Metallurgically integrated Cu-Sn interphases on ultrathin Cu current collectors for Li-inventory-dependent lithium-metal batteries

초록

Current collectors for lithium-metal batteries must control both initial Li nucleation and the formation and evolution of the reconstructed interface established during first lithiation. Here, phase-controlled Cu-Sn interphases were fabricated on ultrathin Cu current collectors by a scalable rolling-annealing route, enabling a systematic transition from a Sn-rich surface layer to mixed Cu6Sn5/Cu3Sn regions and Cu3Sn-rich frameworks. The interphase constitution changed the first-lithiation pathway and suppressed the apparent Li nucleation overpotential from ∼65 mV on bare Cu to near-zero values on CS_280, although alloying reactions and Li nucleation may partially overlap in Cu3Sn-rich samples. Combined microscopy, diffraction, spectroscopy, impedance, and cycling results indicate that Cu3Sn-rich interphases are associated with reduced protrusive Li growth and with thinner, denser Li-containing regions within a reconstructed interfacial zone. Because Li is not directly detected by EDS, this assignment is treated as an interpretation rather than direct Li mapping. In anode-free full cells (N/P = 0), moderately alloyed CS_150-CS_280 electrodes retained approximately 40–50% capacity after 100 cycles and approximately 25–30% after 200 cycles, exceeding bare Cu. Under Li-excess conditions (N/P = 3), the more Cu-rich CS_350 retained ∼80% after 100 cycles. The central contribution of this work is to establish a scalable, phase-controlled metallurgical interphase platform and demonstrate that the initial Cu–Sn phase constitution governs first-lithiation reconstruction, while the balance between reconstruction-induced Li consumption and interfacial stability determines the optimum current collector under different Li inventories. Copyright © 2026. Published by Elsevier Ltd.

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