Preparation Of Manganese Molybdate Nanomaterials And Their Electrochemical Properties

Lithium-ion batteries attract the attention of the public due to their high energy density,long cycle,and environmental friendliness.Graphite is mostly used in commercial batteries for anode materials,but the lower theoretical specific capacity is difficult to satisfy the practical demand.Therefore,it is necessary to develop new anode material with high specific capacity.Manganese molybdate materials have considerable theoretical specific capacity,but low conductivity and capacity decay restrict their practical applications.In this study,manganese molybdate and manganese molybdate/C composites were prepared by hydrothermal-calcining method,which can be used as anode materials for lithium ion batteries.Furthermore,the morphology and microstructure of the prepared products were characterized by using XRD,SEM and TEM,and the electrochemical performance of the Manganese molybdate was tested.The results are as follows:?1?Manganese molybdate was prepared by a hydrothermal-calcining method using manganese acetate and sodium molybdate as raw materials.MnMoO₄ nanorods with a diameter of about 80 nm were prepared by adjusting the molar ratio of Mo to Mn,hydrothermal temperature,hydrothermal time and calcination temperature,but its electrochemical performance was poor.Then,the Mn₂Mo₃O₈ with reticular structure is prepared by replacing the aqueous solution with ethylene glycol,which morphology has a larger specific surface area and it be conducive to speeding up electrolyte immersion into electrode materials.In addition,electrochemical tests show that the material has a high initial Coulomb efficiency,and it specific capacity can be maintained at 645.5 mAh g^-11 after 50cycles at 0.1 A g^-1.?2?Mn₂Mo₃O₈/rGO composites were prepared by solvothermal-calcining method using manganese acetate,sodium molybdate and graphene oxide as raw materials.Furthermore,hierarchical nanorods constructed by Mn₂Mo₃O₈/rGO nanosheet arrays were synthesized at 500?by changing the calcination temperature.Magnified SEM image displays the vertical nanosheets with about30 nm average thickness,whose structure can provides more lithium-ion transport channels and also can effectively alleviate the volume expansion caused by charge and discharge.In this experiment,the effect of graphene on the morphology of the product was investigated,the results show that graphene is beneficial to the formation of hierarchical structure in this reaction environment.Electrochemical measurements showed that the initial Coulomb efficiency?ICE?of the hierarchical Mn₂Mo₃O₈/rGO nanorods was 85%,and it specific capacity can be reached to 762 mAh g^-11 after 50 cycles at 0.1 A g^-1.Although there is a certain improvement in the specific capacity,the long cycle performance has a great improvement space.?3?Using MnMoO₄·H₂O powder as precursor,N-doped MnMoO₄/C nanoparticles were prepared by coating polydopamine at room temperature and calcining at 500?.The SEM images showed significant changes in morphology before and after PDA coating.And then the coating process was studied by changing the coating time.The results showed that dopamine hydrochloride partially dissolved manganese molybdate at the same time in the process of oxidation polymerization.With the extension of coating time,the morphology of dopaminergic hydrochloride changed gradually from bulk to nanoparticles.Moreover,the electrochemical performance tests show that the charge specific capacity of MnMoO₄/C nanoparticles with 657.1 mAh g^-11 after 100 cycles at 0.1A g^-1and 374.7 mAh g^-11 after 200 cycles at 1 A g^-1.Characterization of TEM was carried out to study the active material after 200 cycles,the test showed that the structure of the product is stable and maintained the morphology of the nanoparticles after cycles.