The Regulation Of Hyper Crosslinking Polymer-Derived Porous Carbon And Its Supercapacitor Performance

Owing to their high power densty,long lifetime,fast charging-discharging,and low environmental pollution,supercapacitors have been the focus of academic and industrial attention for energy storage.However,there are still technical challenges in developing supercapacitors that combine low cost,wide voltage operation and high energy density,and one of the most critical aspects of solving these problems is the development of electrode materials for supercapacitors.Porous carbon is a new type of porous electrode material for supercapacitors.Not only does it have good electrical conductivity,good physical and chemical stability and environmental friendliness,but it also has the advantage of achieving ultra-high specific surface area,adjustable pores and multiple morphologies.Currently,porous carbon has a wide range of applications in supercapacitors.Most of the reported work on the preparation and regulation of porous carbon has been devoted to improving the specific surface area of porous carbon or emphasising the doping of heteroatoms to increase the capacitive performance of the electrode material,with little reported attention to the reasonable regulation of the pore structure of porous carbon.It has been shown that a reasonable pore size distribution of porous carbon not only contributes to the high capacitive performance of the material,but also increases the power density of the supercapacitor at the same time.Based on this,the present work focuses on the rational regulation of the pore structure of porous carbon from the instability of chemical cross-linking of small molecules,specific research contents are as follows:1.This work used coal tar（CT）as the carbon source and cyanuric chloride（CC）as the crosslinker to synthesize a carbonized polymer dots（CPDs）-based aromatic polymer composite（CPD@HCP（CC）-120）with own soft and hard template via Friedel-Crafts reaction,as the precursor.The porous carbon with high enrichment mesopores（size of2～10 nm）was hierarchically controlled by CPDs based pore-formation strategy.We focused on a CPDs formation mechanism and propose a new sacrificial template pore-formation method which using CPDs as hard template and hyper crosslinking polymer（HCP）as soft template.During the activation of the precursor,the cross-linking instability of cyanuric chloride in the HCP was exploited to allow the HCP to be preferentially ruptured by KOH etching,thus making the CPDs are removed or exposed from the body materials.The optimum conditions for the forming-pore method were investigated by setting up orthogonal activation pore-formation experiments with different temperatures and different concentrations of KOH.It was found that the CCPD@HCPM（CC）-800-1.0,at 800 ^oC with a coke agent ratio of 1:1,holds 92.07%of 2～10 nm pores,a high specific surface area and pore volume(4241 m²·g^-1and 2.506 cm³·g^-1)and abundant active sites.2.The same preparation conditions as for the（CPD@HCP（CC）-120）precursor,we prepared the comparative precursors CPD@HCP（CB）-120,PHCP-120 by replacing the CC crosslinker with trichlorobenzene（CB）or a control experiment in which the Friedel-Crafts reaction occurred in pure coal tar without crosslinker.Under the same preparation conditions as CCPD@HCPM（CC）-800-1.0,we obtained CCPD@HCPM（CB）-800-1.0and CPHCPM-800-1.0 comparison samples by carbon-activation of CCPD@HCP（CB）-120 and PHCP-120,respectively.The feasibility of the pore-formation strategy for CPDs was demonstrated by analysing the relevant composition and structural differences and by theoretical calculations.3.The porous carbon prepared above was applied as an electrode material in three aqueous electrolytes（neutral,acidic and alkaline）for comparative electrochemical analysis to explore the suitability of porous carbon with high enrichment of 2～10 nm mesopores prepared by the CPDs based pore-formation strategy in aqueous electrolytes.The optimal sample CCPD@HCPM（CC）-800-1.0 carbon electrode was also assembled into a symmetrical organic-based supercapacitor to investigate the match between the best sample and the organic-based electrolyte,as well as to analyse the effect of pore structure on the electrochemical performance of porous carbon from both activation concentration and activation temperature perspectives.In addition,the superiority of the pore formation pattern due to the use of cross-linker small molecules was further explored by analysing the difference in supercapacitance performance between CCPD@HCPM（CC）-800-1.0and the two comparison samples in aqueous or organic systems.In the three-electrode alkaline system,the standard sample electrode can deliver the gravimetric specific capacitance（C_g）of 437 F g^-1 at 1.0 A g^-1 and its capacity retention reached 92.85%with coulombic efficiency 99.99%after 20,000 cycles.Particularly,the symmetric EDLCs assembled with the standard sample electrode in 1M TEATFB/PC electrolyte,the capacitance(C_cell)of the standard sample was 150.4 F g^-1 at 1.0 A g^-1 and still maintained114.6 F g^-1 at 50 A g^-1.The capacity retention of the standard sample can still maintain80.12%with the coulomb efficiency 99.78%after 5000 cycles,and possessing a good rate and excellent cycle performance.The device achieves a high energy density of 47Wh kg^-1 at a power density of 750 W kg^-1 and maintained a high energy density of 35.81Wh kg^-1 even at a power density of 37497 W kg^-1.Compared the electrochemical performance of CCPD@HCPM（CC）-800-1.0 with that of Kuraray’s commercial activated carbon,it was found that its energy storage performance was much higher than that of commercial activated carbon.The final study shows that the hierarchic porous carbons with highly enriched small mesoporous prepared by CPDs based pore-formation strategy can well enhance the high value-added applications of coal tar,whcih expands a new avenue for the application of carbon-based supercapacitors with high energy density and power density.