Study On The Preparation And Performance Of NiCo₂O₄ Anode Materials For Lithium-ion Batteries

In the21^st century,the green renewable energyplays an extremely important role in solving issues of energy crisis and environmental pollution,and reducing the dependence on fossil fuels.As we all know,lithium-ion batteries have long cycle life,high energy density,power densityand wide operating voltage range,which are widely used in electric vehicles,mobile communication devices and portable electronic devicesin the field of new energy.However,the theoretical specific capacity of the graphite anode(372 mAh/g^-1)in commercial lithium-ion battery is too low to meet the demand of current market.Therefore,it is urgent to develop high-capacity anode materials for lithium-ion batteries.It is also a research proposition for researchersto solve.The transition metal oxides prepared on the basis of mechanism of the displacement reaction were reported in 2000.That the transition metal oxides have mang advantages of high theoretical specific capacity?about 500–1000 mAh/g?,rich naturalreserves,low cost and environmental friendliness have attracted great interest of worldwide scientific researchers.This paper describes the anode materials of lithium-ion batteries and their reaction mechanisms.It aims to develop a transition metal oxide NiCo2O4 anode material for lithium-ion batteries with excellent electrochemical properties by the green and environmentally friendly synthesis process.NiCo2O4 with spinel structure electrode material was synthesized by preparation process optimized.X-ray diffractometer?XRD?,Field emission scanning electron microscope?FESEM?,transmission electron microscope?TEM?,energy spectrum analyzer?EDS?,X-ray photoelectron spectrometer?XPS?,thermogravimetric analyzer?TGA?,N₂ adsorption-desorption,galvanostatic charge-discharge and cyclic voltammetry were used to Characterize the morphology,microstructure,elemental composition,surface element valence states and lithium storage properties of NiCo₂O₄.NiCo₂O₄ was also applied as electrodematerial to analysethe electrochemical reaction mechanismin detail.The content of this article is as follows:?1?The tunable hydrothermal method was used to built the NiCo₂O₄ nanowire array,including Nickel nitrate hexahydrate?Ni?NO₃?₂·6H₂O?and Cobalt nitrate hexahydrate?Co?NO₃?₂·6H₂O?used as metal salt sources,and Urea?CH₄N₂O,precipitant?.When the synthesized NiCo₂O₄ was applied tolithium ion battery as a negative electrode,it exhibited good cycle performance,with a reversible specific capacity of 1371 mAh/g after 30 cycles at a current density of 100 mA/g.The rate performance was also pefect with a specific capacity of 946 mAh/g at a current densityof 800 mA/g.?2?Microemulsionsystemconsistingofsodiumdodecyl sulphate/n-butanol/n-heptane/waterwasselectedandurchin-likeNiCo₂O₄microsphereswere successfully prepared by the reaction between nickel nitrate/cobalt nitrate and urea under hydrothermal conditions.The structure can relieve the volume expansion and shorten the diffusion paths of electrons and ions during charge and discharge.When it is used as a negative electrode oflithium ion battery,it exhibits high specific capacity and excellent cycle performance with reversible specific capacity of1128 mAh/g after 40 cycles under current density of 100 mA/g and good C-rate performance which the reversible capacity is still 895mAh/g at a current density of 800mA/g.?3?Another microemulsion system consisting of Cetyl ammonium bromide?CTAB?/n-pentanol/n-hexane/water was selected to achieve NiCo₂O₄ nanoparticles at100? by controlling the reaction time of urea with nickel nitrate/cobalt nitrate.As the anode of lithium-ion batteries,the NiCo₂O₄ exihibited a reversible specific capacity of1036 mAh/g at a current density of 100 mA/g after 50 cycles.In addition,NiCo₂O₄nanoparticles had excellent C-rate performance and their capacity can still retain 644mAh/g at a current density of 1600 mA/g.?4?The fluorine-doped amorphous carbon-coated NiCo₂O₄ nanocomposites?NCO@C-F?was prepared by pyrolyzingthe Ni-Co precursorencapsulated with polyvinylidene fluoride?PVDF?.This complex significantly improves the cycle performance with 1260 mAh/g reversible capacity after 50 cycles at 100 mA/g current density and excellent C-rate performance,which the current density increases to 3200mA/g,its reversible capacity is 398 mAh/g.