Porous silica derived from sago waste and its application for the preparation of SiO2/C composites as air cathodes for primary aluminum-air batteries

In the present study, a porous air cathode made of amorphous silica xerogel (a-SX) derived from sago waste was investigated for treating the first discharge of an aluminum-air (Al-air) battery. Four types of air cathode samples were produced by varying the content of polyvinylidene fluoride (PVDF) binder from 5 wt % to 30 wt % in a composite of a-SX, carbon black (C), and PVDF. The detailed structural characterization of the explored composite samples was performed using various techniques, such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and N2 adsorption-desorption isotherms. The performance of the prepared air cathode in the Al -air battery was tested successfully during the first discharging treatment. The study demonstrated that the volume fraction of the microporous structure in the air cathode sample increases with increasing binder content, while for mesoporous structures, it acts in the opposite direction. The sample containing a binder of 10 wt % provides the mesoporous structure with the largest volume fraction and the formation of discharge products with the smallest fraction in the mesopore, and their presence generates a discharge capacity in an Al-air battery with the longest stable plateau voltage.