Preparation Of Metal Organic Framework Derived Electrode Materials And Applications For Lithium Ion Batteries

Lithium ion batteries（LIBs）have become the main power source of portable electronic products and new energy vehicles because of its advantages of high voltage,high specific energy,wide work temperature,simple maintenance and long cycling life.However,due to the limited theoretical capacity of graphite anode material for commercial LIBs,which can not satisfy the increasing requirement of society.Compared with graphite anode material,transition metal/carbon composites exhibit high theoretical specific capacity,thus they have been considered as promising candidate electrode materials.Nevertheless,transition metal/carbon composites derived from metal-organic frameworks are highly competitive anode materials for LIBs.Based on these issues,in this paper,a kind of metal-organic framework（ZIF-67）materials were used as the sacrificial template to prepare its derived composites by two simple and different composite methods.The obtained composite carbon nanomaterials were used as the anode materials for LIBs,whose electrochemical performance was investigated.The works of this paper are as follows:（1）Preparation of Co/NC/RGO composite as an anode material for LIBsZIF-67 prepared by room temperature solution method was first freeze-dried by combining with graphene oxide（GO）,and then calcined at high temperature under different atmosphere（N2 and Ar/N₂）to prepare Co/NC/RGO composites.The structure and morphology of the composites were studied by XRD,FTIR and SEM,the composites maintained the layered structure of graphene and N and Co could be doped into graphene resulted from the collapse of the ZIF-67.The results of electrochemical performance test showed that both materials after calcination have good electrochemical performance,including high first discharge capacity of 1449.3 and 892.6 m Ah g^-1 at a current density of 0.05 A g^-1.The materials also showed good rate performance,the specific capacity of 290 and 200 m Ah g^-1 can still be maintained when the current density was increased to 2 A g^-1.（2）Preparation of nitrogen-doped carbon nanofibers decorated Co nanoparticle as anode materials for LIBsThe PAN/Co（Ac）2 nanofibers were first prepared by electrospinning,then ZIF-67 was grown in situ on their surface,finally the CNCF-800 composites which loaded Co nanoparticles on the surface of carbon fibers were prepared by high temperature calcination.The result of XRD,FTIR and SEM characterization showed that the ZIF-67 nanoparticles were uniformly distributed on the surface of the fiber,and the composite can maintain the original structure after carbonization.Electrochemical performance test results showed that the discharge and charge specific capacities of the first cycle were 898.1 and 622.6 m Ah g^-1 with the coulombic efficiency of 69.1%.With an extraordinary cycling stability at a high current density of 1 A g^-1,after 1000 cycles,the discharge capacity can still be maintained at 202.2 m Ah g^-1.Meanwhile,the material has good rate performance,the specific capacity can still be maintained at 163.8 m Ah g^-1 at a current density of 2 A g^-1.