Miraculous iodine catalyst enables safe and high-performance red phosphorus/carbon anodes for sodium-ion batteries

The vaporization-condensation-conversion method is the prominent technique used for synthesizing red phosphorus/carbon (P/C) composites. However, its practical application is limited by the inevitable formation of toxic white phosphorus (WP) residues, posing severe safety concerns. Theoretical calculations of the WP polymerization process performed in this study revealed that the introduction of iodine can considerably accelerate the polymerization of WP molecules, yielding P/C composites free of WP residues. Furthermore, in the resulting iodine-doped P/C (I-P/C) composites, iodine forms I-P bonds, considerably enhancing electronic conductivity and promoting faster Na-P redox kinetics compared to those in the original P/C composites. Consequently, an I-P/C electrode exhibited a capacity of 1193 mA h g⁻ 1 , retaining 100 % of its capacity after 100 cycles at 0.2 A g⁻ 1 . Furthermore, an assembled I-P/C||Na 3 V 2 (PO 4 ) 2 F 3 full cell retained 91.9 % of its capacity after 200 cycles at 0.5 A g⁻ 1 . Additionally, the full cell exhibited a high energy density of 132.2 W h kg⁻ 1  at a power density of 9942.1 W kg⁻ 1 , demonstrating potential to complete charging or discharging within ∼57 s. Finally, an I-P/C||Na 3 V 2 (PO 4 ) 2 F 3 pouch cell, with a capacity of 0.36 A h, demonstrated excellent cycling performance even after 150 cycles at 0.05 A g⁻ 1 .