富锂层状正极材料Li2Mn1-xTixO3的合成及电化学性能

应用简单的高温固相烧结法合成了Ti掺杂改性的Li₂MnO₃材料。电子扫描显微镜、X射线衍射以及X射线光电子能谱分析表明Ti元素取代Mn离子掺入到Li₂MnO₃晶格中，且掺杂能有效地抑制一次颗粒的团聚。电化学阻抗和恒流充放电测试结果表明，在2.0~4.6 V的电压窗口下，掺杂改性的样品Li₂Mn_0.9Ti_0.03O₃的首圈放电比容量达到209 mAh·g^-1，库仑效率为99.5%，循环40圈后容量保持率为94%；当电流密度增大到400 mA·g^-1时，掺杂改性的样品仍然可以放出120 mAh·g^-1比容量，远高于同等电流密度下未掺杂的Li₂MnO₃原粉的比容量（52 mAh·g^-1）。Ti掺杂可有效地改善Li₂MnO₃的循环稳定性和倍率性能，有利于促进该材料的商业化应用。

Syntheses and Electrochemical Characterization of Li-rich Li2Mn1-xTixO3 Layered Materials Used for Lithium Ion Batteries

Ti-doped Li₂MnO₃ is synthesized by a conventional solid-state reaction.Scanning electron microscopy,X-ray diffraction and X-ray photoelectric spectroscopy analyses indicate Ti is successfully doped into Li₂MnO₃ structure and the doping could suppress agglomeration of primary particlesis efficiently.Electrochemical impedance spectroscopy and galvanostatic charge/discharge results show that,in the voltage window of 2.0~4.6 V (vs Li/Li⁺),doped sample Li₂Mn_0.9Ti_0.03O₃ delivers an initial discharge capacity of 209 mAh·g^-1 with 99.5% coulombic efficiency;after 40 cycles the capacity retention is 94%.Even the current density increases to 400 mA·g^-1,the doped sample could still deliver 120 mAh·g^-1 capacity,which is more than twice of that of undoped Li₂MnO₃(52 mAh·g^-1).Ti-doped Li₂MnO₃ show greatly improved cycling stability and rate performance,which is beneficial for promoting the commercial application of Li₂MnO₃ material.