Preparation Of Metal Oxides/Carbon Materials As Anode Materials In Lithium-ion Batteries

Metal-organic frameworks?MOFs? which have been used in many applications,for example, gas storage and catalysis, owing to their structural diversity and controllable nature are paid more attention to people. In recent years,MOFs-based which have been explored in electrochemical energy storage is a hot topic. So far,MOFs have been proven particularly suitable for electrochemical applications,since the composition of material can be designed and regulated at the molecular level.Further more, MOFs possess tremendous mesoporous which is good for transportation of mass in the corresponding area. However, MOFs have obvious shortcomings that electrical conductivity is poor,the reason that has been limitting in application of lithium ion batteries. So calcination MOFs is a most promising methods to prepare their derived nanostructures of metal oxide. In the thesis Co-doped ZnO / C,Co oxides / Co / C and NiFe₂O₄ / NC nanocomposites are synthesized with relux,hydrothermal and calcination method. And then the electrochemical performances of as-prepare are investigated.?1? Using Co?NO?₃?6H₂O and Zn?NO?₃?6H₂O as raw materials,the terephthalic acid as an organic ligand synthesize precursor of Co-doped MOF-5 by relux method,and then calcination precursor to obtain Co-doped ZnO / C nanocomposites. Since Co doping and higher carbon content, larger specific surface and more pore size distribution exhibited good electrochemical performance. The initial and 100 th cycle discharge of Co-doped ZnO / C anode are 1270 mAh?g-1 and 784 mAh?g-1 at 0.1 C respectively. It shows that the active material has good stable cycle.?2? Based on previous synthesized precursor of Co-doped MOF-5 synthesize mesoporous Co oxides / Co / C nanocomposite by calcining 1000 °C. Thanks to high temperature process that is to form good conductive network,high specific surface and suitable pore size,in additional, ZnO of gasification to get more loose material which efficient buffer to relax the volume changes. By the electrochemical performance tests show that at 2 C the capacity of 460 mAh?g-1 is still higher than 372mAh?g-1 of conventional graphite.NiFe-MOF precursor is synthesized through hydrothermal method by using FeCl₃?6H₂O and Ni?NO?₃?6H₂O as raw materials,the 2-amino-terephthalic acid as the organic ligand,and then to obtain NiFe₂O₄ / NC nanocomposites by the calcination precursor of NiFe-MOF. Carbon which N-doped not only improves the conductivity of the active material, but also provides way that allow Li+ diffusion rapidly and regulates volume change during charge and discharge process. The tests of electrochemical performance reveals that NiFe₂O₄ / NC nanocomposites is as high as760 mAh?g-1 at 0.2 C after 50 th, it obviously that after calcination there is agglomeration of materials in SEM which influence the performance of lithium ion battery.