Study Of Porous Carbon Materials For High Performance Supercapacitors

Supercapacitors,which is also known as double-layer electric capacitors or electrochemical capacitors,a type of fast charge/discharge energy storage device that has been rapidly developed in the last twenty or thirty years.Compared to conventional capacitors or batteries,the energy density and power density of supercapacitors is larger than that of the conventional capacitors and batteries,respectively.Nowadays,supercapacitors have received great attention as next-generation devices due to their unique advantages including high efficiency,superior power capability and long life-time.Due to the excellent stability,high specific surface area and well-developed pore structure,the carbon materials have widely attracted as high-performance electrode materials for supercapacitors.In this thesis,the carbon-based electrode materials with high specific surface area and large pore structure were designed and prepared by simple high-temperature carbonized and activation methods,meanwhile,the suitable electrolyte solution was chose to construct the new type of symmetric/asymmetric supercapacitor.The main research contents are as follows:1.The porous carbon material(N-ACC),which was using coprinus comatus as biomass material,zinc chloride as a chemical activator and urea as a nitrogen source,have porous interconnected structure,these structures can effectively improve the electron transfer and ion separation rates at the electrode/electrolyte interface.As the electrode materials of a ultracapacitor,the specific capacitance of the N-ACC reach346 Fg-1 at a current density of 1 Ag-1,and the performance is excellent in rate performance(capacitance retention rate of 75% at 10 Ag-1).In addition,a symmetrical supercapacitor based on N-ACC material assembly can achieve a high energy density of 14.63 Wh kg-1 at a power density of 810 W kg-1.These results indicate that the carbon material N-ACC produced by coprinus comatus can be used as an electrode material for high-performance supercapacitors.2.The connected mesh porous carbon material N-CNP-X prepared by carboxymethyl cellulose with CaCl2 as the activator and urea as the nitrogen source at different carbonization temperatures.Tested results shown that N-CNP-750 material has the highest specific capacitance(173 Fg-1)while the current density was 0.5 Ag-1,which was used as the electrode material.The active electrolyte p-phenylenediamine(PPD)was added in the KOH electrolyte to improve the electrochemical performance of the electrode material.The electrolyte was added 0.001 mol PPD in KOH,the specific capacitance value was 482 Fg-1 is increased about 4 times.When the electrolyte was added 0.001 mol PPD in H2SO4,the specific capacitance is 288.0 Fg-1is increased about 62.9%.While,the electrolyte was added 0.001 mol PPD in Na2SO4,the specific capacitance is 104.1 Fg-1 increased about 50.4%.In addition,a symmetrical supercapacitor based on N-CNP-750 material assembly can achieve a high energy density of 25.74 Wh kg-1 at a power density of 639.9 W kg-1.The results show that using a simple method of adding redox active materials can effectively increase the specific capacitance value of the material.3.The Bi2MoO6 electrode material with a cross-platinum nanosheet structure was prepared by a two-step simple and effective hydrothermal method,which has a rich pore structure and an unique structure with a high surface area(40.65 m2g-1)made Bi2MoO6 have excellent electrochemical performance.For example,in the three-electrode system with KOH as the electrolyte solution,At the same time,the Bi2MoO6 has the specific capacitance still retained about 76% of the initial capacitance after the 1500 galvanostatic charge/discharge cycling tests in the solution at a constant current density of 3 Ag-1.In addition,a symmetrical supercapacitor based on N-CNP-750//Bi2MoO6 material assembly can achieve a high energy density of17.2 Wh kg-1 at a power density of 639.7 W kg-1,when the power density increases to6400 W kg-1,its energy density is still to be 8.89 Wh kg-1.The test results show that the Bi2MoO6 electrode material has high specific capacitance,good cycle stability and good cycle stability and capacity retention make us believe this low cost electrode material has great potential.