Research On Preparation Of LiMn₂O₄ Powder By Sol-gel Method And Co-precipitation Method

As three type of important anode materials for lithium ion batterials, LiCoO₂.LiNiO₂ and LiMn₂O₄ are researched intensively in recent.Because that manganese are more abundant in nature,and LiMn₂O₄ can be easily synthesized with low cost and environmentally friendly process.In this paper,LiMn₂O₄ powders with spinel strcture and LiM_xMn_2-xO₄ powders have been synthesized by sol-gel method,the effects of pH value and the sintering condition(including sintering temperature,sintering reaction time and heating rate) on the crystal structure and morphology of the as-synthesized LiMn₂O₄ powder were discussed in detail by using TG-DTA,XRD,SEM,XPS.The main conclusions acquired from the present work are as follows:(1)LiMn₂O₄ powders and LiM_xMn_2-xO₄ powder with good crystallinity and morphology were prepared by sol-gel method.(2)The sintering temperature has important influences on the crystal structure and morphology of the synthesized LiMn₂O₄ powders.Under the feasible sintering temperature(750℃),the pH value,sintering reaction time and heating fete have little influence on the crystal structure of the LiMn₂O₄ powders,whereas they have some effects on the morphology of the products. (3)The optimal sol-gel processing conditions for LiMn₂O₄ powders are suggested as:pH value is 6.5,sintering temperature is 750℃,sintering time is 7h and heating rate is 5℃/min.(4)Doping level of metal ions has some influence on the crystal structure and morphology of the LiM_xMn_2-xO₄ powders,except Co²⁺ ion have large doping level(x≤0.5),other metal ions such as Ni²⁺,Cr³⁺,Cu²⁺ and Zn²⁺ have low doping level,which should be controled x≤0.05,avoiding the formation of impure phase.(5)Doping of different metal ions has some influence on the crystal structure and morphology of the LiM_xMn_2-xO₄ powders,generally,the product doped Co²⁺,Ni²⁺ and Cr³⁺ ion have good crystal structure and morphology.(6)From attempt of doping non-transition metals,it can be seen that the LiM_xMn_<sub>2-xO₄ powders doped with non-transition metals have inferior crystal structure and morphology,and very easily resulting in the formation of impure phase.LiMn₂O₄ powders with spinel strcture and LiM_xMn_2-xO₄ powder have been synthesized via co-precipitation method.By using TG-DTA,XRD,SEM,XPS testing method,the main conclusions acquired from the present work are as follows:(1)The optimal sintering conditions for LiMn₂O₄ powders are suggested as: sintering temperature is 750℃,sintering time is 7h and heating rate is 5℃/min.(2)The doping of different metal ions has some influence on the crystal structure and morphology of the LiM_xMn_2-xO₄ powders.Generally,the product doped with Co²⁺,Ni²⁺ and Cr³⁺ ions have good crystal structure and morphology.