Preparation And Application Of Porous Carbon Composites For Supercapacitors

The energy and environmental crisis brought by the rapid development of modern society has promoted the systematic development of storage and transmission of clean and renewable energy.Energy storage devices,especially supercapacitors,have aroused great interesting from scientists.Supercapacitors have great application potential and value in many fields such as new energy vehicles,mobile electronic equipment and backup power systems due to their ultra-high power density,long cycle stability,wide working temperature range,and better safety.In this paper,a biomass porous carbon material was first prepared by a simple method of pyrolysis and alkali activation using the biomass precursor Beater tea leaves.The carbon material not only has high specific surface area and appropriate pore size distribution,but also is naturally contain nitrogen and oxygen elements,thus having excellent electrochemical capacitance performance.Therefore,this porous activated carbon material has high specific capacitances(311 Fg^-1)at a current density of 1 Ag^-1,and good rate performance and cycle stability?capacity remains 92%after 30000 cycles of charging and discharging?.It provides a high energy density of about 21 Whkg^-1 at a power density of 500 Wkg^-1 after being assembled into a symmetrical supercapacitor.This simple and cheaply prepared porous carbon material is promising in energy storage applications.Secondly,using the above biomass carbon as the substrate and adjusting the initial concentration of KMnO₄ solution,composite materials with different MnO₂ loadings were prepared by simple hydrothermal reaction.This active composite has high specific capacitances of 283.8 and 156.7 Fg^-1 at current densities of 1 and 10 Ag^-1.By using this composite material as a positive electrode,and beater tea leaves porous carbon as a negative electrode,an asymmetric supercapacitor was prepared to achieve a high power density of1620Wkg^-1 and a high energy density of 58.5 Whkg^-1.These excellent energy storage properties come from the heterogeneous nanostructures,highly conductive porous substrates and suitable ion/electron transport paths of this composite material.Finally,a double-layer hollow carbon microsphere?CNHS?was prepared by polycondensation and carbonization of tetraethyl orthosilicate,resorcinol and formaldehyde,and the required composite material?CNHS/MnO₂?is prepared through oxidation-reduction reaction.The material has outstanding energy storage performance,the specific capacitances reaches 300.4 Fg^-1 at 1 Ag^-1 current density,and outstanding rate performance and good cycle performance.