Influence of crystallinity of CuCo2S4 on its supercapacitive behavior

The crystallinity of electrode materials affects the electrochemical performances of supercapacitors, typically for some transition metal oxides. The influence of crystallinity on the capacitive behavior of metal sulfides has not been well investigated so far. In this work, amorphous and crystalline CuCo2S4 materials are prepared by anion-exchange and post-annealing. The annealing treatment under reasonable temperatures does not change the morphology and structure of CuCo2S4 significantly. But, the degree of crystallinity of CuCo2S4 can be easily changed by adjusting the annealing temperature. A high temperature results in a highly crystalline material. The electrochemical performance of CuCo2S4 is investigated and it is obviously influenced by the crystallinity. The material annealed at 200 degrees C exhibits a higher specific capacitance compared to the amorphous and those treated at higher temperatures. The optimal material has the highest specific capacitance of 424 F g(-1) at 1 A g(-1) and good stability. When it is assembled a hybrid capacitor with activated carbon as a negative electrode, the hybrid capacitor shows a high energy density of 22 Wh kg(-1) at a power density of 405 W kg(-1) in a potential window of 1.62 V. (C) 2020 Elsevier B.V. All rights reserved.