Stephanie Sandoval1,Francisco Quintero Cortes2,Emily Klein1,John Lewis1,Pralav Shetty1,David Yeh1,Matthew McDowell1
Georgia Institute of Technology1,Capacitor Foundry2
Stephanie Sandoval1,Francisco Quintero Cortes2,Emily Klein1,John Lewis1,Pralav Shetty1,David Yeh1,Matthew McDowell1
Georgia Institute of Technology1,Capacitor Foundry2
Lithium metal batteries (LMBs) offer higher energy density, but the uncontrollable growth of lithium throughout cycling limits the electrochemical performance of LMBs in liquid electrolytes. The morphology of electrodeposited lithium is strongly correlated to the Coulombic efficiency (CE) and is dictated by the nature of the substrate. Further investigation is required to understand the nucleation and growth of lithium, as well as degradation processes in lithium electrodes, especially in the context of methods designed to spatially control growth of lithium. Here, we investigate how lithium alloy layers affect the electrochemical growth and evolution of lithium during deposition and stripping using electrochemical methods and <i>operando</i> optical microscopy. We find that silver thin films enable improved CE for lithium cycling compared to bare current collectors and other alloy layers (antimony) in a variety of liquid electrolyte systems. Specifically, silver-coated electrodes exhibit an average CE of 93.8% (compared to 82.2% for bare stainless steel) in an ether-based electrolyte. Performance degradation is investigated within the alloy electrodes, and <i>ex situ</i> SEM indicates that the differing mechanical properties of alloy layers play a key role in enabling higher CE. <i>Operando </i>optical microscopy reveals reduced dendritic growth of lithium on silver-coated current collectors at higher current densities (4 mA cm<sup>-2</sup>) compared to bare current collectors, and image analysis enables direct correlation between electrochemical signatures and observed dendritic growth dynamics. The microscopy experiments also show different stripping behavior between alloy and non-alloy electrodes, with spatially non-uniform stripping dominating on bare stainless steel current collectors. This work provides new understanding of the interaction of lithium metal with alloy substrates and highlights the importance of interfacial layers at the current collector that can potentially enable anode-free configurations with long cycle life.