Searching High‐Potential Dihydroxynaphthalene Cathode for Rocking‐Chair All‐Organic Aqueous Proton Batteries

Abstract The lack of acid‐proof high‐potential cathode largely limits the development and competitiveness of proton batteries. Herein, the authors systematically investigated six dihydroxynaphthalenes (DHNs) and found that 2,6‐DHN delivered the best cathode performance in proton battery with the highest redox potential (0.84 V, vs SHE) and a specific capacity of 91.6 mAh g−1 at 1 A g−1. In situ solid‐state electropolymerization of DHNs is responsible for the voltage and capacity fading of DHNs, and 2,6‐DHN's excellent electrochemical performance is derived from its high polymerization energy barrier. By compounding with rGO, the 2,6‐DHN/rGO electrode can maintain a specific capacity of 89 mAh g−1 even after 12 000 cycles at 5 A g−1. When it is paired with the 2,6‐dihydroxyanthraquinone (DHAQ) anode, the assembled rocking‐chair all‐organic proton battery exhibited a high cell voltage of 0.85 V, and excellent energy/power densities (70.8 Wh kg−1/850 W kg−1). This study showcases a new‐type high‐potential proton‐containing organic cathode and paves the way for constructing a high‐voltage rocking‐chair proton battery. Also, in situ solid‐state electropolymerization will inspire the further study of phenol‐based small‐molecule electrodes.