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

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.