Preparation Of Porous Activated Carbon From Double Precursors And Its Application In Energy Storage Devices

With the climate changing and environmental pollution worsening,the development of sustainable and renewable energy has attracted global interest.Due to the merits of high power density,high charging/discharging current,high stability,environmental friendliness,long life and so on,supercapacitors have become a hot topic of energy storage devices.Voltage and specific capacitance are the key factors affecting the energy density of supercapacitors.The electrolyte that affects the voltage is unable to achieve a breakthrough due to technical bottlenecks,so that many researchers turned to developing new active electrode materials for increase of specific capacitance.On the other hand,lithium-sulfur batteries have become the most promising new energy storage device to replace lithium-ion batteries due to the high energy density.However some critical issues have to be solved before the commercialization of lithium-sulfur batteries.For instance,sulfur element has poor conductivity,and the dissolution and reprecipitaion of polysulfides during charging and discharging will result in severe volume expansion of electrode.Because of its high porosity,high specific surface area,excellent electrical conductivity and chemical stability,activated carbon is expected to be a priority as active materials in supercapacitor electrodes and substrate materials of lithium-sulfur battery cathode.Aiming at improving the performance of supercapacitors and lithium-sulfur batteries,two inductive methods have been developed in this work to tune and optimize the microstructure and porosity of carbon materials,and the main contents are described as follows:（1）Using cotton as carbon source and protein as secondary carbon source as well as revulsant,microporous activated carbon with connected mesopores and adjustable pore size distribution has been prepared through pre-carbonization treatment by mixed acid and activation by zinc chloride.In electrolyte of 1 M TEABF₄/AN,a supercapacitor made of the resultant microporous activated carbon had a specific capacitance of 118Fg^-1 at 1Ag^-1,and the capacitance retention rate was 78.1% after 10,000 cycles at a current density of 20Ag^-1.Using supercritical fluid deposition technology,sulfur was impregnated in the channels and pores of activated carbon to prepare activated carbon/sulfur composite,which in the lithium-sulfur battery,exhibited an initial capacity of 1172mAhg^-1 at0.1C and a retention capacity of 497mAhg^-1 at 0.5C after 300 cycles.（2）Using polyacrylamide as carbon source,glucose as auxiliary carbon source and inducer and potassium hydroxide as activator and pore-forming agent,porous carbon materials with three-dimensional pore structure were successfully prepared.At a current density of 1Ag^-1,the specific capacitance of the assembled supercapacitor was 90F g^-1.At the current density of 20Ag^-1,66.2% of the specific capacitance was remained after 10,000 cycles.At the high current density of 10Ag^-1,the specific capacitance was 76Fg^-1.Again,sulfur was impregnated into the pores of activated carbon through supercritical fluid deposition to prepare composite materials of sulfur and activated carbon.In lithium-sulfur battery,the material exhibited an initial capacity of 905.5mAhg^-1and a capacity of 325.6mAhg^-1 after 300 cycles at 0.1C with a retention rate of 50%.