Boosting the electrochemical performance through proton transfer for the Zn-ion hybrid supercapacitor with both ionic liquid and organic electrolytes

Abstract

Zn-ion hybrid supercapacitors have been proposed as a promising energy storage candidate compared to Li-ion hybrid technology due to the highly abundant Zn resources and their low cost. However, simultaneously achieving high volumetric energy density and high power density of the hybrid supercapacitors remains a challenge. Herein, we report new Zn-ion hybrid supercapacitors using functionalized carbon nanosponges as cathode materials and Zn(CF₃SO₃)₂ in both an ionic liquid (IL) and acetonitrile (AN) as the electrolyte. We revealed both experimentally and theoretically a remarkable increase of the performance by controlling macro/mesoporous structure and surface chemistry of the carbon sponge, through the pseudocapacitance induced by proton transfer. The estimated volumetric energy density of the fully packed cell with an IL (2.4 V) is as high as 54.3 W h L⁻¹. An ultrahigh power density of 17.7 kW L⁻¹ with 18.8 W h L⁻¹ was achieved by replacing the IL with AN. The full charge/discharge of the SCs with AN took only 11 seconds. More importantly, a remarkably stable performance was achieved with no capacitance fading for over 60 000 cycles. The results enlighten and promote the design and preparation of functionalized carbon positive electrodes to develop high-performance dual-ion energy storage devices.