Double Potassium Salt Self-Activation Strategy to Construct Hierarchical Porous Carbon for Zinc Ion Hybrid Capacitor

Hierarchical porous carbon exhibits enormous potential as a cathode for zinc ion hybrid capacitor (ZIHC). In this work, three-dimensional (3D) hierarchical porous carbon is prepared by pyrolysis of potassium stearate and potassium polyacrylate using a self-activation strategy. Because of the unique 3D interconnected hierarchical porous framework, high specific surface area and plentiful oxygen functional groups, the HPC-700 electrode shows a specific capacitance of 378.67 F g⁻¹ and excellent cycle stabilization with the capacity retention rate of 98.1% after 10000 cycles. Moreover, the HPC-700//HPC-700 symmetrical supercapacitor provides an energy density of 25.41 Wh kg⁻¹ and superior electrochemical stability and good cycle performance. More interestingly, the assembled HPC-700//ZnSO₄ (aq)//Zn hybrid capacitor delivers a capacitance of 439.2 F g⁻¹ (195.2 mAh g⁻¹) and an energy density of 156.18 Wh kg⁻¹ (99.97 W kg⁻¹). The ZIHC shows excellent electrochemical performance with 96.5% initial capacity after 10 000 cycles. Overall, the research highlights an efficient and facile strategy to prepare HPC cathode materials for high-performance ZIHC.