Preparation and lithium storage properties of nitrogen, sulfur heteroatom hard carbon by pyrolysis of conjugated microporous polymers

A bottom-up approach was employed to build a thiazole-containing conjugated microporous polymer (NSCMP) by choosing bromo-thiazole and triacetylene benzene as monomers. The pyrolyzation and KOH-assisted pyrolyzation of NSCMP were performed to obtain the N, S heteroatom hard carbon (NSHC) and KOH-activated NSHC (KNSHC). NSHC and KNSHC were further characterized by scanning electronic microscope, energy-dispersive spectra (EDS), nitrogen adsorption-desorption, galvanostatic charge-discharging test, etc. The EDS revealed that the N and S mass fractions of KNSHC were 10.42% and 2.23%, respectively. The specific surface area of KNSHC was as high as 2 140 m2.g(-1), which was distinctly higher than that of NSHC (657 m2.g(-1)). The specific capacity of KNSHC after 500 cycles at 0.2 A.g(-1) was as high as 946.2 mAh.g(-1), while that of NSHC was only 493.7 mAh.g(-1). The excellent electrochemical performance of KNSHC may be due to the synergistic effect of N and S heteroatoms as well as the unique porous structure.