Unraveling the hierarchical porous structure in natural pollen-derived Fe-containing carbon to address the shuttle effect and dead sulfur problems in lithium-sulfur batteries

Mesoporous carbon-metal composites with the merits of strong adsorption ability over soluble lithium poly -sulfides (LiPSs), excellent sulfur dispersion, high conductivity, low cost, and rapid catalytic conversion rate to suppress the shuttle effect are promising in lithium-sulfur batteries. However, their application is usually limited by structural collapse and fast fading because of the poorly dispersed metal-based compounds in the mesoporous carbon host during high-temperature synthesis. Herein, a 3D rape pollen-derived carbon (RPDC) containing Fe -based compounds as the sulfur host is prepared through the solid-state reaction of simultaneous carbonization between natural rape pollen and ferrous oxalate. Characterizations confirm that Fe-RPDC composites have stronger physiochemical adsorption and catalytic ability than pure RPDC, Fe-doped commercial activated car-bon, and pure Fe3O4. Then, soluble LiPSs are adsorbed, fixed on the surface of the Fe-RPDC composites and catalyzed by Fe-based compounds to reduce the "dead sulfur". Finally, a mature natural structure-derived hollow carbon-iron compound system is developed. The lithium-sulfur battery assembled using Fe-RPDC as host showed excellent long-term stability and a high electron transport rate. The Fe-RPDC@S composite with 69.6 wt% sulfur content exhibits the highest initial discharge capacity of 955.7 mA h g-1 at a rate of 1 C and can be maintained at 556.3 mA h g-1 even after 150 cycles. The decay rate is only 0.03 % per cycle, and the average Coulomb effi-ciency is approximately 98 %. Hence, the reasonable design of Fe-RPDC composites is of great significance for promoting the transformation of polysulfide intermediates and chemically anchoring soluble LiPSs to restrain "dead sulfur" and can be used to realize low-cost, green and large-scale production.