In Situ-Grown Heterostructured Co 3 S 4 /CNTs/C Nanocomposites with a Bridged Structure for High-Performance Supercapacitors.

As one of the most competitive candidates for energy storage devices, supercapacitors have attracted extensive research interest due to their incomparable power density and ultralong cycling stability. However, the large surface area required for charge storage is an irreconcilable contradiction with the requirement of energy density. Therefore, a high energy density is a major challenge for supercapacitors. To solve the contradiction, Co 3 S 4 /CNTs/C with a bridged structure is designed, where CNTs generated in situ serve as a bridge to connect a porous carbon matrix and a Co 3 S 4 nanoparticle, and Co 3 S 4 nanoparticles are anchored on the topmost of CNTs. The porous carbon and Co 3 S 4 are used for electrochemical double-layer capacitors and pseudocapacitors, respectively. This bridged structure can efficiently utilize the surface of Co 3 S 4 nanoparticles to increase the overall energy storage capacity and provide more electrochemically active sites for charge storage and delivery. The materials show an energy density of 41.3 Wh kg -1 at 691.9 W kg -1 power density and a retaining energy density of 33.1 Wh kg -1 at a high power density of 3199.9 W kg -1 in an asymmetrical supercapacitor. The synthetic technique provides a simple method to obtain heterostructured nanocomposites with a high energy density by maximizing the effect of pseudocapacitor electrode active materials.