Research On Preparation And Electrochemical Performance Of Manganese Niobium-Based Composite Oxide As Anode Materials For Lithium-Ion Battery

With the rapid development of new energy power generation technologies and electric vehicle,lithium-ion batteries play an increasingly important role,and the requirements for energy density,power density,and safety of lithium-ion batteries are also increasing.Traditional lithium-ion battery graphite anode materials have been unable to meet the increasing demands of people.Therefore,finding a lithium-ion battery anode material with a high specific capacity,stable cycle performance and good safety have become one of the keys to the development of lithium-ion batteries.As an anode material for lithium-ion batteries,niobium-based oxides have the same excellent rate and cycle performance as lithium titanate,and the specific capacity is much higher than lithium titanate,so it has become a hot research topic recently.MnNb₂O₆ is a manganese-niobium composite oxide.At present,its research mainly focuses on the field of photocatalysis,but there are few studies on its application to lithium-ion battery anode materials.In this paper,the performance of MnNb₂O₆ as the anode material for a lithium-ion battery is studied,and the research on graphene composite modification is carried out for the disadvantage of poor conductivity.In this experiment,a series of manganese niobium oxides were successfully prepared by the solvothermal method.Then the phase composition and element ratio were analyzed and characterized by XRD and EDS.The effects of different proportions of manganese niobium on the product components were investigated.The results showed that the manganese niobium oxide prepared by the molar ratio of Mn:Nb=1:0.8is pure phase MnNb₂O₆,and the element ratio is also the closest to the stoichiometric ratio of MnNb₂O₆.The morphology of the product was characterized by SEM and TEM.The effects of different proportions of manganese niobium on the product morphology were investigated.The results showed that the pure phase MnNb₂O₆ prepared by the molar ratio of Mn:Nb=1:0.8 has the most regular spherical morphology.The lattice fringe spacing obtained by HRTEM further demonstrates the presence of MnNb₂O₆.The electrochemical test of manganese niobium oxides with different molar ratio showed that the pure phase MnNb₂O₆ prepared by the molar ratio of Mn:Nb=1:0.8exhibited the most excellent electrochemical performance.The reversible specific capacity of pure phase MnNb₂O₆ at 50 mA·g^-1 was 250.7 mAh·g^-1,and the capacity retention rate was 92.4%after 100 cycles of charge and discharge at 500 mA·g^-1.At the same time,pure phase MnNb₂O₆ also exhibits the smallest charge transfer resistance.In this experiment,a solvothermal method was used to study the in-situ composite of graphene on the basis of pure phase MnNb₂O₆,and a series of different proportions of MnNb₂O₆@rGO composites were prepared.The phase of the composites was characterized by XRD.The effects of different ratios of graphene on the product phase were investigated.The results show that the composite of graphene does not change or destroy the phase and structure of MnNb₂O₆.The morphology of the composites was characterized by SEM and TEM.The effects of different ratios of graphene on the products morphology were investigated.The results show that the spherical MnNb₂O₆was composited with graphite sheet in MnNb₂O₆@24.1%rGO.The characterization of TGA further confirmed the presence of graphene,and the actual graphene compounding amount of MnNb₂O₆@24.1%rGO was 16.23%.Electrochemical tests on a series of different proportions of MnNb₂O₆@rGO composites show that MnNb₂O₆@24.1%rGO material exhibits the most excellent electrochemical performance.The reversible specific capacity at 50 mA·g^-1 was increased from 250.7 mAh·g^-1 of pure phase to 346.1mAh·g^-1,and the capacity retention rate was increased from 92.4%of pure phase to129.5%after 100 cycles of charge and discharge at 500 mA·g^-1.At the same time,MnNb₂O₆@24.1%rGO also minimizes the charge transfer resistance of the material.