Na3PO4 assistant dispersion of nano-CaCO3 template to enhance electrochemical interface: N/O/P co-doped porous carbon hybrids towards high-performance flexible supercapacitors

Recently porous carbon hybrids have attracted ever-increasing attention as electrode materials for supercapacitors, but it remains a great challenge to simultaneously control their pore structure and element composition with optimal electrochemical performances. Herein, Na3PO4 assistant dispersion of nano-CaCO3 template in egg white was proposed to fabricate nitrogen/oxygen/phosphorus (N/O/P) co-doped 3D hierarchical porous carbon hybrids. The as-prepared carbon exhibited a high surface area (2576 m(2) g(-1)), well-balanced pore size distribution with a large micropore volume (0.77 cm(3) g(-1)) and multi-heteroatoms doped carbon skeleton (3.9% of N, 12.2% of O and 4.1% of P). These physicochemical advantages were synergistically beneficial to supercapacitive performances: an ultrahigh capacitance of 452 F g(-1) at 0.5 A g(-1) in 6 M KOH electrolyte and excellent stability of 92.4% capacitance retention after 10000 cycles at 10 A g(-1) . The energy density was 22.6 Wh kg(-1) at the power density of 225.0 W kg(-1) in the neutral electrolyte of 1 M Li2SO4 . Especially, a flexible symmetric solidstate supercapacitor was assembled, which delivered a high capacitance (166 F g(-1) ) and excellent flexibility (86.3% capacitance retention) with bending angles to 180 degrees. Thus, this work provides a cost-effective strategy to fabricate multi-element co-doped 3D hierarchical porous carbon and expand its application for flexible energy storage devices.