Hollow Prussian blue analogue/g-C3N4 nanobox for all-solid-state asymmetric supercapacitor

Supercapacitors are highly promising energy storage/conversion devices owing to their outstanding advantages such as high power density, long operational life, flash charge/discharge speed, and low cost. However, the low energy density is the bottleneck limiting their wide application. Acquirement of high-performance supercapacitors with ultrahigh energy density closed to batteries’ is still a challenge. In this study, a mesoporous hollow Prussian blue analogues (PBA) nano-box/g-C3N4 hybrid was successfully synthesized. It shows excellent electrochemical performance with a high specific capacity of 201.6 mAh g−1 and outstanding cycling stability (90.1% capacity retention after 5,000 cycles), which are significantly higher than those of most other PB/PBA based electrode materials. Furthermore, it was coupled with active carbon to construct an all-solid-state asymmetric supercapacitor denoted as H Rb-NiHCF/g-C3N4//AC, which exhibits a high energy density of 46.9 Wh kg−1 at the power density of 808.2 W kg−1, which is closed to that of commercial Ni/MH batteries. It also shows good cycling stability. Furthermore, it can easily light up a LED indicator and efficiently work for more than 3 min. This mesoporous hollow PBA nano-box/g-C3N4 hybrid demonstrates its high practical potential for cathode materials in high-performance supercapacitors.