Clarification of Li deposition behavior on anodes with a porous interlayer in Li-free all-solid-state batteries

Abstract

In Li-free all-solid-state batteries (ASSBs) with a sulfide solid electrolyte (SE), the reactivity between Li and sulfide renders the separation of these two components desirable. A porous interlayer coated on the anode may limit this contact of SE with Li. However, a lack of understanding regarding Li deposition makes the composite anode design difficult. Herein, we identify the factors determining the morphology and location of Li deposits in Li-free ASSBs with a porous interlayer based on the thermodynamics of Li electrodeposition and the kinetics of Li movement through the interlayer. We find the adhesion work as one determining factor for the location of the main Li deposits. We explore several kinetic factors including the pore size of the interlayer, temperature, scaffold materials, and surface modification with Ag nanoparticles. The influence of the pore size on Li deposition suggests that Li moves through the interlayer via Coble creep, with smaller pores, higher temperatures, and a lithiophilic surface facilitating this process. We propose a scenario for pore-size-dependent Li deposition based on diffusional creep, inhomogeneity, and resulting stress within the interlayer. This work increases the fundamental understanding of Li deposition behavior and opens new avenues for the development of highly reversible Li-free ASSBs.