A plant root cell-inspired interphase layer for practical aqueous zinc–iodine batteries with super-high areal capacity and long lifespan

Abstract

Aqueous zinc–iodine batteries are of considerable interest for stationary energy storage because of their safety and cost-effectiveness. Nonetheless, the unstable Zn anode/electrolyte interface and shuttling of polyiodides during cycling have hindered their progress. Herein, these two issues are synergistically addressed by designing a plant root cell-inspired Ti₂O(PO₄)₂·2H₂O/ι-carrageenan (TOP/Carra) interphase layer on a metallic Zn surface. The outer flexible Carra polymer with abundant –SO₃⁻ groups functions similarly to the epidermis of plant roots, dynamically absorbing Zn²⁺ cations and repelling detrimental SO₄²⁻ and I₃⁻ anions through electrostatic interactions. Furthermore, the inner robust TOP nanorods, with high Zn²⁺ ion diffusion coefficients, serve as vascular tissues, facilitating homogenous Zn²⁺ ion flux through rapid one-dimensional ion diffusion channels. Based on the stabilized Zn anode interphasial chemistry, the Zn@TOP/Carra electrode exhibits highly reversible Zn deposition behavior with suppressed interfacial parasitic side reactions. Consequently, the Zn@TOP/Carra electrode demonstrates an outstanding lifespan of over 6000 hours and enables the operation of the Zn@TOP/Carra‖I₂ full battery at an ultra-high areal capacity of 5.77 mA h cm⁻² after 4500 cycles, which is one of the best high-areal-capacity cycling stabilities to date. Most importantly, the assembled high-energy A h-level pouch cell (1.05 A h) also delivers a competitive capacity retention of 80% after 500 cycles, demonstrating its potential for practical applications.