*2.2. Materials Characterization*

X-ray diffraction (XRD) patterns of the samples were collected using a PANalytical Empyrean high-resolution diffractometer equipped with a Cu-Kα X-ray source (λ = 1.5406 Å). The average crystallite size of the TiO2 nanosheets was calculated using the Debye–Scherrer equation (*D=K λ/β cosθ*), where D is particle size, *K* is the shape factor 0.9, λ is the wavelength of the X-ray radiation of Cu-Kα, and β is the full width at half maximum (FWHM) of the highest intensity peak. Room temperature Raman analysis was performed with a Renishaw PLC Raman spectrometer equipped with a 532 nm Nd: YAG laser. Sample damage was avoided by limiting the laser power to 5 mW. FTIR spectra of pristine and cycled electrodes after washing with anhydrous acetonitrile (Sigma-Aldrich, 99.9%) were recorded using a Thermo Scientific Nicolet iS50 in attenuated total reflectance (ATR) mode, in the range of 4000–400 cm<sup>−</sup>1. FTIR spectra of pristine, cycled and non-washed electrodes were also collected for comparison. Microstructural characterization of TiO2 nanosheets was performed using a scanning electron microscope (FEI Helios NanoLab 600i) and highresolution transmission electron microscope (FEI Talos F200X FEG). X-ray photoelectron spectroscopy (XPS) measurements were performed using a SPECS PHOIBOS 150 9MCD instrument equipped with a Multi-Channeltron detector and a monochromatic X-ray source of twin Mg anodes. The binding energies of elements in the XPS spectra were set accordingly to the CC/CH component of the C 1s peak at 284.8 eV. For the quantitative analysis of SEI, high-resolution core-level spectra were used after removing the nonlinear Shirley background.
