Phosphorus and Nitrogen\nDual-Doped Hollow Porous Carbon\nSpheres toward Enhanced Cycling Stability of Room-Temperature Na–S\nBatteries

Development of room-temperature sodium–sulfur\n(RT Na–S)\nbatteries with satisfactory cycling life and rate capability remains\nchallenging due to the unfavorable electric conductivity from S species,\nsluggish redox kinetics of S conversion, and serious shuttle effects\nof sodium polysulfides (NaPSs). To address these issues, a phosphorus\nand nitrogen dual-doped hollow porous carbon sphere (PN-HPCs) is synthesized\nas the S hosts, which enhances the electric conductivity, ion diffusion,\nand conversion of polysulfides. Such a hollow hierarchically porous\nstructure is beneficial to accommodate the volume variations of S\nspecies and shorten the ion/electron transfer distances during electrochemical\nreaction process. As a result, the S@PN-HPCs600 cathode delivers noticeable\ncycling performance (313 mAh g<sup>–1</sup> after 4500 cycles\nat 5.0 C, and capacity degeneration of only 0.01% per cycle) and rate\ncapability (646.4 mAh g<sup>–1</sup>@1.0 and 527.5 mAh g<sup>–1</sup>@3.0 C). This work presents an efficient strategy\nbased on structural confinement and dual-heteroatom doping engineering\nfor long-life RT Na–S batteries.