Phosphor-Doped Carbon Network Electrocatalyst Enables Accelerated Redox Kinetics of Polysulfides for Sodium-Sulfur Batteries.

Lithium-ion batteries, which have dominated large-scale energy storage for the past three decades, face limitations in energy density and cost. Sulfur, with its impressive capacity of 1675 mAh g and high theoretical energy density of 1274 Wh kg, stands out as a promising cathode material, leading to a growing focus on sodium-sulfur (Na-S) batteries as an alternative to address lithium resource scarcity. Nevertheless, the development is restrained by poor conductivity, volume expansion of the sulfur cathode, and the shuttle effect of sodium polysulfides (NaS) in the electrolytes. In this study, a facile method is designed to fabricate phosphor-doped carbon (-C), which is then used as a sulfur matrix. This micromesoporous -C network enhances sulfur utilization, increases overall cathode conductivity, and effectively mitigates the shuttling of NaS. During the discharge process, -C can absorb soluble NaS and increase the conductivity of sulfur, while serving as a reservoir for electrolyte and NaS, thereby preventing their infiltration into the anode and reducing the loss of sodium. As a result, the well-designed sulfur-loaded -C (S/-C) cathode, employed in the Na-S battery, demonstrates a capacity of 1034 mAh g at 0.1 C (1 C = 1675 mA g) and an excellent rate capability of 339 mAh g at 10 C, coupled with a prolonged cycling life up to 2000 cycles at 1 C, exhibiting an ultralow capacity decay rate of 0.013% per cycle. Overall, this study introduces an efficient method for creating long-lasting Na-S batteries.