3D carbon nanocage networks with multiscale pores for high-rate supercapacitors by flower-like template and in-situ coating

3D hierarchical carbon nanocages, a novel carbon-based material, have demonstrated a strong momentum of high rate capability and power density supercapacitors. Herein we report the preparation of 3D carbon nanocage networks by nano coating carbon precursor on flower-like basic magnesium carbonate microspheres combining with in situ MgO template carbonization and KOH treatment. This material features with interconnected 3D network structure, crosslinked carbon nanocages (15-24 nm in size and 2.5-3 nm in shell thickness), high specific surface area (1470-1927 m2 g-1), multiscale pores (macro/meso/micropores) and uniform pore size distribution. Resulting from the multiple synergistic effects of these advantages, the 3D carbon nanocage networks present a remarkably excellent electrochemical performance with a large specific capacitance of 380 F g-1 at 1 A g-1 and high rate capability of 82% when increasing the current density up to 50 A g-1 in three-electrode configuration. For HPCNC-700-a symmetrical supercapacitor, the specific capacitance reaches up to 288 F g-1 at 1 A g-1 and still maintains at 256 F g-1 at 10 A g-1 with the capacitance retention of 89%.