Synergistic P/N/S tri-doping and hollow engineering of hard carbon for high-performance sodium-ion batteries

Herein, phosphorus/nitrogen/sulfur (P/N/S) tri-doped meso-macroporous hollow carbon spheres (PNS-MMHCSs) are fabricated via a heteroatom engineering strategy. This rationally designed architecture features a hollow carbon framework with abundant active sites and an expanded interlayer spacing of 3.86 Å, which optimizes the electronic structure of carbon and mitigates volume expansion during Na+ insertion/extraction. As a result, the PNS-MMHCSs anode exhibits excellent electrochemical performance, delivering a reversible capacity of 127 mAh g−1 after 10,000 cycles at 20 A g−1. Combined structural characterization, electrochemical analysis, and theoretical calculations suggest that the integration of sequential P/N/S regulation with a meso-macroporous hollow architecture promotes Na+ transport and surface-controlled sodium storage. This work highlights an effective design strategy for improving the rate capability and cycling durability of hard-carbon anodes.