Achieving high critical current density in Ta-doped Li7La3Zr2O12/MgO composite electrolytes

Abstract Li-garnet Li7La3Zr2O12 (LLZO) is a promising solid electrolyte for lithium metal batteries owing to its excellent stability and high ionic conductivity. However, there exists serious lithium dendrite problem in LLZO electrolyte under elevated current density, easily leading to internal short-circuit and poor cycling performance. In this work, we demonstrated that Ta-doped LLZO with 4 wt% MgO additive delivered superior endurance to lithium dendrite due to its improved mechanical properties and lower electronic conductivity. The critical current density (CCD) of LLZTO-MgO composite electrolyte reached as high as 1.95 mA⸳cm−2 at room temperature (RT). It also realized stable lithium plating/stripping performance for 1000h under 0.5 mA⸳cm−2. Moreover, the full cell paired with LiNi0·6Co0·2Mn0·2O2 cathode exhibited better cycling stability especially at a high rate. Our work provided an alternative strategy for dendrite-suppression in solid electrolyte besides interfacial modification.