Olive Leaves-Derived Hierarchical Porous Carbon as Cathode Material for Anti-Self-Discharge Zinc-Ion Hybrid Capacitor.

As a promising low-cost and high-safety energy storage candidate, zinc-ion hybrid capacitors (ZIHCs) have received extensive attention. For maximizing the advantages of ZIHC with high energy density and high power density, the structural engineering of the porous carbon materials is the crucial and effective strategy. Herein, an oxygen-enriched hierarchical porous carbon has been fabricated from the pyrolysis of olive leaves combing the chemical activation. The abundant interfacial active sites and short ions/electrons transfer length endow the hierarchical porous carbon cathode with high ions adsorption capacity and fast kinetic behaviors. Meanwhile, the oxygen-rich functional groups can provide extra pseudocapacitance and improve the wettability and conductivity of porous carbon. Benefiting from these advantages, an anti-self-discharge ZIHC device with a high energy-power feature has been assembled. The electrochemical process is studied by ex situ X-ray diffraction (XRD) and scanning electron microscope (SEM) methods. Finally, an excellent energy density of 136.3 W h kg , and high power output of 20 kW kg , as well as long cycle life with 91% capacity retention over 20 000 cycles at 10 A g are realized by as-assembled ZIHC.