Synthesis and lithium storage properties of nitrogen-containing hard carbon from conjugated microporous polymers

Two kinds of hard carbons with controllable nitrogen contents (N1HC and N2HC) were prepared from 2,5-dibromopyridine and 2,5-dibromopyrazine, respectively. The nitrogen contents of N1HC and N2HC are 3.75 wt% and 5.08 wt%, respectively. The pore structure of N2HC was further improved by KOH activation and the activated N2HC is designated as N2HC-K. The specific surface area of N2HC-K is considerable 1328.3 m 2 g −1 , which is distinctly higher than that of N2HC. The rich nitrogen content and developed pores make N2HC-K afford a high lithium storage capacity, rate performance, and excellent cycling performance. The initial reversible capacity of N2HC-K is 604.8 mAh g −1 at a current density of 0.1 A g −1 . The specific capacity of N2HC-K after 500 cycles at 0.6 A g −1 is still as high as 488.2 mAh g −1 .