Chemical confinement of short-chain sulfur into hierarchical porous hard carbon for ultra-stable high-capacity sodium-ion storage
The pursuit of high-energy-density sodium-ion batteries (SIBs) necessitates the development of stable high-capacity anodes. While amorphous carbon is a promising anode candidate for SIBs, its practical application is hindered by limited capacity. Herein, we design a composite anode by chemically confining a high-content (~25 wt%) short-chain sulfur into hierarchical porous hard carbon microspheres (SHHC) derived from microbe yeast. The SHHC anode exhibits a high reversible capacity of ~807 mAh g−1 at 0.03 A g−1 (~3 times that of conventional amorphous carbon) along with superior rate capability, and extraordinary long-term cyclability (almost 100% capacity retention after 2000 cycles at 1.0 A g−1). The high-content sulfur species contribute to superb redox reactivity for high-capacity sodium storage via a surface-dominated storage mechanism. The carbon matrix features an enlarged interlayer distance, which facilitates Na-ion intercalation and deintercalation for high-rate capability. Furthermore, the hierarchical porous structure with built-in cavities facilitates the Na-ion transfer and effectively accommodates the electrode’s volume expansion, achieving fast electrode kinetics and outstanding cyclability. Such a combination of favored properties leads to state-of-the-art comprehensive battery performance for Na-ion storage. Our finding envisions a new perspective on building stable high-capacity anode materials for SIBs.