Regulating interfacial stability of SiOx anode with fluoride-abundant solid–electrolyte interphase by fluorine-functionalized additive

Silicon oxide (SiO x ) has received remarkable attention as a next-generation battery material; however, the sudden decrease in the cycling retention constitutes a significant challenge in facilitating its application. Tris(2,2,2-trifluoroethyl) phosphite (TTFP), which can control parasitic reactions such as the pulverization of SiO x anode materials and electrolyte decomposition, has been proposed to improve the lifespan of the cell. The electrochemical reduction of TTFP results in solid-electrolyte interphase (SEI) layers that are mainly composed of LiF, which occur at a higher potential than the working potential of the SiO x anode and carbonate-based solvents. The electrolyte with TTFP exhibited a substantial improvement in cycling retention after 100 cycles, whereas the standard electrolyte showed acutely decreased retention. The thickness of the SiO x anode with TTFP also changed only slightly without any considerable delamination spots, whereas the SiO x anode without TTFP was prominently deformed by an enormous volume expansion with several internal cracks. The cycled SiO x anode with TTFP exhibited less increase in resistance after cycling than that in the absence of TTFP, in addition to fewer decomposition adducts in corresponding X-ray photoelectron spectroscopy (XPS) analyses between the cycled SiO x anodes. These results demonstrate that TTFP formed SEI layers at the SiO x interface, which substantially reduced the pulverization of the SiO x anode materials; in addition, electrolyte decomposition at the interface decreased, which led to improved cycling retention. Graphical abstract