Design of a mixed conductive garnet/Li interface for dendrite-free solid lithium metal batteries

Abstract

Solid-state batteries (SSBs) with metallic lithium (Li) anodes and nonflammable solid-state electrolytes (SSEs) are viewed as the next-generation batteries because of their potential improvement in energy density and guarantee of safety. However, even though the high-density solid garnet SSE pellets exhibit high ionic conductivity, high transference number, and large shear modulus, the unexpectedly serious occurrence of dendrite propagation remains a problem. Herein, a mixed conductive layer (MCL) consisting of electron-conductive nanoparticles embedded in an ion-conductive network is introduced at the interface between the garnet SSE and the Li anode. Such MCL not only leads to the transition from lithiophobicity to lithiophilicity, but also homogenizes the electric-field distribution inside the MCL and relieves the electronic attacks to the garnet. As a result, the Li/MCL/garnet/MCL/Li cells show a critical current density as high as 1.2 mA cm⁻² and stable cycling for over 1000 h at 0.1 mA cm⁻². The LiCoO₂/Li cells with the MCL-protected interface show excellent cycling and rate performance at room temperature. These results demonstrate a rational design for a stable garnet/Li interface and an effective strategy to enable Li metal anodes in SSBs.