Porous Carbon Nanosphere with Multiple Heteroatom Doping Derived from Silicon Oxycarbonitride as Sulfur Host for Lithium-Sulfur Batteries

The porous carbon nanosphere with multiple heteroatom doping derived from silicon oxycarbonitride (SiOCN) with an interconnected carbon and silica domains is reported as a robust host of the sulfur cathode for lithium-sulfur batteries. The synthesis of the porous carbon nanosphere (SiOCN-H) is straightforward etching spherical SiOCN prepared through pyrolysis of a Schiff-base-SiO2 precursor. The pore structure of SiOCN-H can be easily adjusted by altering the amount of tetraethyl orthosilicate added in the aldimine condensation reaction of 3-aminopropyl-triethoxysilane with glutaraldehyde. The optimized sample of SiOCN-H-1 possesses a larger pore volume of 1.433 cm(3) g(-1) and contains multiple heteroatoms of Si, O, and N with a total amount of about 21 wt%. The sulfur cathode based on SiOCN-H-1 exhibits decent cycling performance, retaining 77.2% of the initial capacity at 0.2C after 100 cycles. At 0.5C, the S/SiOCN-H-1 cathode still maintains remarkable cycling stability, delivering a reversible discharge capacity of 540 mAh g(-1) after 400 cycles with a low decay of 0.076% per cycle. The porous spherical structure and the chemical bonding capability of doped heteroatoms in SiOCN-H-1 primarily contribute to the high performances of the S/SiOCN-H-1 cathode by alleviating the dissolution and shuttle effect of polysulfides