Core-shell hierarchical porous carbon spheres with N/O doping for efficient energy storage

Cost-effective synthesis of core-shell carbon spheres for supercapacitor applications remains a challenge. N/O codoped hierarchical porous carbon spheres with the core-shell architecture (MPG(2)) are fabricated based on the dynamic Schiff-base chemistry free from any templates or complicated procedures. The nanoarchitectures of carbon materials are strongly determined by the addition of glyoxal which not only plays a key role in guiding the reassembly of dynamic imine intermediates to construct a stable core-shell architecture, but also endows carbon spheres with high mechanical strength/stability for the pyrolysis/hybrid modification due to the compact pi-conjugated polymer shell. Benefiting from diffusion highways in hierarchical porous structure, a high ion-matching/adsorbing shell surface (1514 m(2) g(-1)) with abundant micropores (0.5-0.8 nm) and N/O functionalities, the resultant MPG(2)-based symmetric supercapacitor using the lithium bis(trifluoromethane sulfonyl)imide electrolyte (the size of Li+/TFSI is 0.069/0.79 nm) yields the large energy storage of 31.6 Wh kg(-1) at 550 W kg(-1) under the high aqueous voltage of 2.25 V, accompanied with a well-behaved cycling stability (capacitance retention of 86.2% over 10,00 0 rounds at 1 A g(-1)) and broad temperature applicability from 20 to 80 degrees C. Furthermore, MnO2 is further deposited on the robust MPG(2) architecture to obtain the MPG(2)/MnO2 composite as a positive electrode in the asymmetric device, and the overlapped voltage window of the MPG(2)/MnO2 composite and the capacitive MPG(2) paves another efficient avenue toward a high energy-power aqueous device of 43.74 Wh kg(-1) at 450 W kg(-1). (C) 2020 Elsevier Ltd. All rights reserved.