Construction of SnO buffer layer and analysis of its interface modification for Li and LiAlGe(PO) in solid-state batteries.

SnO layer between LiAlGe(PO) (LAGP) and lithium anode was prepared through simple scratch-coating process to improve interface properties. The physical phase, morphology, and electrochemical properties of Li/SnO/LAGP structure were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical analytical methods. It was found that SnO layer effectively improved the interface stability of LAGP and lithium anode. The prepared Li/SnO/LAGP/SnO/Li symmetric cell exhibited a large critical current density of 1.8 mA cm 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 and 0.5 mA cm, respectively. Li/SnO@LAGP/LiFePO solid-state full cells were also assembled, exhibiting a discharge specific capacity of 150 mAh g after 200 cycles at 0.1C with capacity retention rate of 96 %. The good interface properties of Li/SnO/LAGP structure are attributed to the transformation of SnO layer into a buffer layer containing LiO, Sn, and LiSn alloy during cycling process, which effectively inhibits the reduction reaction between LAGP and lithium anode.