Boron dopant- and nitrogen defect-decorated C3N5 porous nanostructure as an efficient sulfur host for lithium–sulfur batteries

Active site implantation and morphology manipulation are efficient protocols for boosting the electrochemical performance of carbon nitrides . As a promising sulfur host for lithium–sulfur batteries (LSBs), in this study, C 3 N 5 porous nanostructure incorporated with both boron (B) atoms and nitrogen (N) defects was constructed (denoted as ND–B–C 3 N 5 ) using a two-step strategy, i.e., pyrolysis of the mixture of 3-amino-1,2, 4-triazole and boric acid to obtain B-doped C 3 N 5 porous nanostructure and then KOH etching under hydrothermal condition to generate N defects. The doped B atoms in the C 3 N 5 porous nanostructure are in the form of B–N bonds and grafted B–O bonds. N defects are primarily created at the C N–C positions of the triazine unit, leaving behind some N vacancies and cyano groups . Benefiting from the involvement of B dopants and N defects, the optimized ND–B–C 3 N 5 –12 sample exhibits ameliorative conductivity, mass transport, lithium polysulfides (LiPSs) adsorption ability, diffusion of Li + ions, Li 2 S deposition capacity, sulfur redox polarization, and a reversible solid–solid sulfur redox process . Consequently, the ND–B–C 3 N 5 –12/S cathode delivers accelerated redox performance of polysulfides for LSBs, revealing capacities of 1091 ± 44 and 753 ± 20 mAh/g at 0.2C for the initial and 300th cycles, respectively. The ND–B–C 3 N 5 –12/S cathode is also endowed with desired sulfur redox activity and stability at 2C for 1000 cycles, holding an initial discharging capacity of 788 ± 24 mAh/g and a low decay rate of 0.05 % per cycle.