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

Abstract

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.