Construction of Heterostructured Multi-Grain Solid Electrolyte Interphase with Trace Alloying for Fast Li ion Transfer and Dendrite-Free Lithium Metal Batteries

Abstract

Lithium metal batteries (LMBs) offer exceptional energy (∼500 Wh kg−1 and 1200 Wh L−1), nearly twice that of conventional LIBs using graphite anodes due to the high theoretical capacity (3,860 mAh g−1) and low redox potential (-3.04 V<inf>SHE</inf>) of Li metal. However, the practical application of Li metal anodes (LMAs) is limited by the growth of dendrites and rapid interfacial failure, which originate from the fragile native solid electrolyte interphase (SEI) and the lithiophobic, host-less nature of conventional Cu current collectors. In this work, we propose a bifunctional interfacial strategy using trace Sn-doped Cu(I)–thiourea nanowires (SCN), fabricated by a rapid pulsed electrodeposition (PED) process. Balancing anodic and cathodic pulses enables uniform nanowire growth with controlled trace Sn incorporation. The SCN layer provides two synergistic functions: (i) a lithiophilic Sn/Li<inf>x</inf>Sn alloy that lowers nucleation overpotential and guides uniform Li nucleation without severe expansion, and (ii) a robust, ion-conductive multi-inorganic SEI (LiCl, Li<inf>x</inf>N, and Li<inf>2</inf>S<inf>2</inf>/Li<inf>2</inf>S<inf>x</inf>) forming a multi-grain structure with abundant grain boundaries for fast Li+ transfer. As a result, Li@SCN exhibits a Li+ diffusivity 24 times higher than that of bare Cu, dendrite-free morphology, and stable cycling. Symmetric cells sustain >900 h of operation with low polarization, while LFP‖Li@SCN full cells deliver 162.0 mAh g−1 with excellent retention (98.2%) over 480 cycles at 1.0 C. © 2026 Elsevier B.V.