流变相法一步合成正交LiMnO_2的结构和性能

Structure and Electrochemical Characteristics of Orthorhombic LiMnO_2 Synthesized by an One-step Rheological Phase Method

以Mn2O3和LiOH·H2O为原料,用流变相法在150℃、无惰性气体保护条件下一步合成正交LiMnO2(简写为o-LiMnO2),并用X射线衍射(XRD)、透射电镜(TEM)和电化学循环测试对反应10h和15h所得产物进行了对比研究。结果表明:前者(110)晶面堆垛层错度高、颗粒小,首次循环即可得到最大的放电容量209.7mAh/g,但衰减较快;后者(110)晶面堆垛层错度低、颗粒大,经活化后在第5次循环可达到最大的放电容量195.3mAh/g,循环稳定性较好。非原位XRD证实,前者经首次循环后o-LiMnO2已完全转变为类尖晶石LiMn2O4和NaCl型结构Li0.5Mn0.5O;后者经5次循环后才能完成整个相变过程。

Orthorhombic LiMnO2 （o-LiMnO2） was synthesized using LiOH·H2O and Mn2O3 by an one-step rheological phase method at 150℃without noble gas. The products prepared at different times were characterized by X-ray diffraction（XRD）, transmission electron microscopy （TEM） and electrochemical measurements. The electrode of o-LiMnO2 prepared after 10h, which had high stacking faults in （110） plane and small particles, achieved its maximum discharge capacity of 209.7 mAhg^-1 in the 1^st cycle but poor cycleability during cycling. The one prepared after 15 h, which had low stacking faults in （110） plane and large particles, achieved its maximum discharge capacity of 195.3mAhg^-1 in the 5^th cycle but good cycleability during cycling. Ex-situ XRD patterns confirmed that the structure of the former o-LiMnO2 after one cycle charge-discharge had completely transformed to the spinel-like phase LiMn2O4 and NaCI structural cubic phase of Li0.5 Mn0.5 O while the latter had completely transformed after 5 cycles.