4.3 Material Characterization
Scanning electron microscopy (SEM) and energy-dispersive X-ray
spectroscopy (EDX) experiments were carried out using a Quanta FEG 650
(FEI) environmental scanning electron microscope operated at a voltage
of 20 kV.
All Raman measurements were carried out using a Bruker Senterra Raman
microscope (Bruker, Germany). Experiments were performed using a 532 nm
green laser at a spectral resolution of 9 to 18 cm–1and a confocal setup. The laser power was set to 10 mW to prevent sample
damage. For the microscope, a 10×objective was used. Five integrations
were carried out with an integration time of 2 s to collect the spectra.
All material surfaces were scanned by recording multiple Raman spectra
pointwise on a grid with an isotropic spatial resolution of 2 μm using a
50×magnification.
For in situ measurements, a Cu/NCM full cell was set up inside an
ECC-Opto-Std (EL-CELL, Germany) cell.[41, 45]NCM532 electrode with a diameter of 10 mm was used as a cathode. A 1 mm
thick glass-fiber separator (EL-CELL, Germany) soaked with ca. 75 μL of
E1 and E2 electrolytes was placed on top of the cathode. 16 mm Cu mesh
was distributed on top of the separator and pressed onto the glass
window of the cell. The cell was cycled at a constant rate of 300 μA
(C/10) between 4.3 V and 3.0 V using a BioLogic SP-200 potentiostat
(BioLogic Science Instruments, France). During cycling, Raman spectra
were recorded with a time step of 2h at the Cu mesh surface with an
isotropic spatial resolution of 2 μm under 50 times magnification.