Phenazine anodes for ultralong cycle life aqueous rechargeable batteries

A nano-phenazine@Ketjen black (nPZ/KB) composite was prepared as an anode for aqueous rechargeable batteries by an in situ dissolution–precipitation method. Due to the uniform precipitation of nano-phenazine on the highly conductive and hierarchical porous Ketjen black surface, it enabled ultrafast transfer of metal cations (Na+, K+, Zn2+etc.) and electrons to almost all the electrochemically active sites of phenazine molecules. Hence, nPZ/KB not only realized the full utilization of a theoretical capacity of 298 mA h g−1 but also exhibited a high rate discharge capacity of 102 mA h g−1 under 100 C in 6 M KOH. Furthermore, the nPZ/KB composite achieved an ultralong cycle life of 100 000 times with a high capacity retention of 76% because of the insolubilities of both phenazine and its reduction products in aqueous electrolytes. The excellent performance of the nPZ/KB-NiOOH battery and nPZ/KB-activated carbon pseudocapacitor demonstrated great promise for grid-scale energy storage devices.