MOFs-Derived Battery-Type Anode Materials For Sodium-Ion Hybrid Capacitors

Electrochemical energy storage devices with high efficeicy and stability have been received extensive attention for using renewable energy siurces.Inwhere,sodium ion hybrid capacitors have become one of the most promising candidates for large scale energy storage systems by reasons of their high energy density,power output and long cycling stability because of the combination of the advantages of a electric double layer capacitor and a secondary metal ion battery in one device.However,two different energy storage mechinisms,the fast electric double layer capacitance in cathode and the slow Faladic reaction in anode,will result in the mismatch between anode and cathode in kinetic behavior in SIHC device.At the same time,it is crucial for seeking robust structural host materials due to the large sodium ionic radius.Therefore,the key for construction a high performance SIHC is to searching suitable battery-type materials with fast kinetic behaviors and robust structural merits..In this dissertation,metal oxid,metallic sulfide or selenide/carbon nanocomposite anode materials with typical morphology,tunable composition and robust structure have been prepared through pyrolyzing of metal organic frameworks（MOFs）modified by polymer.The relationship between the electrochemical performance and microstructures of materials have been studied sufficiently.Finally,a series of high performance SIHCs were assembled by optimization the mass ratios of anode and biomass-derived nanoporous carbon cathode The details of the study and the results are as follows:（1）The ZIF-67 coated by polymer containing N,P,S heteroatoms was synthesized by simple chemical polymerization.Combining the advantages of template of ZIF-67 and confinement of polymer coatinglayer,nanoporous anode materials of hollow core-shell polyhedral Co P_xO_y/C@NPSC were prepared by adjusting the pyrolysis conditions in argon atmosphere.The unique hollow core-shell structure,small particle size and abundant surface heteroatom energy storage sites were responsible for the fast ion/electron transfer,high sodium ion storage specific capacity and good cycling stability.Consequently,based on Co P_xO_y/C@NPSC anode material and tobacco-derived biomass carbon（DTPC）cathode material,the assembled SIHC demonstrated a high energy density(96.47 W h kg^-1),high-power output(21 k W kg^-1)as well as superior rate capability,verifying the structural advantages of as prepared materials.（2）The small grain size metallic selenide distributed uniformly in porous carbon network with abundant energy storage sites were prepared by using the pyrolysis of Ni-MOF,Co-MOF and NiCo-MOF with selenium powder in argon atmosphere.The energy storage characteristics of different materials are investigated.The results showed that NiCo_xSe_y/CN had a high specific capacity,superior rate performance long cycling stability as well as fast kinetic behavior.Matching DTPC as cathode material,the assembled SIHC could provide 107.1 W h kg^-1of energy density and20 k W kg^-1of power output.（3）Bimetallic sulfide/carbon nanopoure composite（NiCo_xS_y/C@CNS）was prepared by high temperature treatment of sulfur and NiCo-bimetal MOF modified with polydopamine in argon atermosphere.NiCo_xS_y nano grains wrapped by organic ligand-decomposed porous carbon distributed uniformly in N and S Co-doped carbon matrix generated from the carbonization of polydopamine.The double confinement of two kinds of carbon matrix could sufficiently reduce the volume change of active material during the charge/discharge process..Meanwhile,the doping of S and N elements could improve the electrolyte wettability of the material and increase the energy storage active sites,resulting in good cycling durability and high sodium storage specific capacity.As as result,the as-constructed SIHC device based on DTPC cathode also exhibited excellent electrochemical performance(137.1 W h kg^-1 of energy density and 21 k W kg^-1 ofpower density).