Preparation Of Porous Carbon Based On Template Strategy And Study On The Performance Of Zinc Ion Hybrid Supercapacitors

The expansion of electrochemical energy storage devices for large-scale energy storage and power transmission is of great significance to the development and progress of today’s society.Zinc-ion hybrid capacitors（ZHC）have attracted extensive attention in academic circles due to its low cost,high performance,environmental friendliness and safety,which is integtated the merits of batteries and supercapacitors at the same time.However,compared with other energy storage devices,there are still some discrepancies for the electrochemical performance of ZHC.Therefore,the main bottleneck issue of obtaining high performance ZHC is to seek porous carbon with suitable pore structure and high specific surface area.Based on this,hierarchical porous carbon materials were synthesized from coal chemical by-products（coal tar pitch or anthracene）using different self-made hard templates coupled with K₂CO₃ activation strategies in this thesis.The pore structure,surface chemical properties and electrochemical performance of the obtained porous carbon were analyzed.The relationship between pore structure and microstructure and electrochemical performance of ZHC was elaborated and the charge storage mechanism of ZHC was also discussed.The main results are as follows:（1）Porous carbon material C-9 with high specific surface area(1292.2 m² g^-1),graphitization degree（I_D/I_G=0.93）and oxygen doping amount（5.0 at.%）was synthesized by using positive-drop Fe-based template prepared by one-step precipitation method and coal tar pitch as carbon precursor companying with K₂CO₃ as activating agent.Meanwhile,the comparative experiments exhibited that the porous carbon prepared by the mixed template has better physical and chemical properties and electrochemical performance than that prepared by the single template.In 2 M Zn SO₄electrolyte,C-9-based ZHC delivered high specific capacitance(102.2 mAh g^-1/0.05 A g^-1),good rate ability(48.9 mAh g^-1/20 A g^-1),high energy density(81.5 Wh kg^-1)and low resistance.In addition,the capacitance retention ratio of C-9 electrode is as high as92.40%after 70000 cycles,revealing excellent cycle performance.（2）In order to further compare the influence of Fe-based template on the physical and chemical properties of porous carbon materials,the flake-like hierarchical porous carbon materials were obtained by using coal tar pitch as carbon source,K₂CO₃ as activating agent and self-made reverse-drop Fe-based material as template.The influence of activation temperature on the microstructure and performance of porous carbon was explored.The comparative experiments certificated that the template and activating agent could optimize the physicochemical properties and electrochemical performance of porous carbon materials.The experimental results all suggested that C-800 has the highest specific surface area(1745.6 m² g^-1),pore volume(0.79 cm³ g^-1) nd suitable oxygen doping amount（1.6 at.%）.When C-800 is utilized as the cathode material of ZHC,the specific capacitance reaches 118.3 mAh g^-1(0.05 A g^-1),the energy density is 94.4Wh kg^-1(36.3 W kg^-1)and the capacitance retention ratio is 86.95%after80000 cycles,representing a long cycle life.（3）In order to prove the universality of the template strategy for preparing porous carbon,anthracene-based porous carbon was prepared by self-made Zn-based template combined with K₂CO₃ activation method.The influence of the amount of K₂CO₃ on the physical and chemical properties of porous carbon was discussed.The experimental results show that C-10 has the highest specific surface area(1612.5 m² g^-1),micropore volume(0.25 cm³ g^-1)and high graphitization degree（I_D/I_G=0.85）.C-10 electrode exhibits high specific capacitance(181.5 mAh g^-1/0.05 A g^-1),outstanding rate performance(78.9 mAh g^-1/20 A g^-1)and excellent energy density(145.0 Wh kg^-1)in 2M Zn SO₄ electroiyte.In addition,the capacitance retention rate of C-10 electrode is94.5%and the Coulomb efficiency is almost unchanged after 38000 charge/discharge cycles,which exhibits excellent cyclic stability.The capacitance attenuation is mainly caused by the formation of（Zn（HSO₄）₂）（H₂（SO₄））₂ dendrites on the electrode.C-10-based ZHC stores charge in the form of double layer capacitance and ion diffusion,but the contribution rate of capacitance increases with the increase of scanning speed,while the ion diffusion is limited,indicating that the performance of carbon electrode determines the ZHC specific capacitance and the speed of electrode chemical reaction kinetics.