Thieno[3,2-b]thiophene-containing conjugated microporous polymer-derived sulfur-doped hard carbon for enhanced lithium storage

It is a significant issue for lithium-ion batteries to develop hard carbon with high capacity and long cycling stability. Here, a sulfur-doped hard carbon (TT-SHC) is synthesized from thieno[3,2-b]thiophene-containing conjugated microporous polymers (TT-CMP), constructed from 1,3,5-triethynylbenzene and 3,6-dibromothieno[3,2-b]thiophene. TT-SHC is composed of nanoparticles in the range of 10-25 nm, with large pore volume, high specific surface area, and a sulfur content of 4.74 wt%. TT-SHC displays an initial specific charge capacity of 871.3 mAh g-1 at a current density of 100 mA g-1. At 600 mA g-1, TT-SHC delivers a charge capacity of 445.5 mAh g-1 after 300 cycles, being slightly higher than the initial capacity. Such a synthesis strategy provides a new insight for the design and preparation of hard carbon.