Developing a Hydrophobic Mixed Conductive Interlayer for High-Performance Solid-State Lithium Batteries

Garnet solid-state electrolytes (SSEs) Li6.5La3Zr1.5Ta0.5O12 (LLZTO) suffer from poor air stability, producing Li2CO3 by-products and causing poor interfacial contact against the Li metal. Obtaining hydrophobic and lithiophilic surface of LLZTO is meaningful for high-performance solid-state batteries. Here, a hydrophobic CFx film is firstly introduced on the LLZTO surface (CFx-LLZTO) by magnetron sputtering the polytetrafluoroethylene (PTFE) target. Benefit from its outstanding hydrophobicity, this CFx film provides the LLZTO a Li2CO3-free surface. Moreover, the LiC-LiF mixed conductive interlayer is formed through the reaction between CFx film and Li metal, resulting in a low interfacial resistance of 73.49 omega/cm2. In addition, the LiC-LiF mixed conductive interlayer can also homogenize the electric-field distribution and enable fast Li+ conduction. As a result, the construction of the hydrophobic mixed conductive interlayer makes the CFx-LLZTO based symmetric Li/Li cell exhibit a high critical current density of 1.2 mA/cm2 and a stable cycling life for over 1200 h at 0.1 mA/cm2. Furthermore, the Li/LiFePO4 cells with the CFx-LLZTO show improved cycling and rate performance at room temperature. This work provides a practical solution for achieving high-performance solid-state lithium batteries. A hydrophobic conductive interlayer: We reported a novel hydrophobic mixed conductive interlayer to enable high-performance LLZTO-based solid-state battery by magnetron sputtering PTFE target.image