Deep Eutectic Solvent‐Induced Polyacrylonitrile‐Derived Hierarchical Porous Carbon for Zinc‐Ion Hybrid Supercapacitors.

Hierarchical porous carbon that possesses large surface area and high porosity has become an important electrode material for supercapacitors. However, some unavoidable issues like complex approach and environmental pollution involved in traditional chemical activation restrict the sustainable development of carbons. Herein, a green, low‐cost, and safe urea‐zinc chloride deep eutectic solvent (DES) is proposed to prepare polyacrylonitrile derived three‐dimensional carbon nanosphere (D‐PC). Specially, the D‐PC efficiently accelerates electrolyte ions migration and enhances charge storage due to its interconnected ionic pathways and large accessible active surfaces. When employing the D‐PC as positive electrode of zinc‐ion hybrid supercapacitors, a high specific capacitance of 261.5 F g−1 at 0.2 A g−1 along with a cycling stability of 91.3 % after 10000 cycles at 5 A g−1. Meanwhile, such device holds the maximum energy/power density of 93.9 Wh kg−1/16.7 kW kg−1 at 0.2 A g−1/20 A g−1, respectively. Thanks to the unique physicochemical properties of as‐obtained D‐PC, an ultrahigh areal capacitance of 2.2 F cm−2 also can be achieved at a mass loading of 23 mg cm−2. The satisfying structure and performance highlight the potential of DESs in the design of functional carbons. [ABSTRACT FROM AUTHOR]