Constructing a Synergistic Triple Layer Interfacial Design for Dendrite-Free and High-Performance Lithium Metal...

Lithium metal anodes offer exceptionally high energy density but are hindered by unstable solid-electrolyte interphase (SEI) formation, nonuniform lithium deposition, and large volumetric fluctuations. Although three-dimensional (3D) hosts have been widely developed to alleviate these limitations, the SEI layer generally forms as a single layer, which is easily destabilized during repeated cycling. To address this, double layer strategies that introduce alloy formation and an artificial SEI have been proposed, often incorporating inorganic species such as LiF and Li₂S for their high ion conductivity. However, their low electronic conductivity still leads to issues such as high interfacial resistance. These limitations indicate the need for an additional layer that can play a complementary role by enhancing electronic conductivity. In this work, we developed a synergistic triple layer generated on nickel foam (STLG@NF) through an in situ electrochemical reaction. During initial cycling, Ni₃S₂ undergoes conversion to generate a Li₂S-rich bottom layer with high ionic conductivity that promotes rapid and uniform Li⁺ transport. The middle carbon layer provides high electronic conductivity and mechanical reinforcement, enabling a more homogeneous electron distribution and accommodating repeated volume changes. On the surface, a well-regulated outer SEI layer forms, acting as a chemical barrier against continuous electrolyte decomposition and regulating Li⁺ flux through more uniform and stable ion transport. The synergistic coupling of these three layers stabilizes interfacial reactions, suppresses Li dendrite growth, and maintains structural integrity throughout cycling. As a result, the Li-STLG@NF anode delivers long-term stability in symmetric cells for over 3000 h with a low overpotential of 11 mV and maintains more than 80% capacity after 500 cycles in LiFePO₄ full cells.