Active Structure‐Directing by Carbon Dots Enables Durable Bismuth Anodes for Wide Temperature Sodium‐Ion Batteries

Bismuth (Bi) is a promising anode for sodium‐ion batteries owing to its high volumetric capacity. However, its practical application is crippled by severe volume expansion and sluggish reaction kinetics. Herein, we demonstrate an active structure‐directing strategy using carbon dots (CDs) to overcome this issue. Combined experimental characterizations and finite element simulations reveal that the abundant surface functional groups of CDs chelate Bi 3+ during synthesis, serving as molecular anchors to transform uncontrollable growth into confined, homogeneous nucleation. This unique architecture achieves triple synergistic effects: shortening Na + diffusion pathways, homogenizing ion flux, and alleviating local stress concentration. Moreover, the CDs further promote the formation of a thin, uniform, NaF‐rich solid electrolyte interphase through preferential PF 6 − adsorption. Consequently, the Bi/CDs anode delivers exceptional rate capability (397.5 mAh g −1 at 30 A g −1 ) and ultra‐long cycling stability (91.8% retention after 10 000 cycles at 5 A g −1 ). Remarkably, it maintains outstanding sodium storage performance across a wide temperature range from −20°C to 60°C. This work establishes CDs as active structure‐directing agents for regulating metal nucleation and constructs robust nanoscale interfaces, providing crucial insights for designing high‐volumetric‐capacity alloy anodes for sodium‐ion batteries.