Preparation Of Metal Organic Frameworks(MoFs)derived Cobaltosic Oxide And Its Lithium Storage Performance

There are many advantages using Metal Organic Frameworks?MOFs?as sacrificial templates when prepared hybrid micro/nanostructures with complex composits or structure as lithium ion battery electrode materials.Their internal carbon conductive network and mesoporous channels provide a good electron and substance transport framework for materials,which makes it possible to act as a non-conductive,binder-free self-supporting electrode material.However,larger particle size and spontaneous growth mode result in great difficulties in preparing stable adherent MOFs films on conductive substrates.In this work,we use titanium nanowire arrays to immobilize the cobalt-based metal organic framework compounds to prepare a variety of Co₃O₄ self-supporting electrode,which improve the rate performance and cycle performance as a lithium ion battery anode material by promoting the electron transport between the material and the conductive substrate and the adhesion of the material to the substrate.?1?The Co₃?HCOO?₆ material supported by titanium nanowire arrays was prepared by one-step solvothermal method,the electrochemical properties of the assembled cells were compared with heat-treatment in different atmosphere.At a high current density of50 A g^-1,the specific capacity of the material heat-treated in the air atmosphere is 70 mAh g^-1,and the specific capacity of the material heat-treated in the argon atmosphere is 120 mAh g^-1,the Co₃O₄ obtained in argon atmosphere was cycled at a rate of 20 A g^-1for a capacity retention rate of 94%,showing excellent rate and cycle performance.The results of scanning electron microscopy showed that the carbon in the MOF was retained by heat-treated under argon atmosphere,carbon nanoparticles played a role in the conductive network as they evenly distributed around the Co₃O₄ particles,thus to ensure the specific capacity of material under high rate performance.?2?In order to further improve the electronic conductivity of the MOF derived material and improve its rate performance,Zn/Co ZIFs metal organic framework were prepared by liquid-phase method at room temperature on the surface of titanium nanowire arrays,and then obtained Co₃O₄/nitrogen-doped carbon nanotubes?NCNTs?anchored on titanium nanowire arrays by two-step heat-treatment method.The threedimensional conductive network composed of NCNTs and titanium nanowire arrays greatly improve the electron conductivity of the material and reduces the charge transfer impedance and ohmic impedance of the material.The composite material loaded on the titanium nanowire arrays exhibit a specific capacity close to 110 mAh g^-1 at a high current density of 50 A g^-1,which greatly improves the performance compared with the conventional process,and it has a specific capacity retention of 95 % after a long cycle with a high rate of 20 A g^-1,exhibiting excellent rate and cycle performance.?3?In order to further improve the binding force of MOF material to the substrate,the ZIF-67 was prepared by in situ electrochemical method,after heat-treated in air,a Co₃O₄/Ti electrode was obtained.The Co₃O₄ material heat-treated in air on a titanium nanowire array exhibits a specific capacity close to 180 m Ah g^-1 at a high current density of 50 A g^-1.And experienced a high rate long cycle of 20 A g^-1,the specific capacity of the electrode did not find significant decay,compared to Co₃O₄ material in situ prepared on titanium foil,showing excellent rate and cycle performance.The Co₃O₄ /Ti electrode prepared by this in situ electrochemical auxiliary method has a better controllability and better synthesis conditions than the first two parts.The active material has better binding to the matrix,so the self-supporting electrode shows superior electrochemical performance.