The influence of S-doped technique on supercapacitor performances for Co(OH)2@nitrogen-doped carbon dots.

Recently, Co-based materials have been widely used as a type of supercapacitor. However, Co-based materials are highly restricted due to their low conductivity, poor cyclic performance, and large structural changes during the charge/discharge process. Carbon materials have been found to improve the electrochemistry performance of Co(OH)₂. In this work, sulfur doping was used to enhance the electrochemistry performance of Co(OH)₂@nitrogen-doped carbon dots (Co(OH)₂@NC) via hydrothermal approach. Here, as-prepared S-Co(OH)₂@NC shows an excellent specific capacitance of 730 F g⁻¹ at 1 A g⁻¹ (much higher than that of pristine Co(OH)₂@NC (592 F g⁻¹ at 1 A g⁻¹)). An asymmetric supercapacitor (ASC) is assembled by S-Co(OH)₂@NC (as a positive electrode) and graphene aerogels@NC (as a negative electrode), which presents a specific energy density as high as 39.59 Wh kg⁻¹ with a power density of 639 W kg⁻¹. Moreover, the ACS manifests extraordinary cycle stability (75% capacitance retention after 8500 cycles). In summary, sulfur doping in electrode material has been proven as an efficient approach for improving the electrochemical performance in supercapacitor devices. [ABSTRACT FROM AUTHOR]