Beyond Nucleation Overpotential: Reframing Deposition Substrates in Anode‐Free Metal Batteries

Although anode‐free metal batteries are often interpreted through nucleation overpotential and metal philicity, these concepts alone are insufficient to explain practical performance. When current‐collector or interlayer properties remain expressed, reversibility is governed by multiple interfacial bottlenecks that extend beyond nucleation to lateral growth, contact retention, interfacial reactivity, and stripping. Here, we reposition nucleation overpotential as one descriptor within a broader substrate‐centered framework for deposition‐interface design. We focus primarily on low‐ or negligible‐pressure conditions and electrolyte/interphase regimes in which substrate effects remain clearly expressed and discuss additional substrate‐controlled factors, including surface migration, adhesion/contact retention, alloying or interfacial reactivity, crystallographic texture/facet exposure, and mesoscale heterogeneity. We further outline a descriptor‐guided workflow that links dominant failure signatures to the most likely controlling bottlenecks, the most informative measurements, and corresponding interface‐design strategies. Because the controlling factor depends on chemistry, architecture, and failure mode, we propose moving from one‐metric ranking toward a more diagnostic, descriptor‐guided design logic for anode‐free metal batteries.