Small organic molecules for aqueous zinc-ion batteries with stable structure and ultrafast H-ion and Zn-ion diffusion kinetics via coating

Aqueous Zn-ion batteries (AZIBs) with excellent electrochemical performance are achieved by using small organic molecules VO(acac)2 (IV) as cathode. The surface area and electrical conductivity of IV are increased by coating wrinkled rGO, thereby improving the electrochemical sluggishness of IV cathode. The VO(acac)2@rGO (IV@rGO) aqueous battery can display a high capacity of 327.2 mAh g−1 at 100 mA g−1. The Zn2+ and H+ con-insertion/extraction reactions within IV@rGO are a joint control of pseudocapacitance and diffusion process. The in-situ XRD combinded with ex-situ Raman and XPS reveal that the multivalent transition of vanadium and coordination reaction of organic functional groups (VO), and no significant volume change of IV structure implying near-zero expansion characteristic during charging/discharging process.