| The continuous progress of science and technology promotes the rapid development of electronic products,which raises higher demands for energy storage devices.Zinc ion hybrid supercapacitors（ZHSCs）combine the advantages of batteries and capacitors,which have both high energy density and high power density.At the same time,the advantages of higher safety and lower cost make it an ideal energy storage device and has attracted extensive attention.Carbon materials are widely used in ZHSCs as excellent capacitive electrode materials,but the low specific capacity of carbon materials has become the main factor limiting the energy density of ZHSCs.Therefore,it is urgent to develop high-performance carbon materials to improve the energy density of ZHSCs.Based on its energy storage mechanism,carbon materials with large specific surface area,porous structure and heteroatom doping usually have better electrochemical properties.Large specific surface area and porous structure are conducive to improve its electric double-layer capacity and rate performance,and heteroatom doping can usually improve its conductivity.As a modification of carbon materials,oxygen functional groups modification can significantly improve the wettability and pseudocapacitance of carbon materials.Therefore,carbon materials that combine the advantages of large specific surface area,porous structure,heteroatom doping and oxygen functional group modification will have better electrochemical properties than activated carbon materials.Based on the principle of preparing carbon materials with large specific surface area,porous structure,heteroatom doping and oxygen functional group modification,three kinds of modified carbon materials were designed and synthesized for ZHSCs.The relevant research contents are as follows:（1）Porous nitrogen doped carbon material（ZPC）was prepared by step-by-step calcination method with metal organic framework ZIF-8 as precursor.The step-by-step calcination method not only maintained the morphology of ZIF-8,but also formed rich pore structure.Furthermore,nitrogen doping can improve the conductivity of the material and increase the chemical adsorption capacity of the material to zinc ion.The ZHSCs assembled with ZPC as cathode has a specific capacity of 216.3 F g-1 and 104.4F g-1 at a current density of 0.2 A g-1 and 10 A g-1 respectively.At the same time,the capacity retention rate reaches 98%after 10000 cycles at a current density of 2 A g-1.（2）The commercial super conductive carbon black（SCCB）was used as raw material,after high temperature calcination activation and acid treatment,the oxygen enriched functional group carbon material（SCCB-800-O）was successfully prepared.The oxygen functional group significantly improved the wettability and pseudocapacitance of the material.The ZHSCs assembled with SCCB-800-O as cathode has a specific capacity of 174.9 F g-1 and 95.4 F g-1 at a current density of 0.2A g-1 and 20 A g-1 respectively.At the same time,the capacity retention rate reaches96%after 10000 cycles at a current density of 10 A g-1.More than that,XRD,XPS and SEM show that the carboxyl and carbonyl groups in the oxygen functional groups contribute to the main pseudocapacitance.（3）The hollow bowl carbon material（HCB）was simply fabricated by low-temperature synthesis,calcination and subsequent etching processes.And then the oxygen functional groups modified carbon bowl material（HCB-O）was obtained by further acid treatment.The obtained materials were applied as cathode for ZHSCs.The results show that the specific capacitance of HCB-O cathode is about 34%higher than that of HCB.The excellent performance are mainly attributed to the large specific surface area,good conductivity and abundant surface oxygen functional groups of HCB-O.Furthermore,the energy storage mechanism of oxygen functional groups was explored by XRD,XPS and SEM,which promoted the research and development of zinc storage mechanism of oxygen functional groups. |
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