Preparparation And Performance Of The Capacitive Carbon Materials For Supercapacitors

Supercapacitor, as a new secondary energy storage device, has the intermediate performance between conventional capacitors and lithium ion batteries. Currently, supercapacitor's march toward ever-increasing energy and power is continuing. As a key component of a supercapacitor, the development of the electrode material is crucial. With the superior performance and low price, carbon materials are very competitive among all the electrode materials. In this paper, three kinds of new carbon materials for supercapacitor was designed and prepared. Furthermore, the effect of the preparation technology on the structure and capacitive performance of the carbon materials was studied. The obtained main achievements and progress are as follows:The nitrogen-doped mesoporous carbon was facilely prepared by direct pyrolysis of a nitrogen-containing organic salt (EDTANa2Ca). The effect of pyrolysis temperature on the nitrogen content, pore structure as well as the capacitive performance of the carbon material in both organic and inorganic electrolyte was explored. The results showed that with the increasing pyrolysis temperature, the prepared carbon exhibited higher surface area and decreasing nitrogen content. The carbon material prepared with pyrolysis temperature of 750 ? exhibited high surface area (1485 m2 g-1), developed mesoporous structure, high nitrogen content (4.12 at%) and the consequent good electrochemical performance. In 6 mol L-1 KOH aqueous electrolyte, the supercapacitor with the nitrogen-doped mesoporous carbon had the best performance (236 F g-1 at 50 mA g-1,173 g-1 at 20 A g-1). The specific capacitance can retain 85.93% after 10000 cycles at a current density of 1 A g-1. Meanwhile, in the organic electrolyte, the nitrogen doping did not play a role to improve the specific capacitance.The activated carbon wrapped in graphene with three-dimensional network structure was designed and prepared by the hydrothermal self-assembly method. The obtained 3D activated carbon/graphene composite electrode material showed both high specific capacity and excellent rate performance. The high specific capacity can be attributed to the activated carbon with high surface area. In 6 mol L-1 KOH aqueous electrolyte system, the composites had high specific capacitance of 294 F g-1 at a current density of 50mA g-1. Meanwhile, the graphene 3D network with high electrical conductivity endowed the composite material with excellent electron and ion conductivity, as well as outstanding rate performance. The specific capacitance retained 207 F g-1 at a current density up to 20 A g-1, showing the high capacitor retention of 70.4%.The mesoporous graphite carbon was prepared by facile pyrolysis of trinickel dicitrate, which plays roles of the carbon source, the template and the graphitization catalyzed agent. The specific surface area and graphitization degree of the mesoporous carbon can be controlled by the reaction temperature. With the increasing pyrolysis temperature, the degree of graphitization of the carbon material was improved and the specific surface area was decreased. The graphitized mesoporous carbon showed extremely excellent cycle performance in 6 mol L-1 KOH aqueous electrolyte. The specific capacitance can retain 99.0% after 10000 cycles at a current density of 2 A g-1.