Gradient LiCl-LiF-LiIn Solid-Electrolyte-Interphase for Dendrite-Free Li-Metal Anode

Building a robust artificial composite interphase layer is a promising approach for stabilizing lithium-metal anode, however, fully exploiting the synergistic effects of composite structures and developing scalable manufacturing methods are the keys to optimizing battery performance and promoting practical applications. Here, we propose a ternary heterostructural gradient design, and develop a universal chemical metathesis to in-situ constructing a gradient LiCl-LiF-LiIn composite interphase layer onto lithium-metal. This composite layer exhibits an interpenetrated gradient structure with controllable morphology and thickness. The modified electrode shows a plat and dense interface layer, with its structure presenting a heterogeneous, vertically oriented components, which bears low interfacial impedance, rapid Li-ion diffusion dynamics and high electrochemical stability, thus enabling fast charge-transfer and uniform Li plating/stripping, finally suppressing side-reactions and Li-dendrites. Consequently, the lithium electrode cyclability can be markedly enhanced. Symmetric cells of modified lithium electrode achieve 1600 h stable cycling at 1 mA cm⁻² current density, and asymmetric cells coupled with high-loading LiFePO₄ or LiNi_0.8Co_0.1Mn_0.1O₂ cathodes show significantly improved cycle-life (500 cycles of modified Li//LiFePO₄ vs. 205 cycles of bare Li//LiFePO₄, and 300 cycles of modified Li//LiNi_0.8Co_0.1Mn_0.1O₂ vs. 128 cycles of bare Li//LiNi_0.8Co_0.1Mn_0.1O₂). This gradient heterostructural concept would invoke a paradigm shift to future lithium-electrode interface technologies.