The propensity of sodium anode to form uniform electrodeposit is bound up with the nature of electrode surface and regulation of Na-ion flux, as well as distribution of electronic field, which is quite crucial for high-areal-capacity sodium metal batteries (SMBs). Herein, a novel metallic sodium/sodium-tin alloy foil anode (Na/NaSn) with 3D interpenetrated network and porous structure is prepared through facile alloy reaction. The strong sodiophilic properties of sodium-tin alloy can lower the nucleation energy, resulting in smaller depositing potential and strong adsorption of Na+ , while synergistic effect of porous skeleton and additional potential difference (≈0.1 V) between Na and Na-Sn alloy (Na15 Sn4 ) can alleviate volume expansion, redistribute the Na-ion flux and regulate electronic field, which favors and improves homogeneous Na deposition. The as-fabricated Na/NaSn electrode can endow excellent plating/stripping reversibility at high areal capacity (over 1600 h for 4 mAh cm-2 at 1 mA cm-2 and 2 mAh cm-2 at 2 mA cm-2 ), fast electrochemical kinetics (500 h under 4 mAh cm-2 at 4 mA cm-2 ) and superior rate performances. A novel strategy in the design of high-performance Na anodes for large-scale energy storage is provided.
Keywords: anode; high areal capacity; ion flux; metallic sodium batteries; surface-preferred.
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