Controllable Synthesis ZnO And N Doped Porous Carbon For Supercapacitor And Zinc Ion Battery

As new styles of eco-friendly energy storage devices,supercapacitors and zinc-ion batteries have been widely reported and intensively explored by researchers.However,supercapacitors based on store charges predominantly at the interface between electrode and electrolyte,which makes the low energy density and limits their further development.Up to now,zinc ion batteries are mainly hampered by the lack of suitable cathodes materials which can provide high capacity and long cycling stability.Porous cabon materials derived from biomass featured with low cost,high specific surface area,high chemical stability and thermal stability,abundant pore structure,controlled surface chemisty and superior conductivity,are considered as one of the most widely used electrode materials.Improving the specific capacity is a primary task to obtain supercapacitors and zinc ion batteries with excellent electrochemical performance.In order to improve the electrochemical capacity of porous carbon materials,this paper focuses on adopting the strategies of developing pore structure and composites,expounding the effects of structures and surface chemical properties of porous carbon materials on their electrochemical properties.This paper provides possibility for supercapacitors and zinc ion batteries with excellent electrochemical properties.This paper includes the following parts:（1）Preparation of ZnO and N doped corn silk derived porous carbon（ZNC/ZnO/CSPC）.Using the corn silk as the precursor,the hierarchical porous carbon（CSPC）with honeycomb structure was prepared by facile one-step carbonation and activation.In order to further improve its electrochemical performance,metal oxide（ZnO）was introduced and used as template to further synthesize ZIF-8/ZnO/CSPC,N and ZnO doped hierarchical porous carbon composite（ZNC/ZnO/CSPC）was obtained by simple calcination.XRD,SEM,TEM,BET and XPS were used to characterize the composition,morphology and pore distribution of synthesized samples.（2）Study on electrochemical properties of ZNC/ZnO/CSPC as electrode material for supercapacitor.In the three electrode system,ZNC/ZnO/CSPC composites delivered high specific capacitance of 347 F g^-1 at 0.5 A g^-1,excellent rate performance(64%capacitance retention even at 30 A g^-1),and its electrochemical performance is better than ZnO/CSPC and CSPC samples.In addition,the as-assembled ZNC/ZnO/CSPC//ZNC/ZnO/CSPC symmetric supercapacitor has been tested at 6 mol L-1 KOH where a superior energy density 9.46 Wh kg^-1 was achieved,still maintaining 6.22 Wh kg^-1 even at high power density 7721 W kg^-1.Outstanding cycle ability（90.1%retention of the intial capacitance after 10000 cycles）was also achieved at 4 A g^-1.（3）In order to reduce the cost of aqueous zinc ion battery and improve the rate performance and cycle stability,we reported an aqueous zinc ion battery based on the above prepared ZNC/ZnO/CSPC as cathode material,zinc metal as anode and 1 mol L-1 ZnSO4 as electrolyte.Due to the unique 3D hierarchical porous structure and the synergistic effect of heteroatoms and ZnO,the aqueous zinc ion battery showed excellent electrochemical properties,such as high reversible capacity of 168.4 mAh g^-1 at a current density of 0.3 A g^-1,excellent rate performance,long-term cycling stability of 93%capacity retention after 10000 cycles and high energy density of 112.8 Wh kg^-1.Excellent electrochemical performance proves that heteroatom and ZnO-doped porous carbon composite can be used as candidate for aqueous zinc ion battery.