A Crystalline Dihydroxyanthraquinone Anodic Material for Proton Batteries

Abstract As a class of redox-active compounds, anthraquinones (AQ) have been investigated in rechargeable metallic ion batteries. In this work, it is found that protons (H+) can be reversibly intercalated and de-intercalated in crystalline 2,6-dihydroxyanthraquinone (DHAQ) at potential of -0.21 V vs. Ag/AgCl in acidic solution and exhibits a specific capacity of 110 mAh g-1. This unique property is leveraged in a rechargeable proton battery system with a DHAQ anode and a Mn2+ cathode. During battery cycling, a morphology evolution from particulate DHAQ into centimeter scale nanofibers is observed. It is revealed that the evolution of morphology stems from a realignment of the DHAQ molecule. The quinone proton battery delivers equilibrium voltage of 1.1 V and the capacity retention rate could be as high as 100% after 2600 cycles. This study showcases a unique proton (de)intercalation chemistry in crystalline anthraquinone and demonstrates the viability of organic proton battery system.