Amorphous anion skeletons induce rapid and cation-selective ion flux towards stable aqueous zinc–iodine batteries

The aqueous zinc–iodine battery is considered a promising technology for large-scale energy storage due to its high safety, large energy density, and easy accessibility. However, its development suffers from two challenges: parasitic side reactions on Zn anodes and polyiodide shuttling effects. To overcome them, we designed an artificial protective layer on the Zn anode based on amorphous zeolite-like Na2Zn2(TeO3)3, whose crystalline counterpart possesses periodic ion channels and an anion skeleton. It not only preserves the original coordination environments and pore structures of the Na2Zn2(TeO3)3 crystal, but also exhibits broadened ion channels and shortened ion diffusion pathways. Combined with the superior structural stability of the amorphous Na2Zn2(TeO3)3, the Zn anode can cycle stably for 2790 h at 1 mA cm−2 with a low overpotential. Meanwhile, the Zn2(TeO3)32− anion skeleton can also repel I−-species and SO42− anions from the anode surface, thus enabling outstanding Zn plating/stripping reversibility and excellent cycling ability of the full cells coupled with different cathodes. Significantly, the capacity retention of the high mass loading zinc–iodine pouch cell was 92.7% after 600 cycles. This work provides a novel strategy to achieve high-performance zinc–iodine batteries, which has great promise for practical applications.