Study On The Preparation And Electrochemical Properties Of Nanoporous Material Based On ZIFs

As a new type of energy storage device,supercapacitor have the advantages of high specific capacitance and good cycle stability.The most important factor to determine the performance of supercapacitor is electrode material.Zeolite-like imidazole framework materials?ZIFs?,as a novel porous structure have the advantages of high specific surface area,controllable structure and strong thermal stability.In addition,the high thermal and chemical stability of ZIFs can be used as an excellent template for the preparation of porous nanomaterials,which are subsequently applied to supercapacitor materials.The specific research content based on this paper is as follows:?1?Preparation and testing the electrochemical performance of the cubic hollow ZnCo₂O₄:The cubic bimetallic zinc-cobalt zeolite imidazole framework material?Zn-Co-ZIF?was prepared by a liquid deposition method.Then we investigated impact the oxidation temperature and phase and morphology of ZIFs by using Zn-Co-ZIF as precursor.The cubic hollow structure ZnCo₂O₄ was obtained under oxidized condition of 375°C.After a series of electrochemical performance tests,the results show that the hexagonal hollow structure of ZnCo₂O₄ can reach 338 F·g^-1 at a current density of 10 A·g^-1 at a current density of 10 A·g^-1.After 5000 cycles of charge and discharge,the specific capacity can be maintained 92%of the initial specific capacitance.?2?Preparation and Electrochemical Properties of Zinc Cobalt Bimetallic Sulfide??Zn,Co?S?:The?Zn,Co?S nanomaterials were prepared by a one-step hydrothermal method which using Zn-Co-ZIF as the precursor and thioacetamide as the sulfur source.Then,by optimizing the vulcanization temperature,?Zn,Co?S were obtained under the sulfide condition of 140°C.The specific capacity of?Zn,Co?S reaches 836F·g^-11 at a current density of 1 A·g^-1,when the current density increased to 10 A·g^-1,the corresponding specific capacitance can also reach 545 F·g^-1.Owing to a cycle life of74.8%after 5000 charge and discharge cycles at a current density of 10 A·g^-1.In the preparation of the anode material,the cubic structure ZIF-8 nanomaterial was first prepared.Subsequently by optimizing the carbonization temperature,a porous carbon?ZPC?material was obtained under carbonization temperature of 850°C.Its specific capacitance reaches 160.6 F·g^-1 at a current density of 1 A·g^-1.Finally,the nanoporous carbon material is assembled with the previously prepared?Zn,Co?S into?Zn,Co?S//ZPC Asymmetric supercapacitors?ASCs?.The test results showed that ASCs energy density can reach 28.6 Wh·g^-1,and the corresponding power density is 798 W·kg-1.?3?Preparation and electrochemical properties of core-shell polyhedra Co₃O₄/MnCo₂O_4.5:In this chapter,ZIF-67 crystal with dodecahedral structure was prepared by liquid deposition method.By optimizing the amount of Mn?NO₃?₂·4H₂O added,Co²⁺/Co³⁺released from ZIF-67 together with Mn²⁺would form ZIF-67/Co-Mn hydroxide nanocages particles.Finally,by anneal ZIF-67/Co-Mn hydroxide precursor,Co₃O₄/MnCo₂O_4.5 was obtained.Benefiting from this unique core-shell structure and the synergistic effect of bimetallic manganese-cobalt oxides,the obtained multi-shelled Co₃O₄/MnCo₂O_4.5 showed an outstanding specific capacitance than Co₃O₄ acquired from pure ZIF-67.The Co₃O₄/MnCo₂O_4.5 reaches a specific capacity of 636 F·g^-1 at a current density of 1 A·g^-1.Owing to a cycle life of86%after 5000 charge and discharge cycles,its electrochemical performance had been improved significantly,compared with the Co₃O₄ acquired by pure ZIF-67 at a specific capacity of 320 F·g^-1.At the same time,the asymmetric supercapacitor assembled by Co3O4/MnCo2O4.5//ZPC exhibits an excellent electrochemical performance.The energy density reached 23 Wh·kg^-11 at a current density of 1 A·g^-1,the power density is 796 W·kg^-1.