Synergistic engineering of ultrafine SnO₂-SnS heterojunctions spatially confined within a hierarchical graphene aerogel boosts sodium-ion storage

High-capacity Sn-based anodes for sodium-ion batteries (SIBs) face challenges from volume expansion, active material aggregation, and poor conductivity, collectively hindering electrochemical performance. Herein, we propose a synergistic spatial confinement strategy: Ultrafine SnO₂-SnS heterojunctions are uniformly anchored within a hierarchical porous graphene aerogel (GA/CSOS) via controlled sequential hydrothermal-sulfidation and SDS-assisted self-assembly. The GA/CSOS composite delivers exceptional stability and rate capability, achieving 554 mAh g⁻¹ after 200 cycles at 0.1 A g⁻¹ (with almost Coulombic efficiency >95 % after initial activation) and retaining 234 mAh g⁻¹ at 2 A g⁻¹ . The remarkable electrochemical performance originates from: (i) spatially confined ultrafine heterojunctions with uniform distribution suppressing aggregation/pulverization, and (ii) the hierarchical graphene providing conductive networks and volume buffering via mesopores. This structural design dramatically releases the theoretical capacity of the active material and promotes efficient charge transfer kinetics through continuous electronic pathways and layered ion diffusion channels. Our work establishes a novel design paradigm for high-energy-density SIBs through spatial confinement of uniformly dispersed ultrafine heterojunctions in hierarchical conductive frameworks.