Preparation And Electrochemical Properties Of Porous Carbon Derived From Coal Tar Pitch

Thanks to adjustable pore size,the large specific surface area as well as high electrical conductivity,porous carbon materials have been widely used as electrode material for electrochemical energy storage.Coal tar pitch（CTP）is a by-product from coal tar distillation process.It is considered as a promising precursor for the functional carbon materials because of its high carbon content,abundant reserves and low cost.In the present thesis,Using CTP as the carbon precursor,the porous carbon materials were prepared by chemical activation method,chemical foaming method and other methods.The obtained porous carbons were used as the supercapacitor or lithium-ion batteries electrode materials.The effects of structure and composition of porous carbon on their electrochemical properties was researched.The main research contents and results are as follows:1.The coal tar pitch-based porous carbon material（PPC）has prepared though chemical activation process and KOH as an activator.And the effects of activation conditions on the physical structure,chemical composition and electrochemical properties of porous carbon materials were studied.The results show that the PPC-3presents the 3D mesh-like porous structure,a high specific surface area of 2583.8 m²g^-1when the mass ratio of KOH to CTP is 3:1 and the carbonization temperature is 700℃;the specific capacitance of PPC-3 achieves 623.6 F g^-1 at a current density of0.5 A g^-1in the three-electrode system of 1M H₂SO₄ electrolyte.When the current density is increased to 100 A g^-1,the specific capacitance remains to 305.9 F g^-1.2.Using the CTP as a carbon source,（NH₄）₂SO₄ as foaming agent and KOH as an activator simultaneously a Nitrogen-doped porous carbon materials were prepared by ball-mill mixing and melt-activation process.The effects of preparation conditions on the surface morphology,structure,specific surface area and electrochemical performance of nitrogen-doped porous carbon materials were studied.The results show that when the carbonization temperature is 700℃and the mass ratio of KOH to coal tar pitch carbon ratio is 2:1,the NPC-2 has high specific surface area(1636.928 m² g^-1)and abundant nitrogen content（5.27%）.The capacitance of NPC-2is 374.2 F g^-1 at a current density of 0.5 A g^-1in 6 M KOH electrolyte.When the current density is 100 A g^-1,its specific capacitance remains at 249.5 Fg^-1,which showed favorable rate performance.3.Using CTP as carbon source,（NH₄）₂SO₄ as foaming agent and nitrogen,Nitrogen-doped porous carbon materials were prepared through ball-mill mixing and high-temperature co-carbonization process.The phyical structure and chemical composition of obtained carbon materials were charactered,and their lithium storage performance was analysed also.The rusults show that the N-PPC-4 has interconnected and hierarchical porous structure,the specific surface area of 581 m²g^-1,abundant nitrogen content on the surface（3.67%）when the mass ratio of（NH₄）₂SO₄to coal tar pitch is 4:1.The reversible specific capacity reached 613.8 mAh g^-1 at the current density is 0.1A g^-1,it remained 620.2 mAh g^-1 after 100 cycles.When the current density increasing to the 2 Ag^-1,its reversible specific capacity is247.1 mAh g^-1.