Vertex v70 spectrometer

SEM observations were performed on SEM (Nano630 FE-SEM). FT-IR was performed on a Bruker Vertex V70 spectrometer in diffuse reflection mode with a Spectra Tech Collector II accessory. XPS measurements were carried out with a Kratos XSAM800 Ultra spectrometer. ¹³C NMR characterization was performed on a Bruker AV-3-HD-500. AFM (Digital Instrument Multimode scanning probe microscope) was used to investigate the surface morphology and analyze the mechanical property of the SEI layer under inert atmosphere. The 3D topographic images of SEI layers were recorded through tapping mode imaging with sharp AFM tips (BRUKER TESPA-V2). The scan size was 10 × 10 μm. Another kind of silicon tip (BudgetSensors Multi75Al-G) was employed to test the mechanical behavior of different SEI layers. The spring constants of the AFM cantilevers were calibrated by the Sader method (around 3.2–3.4 N/m)^{60 (link)}. All tips were cleaned with UV/ozone to remove organic contaminants. The force-distance curve was obtained from AFM indentation test. The maximum indentation force was kept constant at 150 nN for each test and the vertical probe rate was 316 nm/s. Zygo 3D Optical Surface Profilers were used to investigate the thickness and coverage degree of SEI layers under inert atmosphere. The scan size was 450 × 450 μm.