Rational Structure Design,preparation And Electrochemical Performance Of Transition Metal Compounds

In the 21th century,as a pillar of science and technology,energy industry affects our lives in all aspects.However,the contradiction between people’s ever-growing energy needs and the increasingly exhausted fossil energy is more and more intensified,so it is urgent to find the substitute of fossil energy.Battery the most important core device in the energy industry,and its development plays a decisive role in the progress of science and technology.At present,commercial lithium ion batteries（LIBs）are commonly used,but they have suffered many shortages such as high cost,low safety,limited and unstable working conditions,high technology content and so on.Most importantly,graphite is used as anode material in LIBs,it suffers low energy density and can no longer meets the demands for high density energy storage equipment.Looking for high specific capacity anode materials or alternatives to LIBs is imminent.In this paper,a sort of organic-inorganic hybrid material with high energy density was explored as cathode materials for zinc ion battery.And we designed a hollow Fe₃O₄nanospheres coated with C and Si O_x as anode for LIBs,which can deliver outstanding energy storage performance.The specific research contents are as follows:Firstly,an in-situ carbon-coated hybrid of organic and inorganic material of vanadyl ethylene glycolate（VO（CH₂O）₂,VEG）,is successfully synthesized and investigated as a potential cathode material of zinc ion battery.And its structural information during the electrochemical process is evaluated for the first time using in-situ x-ray diffraction technique.Extensive characterization was initiated for studying its mechanism during the electrode reaction process.Our results reveal that carbon-coated vanadyl ethylene glycolate can effectively achieve high electronic conductivity and exhibit outstanding energy storage performance.High specific discharge capacity of 364 m A h g^-1 can be achieved at 100 m A g^-1.And after 100 cycles of discharge-charge process,VEG electrode still remains 80%of the initial capacity.Increasing the current density,VEG can still achieve high energy density,and exhibits excellent cycle stability.74%and 65%initial specific capacity can be achieved after1000 and 2000 cycles of discharge-charge process at current density of 2000 m A g^-1 and 5000m A g^-1.Excellent rate performance can be delivered under different current density,which is clearly suppress those in previous reports.Our report reveals that in-situ carbon-coated VEG as a cathode material for zinc ion battery presents some significances in both material science and material industry.Secondly,for the purpose of solving the low energy density shortcoming of graphite,we successfully designed a hollow Fe₃O₄@C/Si O_x nanosphere structure.Fe₃O₄ material can deliver high specific capacity in the application of anode material in LIBs.And its redox potential is close to 0.8 V,which makes it hard to form lithium dendrites during the intercalation process of lithium ions.However,violently volume expanding of Fe₃O₄ electrode during the electrochemical process and low ionic conductivity,electron conductivity suppressed its utilization in energy storage equipment.Benefit from hollow structure of Fe₃O₄@C/Si O_xnanosphere material,volume expansion and contraction can be alleviated and the structure can be stabilized.Besides,C layer can improve the ionic conductivity and electronic conductivity of the electrode material,which leads to high power density and energy density.And Si O_x layer can improve the energy density which reduced by excessive C content.Our experiment confirms,hollow Fe₃O₄@C/Si O_x structure can deliver outstanding energy storage performance as negative material for LIBs.Fe₃O₄@C/Si O_x electrode can release 1591 m A h g^-1 specific capacity under 100 m A g^-1 of current density,and 887.5 m A h g^-1 specific capacity under 1000m A g^-1 of current density.Fe₃O₄@C/Si O_x also has high rate performance under various current densities.In the end,we studied the dynamic characteristics through cyclic voltammetry curve at various sweep rates and Electrochemical Impedance Spectroscopy plots,and further proved Fe₃O₄@C/Si O_x electrode has better ionic conductivity and electronic conductivity.