Sc~(3+)掺杂LiMn_xSc_(1-x)O_2材料的合成及电化学性能研究

采用水热反应的方法,以LiOH·H_2O,MnOOH和Sc_2O_3为原料,合成了一系列Sc~(3+)掺杂的锂离子电池正极材料LiSc_xMn_(1-x)O_2(x=0.01,0.02,0.03,0.05).利用X射线衍射和X光电子能谱测试研究了材料的结构和元素的化学状态.掺杂后的LiSc_xMn_(1-x)O_2材料仍保持正交相结构.电化学测试结果表明,掺杂后材料表现出较好的电化学性能,Sc~(3+)的掺入使材料的循环稳定性能大幅度提高,掺杂量为2%时LiMn_(0.981)Sc_(0.019)O_2材料的初次放电容量为140.5 mAh·g~(-1),60次循环后放电容量高达169.6 mAJl·g-.,远高于未掺杂的LiMnO_2材料的放电容量107.7 mAh·g~(-1).这种提高源于Sc~(3+)的加入,很好地起到了稳定晶体结构、有效抑制Jahn-Teller效应的作用.电化学阻抗测试结果表明,Sc~(3+)的掺人能改善材料的导电性能.

Synthesis and Electrochemical Properties of Sc-doped LiSc_xMn_(1-x)O_2 Orthorhombic Structure Cathode Material for Lithium-ion Batteries

A series of Sc~(3+) -doping layered lithium manganese oxides LiSc, Mn_(1-x)O_2 (x = 0.01, 0. 02, 0.03 and 0. 05) were synthesized by a hydrothermal reaction using LiOH·H_2O, MnOOH, and Sc_2O_3 as starting materials. The structure and the ehemical states of elements were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). The results indicated that the Sc-doped LiSc_xMn_(1-x)O_2 mate-rials maintained the orthorhombie structure. The elec-trochemical analyses exhibited better electrochemical properties after Sr~(3+) -doping, especially, the better cyclic capability. The initial discharge capacity of the doped LiMn_(0.98)Sc_(0.019)O_2 material reached 140. 5 mAh·g~(-1), and the discharge capacity after 60 cycles was 169.6 mAh·g_(-1), which was much higher than that of the un-doped LiMnO_2 materials (107.7 mAh·g_(-1) after 60 cy-cles). It was due to that Sc~(3+) doping effectively re-stricted Jahn-Teller effect and stabilized the crystal structure of layered LiMnO_2. The EIS analysis showed that the conductivity of the as-prepared samples was evidently improved by the Sc~(3+) doping.