High-performance hybrid supercapacitor enabled by a high-rate Si-based anode

A hybrid supercapacitor constructed of a Si-based anode and a porous carbon cathode is demonstrated with both high power and energy densities. Borondoping is employed to improve the rate capability of the Si-based anode (B-Si/SiO₂/C). At a high current density of 6.4 A/g, B-Si/SiO₂/C delivers a capacity of 685 mAh/g, 2.4 times that of the undoped Si/SiO₂/C. Benefiting from the high rate performance along with low working voltage, high capacity, and good cycling stability of B-Si/SiO₂/C, the hybrid supercapacitor exhibits a high energy density of 128 Wh/kg at 1229 W/kg. Even when power density increases to the level of a conventional supercapacitor (9704 W/kg), 89 Wh/kg can be obtained, the highest values of any hybrid supercapacitor to date. Long cycling life (capacity retention of 70% after 6000 cycles) and low selfdischarge rate (voltage retention of 82% after 50 hours) are also achieved. This work opens an avenue for development of high-performance hybrid supercapacitors using high-performance Si-based anodes.