Study On The Preparation Of Electrode Materials For Electric Double-Layer Capacitor From A Loose Medium Component Of Tongting Coal

The electrode material is an important factor that affects the performance of electric double layer capacitors.Carbon material is the first choice for electrode materials of electric double layer capacitors because of its abundant resources,low price,simple preparation method and good conductivity.How to optimize the properties of carbon materials is the focus of many researchers in the field.Taking this as the target in this paper,the coal with rich reserves as the carbon source,the specific group of loose medium component(LMC)separated from coal as the research object,which prepared the hierarchical porous carbon materials by different methods,and further assembled the electric double layer capacitor.And The effects of preparation methods and conditions on the electrochemical properties of the electric double layer capacitors were also investigated.These preparation methods include:(1)LMC was prepared into foamed carbon and then broken into smooth carbon sheets.The smooth carbon sheets were etched by KCl and KOH co-activation to prepare controllable carbon materials with hierarchical pore structure.(2)LMC and KOH were directly mixed and calcined with the aid of KH₂PO₄ to prepare the hierarchical porous carbon materials with uniform micron-size,bubble-like pore structure.(3)LMC and KOH were directly mixed with lignin synergistic action.The hierarchical porous carbon materials of mountain shape pore distribution with micron-size,bubble-like pore structures were prepared by two-step method of hydrothermal reaction with water-ethanol as solvent and calcination reaction.The results show as follows:(1)Hierarchical pores carbon was fabricated by KOH etched carbon sheet with KCl-assisted.A smooth and defectless carbon sheet with thickness of 1?2?m was prepared by foamed carbon from LMC.KOH can be used as an activator to etch micropores and mesopores on carbon sheets through deuterogenic K₂CO₃and K₂O.And KCl exhibits a melting flow state at activation temperature,thus dispersing partially stacked K₂CO₃and K₂O onto more larger carbon surfaces,which leads to an increase in the number of micropores and mesopores on carbon surfaces.Controlling the content of KCl and KOH can directly control the pore number and pore size distribution,and improve the electrochemical properties of carbon material.When carbon sheet/KCl/KOH was at a mass ratio of 1:3:4,the best specific surface area and electrochemical properties can be obtained by adjusting the contents of KCl and KOH properly.The specific surface area was 3627 m²·g^-1.And the specific capacitance reached up to 346 F·g^-1 at the current density of 0.1 A·g^-1 with high energy density and power density of 12 Wh·kg^-1 and 25 W·kg^-1,respectively.(2)Hierarchical pores carbon rich in uniform micron-sized,bubble-like pores was prepared by one-step method with KH₂PO₄-assisted LMC.KH₂PO₄ was melted and dehydrated into(KPO₃)_n during calcination to produce a template for the LMC to form micron-sized,bubble-like pores carbon materials.KOH was further activated to formed micropores and mesopores.The abundant micron-size,bubble-like pores acted as a reservoir for charge from the electrolyte and as a disturbance to incoming charge,causing the charge to move in all directions,thus,increasing the effective specific surface area.This experimental scheme also doped the hierarchical porous carbon material with O,which increased the surface wettability and improved the electrochemical performance.When the mass ratio of LMC,KH₂PO₄ and KOH was 1:1:5,the specific surface area of the prepared hierarchical pores carbon materials rich in uniform micron-sized,bubble-like pores was 3011 m²·g^-1,and the high specific capacitance was 336 F·g^-1,cycling performance was 92%,energy density was 11.47Wh·g^-1,and power density was 24.79 W·g^-1.(3)Hierarchical pores carbon with micron-sized,bubble-like pores was prepared by two-step method with lignin-synergetic LMC.The hydrothermal reaction in the solvent of water-ethanol promotes the close and uniform contact of LMC,lignin and KOH,which makes the decomposition of lignin in the second step of calcining process produce a large amount of gas,and the space occupied by lignin shrinks,resulting in the formation of microbubble structure.The activation of homogeneously distributed KOH makes the further formation of micropores and mesopores more conformable to the characteristics of mountain shape pore distribution.By controlling the amount of lignin,the pore size distribution of carbon materials can be changed.When LMC:lignin:KOH was 1:3:4,the carbon material with micron-sized,bubble-like pores structure has a high specific surface area of 2680 m²·g^-1.The specific capacitance reaches 336F·g^-1 when the current density is 0.1 A·g^-1,and 89%of the capacitance is retained after5000 cycles of charging and discharging under the current density 2 A·g^-1.There are 50 figures,21 tables and 223 references in this paper.