2.2. Material characterization
The morphologies of the cathode were observed by using a scanning electron microscope (SEM, JWOL-6700F) at an acceleration voltage of 5.0 kV. Transmission electron microscopy (TEM) images were obtained by operating a high-resolution JEOL 2010F TEM system with a LaB6 filament at 200 kV. Nitrogen adsorptiondesorption was used to examine the BET surface area of the active materials. Raman measurement was performed with a RM 3000 (Renishaw) micro-Raman spectrometer at 514.5 nm. X-ray photoelectron spectroscopy (XPS) characterization was performed by using Physical Electronics PHI 5600 multi-technique system using an Al monochromatic X-ray at a power of 350W. Thermogravimetric analysis (TGA) was measured using a Perkin-Elmer system (TGA Q500) under air atmosphere from 25 to 800 C, with a heating rate of 10 C per minute. A Fourier-transform infrared (FTIR) test was carried out on a ectrometer (Vertex 70, Bruker) in the
frequency range of 400–2000 cm1
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