Study On The Preparation And Performance Of Nano Self Assembly And Composite Structure MgFe₂O₄ Anode Material

With the rapid development of new energy industry,as the best one of them,Lithium-ion battery also gradually highlights with the advantages of energy density,safety,cost and so on.Its electrochemical performance is influenced by many factors,such as negative and anode materials,conductive agents,binder,electrolyte,separator,production processes and so on.But anode materials play an important role in enhancing the electricity performance.Mg Fe₂O₄ have capacity much higher than carbon and the other materials.But so far,people have less research on Mg Fe₂O₄ anode material.In the studied reports,the synthetic methods are complicated and experiment conditions are severe.Moreover,it is semiconductor itself,so its electrical conductivity is poor.As anode material,its rate performance in the high current density is not good.While at the same time,the intercalation/deintercalation of lithium ions can cause volume change,severe pulverization and poor electrical conductivity which can result in the unstable cycling performance of Mg Fe₂O₄.The work of this paper is focused on employing different methods to prepare nano structure or nano assembly structure such as hollow sphere,solid sphere and core-shell structure,and nano composite structure（Mg Fe₂O₄/C、Mg Fe₂O₄/CNTs）Mg Fe₂O₄ material.The electrochemical performance is researched.First,this paper chooses the lower melting point and low cost nitrate and citric acid as raw material to prepare nano-sized Mg Fe₂O₄.Then it reports a facile approach for the synthesis of Mg Fe₂O₄/C using glucose as carbon source.And its electrochemical performance is characterized.The composites electrode material delivers a capacity of about 1965 m Ah g-1 after 100 cycles at 0.1 C,showing excellent cycling performance.In order to enhance the capacity retention rate and at the same time try to modify on the morphology structure,this paper employs the solvothermal method to synthesize the hollow spherical Mg Fe₂O₄.And the synthesis mechanism is elucidated.The electrochemical performance of the hollow spherical Mg Fe₂O₄ is tested.The first discharge specific capacity at 0.1 C（107.2 m A g-1）is 1344 m Ah g-1 with an initial irreversible capacity loss of about 28%.The capacity hardly decays and stabilizes at about 900 m Ah g-1 after 70 cycles,exhibiting higher discharge specific capacity and better cycling performance.This paper also tries to use the vacuum impregnation method,chooses multi-walled carbon nanotubes（MWCNTs）as carbon source and supporter and then in-situ synthesizes Mg Fe₂O₄/MWCNTs material with both advantages by high temperature treatment.It discusses the influence that the radio and temperature have on the phase formation and electrochemical performance of Mg Fe₂O₄/MWCNTs.The electrochemical performance indicates that the capacity and stability of Mg Fe₂O₄/MWCNTs is better.