High-Performance Bipolar Small-Molecule Organic Cathode for Wide-Temperature-Range Aqueous Zinc-Ion Batteries.

Abstract

Organic small-molecules with redox activity are promising cathode candidates for aqueous zinc-ion batteries (AZIBs) due to their low cost, high safety and high theoretical capacity. However, their severe dissolution leads to unsatisfactory electrochemical performance. Here, a dihydro-octaaza-pentacene (DOP) compound is synthesized as a cathode for AZIBs by extending its N heterocyclic molecular structure. The extended N heterocyclic structure provides dual active sites of n-type (C═N) and p-type (-NH-) redox reactions while reducing dissolution through enhanced π-conjugation. Hence, the Zn//DOP battery demonstrates improved performance, e.g., an enhanced capacity of 360 mAh g^-1 at 0.05 A g^-1. Even under extended temperature conditions of - 50 and 50 °C, the batteries still maintain the capacities of 172 and 312 mAh g^-1, respectively. In/<i>ex-situ</i> spectroscopy provide a thorough understanding of the storage mechanisms of cations and anions (Zn²⁺/H⁺ and ClO₄^-) through multielectron transfer process occurring at dual electroactive sites. This strategy offers a promising approach to designing high-performance zinc-organic batteries for sustainable energy storage.