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.