Robust Conversion-Type Li/Garnet interphases from metal salt solutions

Garnet-type Li7La3Zr2O12 (LLZO) electrolytes show considerable potentials in solid-state Li metal batteries, yet the serious interfacial problem has hindered its practical application. Herein, we propose a facile strategy to construct conversion-type metal oxides (eg. PbO, ZnO or Co3O4) as lithiophilic layers on garnet surface from metal salt aqueous solutions. Robust garnet/Li interface and greatly reduced interfacial resistance to as small as ~ 10 Ω cm2 can be obtained. Combined with experimental analysis and theoretical calculation (ΔG), the mechanism of lithiophilicity of different metal oxides was explained. The mixed ionic and electronic conductive interlayer which can lead to uniform Li-ion flow is superior to the electronic conductive metal interlayer with poor ionic conductivity causing gradual failure of the interface. As expected, the Li|PbO/LLZTO/PbO|Li cells show the improved critical current density of 1.1 mA cm−2 and excellent cycling stability for 1000 h at 0.3 mA cm−2. With PbO modified garnet, LiNi0.5Co0.2Mn0.3O2|garnet|Li cells operate well at room temperature and all-solid-state LiFePO4/PEO|garnet|Li cells run stably at 0.3 mA cm−2 for at least 100 cycles at 60 ℃.