Self-assembled N/O-doped carbon microflowers from benzimidazole-containing polyimides for supercapacitors

Herein, a kind of flower-like polyimide (PI) particles are first prepared via a self-assembly method using 2-(4-aminophenyl)-5-aminobenzimidazole (APBIA) and pyromellitic dianhydride (PMDA) as monomers. Subsequently, the N/O-doped carbon microflowers are obtained through pyrolysis. When the polymer solution concentration is 40 mg mL⁻¹, and the solvothermal time and temperature are 8 h and 200 °C, the resulting carbon sample demonstrates high O and N contents (3.67 % and 10.07 %, respectively), leading to a capacitance of 178.1 F g⁻¹ at 0.5 A g⁻¹. After further activation with HNO₃, the optimized sample exhibits an enhanced specific capacitance (335.3 F g⁻¹). Additionally, the symmetric coin SC cell constructed with ABPC-80-6-36 achieves a specific capacitance of 98.1 F g⁻¹, along with an energy density of 13.63 Wh kg⁻¹ at a power density of 250 W kg⁻¹. Even after 15,000 charge-discharge cycles, the capacitance retention remains approximately 100 %, indicating its potential as a high-performance electrode material.