Unveiling the Role of Local Atomic Configurations of Tin on Enhanced Na Storage for Carbon Anode Materials

Abstract Elucidating the interplay between Na⁺ electrochemical behavior and the local atomic configurations of sub‐nano metal species in carbon‐based anodes remains pivotal for advancing sodium‐ion battery technology. Here, nitrogen‐fluorine co‐doped carbon matrices (NFC) embedded with abundant Sn single atoms (SnSAs) and slight clusters (Sn─Clu) are engineered via a one‐pot synthesis. Precise modulation of SnCl 2 precursor content enables tailored Sn─NFC architectures with optimized specific surface areas (SSA: 208.1 m 2 g −1 for 17% Sn─NFC), tunable Sn─Clu sizes, and SnSA/Sn─Clu ratios. Synchrotron spectroscopy and density functional theory reveal that coexisting SnSAs and Sn─Clu synergistically enhance Na⁺ adsorption (Δ E = −2.56 to −2.64 eV) and electronic conductivity through coordinated Sn─N bonding and cluster‐mediated charge redistribution. The 17% Sn─NFC anode achieves exceptional sodium storage performance, delivering 362.2 mAh g −1 at 0.05 A g −1 and 140.1 mAh g −1 at 20 A g −1 with 87.4% capacity retention over 500 cycles in ester‐electrolyte, surpassing most carbon‐based counterparts. Ether‐electrolyte optimization further amplifies kinetics, yielding 366.7 mAh g −1 (0.05 A g −1 ) and 206.3 mAh g −1 (20 A g −1 ). This work establishes a multi‐scale design framework, bridging atomic‐scale Sn configurations to macroscopic electrode performance, and propels high‐power sodium‐ion battery development.