Abstract: Garnet-based all-solid-state lithium batteries (ASSLBs) were considered as the most promising energy storage device due to their high energy density and good safety. However, interface problems caused by impurities such as Li₂CO₃ on the surface still hinder the practical application of garnet-based ASSLBs. Here, we use a simple ultrasonic spraying method to coat SiO₂ on the Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) surface, and in-situ construct Li₄SiO₄/Li₂O/Li₂₁Si₅ nano-multifunctional interlayer through the high-temperature conversion reaction of SiO₂. Experiments and density functional theory (DFT) calculations demonstrate that the introduced Li₄SiO₄/Li₂O/Li₂₁Si₅ nano-multifunctional interlayer at the LLZTO/Li interface can significantly improve the air stability and interface contact of LLZTO/Li. As a result, the interface impedance of Li/SiO₂@LLZTO/Li was reduced to 24.2 Ω cm^-2, and it can operate stably over 2400 and 1000 h at current densities of 0.05 and 0.2 mA cm^-2, respectively. The full cell assembled with LiFePO₄ (LFP) as cathode (Li/SiO₂@LLZTO/LFP) also exhibits excellent cycling performance (capacity retention rate of 95% after 50 cycles at 0.1 C) and rate performance (140 mAh g^-1 at 0.1 C and 107 mAh g^-1 at 1 C). This research provides a strategy to improve interface problems and achieve dendrite-free ASSLBs through in-situ transformation constructed nano-multifunctional interlayers.

Key words: Garnet electrolyte, In-situ construction, Ultrasonic spraying, Nano-multifunctional interlayer, All solid-state lithium batteries (ASSLBs)