Precursor chemistry-mediated defect regulation of asphalt-derived carbonaceous materials for slope-dominated sodium storage

Intrinsic defects are prevalent in carbonaceous materials and play a key role in electrochemical sodium storage. As a result, the controllable regulation of the defects within carbonaceous materials has been widely concerned. By using the low-cost and widely available petroleum asphalt as the precursor, we discover that the fundamental properties of the precursor are of importance in regulating the defects of petroleum asphalt-derived carbons (PACs), thus their sodium storage performance. The carbonaceous materials derived different petroleum asphalts offer different contents of defects where a clear relationship has been established with the fractions or the H/C ratio of the precursors. The petroleum asphalt with higher light fractions and larger H/C ratio contributes to electrode materials with a higher content of defects. Specifically, the petroleum asphalt with a light fraction as high as 61 wt% affords the highest slope capacity of 220 mAh/g at a low current density and a decent capacity retention. Density functional theory calculation confirms that the defects optimize local electronic configurations, facilitating sodium storage. These results may provide valuable guidance for the rational selection of low-cost precursors to produce anode materials for sodium storage and rationally combine the emerging new energy and the current petroleum industry.