Fabrication of high-energy hybrid capacitors by using carbon-sulfur composite as promising cathodes

The full realization of the high energy density concept in current hybrid capacitors is still a challenge due to the huge difference in specific capacity and reaction kinetics of the commonly used cathode and anode materials. Herein, for the first time, the carbon-sulfur composite is proposed as the high-capacity cathode for hybrid capacitors to achieve a high energy density. The as-prepared carbon-sulfur composite delivers a high specific capacity of 212.2 mAh g−1 (424.4 F g−1) at 4 A g−1, which is much higher than that of the pure carbon cathode. Additionally, the kinetics gap between cathode and anode is narrowed by using carbon-sulfur composite as the cathode. As a result, the carbon-sulfur composite based hybrid capacitor delivers a high energy density of 258.4 Wh kg−1 at 995 W kg−1. Even at high power density of 17350 W kg−1, the energy density can still remain 125.3 Wh kg−1. This study provides an alternative approach for designing hybrid capacitors with both high energy and power density by using carbon-sulfur composite as the cathode, and also paves a way to extend the application of sulfur to a new field for taking its advantages of high-capacity, environmental friendliness, low-cost.