Impact of pitch fraction oxidation on the structure and sodium storage properties of derived carbon materials

Pitch produced by the liquefaction of coal was divided into two fractions: soluble in toluene (TS) and insoluble in toluene but soluble in pyridine (TI-PS), and their differences in molecular structure and oxidation activity were studied. Several different carbon materials were produced from them by oxidation in air (350 °C, 300 mL/min) followed by carbonization (1000 °C in Ar), and the effect of the cross-linked structure on their structure and sodium storage properties was investigated. The results showed that the two pitch fractions were obviously different after the air oxidation. The TS fraction with a low degree of condensation and abundant side chains had a stronger oxidation activity and thus introduced more cross-linked oxygen-containing functional groups C(O)―O which prevented carbon layer rearrangement during the carbonization. As a result, a disordered hard carbon with more defects was formed, which improved the electrochemical performance. Therefore, the carbon materials derived from TS (O-TS-1000) had an obvious disordered structure and a larger layer spacing, giving them better sodium storage performance than those derived from the TI-PS fraction (O-TI-PS-1000). The specific capacity of O-TS-1000 was about 250 mAh/g at 20 mA/g, which was 1.67 times higher than that of O-TI-PS-1000 (150 mAh/g). Download: Download high-res image (107KB) Download: Download full-size image