Sulfhydryl-based polyimides were synthesized by the nucleophilic
ring-opening reaction of thiolactone monomers (BPDA-T, ODPA-T, BTDA-T)
with polyethylenimine (PEI), and they were coated on carbon nanotubes
as host materials (BPTP@CNT, ODTP@CNT, and BTTP@CNT) of the sulfur
cathode. BPTP@CNT/S, ODTP@CNT/S, and BTTP@CNT/S as cathode materials
not only promote the covalent bonding of sulfur and polysulfide with
sulfhydryl-based polyimides but also reduce the shuttle effect of
soluble polysulfide in the redox process. Moreover, sulfhydryl-based
polyimides can help improve the compatibility and interfacial contact
between sulfur and conductive carbon while alleviating the volume
expansion of the cathode. In addition, the conductive network of carbon
nanotubes improves the electronic conductivity of the cathode materials.
The BTTP@CNT/S cathode showed superior stability (the initial capacity
was 902 mAh g–1 at 1C, and the capacity retention
rate was 88.58% after 500 cycles) and the initial capacity could reach
718 mAh g–1 when the sulfur loading was 4.8 mg cm–2 (electrolyte/sulfur ratio: 10 μL mg–1), which fully proves the feasibility of the large-scale application
of sulfhydryl-based polyimide materials.