Li_2MnSiO_4/CNTs复合正极材料的合成与电化学性能

Preparation and Electrochemical Performance of Li_2MnSiO_4/CNTs Composite Cathode Material for Lithium Ion Batteries

采用水热辅助溶胶-凝胶工艺,通过原位复合的方法合成了锂离子电池用Li2MnSiO4/CNTs复合正极材料.分析了复合正极材料的形貌和组成特征,并对每摩尔分别复合5,10,20和30 g碳纳米管(CNTs)及未复合CNTs的样品进行了电化学性能测试.结果显示,所合成的Li2MnSiO4颗粒尺寸分布均匀,粒径在100 nm左右,易团聚.但随着CNTs复合量的增加,团聚现象逐渐改善.合成的Li2MnSiO4材料结晶度良好,属于正交晶系Pmn21空间群.电化学测试结果表明,每摩尔复合20 g CNTs的样品电化学性能最佳,在10 mA/g电流密度下,首周放电容量为150 mA.h/g,循环20周后仍保持在80 mA.h/g;CNTs的原位复合可提高Li2MnSiO4材料的导电性能,并改善其电化学性能.

Li2 MnSiO4/CNTs composite cathode material for lithium ion batteries was in situ synthesized by the sol-gel process assisted with hydrotherrnal method. The crystalline structure and morphology of the obtained samples containing 0, 5, 10, 20 and 30 g carbon nanotubes（CNTs） in 1 tool Li2MnSiO4, respectively, were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and their electrochemical per- formances were evaluated by different electrochemical test. The results show that the grains of samples have narrow size distribution and their dimension is about 100 nm. They are easy to be an agglomerate mass and the agglomeration of the samples is gradually reduced with the increase of the contents of CNTs. The XRD patterns reveal that the well-crystallized Li2MnSiOJCNTs materials are orthorhombic with space group Pmn21. The sample with 20 g CNTs in 1 tool Li2MnSiO4（ the carbon content is 16.74% ） demonstrates the best electro- chemical performance, showing an initial discharge capacity of 150 mA · h/g and a discharge capacity of 80 mA · h/g after 20 cycles at 10 mA/g current density. The in situ composite of CNTs could improve the overall conductivity and the electrochemical performance of Li2 MnSiO4 cathode materials.