Combination of multiple active sites in N, O co‐doped defective carbon materials for high performance aqueous supercapacitors

Supercapacitors have been used in a broad range of fields including electronics, transportation, and energies. Electrode materials with high capacitance and good rate performance are crucial for the future development and application of supercapacitors. Herein, we prepared N, O co‐doped defective carbon blocks (NO‐DCBs) with abundant active sites through carbonization and ball‐milling of polyimide. The as‐obtained NO‐DCBs exhibit high atomic content of N and O inherited from polyamic acid (PAA) precursor, as well as large amounts of intrinsic defects introduced by ball‐milling. Benefiting from the synergy of pseudocapacitance and electrical double‐layer capacitance provided by heteroatoms and intrinsic defects respectively, the NO‐DCBs assembled symmetric aqueous capacitor shows high capacitance of 329 F g−1 at 0.1 A g−1, good rate performance of 48% capacitance retention at 50 A g−1, and superb cycling stability. This work promotes the deep understanding of the synergy effect of functional groups and intrinsic defects for capacitive energy storage, and broadens the avenue for structural design of active sites in carbon materials. The N, O co‐doped carbon prepared through carbonization and ball‐milling from polyamic acid precursor exhibits good comprehensive capacitive performance.