Surface Modification of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 by V2O5- Coating

摘要:

在采用低温共沉淀-水热-煅烧法合成锂离子电池Fe-Ni-Mn体系正极材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的基础上，对合成的材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6进行V2O5的包覆改性研究，以提高材料Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的首次放电比容量和循环性能。用XRD、SEM、TEM、ICP光谱和恒流充放电测试研究包覆材料的结构和电化学性能。结果表明，V2O5包覆并没有改变材料的晶体结构，只存在于材料的表面，与未包覆的材料相比，V2O5包覆后的材料具有更好的首次放电容量和容量保持率。50周循环后，添加质量分数3%V2O5样品Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的放电比容量可以维持在200.3 mAh/g，大于未添加V2O5样品Li1.6(Fe0.2Ni0.2Mn0.6)O2.6的194.0 mAh/g。CV测试表明，包覆层的存在有效抑制了材料层状结构的转变及电极与电解液的负反应

Abstract:

We presented a method to improve the first discharge capacity and the cycling performance of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 which was synthesized by a coprecipitation-hydrothermal-calcinations method and coated by a V2O5 layer on the surface of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6. The crystal structure and the charge/discharge performance of Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), inductively coupled plasma (ICP) and electrochemical performance measurement. Results show that V2O5 exists only on the surface, and has no effect on the crystal structure; the Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 coated with V2O5 exhibits better first discharge capacity than the bared Li1.6(Fe0.2Ni0.2Mn0.6)O2.6. The electrochemical tests demonstrate that Li1.6(Fe0.2Ni0.2Mn0.6)O2.6 coated with 3 wt% V2O5 shows the best electrochemical performance with the discharge capacity 200.3 mAh/g after 50 cycles, while the bared sample has 194.0 mAh/g only. CV results indicate that the V2O5 coating can suppress the phase transitions and prevent the surface of cathode materials from the direct contact with the electrolyte