Improve the Lithophilicity of Garnet Solid Electrolyte by Ultrasonic Sprayed Al₂O₃ Layer

Garnet-type solid electrolyte Li6.25Ga0.25La3Zr2O12(LGLZO) is considered as one of the most promising solid electrolytes because of its high ionic conductivity, broad electrochemical window, and excellent stability toward lithium. However, contaminants such as lithiophobic Li2CO3/LiOH have inevitably formed on the electrolyte surface, leading to an increasing interfacial impedance and lithium dendrite formation. Herein, Al2O3 was introduced via ultrasonic spraying on the surface of LGLZO, and in situ converted Li2CO3 into LiAlO2, resulting in Al2O3/LiAlO2 mixed conductive layer (MCL) during the annealing. Experiments and density functional theory (DFT) calculations showed that this MCL interface not only effectively improved the wettability but also suppressed the dendrite growth. The interfacial area-specific resistance (IASR) is decreased from 700 to 8 Ω cm2, while the critical current density (CCD) is increased from 0.34 to 1.4 mA cm–2. Simultaneously, the Li/MCL@LGLZO/Li cell exhibited a prolonged cycle life of 5500 h at a current density of 0.15 mA cm–2. Especially in the high voltage range of 2.5–4.5 V, the Li/MCL@LGLZO/LFP full cell delivers excellent rate and prolonged cycle lifespan. These results mean that introducing MCL is a strategy for improving the lithiophobic of the garnet electrolyte.