proposed work, a coupled experimental and computational approach will be used, conducting a range of temperature dependent Nanoindentation tests on lithiated and sodiated germanium anodes, and LLZO, LAGP, LSPS, and LPSC SEs. These experimental results will be coupled with finite element continuum modeling to further elucidate the experimental results, helping to determine fundamental chemo-mechanical characteristics of the material systems. This knowledge will assist in the making these SEs and high capacity battery anodes commercially viable.