P-doped porous carbon from camellia shell for high-performance room temperature sodium-sulfur batteries

Room-temperature sodium-sulfur batteries are still hampered by severe shuttle effects and sluggish kinetics. Most of the sulfur hosts require high cost and complex synthesis process. Herein, a facile method is proposed to prepare a phosphorous doped porous carbon (CSBP) with abundant defect sites from camellia shell by oxidation pretreatment combined with H₃PO₄activation. The pretreatment can introduce pores and adjust the structure of biochar precursor, which facilitates the further activation of H₃PO₄and effectively avoids the occurrence of large agglomeration. Profiting from the synergistic effects of physical confinement and doping effect, the prepared CSBP/S cathode delivers a high reversible capacity of 804 mAh g^-1after 100 cycles at 0.1 C and still maintains an outstanding capacity of 458 mAh g^-1after 500 cycles at 0.5 C (1 C = 1675 mA g^-1). This work provides new insights into the rational design of the microstructures of carbon hosts for high-performance room temperature sodium-sulfur batteries.