Secondary Amines Functionalized Organocatalytic Iodine Redox for High-Performance Aqueous Dual-Ion Batteries

Aqueous dual-ion batteries (ADIBs) based on the cooperative redox of cations and iodine anions at the anode and cathode respectively, are attracting increasing interest because of high capacity and safety. However, the full-cell performance is limited by the sluggish iodine redox kinetics between iodide and polyiodide involving multiple electron transfer steps, and the undesirable shuttling effect of polyiodides. Here, this work reports a versatile conjugated microporous polymer functionalized with secondary amine groups as an organocatalytic cathode for ADIB, which can be positively charged and electrostatically adsorb iodide, and organocatalyze iodine redox reactions through the amine groups. Both theoretical calculations and controlled experiments confirm that the secondary amine groups confine (poly)iodide species via hydrogen bonding, which is essential for accelerating iodine redox kinetics and reducing the polyiodide shuttling effect. The ADIB achieves an ultrahigh capacity of 730 mAh g^-1 with an ultrasmall overpotential of 47 mV at 1 A g^-1, which also exhibits excellent rate performance and long cycling stability with a capacity retention of 74% after 5000 cycles at a high current density of 5 A g^-1. This work demonstrates the promise of developing organocatalysts for accelerating electrochemical processes, which remains a virtually unexplored area in electrocatalyst design for clean energy applications.