Synergistic Lithium Alloying and Plating in 3D Cu/CNT/Sn Electrodes for Stable Lithium Metal Batteries

Anode-less Li-ion batteries, in which Li is reversibly plated onto and stripped from a metal current collector during charge and discharge, theoretically offer the highest possible anode energy density. However, such systems suffer from rapid self-discharge, excessive solid electrolyte interphase (SEI) formation, and dendritic lithium growth, resulting in severe performance degradation and safety concerns. Here, these challenges are addressed by introducing a novel 3D current collector that enables energy storage via a hybrid mechanism of alloying and plating. The 3D current collectors are fabricated through two scalable electroplating processes involving a porous Cu plating process followed by a Sn surface coating, and are structurally reinforced with carbon nanotubes (CNTs) to form a mechanically robust and conductive scaffold. The relative contributions of the alloying and plating reactions to the cell capacity are modulated by adjusting the thickness of the Sn layer, which governs the extent of lithiation through alloy formation. By optimizing the capacity distribution between Sn alloying and Li plating, the resulting half-cell exhibits stable cycling over 200 cycles with an average Coulombic efficiency of 93.9%, significantly outperforming a control cell with planar Cu foils, which retain only 71.3% efficiency after 110 cycles.