| dc.description.abstract | With the rapid growth of battery usage in both grid-storage and electric vehicle applications,
the incentives for exploring alternative batteries outside the traditional lithium-ion batteries
have increased exponentially. Sodium, being inherently more abundant with a lower cost,
has gained increased interest among researchers in the last decades for its storage capacity
and longevity. As the increased atomic radius of sodium present difficulties in using traditional anode materials like graphite, hard carbons have presented desirable properties in
recent years following the development of new technology and improved electrode designs.
Petroleum coke, a byproduct derived from oil refinery units presents encouraging properties
for its use in sodium-battery anodes due to its high-carbon content and porous structure.
This thesis aims to present a comprehensive study on the use of petroleum coke as an anode
material for SIBs, by first providing a theoretical framework of the working principles that
are involved in using heat treated petroleum coke for SIBs, before employing several material
and electrochemical analysis techniques to evaluate its performance. Experimental procedures involved treating milled petroleum coke powder at high carbonization temperatures
of 950 ◦C, 1100 ◦C, 1300 ◦C, and 1500 ◦C. These materials was then characterized by employing BET, SEM, XRD, and TGA analyses, before constructing them into half cells and
symmetrical cells for battery testing through cycling, CV analysis and EIS. Results indicate
that higher carbonization temperatures initially decrease the surface area but reverts to an
increase at 1500 ◦C. The crystallinity was found to increase with temperature, suggesting regional graphitization at 1500 ◦C. This was further suggested in the visual insights is provided
through SEM, where particle size was observed to increase slightly with respect to treatment
temperature. The sodium storage capacity measured at 103, 114, 90 and 103 mAh/g for
materials treated at 950 ◦C, 1100 ◦C, 1300 ◦C and 1500 ◦C respectively indicate adequate
storage capability for all materials. This was further outlined with an average Coulombic
efficiency of 97 % through 50 cycles for the constructed cells. The capacitive nature of the
cells was found to be reduced slightly with increasing temperature treatment because of increased reactive sites at the surface. These combined results indicate that while all materials
are suitable for use in SIBs, they present differences in material structure that affects the
electrochemical performance in different ways. Further analysis is therefore needed to establish the direct implications of these differences when used in energy storage applications. | |
