| With the booming energy storage industry,lithium-ion batteries stand out among many energy storage devices.The new energy industry is constantly upgrading and improving,and the application fields of lithium-ion batteries are increasingly widespread.At the same time,as the demand for society increases,the energy density and power density of lithium-ion batteries still need to be further improved.As a main component of lithium ion batteries,electrode materials are an important factor affecting the performance of lithium ion batteries.Therefore,the development of high-performance electrode materials is expected to break the existing development bottleneck of lithium-ion batteries.The metal organic framework is an emerging porous material that has been widely used in many aspects including energy storage.It is of great significance to develop metal oxides and metal oxides/carbon composites derived from metal organic frameworks as electrode materials.In this paper,metal-organic frameworks derived from different metals and organic ligands were used as precursors and templates.And then,derivatives of different types and morphologies were obtained by pyrolysis.The metal organic framework was combined with graphene to explore the synergistic effect between the materials and study the lithium storage properties.(1)The tablet-shaped Ti-MOF was prepared by solvothermal method.The anatase Ti02 and rutile Ti02 were obtained by pyrolysis at different temperatures in air atmosphere,which maintained the morphology of the precursor.After 100 cycles at a current density of 100 mA·g-1,the specific capacities of anatase Ti02 and rutile Ti02 were maintained at 160.5 mAh·g-1 and 110.5 mAh·g-1,respectively.Based on the crystal structure of anatase Ti02,it is considered to be more suitable for the anode material of lithium ion battery.Subsequently,the anatase Ti02/C composite was obtained by pyrolysis under nitrogen atmosphere.The Ti02 nanoparticles were uniformly embedded in the interior of the amorphous carbon framework,effectively avoiding agglomeration between the particles.The anatase TiO2/C composite anode maintained a specific capacity of 374.8 mAh·g-1 after 100 cycles,showing excellent cycle stability.Moreover,the anatase Ti02/C composite anode showed excellent rate performance.When the current density were 500 mA·g-1 and 1000 mA·g-1,its specific capacities were 289.1 mAh·g-1 and 232.7 mAh·g-1,respectively.(2)Ti-MOF@rGO was prepared by solvothermal method.Ti-MOF was uniformly grown on the surface of graphene.After that,the Ti02/C@rGO nanocomposites was obtained by pyrolysis.The TiO2/C@rGO also behaved excellent electrochemical properties.After 100 cycles at a current density of 100 mA·g-1,the specific capacity was maintained at 545.9 mAh·g-1,which was much higher than that of Ti02/C.At a current density of 1000 mA·g-1,the specific capacity still reached at 328.8 mAh·g-1.When the current density returned to 100 mA·g-1,the specific capacity was maintained at 567.9 mAh·g-1.After studying the composite materials with different graphene content,we found the additive effect is the most significant when the content of graphene is 15%.(3)Mn-MOF with different morphologies were obtained by varying manganese sources.The Mn2O3 with different structures were obtained by pyrolysis under air atmosphere.After 100 cycles at a current density of 100 mA·g-1,the specific capacities of Mn203(L)and Mn203(C)were maintained at 1256.3 mAh·g-1 and 638.7 mAh·g-1,respectively,indicating that the structures of the anode materials have obvious influence on electrochemical performance.The specific capacity was 719.6 mAh·g-1 after 100 cycles at a current density of 100 mA·g-1.Besides,after 500 cycles at a current density of 1 A·g-1,the specific capacity was 407.0 mAh·g-1.The combination of MnO nanoparticles and carbon improved the electrical conductivity of the material,avoided the agglomeration between MnO nanoparticles and increased the structural stability of the anode materials.(4)Mn-MOF@rGO with special structure and morphology was prepared by solvothermal method.MOF was grown on graphene sheets and exhibited parallelepiped morphology.The interaction between MOF and graphene affected the extending direction of the graphene sheets.The MnO/C@rGO nanocomposite obtained by pyrolysis showed high reversible specific capacity,stable cycle performance and excellent rate performance.After 100 cycles at a current density of 100 mA·g-1,the specific discharge capacity was 1536.4 mAh·g-1.Moveover,after 500 cycles at a current density of 1 A·g-1,the specific discharge capacity was maintained at 909.1 mAh·g-1.(5)By adjusting the ratio of the organic ligands,biorganic ligand metal organic frameworks with different structures were prepared.And then,the mixed metal oxide and carbon composite was obtained by pyrolysis.The MnxOy/C(221)showed good structural stability and electrochemical performance.After 150 cycles at a current density of 100 mA·g-1,the specific discharge capacity was 984.2 mAh·g-1.The porous structure provides a large number of channels for the transfer of lithium ions and electrons,showing better rate performance.(6)Based on the special structures and properties of MOF materials,LiMn-MOF was synthesized and the octahedral shape LiMn2O4 with good crystallinity was obtained by pyrolysis.The first discharge specific capacity was 122.1 mAh·g-1 at 0.1 C,which remained at 81.3 mAh·g-1 after 100 cycles.The use of MOF as a precursor also provides a new idea for the development of cathode materials. |
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