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 Li6.5La3Zr1.5Ta0.5O12 (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.