Structural Changes in the Silver-Carbon Composite Anode Interlayer in Solid-State Batteries

Solid-state batteries, in which a lithium foil anode is used in conjunction with a ceramic solid electrolyte, promise to improve the energy density and safety of cells. However, charging solid-state batteries at practical rates on the order of 1-10 mA cm^-2 can lead to cell failure. Solid-state batteries fail at high rates of charge because, as Li metal is plated to the anode, dendrites (filaments of Li metal) penetrate through the ceramic electrolyte, short-circuiting the cell. One approach to mitigate this problem has been to introduce an interlayer between the ceramic electrolyte and the lithium anode to facilitate homogeneous Li deposition and protect against dendrite penetration; with inorganic, metal, and carbon-based interlayers having been shown in the literature to increase charging critical currents.<br/>In this work, we study the structural changes of interlayers in cells pairing a lithium metal anode and a Li₆PS₅Cl solid electrolyte by a combination of techniques including electrochemistry and <i>operando</i> powder X-ray diffraction. In addition, the relationship between the rate of charge, the Li-ion diffusivity of the interlayer, and the effectiveness of the interlayer in protecting against dendrite growth are discussed.