Controlling stack pressure inhomogeneity in anode-free solid-state batteries using elastomeric interlayers

Abstract

“Anode-free” solid-state batteries (SSBs) can enable high energy densities through in situ formation of a lithium (Li)-metal anode. This work investigates the effects of inhomogeneous stack pressure on Li plating and stripping at the interface between a Li₆PS₅Cl solid electrolyte and copper current collector. Elastomeric interlayers are shown to promote a uniform pressure distribution, which can compensate for interfacial roughness and/or misalignment of the external plates used to apply stack pressure. Owing to the improved pressure uniformity, the Li plating coverage increases from 49% to 70% after charging to 2 mAh/cm², and Coulombic efficiency increases from 89% to 94%. The interfacial stress distribution is quantified using finite-element simulations under different interlayer conditions. This work demonstrates that stack pressure should not be defined as a singular quantity but as a parameter that varies in space and time as cycling evolves. This highlights the importance of packaging and component design for SSBs.