Commercial LIBs are often exposed to high temperatures, which can severely shorten their shelf life20,21. Calendar aging describes time- and temperature-dependent performance degradation, usually attributed to the reactive interface between the anode and the electrolyte, the mechanism of which has been extensively studied for conventional Li-ion batteries containing graphite anodes 22 . However, for silicon-based Li-ion batteries, much attention has been focused on cycle life, while their lifetime without cycling remains unknown. There are recent reports on the aging of Si-based LIBs at high temperatures, but their experimental conditions included battery cycling, which can interrupt the deconvoluted calendar aging of the entire battery aging23,24. In this regard, a comprehensive study on the calendar aging mechanism of graphite/SiO composite anodes is urgently needed to realize the general application of SiO in the battery market. Calendar aging of SiO2-containing anodes is also expected to be attributed to their interfacial reactivity with the electrolyte in the absence of degradation issues due to volume changes during cycling25. Several studies have observed unstable interfaces of Si-based anodes, but they provide only the slightest hint for diagnosing calendar aging of SiO2-containing anodes
sio compound name

In this study, we focus on the thermal aging of graphite/SiO anodes and compare them with graphite anodes in a charged full cell configuration. First, electrochemical experiments confirmed the poor capacity retention of graphite/SiO batteries compared with graphite batteries. With this result, we observed accelerated deintercalation of lithium from graphite in the presence of SiO during high-temperature storage by in situ optical microscopy and in situ X-ray diffraction (XRD) analysis. To reveal the origin of this phenomenon, we investigated the compositional changes occurring on the anode using scanning electron microscopy and transmission electron microscopy (SEM and TEM, respectively). From energy dispersive X-ray spectroscopy (EDS) obtained from electron images, we found that the interesting increase of fluorine was completely concentrated on SiO. X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) were performed to reveal changes in SEI chemistry in detail. Finally, we have illustrated a model that fully permeates our observations in terms of electron-level interactions.