Template-free strategy for constructing polyaniline/polypyrrole derived carbon sphere as supercapacitors electrode use in acidic and alkaline electrolytes

Undesirable energy density and storage ability hinder the pure carbon-based symmetric supercapacitor commercial application. Constructing hierarchical pore structure carbon material is expected to overcome this challenging issue. How to effectively reduce the multi-step and improve efficiency is worthy of in-depth study. Herein, a template-free strategy is proposed to construct N-doped hollow carbon sphere, combining a pore-forming agent and alkali treatment to build a hierarchical pore structure. Investigating the various pore structure contents in carbon spheres reveals its effect on the capacitive performance of as-prepared samples. From the robust walls structure (~50 nm) and rational micropores proportion (68.3 %), HCZK carbon sphere is equipped with a specific capacitance of 550.6 and 273.3 F g−1 in acidic and alkaline electrolyte, respectively, at a current density of 1 A g−1. After 10,000 cycles charge/discharge test, the specific capacitance of HCZK sample does not lose in acidic electrolyte, and 4.1 % in alkali electrolyte. Symmetric supercapacitors assembled by HCZK carbon sphere deliver a specific capacitance of 247.1 F g−1 at 1 A g−1, outstanding coulombic efficiency of 100 % after 10,000 cycles and excellent energy density of 87.8 Wh kg−1 at a power density of 1288.0 W kg−1. Achieve the above excellent properties can be attributed to the synergistic effect of rational pore structure and surface chemical composition. This work will reveal the contribution of micropores to the electrochemical of carbon materials and provide a reference for selecting electrolytes.