The Effect of Alloying Interlayers on Lithium Anode Morphology and Microstructure in “Anode-Free” Solid-State Batteries

“Lithium–metal-free” manufacturing of solid-state battery cells could simplify cell assembly and increase the energy density. However, the performance of these cells benefits from a more homogeneous anode formation. The use of thin alloying interlayers in “lithium–metal-free” cells can improve cycle life, but their influence on the morphology and microstructure of plated lithium is yet unknown. Gold and silver interlayers allow for lithium plating at higher current density (0.25 mA cm^–2) without short-circuiting compared to cells without interlayers. The lithium homogeneity is substantially improved, as shown by optical microscopy and 3D profiling. In addition, electron backscatter diffraction determined that the grain size and grain boundary orientation can be controlled by changing the lithium layer composition in the case of silver or by introducing inert particles when using gold interlayers. These findings further the understanding of how thin alloying interlayers can substantially alter the cycling performance of lithium in “lithium–metal-free” solid-state batteries.