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

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.