Study On The Controllable Preparation And Performance Of Spinel Lithium Manganate

In the current,with the shortage of resources and the hostile environment,the demand of alternatives circular clean energy is increasing.Lithium-ion secondary battery is one of the best alternatives of fossil energy.As one of the most research value and industrial prospects for lithium ion battery cathode materials,spinel lithium manganate has been widely used in electric vehicles or plug-in hybrid vehicles,because it is safe,environment friendly,raw materials are cheap,and has advantages such as high voltage and fast charge/discharge capacity.In this paper,two kinds of the preparation methods of spinel lithium manganate precursors were compared,they are pyrolysis manganese carbonate method and pressurized gas hydrothermal method,respectively.The precursors were further calcined to prepare spinel lithium manganate.The influence of calcination temperature,manganese-lithium ratio and calcination time on the morphology,structure and electrochemical properties of spinel lithium manganate were investigated,then obtained the best experimental condition.Two methods were used to prepare spinel lithium manganate with different morphologies.Firstly,the precursor was prepared by pyrolysis manganese carbonate method then synthesize spinel LiMn₂O₄ with Li₂CO₃.The optimum pyrolysis temperature of manganese carbonate is 520?which was determined by TG-DSC.Mn₂O₃ and Li₂CO₃ were calcined at 700°C for 10h to obtain the sample,and the Mn:Li=2:1.2.The charge/discharge test was carried out at 0.5 C.The results show that the first discharge specific capacity was 114.76 mAh/g,the capacity retention rate was 93.20%after 100 cycles,and the charge and discharge efficiency was maintained above 97%.Secondly,the precursor of spinel LiMn₂O₄ was prepared by pressurized gas hydrothermal method.The precursor Mn₃O₄ sample with the best crystal morphology was obtained by oxidant10ml,initial pressure 2MPa,hydrothermal temperature160?and hydrothermal time 10h.The precursors Mn₃O₄ and Li₂CO₃ were calcined at Mn:Li=2:1.2,700°C for 10 h to obtain samples with the best electrochemical performance.The charge/discharge test was carried out at 0.5 C.The result shows that the first discharge specific capacity was 120.15 mAh/g,and the capacity retention rate after the cycle was 95.69%.At last,the electrochemical properties of spinel lithium manganate prepared by two methods were compared at different temperatures.At room temperature?25??,the cycle performance of both samples were good.After 100 cycles,the capacity retention rates are all above 93%.However,the sample obtained by the pressurized gas hydrothermal method had better electrochemical properties at high temperature?55??,and the capacity retention rate is 90%after 100 cycles,the sample obtained by the pyrolysis manganese carbonate method is only 85%.It is indicated that the pressurized gas hydrothermal method can improve the high temperature performances of the spinel LiMn₂O₄.