A highly conductive gel electrolyte with favorable ion transfer channels for long-lived zinc-iodine batteries.

Aqueous rechargeable zinc-iodine batteries (ARZIBs), as a powerful energy alternative, have inherent advantages, such as low cost, good safety and environmental friendliness. Unfortunately, uneven Zn deposition with dendrite growth and undesirable side reactions seriously compromises the safety and stability of ARZIBs. Herein, a novel strategy is demonstrated to fabricate highly conductive iota-carrageenan (IC) gel electrolyte. The unique double helix structure with good mechanical properties provides favorable Zn channels guided by sulfate groups, which enables confinement effect and orderly guidance of Zn deposition. Additionally, the activity of water molecules confined in the gel electrolyte is reduced, thus inhibiting the corrosion reactions of the zinc electrode. As a result, the gel electrolyte with remarkable ionic conductivity (42.95 mS cm) showed a good cycling stability over 1000 h. Importantly, the Zn-I batteries with the IC-Zn gel electrolyte demonstrated remarkable reversibility with an impressive capacity retention (91.9%) over 5000 cycles and high average coulombic efficiency (99.86%). This work provides a reliable strategy to develop natural polymer gel electrolytes to regulate the Zn deposition for advanced rechargeable Zn-I batteries.