Preparation Of MOF Material And Their Application For Lithium Ion Battery

Metal-organic frameworks(MOFs),as a novel class of organic-inorganic porous materials,are formed by metal ions and organic ligands by strong bonds [1].On the one hand,MOFs materials can be directly used as cathode materials,anode materials and even electrolytes in LIBs[2].On the other hand,in an inert atmosphere,MOFs materials can also act as a selfsacrificing template to produce a porous carbon with well-defined morphology and high electrical conductivity under high temperature carbonization conditions [3].This MOFs derived carbon not only can be directly used as electrode material but also can be utilized as a coating carbon layer to modify electrode materials.The main content was represented this thesis:(1)We have successfully synthesized a Si O@C composite by a facile and green method.A carbonization of metal-organic frameworks is utilized to enhance the electrochemcial performance of Si O as a promising anode for Li-ion batteries.XRD,SEM,TEM and EDS results show that the composite consists of Si O particles uniformly coated with carbon from ZIF(Zn,Co).The Si O@C composite shows considerably better cyclability,with 46.8 % charge capacity retention with respect to the first charge capacity after 500 cycles.The Si O@C composite can still deliver a specific capacity of ~171 m Ah g-1at a high current density of 2 A g-1,while the milled Si O can only achieve a low capacity of ~87 m Ah g-1.When the current density returns to 100 m A g-1,the Si O@C composite recovers its capacity of ~460 m Ah g-1and then stabilizes in subsequent cycles.The Si O@C composite shows superior performance compared with the milled Si O,including enhanced rate capability and better capacity retention.The much improved electrochemcial performance of the Si O@C composite could be ascribed to the carbon coating,which can enhance the conductivity and alleviate the repeated volume changes of Si O during cycling.(2)We have examined the electrochemical properties of solvothermally synthesized[Cu2(BIP-Tn C)(DMA)2]n(MOF)as anode material for lithium-ion battery(LIB).Compared with organic ligands,the MOF shows superior electrochemical performance.The specific capacity of 400 m Ah g-1is achieved at a current density of 100 m A g-1after 500 cycles,which is4 times higher than organic ligands at the same conditions.It also shows superior rate capability.By comparing the electrochemical impedance spectra of MOF and organic ligands,the MOF materail gives better conductivity,which is due to the Cu metal in the MOF.