Flexible PEDOT:PSS nanopapers as “anion-cation regulation” synergistic interlayers enabling ultra-stable aqueous zinc-iodine batteries

Aqueous zinc-iodine (Zn-I₂) batteries are promising candidates for low-cost grid-scale energy storage systems. However, the long-term stability and energy density of the Zn-I₂ batteries are largely hindered by the lack of feasible and scalable methods that coherently suppress polyiodide shuttling and Zn dendrites growth, especially at high current densities. Herein, a flexible, thin and lightweight poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) nanopaper is designed as an “anion-cation regulation” synergistic interlayer to tackle the above issues. The PEDOT:PSS interlayer exhibits a 3D nanofibrous network with uniformly distributed mesopores, abundant polar groups and intrinsic conductivity, which renders an even Zn²⁺ flux at Zn anode and facilitates homogeneous current distributions at I₂ cathode. Meanwhile, such interlayer can act as physiochemical shield to enhance the utilization of I₂ cathode via the coulombic repulsion and chemical adsorption effect against polyiodide shuttling. Thus, long-term dendrite-free Zn plating/stripping is achieved at simultaneous high current density and high areal capacity (550 h at 10 mA cm⁻²/5 mAh cm⁻²). Zn-I₂ batteries harvest a high capacity (230 mAh g⁻¹ at 0.1 A g⁻¹) and an ultralong lifespan (>20000 cycles) even at 10 A g⁻¹. This work demonstrates the potential use of the multifunctional interlayers for Zn-I₂ battery configuration innovation by synergistic regulation of cations and anions at the electrodes/electrolyte interface.