Electrochemical Energy Storage with an Aqueous Quinone–Air Chemistry

Organic electrode materials such as quinones are drawing rising attention as promising redox-active materials for the development of rechargeable batteries. In aqueous solutions, the redox potential of quinones is dependent on the alkalinity and acidity of the medium. Under an alkaline condition, the oxidation potential of hydroquinone (existing as diphenolate) is ca. 0.8 V lower than that under an acidic condition. On the other hand, under an acidic condition, the reduction potential of oxygen is ca. 0.8 V higher than that under an alkaline condition. By taking these advantages, a quinone–air cell with a rational voltage is strategically demonstrated with an alkaline anode electrolyte and an acidic cathode electrolyte, which are physically separated by a Na+-ion conductive solid-state electrolyte membrane. The Na+-ions shuttling through the solid-state membrane act as ionic mediators/messengers to sustain and link the redox reactions at the two electrodes.