Preparation And Properties Of Energy Storage Materials Based On MOF

A novel burgeoning application of Metal-Organic Frameworks(MOFs)has been used as precursors to synthesize hollow/porous structured inorganic nanomaterials via thermolysis.The advantage of this approach is that the obtained inorganic nanomaterials can retain a similar morphology and porous structure characteristics of the precursors,which are conducive to improving the electrochemical performance.Herein,rod-shaped Co3O4 and ball-like Co3O4 and ZnCo2O4 were synthesized by a facile and cost-effective approach via the calcination of MOF-74 precursors and tested as anode materials for lithium ion batteries.The main research contents are as follows:(1)Rod-shaped Co3O4 was successfully synthesized by directly annealing MOF-74 precursor under air flow.According to datum of XRD,SEM and TEM,the abtained Co3O4 showed a similar morphology to that of the corresponding MOF-74 precursor.The rod-shaped Co3O4 was composed of numerous nanoparticles and these primary nanoparticles can further aggregate to form a ruleless porous structure.The capacities and cycling performances of the rod-shaped Co3O4 electrode were evaluated by galvanostatic charge-discharge cycling at constant current density of 100 mA g-1.The first discharge capacity was 989 mAh g-1 and it displayed a high reversible discharge capacity of 683 mAh g-1 after 80 cycles.Coulombic efficiencies for most of the cycles were larger than 95%except the first one,indicating that the electrode had good cycling performance.After each eight cycles at 50,100,200 and 400 mA g-1,the rod-shaped Co3O4 electrode showed average discharge specific capacities of about 1231,1026,733 and 502 mAh g-1,respectively.When the current density was decreased from 400 mA g-1 to 50 mA g-1,the average discharge specific capacity recovered to 1002 mAh g-1.Coulombic efficiencies for most of the cycles were larger than 95%except the first one,indicating that the electrode had an enhanced rate capability.(2)Ball-like ZnCo2O4 and Co3O4 were synthesized by a facile and cost-effective approach via the calcination of MOF-74 precursors.The obtained nano structured Co3O4 and ZnCo2O4 retain similar morphology and porous structure characteristics of the MOF-74 precursors.The specific surface area and pore volume of ZnCo2O4 were estimated to be 110.2 m2/g and 0.5902 cm3/g,which were larger than the Co3O4(92.49 m2/g,0.3979 cm3/g)and the previous reported ZnCo2O4.When used as an anode material in LIBs,the as-synthesized porous ZnCo2O4 delivers much higher capacity,more excellent cycling stability and better rate capability than the Co3O4.It demonstrates a reversible capacity of 1243 mAh g-1 after 80 cycles at 100 mA g-1 and an excellent rate performance with high average discharge specific capacities of 1587,995,760 and 509 mAh g-1 at 200,400,600 and 800 mA g-1,respectively.The satisfactory electrochemical performances suggest that this porous nanostructured ZnCo2O4 is potentially promising for application as an efficient anode material for lithium ion batteries.