Construction of SnO₂ buffer layer and analysis of its interface modification for Li and Li_1.5Al_0.5Ge_1.5(PO₄)₃ in...

SnO₂ layer between Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) and lithium anode was prepared through simple scratch-coating process to improve interface properties. The physical phase, morphology, and electrochemical properties of Li/SnO₂/LAGP structure were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical analytical methods. It was found that SnO₂ layer effectively improved the interface stability of LAGP and lithium anode. The prepared Li/SnO₂/LAGP/SnO₂/Li symmetric cell exhibited a large critical current density of 1.8 mA cm^-2 and demonstrated excellent cycling characteristics. The polarization voltages of symmetric cell were 0.1 V and 0.8 V after 1000 h of cycling at current densities of 0.04 mA cm^-2 and 0.5 mA cm^-2, respectively. Li/SnO₂@LAGP/LiFePO₄ solid-state full cells were also assembled, exhibiting a discharge specific capacity of 150 mAh g^-1 after 200 cycles at 0.1C with capacity retention rate of 96 %. The good interface properties of Li/SnO₂/LAGP structure are attributed to the transformation of SnO₂ layer into a buffer layer containing Li₂O, Sn⁰, and Li_xSn_y alloy during cycling process, which effectively inhibits the reduction reaction between LAGP and lithium anode.