Reciprocal enhancement of iodine and manganese redox kinetics towards high-performance rechargeable zinc-iodine-manganese hybrid batteries

Abstract

Aqueous Zn-I₂-Mn hybrid batteries demonstrate enhanced capacity, superior redox reaction kinetics, and prolonged cycle life compared to their Zn-I₂ and Zn-Mn counterparts, making them promising candidates for grid-scale energy storage. Nevertheless, challenges remain in developing multifunctional positive electrode materials and elucidating the mechanistic synergy governing iodine and manganese redox reactions. Herein, we present a high-performance free-standing electrode composed of birnessite (KMnO) nanosheet arrays in situ grown on carbon cloth (CC@KMnO) for constructing a Zn-I₂-Mn hybrid battery. Combined theoretical studies and in situ characterizations reveal that CC@KMnO enhances iodine species adsorption, lowers the Gibbs free energy change for iodine reduction, and significantly accelerates I⁻/I₃⁻/I₅⁻ redox kinetics while suppressing polyiodide shuttling and corrosion effects. Synchronously, the ZnI₂ electrolyte facilitates the dissolution of residual and exfoliated KMnO, thereby improving manganese redox reaction kinetics, reversibility, and enhancing cycling stability. Leveraging this mutually reinforcing effect, the Zn-I₂-Mn hybrid battery achieves an impressive areal capacity of 2.02 mAh cm⁻² and maintains long-term durability over 3600 cycles at 2 mA cm⁻². This work provides valuable insights into designing efficient and durable hybrid energy storage systems.