Control of D-Spacing and Graphitic Defects in Asphaltene-Derived Hard Carbons for Energy Storage

Abstract

With the increasing demand for energy storage and declining lithium stores around the globe, sodium is emerging as an alternative source due to its natural abundance and similar reaction kinetics and chemical properties to lithium. While sodium-ion and lithium-ion batteries started development at approximately the same time, sodium-ion batteries were cast aside as sodium has a larger ionic radius, leading to incompatibilities with graphite and its interlayer spacing. Asphaltenes are the heaviest components, with a relatively high percentage commonly found in the Alberta Oilsands bitumen. They are currently being explored for their purposes in energy storage as they can form hard carbons after treatment. Asphaltenes are the portion of materials in oil soluble in toluene and insoluble in excess n-heptane. These carbons are an excellent choice for sodium-ion batteries as they have large interlayer spacing, lattice defects, and disorder, which can better accommodate the size of sodium ions. This thesis explores the various treatment conditions used to tailor the interlayer spacing and graphitic defects of asphaltene-derived hard carbons to better accommodate the intercalation of sodium ions during charge/discharge processes for future applications. Conventional graphite has a d-spacing of 0.336 nm, and the results from these experiments have resulted in an extensive range of interlayer spacing ranging from a low of 0.373 nm to a high of 0.392 nm. This increase was accomplished by altering the hold temperature, hold time, and heating rate for the stabilization/oxidation and carbonization processes of asphaltenes to convert them into usable materials for energy storage. The increase in interlayer spacing seen from these results allows for the potential usage of Alberta asphaltenes in sodium-ion batteries.