Design of a mixed conductive garnet/Li interface for dendrite-free solid lithium metal batteries
Solid-state batteries (SSBs) with metallic lithium (Li) anodes and non-flammable 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 electronic conductive nanoparticles embedded in an ionic conductive network is introduced at the interface between the garnet SSE and the Li anode. Such MCL not only leads to transition of lithiophobicity to lithiophilicity, but also homogenizes 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 performances 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.