Design And Optimization Of Carbon Cathode Materials For High-performance Zinc Ion Hybrid Capacitors

At present,more attention is focused on advanced energy storage systems.The booming development of new energy vehicles stimulates great demands on new pattern energy storage device.Affordable,safe and eco-friendly hybrid capacitor is a new type of electrochemical energy storage device that combines the advantages of supercapacitors and batteries.Among them,zinc-ion hybrid capacitors(ZIHCs)have become one of the current research hotspots due to the advantages of rich zinc metal resources,low cost,no corrosiveness and toxicity.It is essential to design and optimize desirable capacitive cathode materials in order to realize high-efficiency energy storage of ZIHCs.The main research contents and conclusions of this paper are shown in the following:(1)Ordered mesoporous carbons(TOMCs)were successfully prepared by a modified green EISA method using plant polyphenol tannin acid as the carbon source and less organic solvent.The ratio of alcohol to water and the pyrolysis temperature were optimized by investigating the pore structure and electrochemical properties of the resultant materials.The obtained TOMC-3-700 has a high specific surface area(967 m2 g-1),and a long-range ordered mesoporous structure.The constructed Zn//2M ZnSO4(aq)//TOMC-3-700 ZIHC device has a wide potential window(0～1.8V),high energy density(148.85 Wh kg-1 at 180 W kg-1)and excellent cycling stability(85.7%capacity retention after 10,000 cycles).In addition,the assembled all-solid-state Zn//PAMZnSO4(gel)//TOMC-3-700 ZIHC can also achieve an energy density of 121.25 Wh kg"1 at a power density of 180 W kg-1.(2)On the basis of the above research work,nitrogen-doped tannin-derived mesoporous carbon material(NTMCs)was synthesized using urea as the nitrogen source and porogen.And the amount of urea adopted in the preparation process was optimized.The as-prepared NTMC-1 material has a large specific surface area(990 m2 g-1)and a desirable mesoporous structure.The Zn//2M ZnSO4(aq)//NTMC-1 ZIHC device exhibits high specific capacitance(454.56 F g-1 at 0.2 A g-1),ultrahigh energy density(204.55 Wh kg-1)and power density(18 kW kg-1),and excellent capacity retention rate(88.34%after 10,000 cycles at 5 A g-1).(3)The hierarchical porous carbon materials(CnNNm-x-y-z)were prepared by molten salt-assisted method using chitin as carbon source,NaCl as template and NaNO3 as etchant.By designing the L9(34)orthogonal experiment,the influence of chitin/NaNO3 mass ratio,pyrolysis temperature,pyrolysis time and heating rate on the pore structure and electrochemical characteristics of the materials was systematically investigated employing specific surface area and pore volume as optimized parameters.The C2NN1-800-1-5 prepared under the optimal conditions has a high specific surface area of 1256 m2 g-1 and a large pore volume of 0.785 cm3 g-1.Zn//2M ZnSO4(aq)//C2NN1-800-1-5 ZIHC device has high energy density(133.4 Wh kg-1 at 180 W kg-1)and excellent cycling with an outstanding capacity retention of 100%after 10,000 cycles.