Ultra-homogeneous dense Ag nano layer enables long lifespan solid-state lithium metal batteries

The unstable electrolyte/lithium (Li) anode interface has been one of the key challenges in realizing high energy density solid-state lithium metal batteries (LMBs) applications. Herein, a dense and uniform silver (Ag) nano interlayer with a thickness of ∼35 nm is designed accurately by magnetron sputtering technology to optimize the electrolyte/Li anode interface. This Ag nano layer reacts with Li metal anode to in-situ form Li-Ag alloy, thus enhancing the physical interfacial contact, and further improving the interfacial wettability and compatibility. In particular, the Li-Ag alloy is inclined to form AgLi phase proved by cryo-TEM and DFT, effectively preventing SN from continuously "attacking" the Li metal anode due to the lower adsorption of succinonitrile (SN) molecules on AgLi than that of pure Li metal, thereby significantly reinforcing the interfacial stability. Hence, the enhanced physical and chemical stability of electrolyte/Li anode interface promotes the homogeneous deposition of Li+ and inhibits the dendrite growth. The Li-symmetric cell maintains stable operation for up to 1700 h and the cycling stability of LiFePO4|SPE|Li full cell is remarkably improved at room temperature (capacity retention rate of 91.9% for 200 cycles). This work opens an effective way for accurate and controllable interface design of long lifespan solid-state LMBs.