Synthesis,Modification And Electrochemical Performance Of Transition Metal Oxide As Anodes For Lithium-Ion Battery

In recent years,the traditional graphite anode material of the lithium-ion battery has not been able to meet the high-energy density and high power density requirement because of its lower theoretical capacity(372 mAh g^-1).Therefore,the development of high-capacity anode materials has become one of the key technologies in the development of lithium-ion batteries.As a potential anode material,transition metal oxides have been widely studied because of their high capacity.However,transition metal oxides?TMOs?exhibit huge volume changes during charge-discharge cycling,resulting in rapid attenuation of their specific capacity and poor rate performance.In this work,core-shell MgFe₂O₄@TiO₂,porous MgCo₂O₄ and ZnCo₂O₄@N-C nano-composite were ingeniously designed and synthesized,thus improving the electrochemical properties of three transition metal oxides.The main research contents are summarized as follows:?1?Uniform and well dispersed MgFe₂O₄ nanospheres were synthesized by solvothermal method,and core-shell MgFe₂O₄@TiO₂ nano-composite were synthesized by hydrolysis of tetrabutyl titanate.Compared with bare MgFe₂O₄,the MgFe₂O₄@TiO₂composite showed improved cycle performance and rate capability when used as anode material for lithium ion battery.It delivered a high specific capacity of 620 mAh g^-1 at 0.1 C for 100 cycles.?2?The MgCo₂O₄ with porous network structure was prepared by solvothermal method and subsequent heat treatment route,which was assembled by secondary nano-particles.The porous MgCo₂O₄ showed excellent lithium storage performance as anode material for lithium ion battery with a high reversible capacity of 824 mAh g^-1 at 0.5 A g^-1 current density for 150 cycles.The excellent electrochemical performance of porous MgCo₂O₄ electrode material can be attributed to the construction of this unique porous network structure.The porous structure can promote the full contact between the electrode material and electrolyte,improve the utilization rate of the electrode material,and shorten the transmission path of lithium ion effectively.In addition,this unique porous structure can effectively alleviate the volume expansion of electrode materials during the charge/discharge process.?3?15-30 nm ZnCo₂O₄ nano-particles were prepared by a simple sol-gel self-propagating combustion method,and the ZnCo₂O₄ nano-particles were coated by carbon through chemical polymerization of dopamine hydrochloride.The carbon coating can prevent the direct contact between the highly electrochemically active ZnCo₂O₄ nano-particles and the electrolyte,can effectively improve the conductivity of the composite,can alleviate the volume effect of the ZnCo₂O₄ during charge and discharge process,also can ensure a stable SEI layer formation.The Zn Co₂O₄@N-C electrode exhibited a high reversible capacity 1146 mAh g^-1 at 500 mA g^-1 for 100 cycles,showing excellent electrochemical performance.In addition,even at 2000 mA g^-1 for 200 cycles,ZnCo₂O₄@N-C electrode can still retain a high reversible capacity of 811 mAh g^-1,indicating excellent cycle stability.