2D Vermiculite Nanosheets Encapsulated in Hydrogel Electrolyte for Shuttle-Free and Dendrite-Inhibited Zinc-Iodine Batteries.

Aqueous zinc-iodine (Zn-I2) batteries are a promising next-generation energy storage technology due to their intrinsic safety, low cost, and high energy density. However, their application is blocked by the shuttle effect of polyiodide in the I2 cathode and dendrite formation/side reactions in the Zn metal anode. Here, a dual-network hydrogel electrolyte consisting of polyacrylamide (PAM), chitosan (CS), and 2D vermiculite nanosheet (VN) is designed as PAM/CS/VN (PCV) to simultaneously address issues in the I2 cathode and Zn metal anode. The 3D PCV network and 2D VN synergistically suppress the shuttle effect through physical confinement and strong adsorption. Hydrophilic/zincophilic groups in PCV reduce free-water activity and promote uniform Zn deposition, while electronegative VN sites coordinate Zn2+, lowering the desolvation barrier and inhibiting dendrite formation. Under the regulation of multifunctional PCV, Zn||Zn symmetric batteries work for over 1100 h at 5 mA cm-2 and Zn-I2 batteries achieve a capacity retention of 97.4% after 10 000 cycles at 2 A g-1. The pouch battery delivers a capacity retention of 89.3% after 400 cycles at 0.5 A g-1. This novel electrolyte and its effective additive offer valuable insights into enhancing the stable operation of Zn-I2 batteries.