Turning many into one: Single-crystal metal foils are valuable for their surface properties that allow for synthesis of materials like graphene. Jinet al.present a strategy for creating colossal single-crystal metal foils called “contact-free annealing” (see the Perspective by Rollett). The method relies on hanging and heating commercially available, inexpensive, cold-rolled metal foils. Almost as if by magic, the polycrystalline grains rotate and anneal into a large single-crystal sheet with a specific crystal orientation. The strategy allows for the creation of much larger and much cheaper single-crystal metal foils.Science, this issue p.1021; see also p.996

Anode-free lithium (Li) batteries that function via direct Li plating/stripping on metal current collectors have garnered significant interest in the field of metallic Li as an ideal negative electrode. However, dendritic Li growth creates unoccupied space in the battery, diminishing volumetric energy density. Our research reveals that Li adatoms can reposition on metal substrates via surface migration by interacting with individual grains at the atomic level after electro-adsorption of Li ions. By examining Li morphologies on diverse types of substrates, we find that the near-zero migration barrier of Li adatoms, especially on single crystal Cu(111) foils, is a key parameter that inhibits Li dendrites by initiating horizontal growth in an isotropically faceted nucleation shape, with 80% capacity retention even after 120 cycles (versus 29 cycles for polycrystalline Cu), paired with LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathodes with a high-loading level (5.3 mA h cm⁻²). Based on our findings, we highlight the importance of metal substrates that promote favorable surface dynamics of Li adatoms.