Unlocking the Potential of Li–Ag Alloys: Phase Selection and Practical Application

Abstract

Dendrite formation, contact loss, and continuous formation of the solid electrolyte interphase (SEI) preclude the practical use of the energy-dense lithium (Li) metal. Li–Ag alloys have the potential to address these issues due to their exceptional lithiophilicity, outstanding mechanical stability, and moderate chemical stability. This study evaluates all phases in the Li–Ag phase diagram based on lithiation capacity, Li insertion, mechanical property, and chemical stability. Our findings suggest that Li4Ag is the most promising phase, and the Gibbs free energy of nucleation (∆Gnucle) for Li–Ag alloys is 3 to 5 orders of magnitude smaller compared to pure Li, resulting in uniform nucleation and deposition behavior. We proposed practical applications within the Li4Ag phases or from the Li9Ag4 to the Li4Ag phases, which may provide a usable capacity of 409 to 696 mAh/g, respectively. Experiments indicate that Li4Ag exhibits not only the smallest impedance but also the highest capacity retention compared to Li9Ag4 and pure Li. The study provides valuable guidance for the selection and application of Li-containing alloys in future battery development.