高镍LiNi0.8Co0.1Mn0.1O2的锂离子导体Li3PO4的包覆改性及电化学性能研究

采用典型的溶胶-凝胶法,在高镍LiNi_0.8Co_0.1Mn_0.1O₂正极颗粒表面包覆不同含量的Li₃PO₄锂离子导体。利用X射线衍射仪,扫描电镜对Li₃PO₄包覆前后的LiNi_0.8Co_0.1Mn_0.1O₂样品的晶体结构和微观形貌进行分析。结果表明,合成材料的层状结构明显,阳离子混排度低,并且Li₃PO₄成功包覆在LiNi_0.8Co_0.1Mn_0.1O₂颗粒表面。另外,对4个样品进行了首次充放电,倍率放电和循环性能比较,结果表明经过Li₃PO₄包覆后的正极材料的综合电化学性能明显比未包覆样品优越。首次库伦效率从未包覆样品的84.2%提高到2%(质量分数)Li₃PO₄包覆样品的89.2%。而且在5C高倍率,2%(质量分数)Li₃PO₄包覆LiNi_0.8Co_0.1Mn_0.1O₂的放电比容量是129.7 mAh/g,远远高于未包覆样品的92.6 mAh/g。同时,在常温和高温环境下循环100次后,2%(质量分数)Li₃PO₄包覆LiNi_0.8Co_0.1Mn_0.1O₂的容量保持率比未包覆样品分别高出7.1%和9.9%。

Surface modification and electrochemical properties of Ni-rich LiNi0.8Co0.1Mn0.1O2 by Li+-conductor Li3PO4 coating

Ni-rich LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials are coated by the different contents of Li₃PO₄ Li+-conductor via the typical Sol-Gel method.The crystal structure and micro-morphology of Li₃PO₄ coated LiNi_0.8Co_0.1Mn_0.1O₂ are investigated by the X-ray diffraction(XRD)and scanning electron microscopy(SEM).The results indicate the prepared samples demonstrate the well layered structure and lower cation mixing degree.The Li₃PO₄ is successfully covered on the surface of LiNi_0.8Co_0.1Mn_0.1O₂.In addition,the results of initial charging-discharging,rate capacity and cycling tests for the four samples demonstrate the cathodes after Li₃PO₄ coating deliver the obvious enhanced electrochemical properties than that of the pristine one.The initial coulombic efficiency of pristine cathode could be enhanced from 84.2%to 89.2%when the Li₃PO₄ coating content increases to 2 wt%.Moreover,the 2wt%Li₃PO₄ coated LiNi_0.8Co_0.1Mn_0.1O₂ delivers a discharge capacity of 129.7 mAh/g at 5 C high rate,much larger than that(92.6 mAh/g)of the pristine one.Meanwhile,the 2 wt%Li₃PO₄ coated LiNi_0.8Co_0.1Mn_0.1O₂ respectively demonstrates the capacity retention of 7.1%and 9.9%higher than those of the pristine cathode at 25℃and 45℃condition after 100 cycles.