| Ethylenediaminetetraacetic acid?abbreviated as EDTA?,one kind of important complexing agent,has been attracted broad attentions in fields of food processing,health care,chemical processing and nanomaterial assembly owing to its strong coordination ability.It can often be used as inhibitors for nuclease and protease,auxiliaries for dyeing,additives for cosmetics,anticoagulants for blood,initiator for polymerization of rubber and chemicals for water treatment.At present,although the synthesis,structures and characterization of this kind of complexes have been achieved great process,the studies on thermo-chemical properties and other new applications reported in literatures are rare.In order to further develop the applications on industrial production and more new areas,thermochemical properties of such complexes and lithium ion battery performance of MnO/N-C composites derived from manganese ethylenediaminetetraacetate were studied in this thesis,which was starting from preparing the single crystal structure of ethylenediaminetetraacetic acid metal complexes.The main works in this thesis are as follows:1.Synthesis and structure characterization of ethylenediaminetetraacetic acid metal complexes.Firstly,nine ethylenediaminetetraacetate crystals were synthesized by natural evaporation at room temperature.Then,the crystal structures and compositions were tested by X-ray single crystal diffraction.Finally,compelexs structures were presented according to the obtained single crystal data.From crystal structures,it can be seen that this series of complexes are both contain crystalline water and with the atom number and atom radius increase,maximum coordination number of central atom increases gradually for the same main group metal elements.From crystal lattice changes,it can be seen that,due to changes of metal ion charge,the lattice energy of alkaline earth metal complexes is larger than that of alkali metal complexes and at the same time,lattice energy increase with the molecular volume decreases for the same main group metal elements.2.Study on thermo-chemical properties of metal ethylenediaminetetraacetate.The detail contents could be divided into two parts:?1?Determination of molar heat capacities and thermodynamic functions of the complexes.Firstly,the molar heat capacities of the complexes were measured by precision automatic adiabatic calorimeter in temperature range of 78-400 K.Then,according to results of measured heat capacities,polynomial equations were fitted by least-squares method and the results of thermodynamic function values relative to 298.15 K were listed in tables.The results of determination of molar heat capacities suggest that these complexes are stable in temperature range of 78-400 K.Except for calcium ethylenediaminetetraacetate,molar heat capacities increase with the increase of molecular weight and relative basic thermodynamic function of values are also in line with this trend.?2?Determination of standard molar enthalpies of formation.A reasonable thermo-chemical reaction cycle was designed on the basis of Hess' s law and apposite thermal solvent was chosen.Dissolution enthalpies of each compound mentioned in thermo-chemical reaction were measured by isoperibol solution-reaction calorimeter,and then the reaction enthalpy of thermo-chemical reaction was calculated by using above measured dissolution enthalpies.The standard molar enthalpies of formation for these complexes were calculated by combination of the reaction enthalpy with other auxiliary thermodynamic datas.Finally,UV-vis spectra was used to verify the reliability and reasonableness of the designed thermo-chemical cycle reactions.The results indicate that these compouds with lower energy are relatively stable and for the same main group metal elements,the values increase with the increase of formula weight,with exception of cesium and barium ethylenediaminetetraacetate.3.Lithium ion battery applications of MnO/N-C composites prepared by thermal decomposition of manganese ethylenediaminetetraacetate crystal.Considering that MnO nanomaterials as anode material for lithium ion battery have disadvantages of poor cycling stability,carbon and nitrogen were codoped into nanomaterials to improve the lithium ion battery performance.The single crystal of manganese ethylenediaminetetraacetate was prepared by natural evaporation at room temperature,then,the MnO/N-C nanocomposite was obtained by calcinated above crystal at argonatmosphere.In this experimental,the influence of calcinations temperature on anode material composition,morphology and lithium ion performance was discussed emphatically.As result,MnO/N-C nanocomposite obtained at 400 °C shows excellent cycling performance.The specific capacity maintains at 874.4 m A h g-1 at current density of 1Ag-1 after 800 cycles. |
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