Toward Shuttle‐Free Zn–I2 Battery: Anchoring and Catalyzing Iodine Conversion by High‐Density P‐Doping Sites in Carbon Host

Abstract Zn–iodine (I 2 ) battery, as a promising energy storage device, especially under high I 2 loading, is harassed by the shuttle effect of the soluble polyiodide intermediates. Herein, the bifunctional role of 2D carbon nanosponge with rich P‐dopant (4.2 at%) and large specific surface area (1966 m 2 g −1 ) in anchoring I 2 /I x − ( x = 1, 3 or 5) and catalyzing their mutual conversion is reported. Both experiment and computational results reveal the transfer of electrons from the P‐doped site to iodine species, showing strong interfacial interaction. When being used as a host, it possesses high specific capture capacity for I 2 (3.34 g iodine g −1 or 1.6 mg iodine m −2 ) and I x − (6.12 g triiodide g −1 or 3.1 mg triiodide m −2 ), which thus effectively suppresses the shuttle effect, supported by in situ UV–vis and Raman spectra. In addition to the strong interfacial interaction that favors iodine conversion, the P‐doped sites can also catalyze the conversion of I 5 − to I 2 , which is the rate‐determining step. Consequently, Zn–I 2 batteries under a high I 2 content (70 wt%) deliver high specific capacity (220.3 mAh g −1 ), superior Coulombic efficiency (>99%), and low self‐discharge rate; moreover, they can also operate steadily at 2 A g −1 with ignorable capacity decay for 10 000 cycles.