Alloy Anodes in Sulfide-Based Solid-State Batteries

Alloy anodes offer high theoretical capacity, but they typically exhibit fast capacity decay in lithium-ion batteries because of excessive solid-electrolyte interphase growth. Here, we investigate a variety of alloy anodes in sulfide solid-state batteries, and we show that they can exhibit significantly improved interfacial stability and enhanced cyclability when engineered effectively. <i>In situ</i> measurement of stack pressure evolution during cycling shows that the volume changes of alloy anodes can lead to large pressure swings within the solid-state battery cell, giving insight into electrode composite evolution. We further investigate the fundamental electrochemical behavior of 12 different foil-based alloy anode materials in solid-state batteries, and we find that lithium trapping by the delithiated phase can play a key role in limiting performance. Based on these insights, we present a new design for dense foil aluminum-based alloy anodes with multiphase microstructure that offers significantly improved performance due to retained transport pathways within the foil. This design offers a paradigm that does away with slurry coating, potentially reducing manufacturing costs. In addition, we investigate solid-state dealloying of foil anodes to understand the interplay between densification and interfacial contact evolution at different stack pressures. Taken together, these findings show the importance of controlling chemo-mechanics and interfaces in alloy anodes for sulfide-based solid-state batteries for improved energy storage capabilities.