Nowadays, SC is recognized as a key element of hybrid energy storage system in modern energy supply chain for electric vehicles (EVs). Co9S8 as a promising electrode material attracts much attention for supercapacitor owing to its superior electrochemical capacity. However, its poor stability and electronic conductivity, which result in inferior cycling performance and rate capability, have seriously limited the practical application of Co9O8 in supercapacitors.
In this article, Co9S8 nanoparticles were embedded in reduced graphene oxide (rGO) via a simple anneal approach as high efficient and stable electrodes for SCs. The Co9S8/rGO composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The Co9S8 nanoparticles were inserted tightly between the rGO layers due to strong intermolecular forces, preventing the cluster in reduction process of rGO from graphene oxide (GO). The rGO provides the conductive network for Co9S8 and shortens the ion diffusion paths, improving rate performance and enhancing the stability of the electrode material. The as-prepared Co9S8/rGO takes full advantages of high capacitance performance of Co9S8 nanoparticles and excellent conductivity and electrochemical stability of rGO. Thus, Co9S8/rGO composites exhibit high specific capacity of 708.3 F g−1 with the active material mass of 2 mg at current density of 1A g−1. In addition, the asymmetric hybrid SC (Co9S8/rGO//rGO) delivered an excellent energy density of 41.1 Wh kg−1 and a high power density of 750.3 W kg−1. The Co9S8/rGO composites introduced here represent a high efficiency ideal electrode that can be easily applied in automotive field with excellent performance.
