软化学法合成层状结构LiMnO_2阴极材料

Synthesizing layered LiMnO_2 as cathode material composed by soft-chemical route

研究了以氢氧化锂和醋酸锰为原料,用软化学法制备锂离子蓄电池阴极材料LiMnO2。用X射线衍射法确定了材料的结构及其结构转变,结合循环伏安法研究了材料组织结构与电化学性能之间的关系。实验结果显示,层状结构LiMnO2的最佳热合成温度是600 ℃,随着温度升高,材料由层状结构向尖晶石结构转变,层状结构中Mn原子的最密排原子面(003)重排成为尖晶石结构的(111)面;而部分层状结构材料(104)原子面上的Li原子发生转移,Mn原子重排形成尖晶石LiMn2O4的(400)原子面,这两个原子面的面间距不一样,造成XRD图谱上(104)峰的位置上出现新的衍射峰,并且由于原子面上原子种类和排布方式的不同,衍射峰强度也发生变化。热处理温度升高,使材料中相伴出现杂相Li2MnO3和尖晶石型的LiMn2O4,破坏材料的层状结构,降低电化学性能。

LiMnO2 samples were prepared as cathode materials of lithium-ion battery by soft-chemical reaction from LiOH and Mn(CH3COO)2. X-ray diffraction patterns of prepared samples were identified as the layered structure. Cyclic voltammetry was used to study the correlation between the structure of layered LiMnO2 and its electrochemical properties. The results show that the optimistic sintering temperature is 600 ℃. Increasing sintering temperature will result in phase transformation of layered LiMnO2 to spinel LiMn2O4. During the process of phase transformation, the Mn atoms in (003) plane of LiMnO2 are rearranged to constitute the (111) plane of LiMn2O4, and Li atoms in (104) plane are moved and part of Mn atoms are used to form the (400) plane of LiMn2O4, as a result, (104) peak in XRD pattern is separated into two peaks. Li2MnO3 and LiMn2O4 impurities are formed in layered LiMnO2, and they are harmful to the electrochemical performance of LiMnO2.