Biomass‐Derived Micro‐Mesoporous Carbon with Oxygen Functional Groups for High‐Rate Na–S Batteries at Room Temperature

Room‐temperature sodium–sulfur batteries are potential candidate for sustainable large‐scale energy storage systems due to their high energy density and low cost. However, the shuttling effect of high‐order polysulfides (Na2Sn, 4 < n ≤ 8) usually leads to rapid capacity fading, while the reaction kinetics of low‐order polysulfides (Na2Sn, 1 ≤ n ≤ 4) are slow. In this work, microporous‐mesoporous carbon derived from mangosteen peels is reported as cathode materials for RT Na–S batteries. The designed micro‐mesoporous structure not only effectively suppresses the shuttling effect of sodium polysulfides (NaPS), but also has high electrical conductivity and porosity, which facilitates electron/ion diffusion. Oxygen functional groups on the surface provide high catalytic activity for efficient low‐order NaPS conversion. The obtained Na–S battery exhibits high reversible capacity with excellent long‐term cycle performance (526.1 mAh g−1 at 4 A g−1 after 1000 cycles) and outstanding rate performance (676.59 mAh g−1 at 16 A g−1). This work demonstrates a novel activation strategy of biomass‐derived carbons for high‐performance Na–S batteries. Micro‐mesoporous carbon with oxygen functional groups is designed and fabricated by sequential calcination and activation from mangosteen peels. The micro‐mesoporous structure not only limits the loss of active sulfur, but also accelerates the transport of sodium ions and electrons, while the oxygen functional groups remarkably promote the redox kinetics of sulfur, thus realizing high‐performance sodium‐sulfur batteries at room temperature.