Preparation Of MOF-based Bimetallic Oxide And Its Application In Lithium-ion Batteries

Lithium-ion batteries?LIBs?,which show great potential for application in smart electronic devices and electric vehicles,have been developing rapidly in recent years owing to their high energy,long-life and no pollution.Among many kinds of potential substitutes for anodes in LIBs,transitional metal oxides have attracted great interest from most researchers because of their larger theoretical capacities,which can deliver 2–3 times than that of commercial graphite anode(372 mAh g^-1).However,it is found that transitional metal oxides have some defects in the application of Lithium-ion batterys,such as travel conductivity,serious volume change and so on.Therefore,these problems are mainly solved in three aspects:firstly,MOFs are used as the precursor to synthesize metallic oxides to enhance the porosity and specific capacity.Secondly,MOFs and bimetallic oxides with regular morphology are synthesized by regulating the reaction conditions to mitigate the volume change.Thirdly,two suitable metal sources are selected to increase the conductivity of the electrode.The main contents of this thesis are as follows:Ni-Co-MOF with 1,4-benzenedicarboxylic acid?H₂bdc?as ligand was synthesized by hydrothermal method.Hollow spherical compounds NiO/NiCo₂O₄ were prepared by calcination at 400?in air atmosphere.A superstructure with size of 300-400 nm was formed.When this material was used as an anode of LIBs,the initial discharge specific capacity with 100 mA g^-11 could reach 1778 mAh g^-1,the charge specific capacity was about1354 mAh g^-1,and the capacity remained at 920 mAh g^-11 after 100 cycles.This result shows that the material has excellent cycling performance.When the material was tested at different current densities of 100,200,400,800 mA g^-11 of each 8 cycles,the average charge-discharge capacities were respectively 1109,978,830,623 mAh g^-1.It can be found that with the increasing of current density,the specific capacities were decreasing.When the current density returned to initial current density 100 mA g^-1,the specific capacity of the battery increased to 1075 mAh g^-1,indicating this electrode material had excellent rate performance.?1?The precursor Ni-Co-MOF with 1,4-Cyclohexanedicarboxylic acid?H₂chdc?as ligand was synthesized by microwave method.The rod-like bimetallic oxides NiO/NiCo₂O₄were obtained by high temperature calcination.It was used as anode material for LIBs to test its electrochemical performance.The results showed that the initial discharge specific capacity reached 1800 mAh g^-11 at 100 mA g^-1,and the discharge specific capacity kept about1198 mA h g^-11 after 120 cycles.When the current densities were 100,200,400,800 mA g^-11 in turn,the stable specific capacities were about 1304,1108,974,778 mAh g^-1.In addition,when the current densities returned from 800 mA g^-11 to 100 mA g^-1,the specific capacity of the bimetallic oxides NiO/NiCo₂O₄ also increased to 1263 mAh g^-1.It was proved that the rod-shaped bimetallic oxides NiO/NiCo₂O₄ had good rate performance.