Multi-Dimensional Carbon Network Engineering for Durable Na 2+2 x Fe 2– x (SO ₄ ) ₃ Cathodes: Accessing High-Rate Sodium Storage and Air-Stable Storage

Na2+2xFe2-x(SO₄)₃ (NFS) is a promising high-voltage cathode of Sodium-Ion Batteries (SIBs), but its commercialization is limited by poor air stability, low electronic conductivity, and phase impurities. Carbon compositing has been widely recognized as an effective strategy, yet the correlation between carbon dimensionality and functional mechanisms remains insufficiently understood. This study conducts a dimension-engineered carbon coating with acetylene black (0 D), carbon nanotubes (1 D), and graphene oxide (2 D). Structural characterization verifies enhanced phase purity and tailored carbon incorporation enabled by all dimensional carbon coating. NFS@CNT demonstrates 83.21% capacity retention after 1000 cycles at 1 C and retains 93.10% of its 0.1 C discharge capacity even at 5 C. As to thermal and air stability, Carbon nanotubes unexpectedly enable phase integrity up to 500 °C. Graphene oxide can provide effective physical shielding with strong hydrophobicity and layered structure. Moreover, acetylene black exhibits 95.36% capacity retention after 42 days of ambient exposure. This study not only elucidates the mechanism of dimension-dependent carbon interface engineering but also presents a practical strategy for enhancing the durability of NFS cathodes.