A Rocking-Chair Type Aqueous Nickel-Organic Battery with Azobenzene Anode

Aqueous nickel-organic batteries have the potential for grid-scale energy storage due to their high safety and sustainability merits. However, organic anodes generally store charge by coordinating with alkaline metal cations, which could cause electrolyte consumption. Here, azobenzene (AZO) is screened out from carbonyl, imine, and azo compounds to serve as anodes, combining it with Ni(OH)₂ cathodes to construct a "rocking-chair" type battery system. Qualitative and quantitative analyses demonstrate the N═N group acts as the active center, while protons serve as charge carriers during the electrochemical reaction. Benefiting from the small ionic radius and fast ions transport of protons, this battery not only delivers an excellent rate performance, with a capacity of 281.5 mAh g^-¹ at a current density of 1C (0.3 A g^-¹) and maintains 274.4 mAh g^-¹ at 100C, but also exhibits remarkable long-term cycling stability, retaining 92.5% of its initial capacity after 10 000 cycles. Additionally, a pouch cell with a discharge capacity of 1.36 Ah is also assembled, yielding an energy density of 64.3 Wh kg^-¹ (based on the total mass). This work expands the range of organic anode materials, and inspires the development of aqueous nickel-organic batteries with a proton "rocking-chair" mechanism.