磷酸锰锂正极材料的可控合成与电化学性能研究

Controllable Synthesis of LiMnPO_4 Cathode Materials and the Investigation of Their Electrochemical Performance

研究了磷酸锰锂(LiMnPO4)微纳米材料的水热合成过程及其电化学特性。在水热合成过程中,改变各种参数,如反应温度、反应物LiOH浓度、铁元素掺杂等,制备一系列LiMnPO4粉体。使用X射线衍射仪(XRD)、扫描电镜(SEM)等分析手段对其进行分析表征,获得了优化的水热合成LiMnPO4工艺,制备了性能稳定的LiMnPO4正极材料。研究发现,水热合成温度是形成LiMnPO4物相的主要因素,在140℃以上温度合成时,可以得到纯相LiMnPO4;LiOH浓度对合成物相的影响不大,但是它改变了晶体的生长习性,导致粉体显微形貌从针状向颗粒状、片状转化,材料的电化学性能随之增加;纯相LiMnPO4的电化学性能无法满足应用需求,可以通过Fe元素掺杂形成固溶体,使LiMnPO4的电化学性能得到一定的提升,有望在动力电池领域得到应用。

The hydrothermal preparation and electrochemical performance of LiMnP04 cathodic materials were investigated. By varying the hydrothermal parameters, such as the reaction temperature, LiOH concentration, and the doping of Fe ions in the lattice, series of LiMnP04 powders were prepared with different morphology. Employing XRD and SEM cyclic tests, an optimal hydrothermal route was ob- tained to provide LiMnP04 materials with stable electrochemical behavior. It was found from the experi- ments that the reaction temperature was the key factor determining the final phase purity, while the LiOH concentration controlled the morphology. When the samples were hydrothermally treated above 140 ~C, pure phased LiMnP04 powders could always be obtained. With the increasing in LiOH concen- tration, the morphologies of the prepared powders change, from needle like shape to granular shape, and finally plate like shape. Such changes in shape indicated the difference in growth manner and thus led to big differences in electrochemical performance. Although the intrinsic LiMnP04 materials were not good enough for future application, further works to enhance the electrochemical properties were realized by doping Fe ions into Mn lattice site, which was expected to be used in powerful cells.