Preparation And Performance Study Of Petroleum Coke-Based Activated Carbon Composite Materials And Their Applications In Supercapacitors

Petroleum coke is a black solid coke obtained by thermal cracking of heavy oil,which is obtained by vacuum distillation of crude oil.The large amount of SO₂ gas produced by high-sulfur coke,which is mainly used as fuel,will cause serious damage to the environment.Therefore,there is an urgent need to find a clean,environmentally friendly and high-value utilization method for high-sulfur coke.Supercapacitors refers to a new type of energy storage device between traditional capacitors and rechargeable batteries,which has both the fast charging and discharging performance of traditional capacitors and the energy storage characteristics of rechargeable batteries.It has received extensive attention in recent years.Activated carbon is the most widely used electrode material in supercapacitors due to its large specific surface area,wide pore size distribution and high electrochemical stability.Because of its high carbon content,low ash content and high graphitization characteristics,petroleum coke is an ideal raw material for preparing activated carbon for supercapacitors.First of all,this study used KOH as the activator to obtain oxygen and sulfur-doped hierarchical porous carbon with a specific surface area of 3318 m² g^-1 by one-step carbonization and activation of petroleum coke.The obtained activated carbon was prepared into an electrode,and the maximum specific capacitance of 327 F g^-1 was obtained at a current density of 1 A g^-1 under the three-electrode system.When the assembled symmetrical supercapacitor used 6 M KOH as the electrolyte,the capacitance retention rate reached 96.5%after 5000 cycles of charging and discharging.With 1 M Na₂SO₄ as the electrolyte,the highest energy density of 29.6 Wh kg^-1 was obtained when the power density was 900 W kg^-1.Secondly,on the basis of the above work,using the strong oxidizing properties of KMnO₄,MnO₂ with nanowire-like structure was deposited in situ on the framework of activated carbon.The composite material HPC/MnO₂^-100 still had a loose porous structure with the specific surface area of 2079 m² g^-1.The specific capacitance reached 480 Fg^-1 at a current density of 1 A g^-1 under the three-electrode system.The asymmetric supercapacitor composed of HPC/MnO₂^-100 and HPC4 had a high energy density of 49.7 Wh kg^-1 at a power density of 450 W kg^-1.By performing 5000 cycles of charge and discharge at a high current density of 10 Ag^-1,the capacitance retention rate reached 79.1%.