Redesigning Interlayers for Anode‐Free Batteries: Harnessing Continuity and Metal Inventory

ABSTRACT

This Perspective establishes a design filter to guide the rational design of interlayers in anode‐free batteries. Roughness‐dependent closure models are combined with active‐metal inventory accounting during alloying and conversion, including incomplete recovery during cycling. The analysis shows that interlayer feasibility is governed by a narrow intersection of morphology, chemistry, and deposition physics: coatings must be continuous on practical battery substrates while remaining compatible with the finite cathode‐derived metal inventory. Low‐uptake alloy‐forming interlayers can remain inventory‐efficient at moderate thicknesses, whereas conversion oxides and nitrides generally require ultrathin designs unless partial transformation or high recovery efficiency is demonstrated. Deposition route selection is equally critical: line‐of‐sight PVD offers broad materials flexibility but may require inventory‐expensive closure thicknesses on rough substrates, whereas ALD‐type growth can enable conformal coverage at much lower nominal thickness. The resulting design maps provide a unified basis for selecting interlayer chemistry, thickness, substrate roughness, cathode loading, and deposition route under a finite cyclable‐metal inventory.