正极材料LiMn_2O_4的高温改性研究

Study on the modification of positive electrode material LiMn_(2)O_(4)at high temperature

为提高锂离子电池正极材料L iMn2O4在高温下的循环性能,以正硅酸乙酯为原料,采用溶胶-凝胶法在L iMn2O4表面包覆了一层稳定的二氧化硅层。用X射线粉末衍射和扫描电镜对包覆前后L iMn2O4的结构进行了表征。结果表明,二氧化硅包覆层的存在减少了L iMn2O4和电解液的直接接触,有效地抑制了高温下L iMn2O4与电解液的相互作用,减少了锰在电解质中的溶解;经表面修饰处理后,L iMn2O4正极材料的初始容量虽稍有下降,但其在高温下(55℃)其充放电循环稳定性能得到了显著提高,100次循环后仅衰减20%,并且电池的自放电速率也显著减小。

In order to improve electrochemical performance of LiMn2O4 for positive electrode material of lithium ion battery at high temperature （55℃ ） , the stable SiO2 film was coated on the surface of LiMnEO4positive electrode material by solgel method with Si（OCH2 CH3）4. The structures of the coated and uncoated LiMn2O4 were characterized by XRD and SEM. The results show that the SiO2 layer can reduce the direct contact between LiMn2O4 and electrolyte,and thus effectively restrain the harmful interactions between them at elevated temperature and reduce the dissolving of manganese in eletrolyte. Although the initial electric volume of positive electrode material LiMn2O4 decreases a bit after modified, the cycling stability of charge/discharge of it increases remarkably,its reduction is only 20% after 100 times cycling. And the self - discharge of the battery is largely reduced.