Kinetics in Li Plating onto Ag-C Porous Interlayer in Li-Free Solid-State Batteries

Li-free solid-state batteries, which contain no excess Li metal initially, are considered promising next-generation energy storage systems due to their high energy density and enhanced safety. However, heterogeneous Li plating onto the current collector leads to early failure and low energy efficiency. Porous interlayers positioned between the current collector and solid electrolyte have the potential to guide uniform Li plating and improve electrochemical performance [1]. In this configuration, both the electrochemical reduction of Li ions and mechanical deformation, which allow Li metal to flow into the porous interlayer, occur simultaneously [2]. These complexities make understanding Li plating kinetics challenging. Factors such as stack pressure, interlayer composition, current density, and the mechanical response of the interlayer can influence Li deposition kinetics. This study explores how these factors impact Li movement through the interlayer and the morphology of Li electrodeposits. We employed a porous Ag-C interlayer with two different Ag particle sizes and observed Li plating behavior under various stack pressures and current densities. While Ag nanoparticles in the interlayer can facilitate Li movement, they can also induce internal stress, leading to void formation that impedes Li flow. Nanostructure analysis using cryo-FIB are combined with chemomechanicl modeling to uncover the mechanical interaction of interlayer during the alloying reaction between Ag and Li. When comparing the morphology of Li electrodeposits at different conditions, morphological changes correlate with the creep strain rate over Li ion flux. The electrochemical performance is determined by the morphology of Li electrodeposits rather than the Li plating current density.<br/><br/>[1] Lee, Yong-Gun, et al. "High-energy long-cycling all-solid-state lithium metal batteries enabled by silver–carbon composite anodes." Nature Energy 5.4 (2020): 299-308.<br/>[2] Park, Se Hwan, et al. "Clarification of Li deposition behavior on anodes with a porous interlayer in Li-free all-solid-state batteries." Journal of Materials Chemistry A 10.41 (2022): 21995-22006.