Study On New Manganese-based Spinel Anode Material

With the rapid development of the new energy vehicle industry,the requirements for lithium-ion batteries are also getting higher and higher,which makes more and more companies invest in the research and development of lithium-ion batteries and related electrode materials.At present,most commercial lithium-ion batteries still use low-cost,cycle-stable graphite as the anode material.However,graphite's theoretical specific capacity(372 mA h g-1)is very low.It is danger at low temperatures and high rate charging.It is unable to meet the development needs of the new generation of lithium-ion batteries.Therefore,research on new lithium-ion battery anode materials with higher energy density and better safety has become the focus of current research on batteries.Among them,the AMn2O4-type(A=Zn,Cu,Ni,Mg...)binary manganese-based anode material with a spinel structure has a high theoretical specific capacity(700-900 mA h g-1)and low price,It's structure is very stability.Quickly it become a focus of related research.However,materials still have problems such as low electrical conductivity,poor cycle stability,and low Coulombic efficiency.In this paper,the surface modification and equivalent substitution methods are used to modify the material.The main work is as follows:1.The sol-gel method was used to synthesize MgMn2O4 with spinel structure and a series of AZO-coated MgMn2O4 materials.The effects of AZO coating on its structure,morphology and electrochemical properties of the MgMn2O4 were Systematically investigated It is shown that AZO coating can effectively improve both the electronic conductivity and Li+diffusion,consequently improved its rate capability.Moreover,AZO coating can also remain the continuous conductive network of the electrode,therefore improve its cyclic stability.The reversible capacity of 5wt%AZO-coated MgMn2O4 is 590.3 mAh·g-1 after 200 cycles,much higher than that of the bare MgMn2O4(295.9 mAh·g-1)and the reported value in literatures.2.The sol-gel method was used to synthesize ZnMn2O4,MgMn2O4 and a series of Mg2+partially substituted Zn2+composites.The effects of Mg substitution on the structure,morphology and electrochemical performance of ZnMn2O4 materials were systematically studied.The experimental results prove that after partially replacing Zn2+ by Mg2+,a solid solution material with a uniform phase is formed.Significantly changed the electrochemical characteristics of the material such as the potential platform and reversible specific capacity,and confirmed that the introduction of new A-site ions can effectively buffer the stress caused by the volume change of the material and maintain the integrity of the material structure,thereby greatly improving the cycle performance of the material.It was confirmed that by changing the composition and ratio of metal cations at the A site in AMn2O4,the electrochemical performance of the material can be effectively changed.