Cu-Doped Alloy Layer Guiding Uniform Li Deposition on a Li–LLZO Interface under High Current Density

Li₇La₃Zr₂O₁₂(LLZO)-based ceramics as promising solid-state electrolytes (SSEs) have received much attention for use in high-energy lithium (Li) metal batteries. However, the Li growth through the solid garnet electrolyte under a low current density hinders its practical application. In this work, the Cu doped Li₃Zn was designed to guide uniform Li deposition by magnetron cosputtering and an in situ alloying reaction on Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO) pellets. After introducing the composite layer, a small interfacial area specific resistance (∼30 Ω·cm²) can be obtained. Improved lithium plating/stripping performance, including a long-life span of 450 h (under a current density of 0.8 mA cm^–2 without short circuit) and a high critical current density (CCD) of 2.8 mA cm^–2 is performed by the composite interlayer with a Zn:Cu ratio of 10:1. And the Li/Cu–Li₃Zn SSEs/LFP full cell exhibits good electrochemical performance. Accordingly, the Li deposited behavior in the Li plating/stripping process at the intermediate layer is discussed in detail. This work provides a new sight for the alloy interface designed on the solid-state garnet SSEs for high performance lithium metal batteries under high current density.