Achieving efficient and stable interface between metallic lithium and garnet-type solid electrolyte through a thin indium tin oxide interlayer

Garnet-type Li7La3Zr2O12 (LLZO) ceramic electrolytes are promising solid electrolytes in solid-state lithium-ion batteries due to their relatively high ionic conductivity and high stability against lithium metal. However, the poor contact between garnet electrolytes and Li metal causes high interfacial resistance. In this work, we report a strategy to tackle this problem by modifying the surface of the Li6.4La3Zr1.4Ta0.6O12 (LLZTO) pellets with indium tin oxide (ITO), which is widely used as transparent conductive films in electronic devices. Lithium is tightly soldered on the garnet pellets through rapid reaction with the ITO interlayer. Thus the interfacial resistance of Li/LLZTO dramatically decreases from 1192 Ω cm2 to 32 Ω cm2. Due to the superior ability to homogenize current distribution, the lithiated ITO layer can protect the LLZTO pellets with low relative density (~92%) surviving at a critical current density up to 1.05 mA cm−2. Moreover, the Li/ITO-LLZTO-ITO/Li symmetric cell shows stable lithium plating/stripping over 800 h at 0.2 mA cm−2 without polarization increasing. Hybrid solid-state Li/ITO-LLZTO/LiFePO4 cell with good cycle stability and rate performance is also achieved. This work demonstrates that the ITO thin film, through conversion and alloying reactions, can effectively solder lithium anode on garnet-type solid electrolyte for high-performance lithium batteries.