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

Abstract

AbstractGarnet 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 Ω/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.