Zinc-ion hybrid capacitors: Electrode material design and electrochemical storage mechanism

With the increasing demands for high-performance energy storage devices, aqueous zinc-ion hybrid capacitors (ZICs) attract lots of attention due to the integration of high-energy-density zinc-ion batteries (ZIBs) and high-power-density supercapacitors (SCs). In addition, they hold some unique features such as high safety, low cost, and capable energy storage ability. Until now, many great results about ZICs have been achieved especially in the electrode materials exploring, ions storage mechanism, and device design. Herein, we exhaustively discuss the electrochemical characteristics, charge storage mechanism, and kinetic analysis of capacitor- and battery-type of electrode materials as well as summarize recent advances in materials and devices. Meanwhile, we point out the limitations and directions of their present development, which may give some guidance for commercializing Zn2+ storage devices.