Preparation,Characterization And Electrochemical Performances Of Some Novel Metal Organic Frameworks

As we know,specific capacitance and potential window are two key controlling factors for energy density of supercapacitors.Although activated carbon based asymmetric supercapacitor?ASC?has a relatively larger window and better cycle stability than the conventional three-electrode system,but its power density and energy density can still not satisfy the real requirements.In recent years,asymmetric supercapacitor using the metal organic frameworks?MOFs?material with relatively higher specific capacitance as positive electrode material has attracted great attention and showed promising application potential.In this thesis,four kinds of novel nanoscale porous MOFs were designed and applied to assemble MOFs//ACS?Activated carbon nanosheets?aqueous based ASC with large potential window and high energy density.These materials have high specific capacitance,good cyclic stability as well as simple operation and low cost.The thesis consists of four parts as follows:?1?Using hexadecyltrimethyl ammonium bromide?CTAB?and urea as the structure controlled agents and imidazole?IM?,2-methylbenzimidazole?2-mbIM?,Co?NO₃?₂·6H₂O,Ni?NO₃?₂·6H₂O as raw materials,a new ZIF material NPZ was synthesized successfully by a simple solvothermal method.And then by directly high-temperature carbonizing the NPZ a novel bimetallic porous carbon material was obtained.This carbon material showed the highest specific capacitance of 1059 F·g^-1at a current density of 1.0 A·g^-1.When the current density rose to 5.0 A·g^-1,the specific capacitance remained 94%of the initial value.Using it as positive electrode material and 0.1 M Na₂SO₄ as neutral electrolyte the assembled NPCZ-3//ACS ASC possessed a wide potential window of 0¹.6 V,high energy density of 20.35 Wh·kg^-1.The device also exhibited an excellent cycling behavior with 91.67%retention of the initial capacitance after 10000 charge/discharge cycles.?2?A cobalt complex Co-PZM,a Ni-Co bimetallic complex PZM with 2-mbIM,pyromellitic dianhydride?PMDA?as ligands and a Ni-Co bimetallic complex PM with PMDA were prepared.Crystal structure of Co-PZM was determined by X-ray single crystal diffraction method.The obtained PZM and PM exhibited both good electrochemical properties and their specific capacitances were 2200 F·g^-1 and 2800F·g^-1 at 1 A·g^-1 of current density.As a result,by employing PM with relatively better electrochemical performance as positive electrode and activated carbon as negative electrode,1 M KOH as electrolyte a PM//ACS ASC with a wide potential window of0¹.4 V,high energy density of 86.7 Wh·kg^-1 at the power density of 700 W·kg^-1 and good cyclic stability?specific capacitance rentention of 87.5%after 5000 cycle?was assembled,which showed a good potential application.?3?A novel Viburnum blossom-like nanostructure 1,2,5,8-tetrahydroxy-anthraquinone?THAQ?zeolitic framework TZM was prepared by using THAQ to substitute imidazolate of ZIF-67.Its highest specific capacitance reached 2030 F·g^-1 at1 A·g^-1 of current density in 3 M KOH.When the current density increased to 5 A·g^-1,the specific capacitance rentention rate was 82%.TZM possess the hybrid structure of the micropores and mesopores.The TZM//ACS asymmetric supercapacitor with 1M KOH as the electrolyte possessed a voltage window of 0¹.5 V and delivered an energy density of 47 Wh·kg^-11 at the power density of 750 W·kg^-1.At the same time,the device exhibited a good cycling behavior with 83%retentions of the initial capacitance after 2000 charge/discharge cycles.At last,an all-solid state ASC was successfully assembled with PVA-KOH gel as solid electrolyte and diaphragm.?4?A novel NFM MOF was prepared as a positive electrode material by using a low-temperature solvothermal procedure using nitrogen-rich diphenylcarbazone as a ligand.The electrochemical test exhibited that the specific capacitance was 1829.3F·g^-1 at the current density of 1.0 A·g^-11 and when the current density increased 5 times,the specific capacitance remained 79.5%.The assembled NFM//ACS ASC with 1 M KOH as the electrolyte displayed an excellent electrochemical performance.The potential window was 0¹.5 V and when power density was 750 W·kg^-1,it delivered a high energy density of 47.9 Wh·kg^-1.