Morphology Control Of MIL-125（Ti） And Its Application In Li-ion Batteries

The development of high-performance energy storage systems has great social significance.Among various energy storage systems,lithium-ion batteries（LIBs）have received the much attention due to their high energy storage efficiency and low environmental pollution,and the anode material is a key factor to determine their performance.Metal-organic frameworks（MOFs）are believed as the ideal anode for LIBs because they are not only possessing the properties of metal substrates and organic ligands,but easily modified and controlled by chemical and physical methods to meet various application.In this work,we investigate the MOF and its derived materials by adding surfactants and preparing multidimensional composites to control the crystallization kinetics of MOF on the basis of Ti-MOF,and we also study the microscopic properties and electrochemical properties of different composites.The important contents of this work are as follow:（1）The morphology of Ti-MOF is controlled by using PVP and F127 as structure directing agents,and a series of Ti-MOF materials with different morphologies are prepared through the solvothermal method.The as-prepared materials possess good crystallinity,different preferred orientations of crystal planes and unique morphological structures.The electrochemical performance results show that:the PVP-type regulation causes the lithium storage capacity to decay from 165 to 98 m Ah g^-1 at initial rate;The F127-type regulation,participating in the MOF coordination reaction,reduces the particle size of the material,improves the reactivity and increases the capacity to198m Ah g^-1.（2）A series of MIL-125-F127（Ti）materials with different ratios are prepared by solvothermal method with the dosage of F127 and terephthalic acid（BDC）as independent variables of crystallization kinetics.The as-prepared materials achieve morphology evolution,and the results show that the material with a ratio of 0.5:1（F127:BDC）has the hierarchical pore structure,abundant ion channels,and excellent structural stability.The capacity of F127-Ti O₂（0.5:1）can reach 322 m Ah g^-1 at initial rate,and the capacity retention rate can still reach 89%after 200 charge-discharge cycles.（3）The two-dimensional（2D）nanosheets are used as structural agent to further tune the morphology of Ti-MOF through combining solvothermal and hydrothermal methods.The as-prepared 2D/3D Ti O₂@C@Mo S₂ composites exhibit both the properties of Ti-MOF porous material and the high capacity of Mo S₂ material,and possess high specific surface area,high lithium storage capacity and excellent electrical conductivity.The electrode material still has a capacity of 918 m Ah g^-1 at a higher rate,and 822 m Ah g^-1 after 1000 cycles with only 0.089%of the initial initial capacity is per cycle.