Structure and mechanical properties of electroplated mossy lithium: Effects of current density and electrolyte

Abstract

Mechanical suppression, e.g., by applying stack pressures and using functionalized coatings, has been considered a promising approach to inhibit the formation of lithium (Li) dendrites and improve the cycling stability of the Li metal electrode. However, a lack of understanding of the mechanical behavior of electroplated mossy Li, consisting of loosely packed Li dendrites that are covered by solid electrolyte interphase, hinders the development of mechanical suppression strategies and limits the understanding of the electromechanical behavior of mossy Li. In this study, we investigated, using flat punch indentation in an argon-filled glovebox, the room temperature mechanical behavior and its relationship with the microstructure of mossy Li electroplated using different current densities (between 0.25 and 10 ​mA/cm2) in several electrolytes. The dendrite size decreases and the porosity of mossy Li increases with increasing current density. Mossy Li has lower Young’s modulus (E) but significantly higher creep resistance than bulk Li. A scaling relationship between E and porosity is established for mossy Li. The creep behavior of mossy Li exhibits a strong size effect, i.e., the steady-state impression velocity decreases with decreasing dendrite size. These findings provide a comprehensive understanding of the relationship between the microstructure and mechanical behavior of mossy Li.