SrF_2包覆锂离子电池用正极材料0.5Li_2MnO_3·0.5LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2的电化学性能研究

Electrochemical performance of SrF_2-coated anode material 0.5Li_2MnO_3·0.5LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 for Li-ion batteries

采用化学沉淀法在富锂层状正极材料0.5Li2MnO3？0.5LiNi1/3Co1/3Mn1/3O2表面包覆一层SrF2薄膜。利用X射线衍射仪、扫描电子显微镜、透射电子显微镜和充放电测试技术研究SrF2包覆对正极材料的晶体结构、微观形貌和电化学性能的影响。结果表明,正极材料表面包覆了一层厚约20-30nm的SrF2膜。包覆SrF2后,材料的首次库仑效率从70.5%增加到72.7%,且包覆改善了材料的倍率性能和循环性能。随着充放电倍率的增大,包覆样与未包覆样的放电容量差值随之增大;包覆样循环40次后容量保持率为95.1%,高于未包覆样84.8%的容量保持率。

Lithium-rich layered anode materials with a composition of 0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2 were prepared and coated by SrF2via chemical precipitation method.The crystalline structure and micromorphology and electrochemical properties for the pristine and SrF2-coated anodes were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）and charge-discharge tests.The results showed that a layer of SrF2 with a thickness of 20-30nm was successfully coated on the surface of anode.The initial coulombic efficiency of the anode material was enhanced from 70.5%to 72.7% by coating SrF2.The coated material also exhibited better rate capability and cyclic performance compared with the pristine one.With increasing the rate,the difference value of discharge capacity between the two samples became larger.The SrF2-coated sample maintained higher capacity retention of 95.1%after 40cycles in comparison with only 84.8% of the pristine one.