高镍LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)的锂离子导体Li_(3)PO_(4)的包覆改性及电化学性能研究

Surface modification and electrochemical properties of Ni-rich LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) by Li^(+)-conductor Li_(3)PO_(4) coating

采用典型的溶胶-凝胶法,在高镍LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)正极颗粒表面包覆不同含量的Li_(3)PO_(4)锂离子导体。利用X射线衍射仪,扫描电镜对Li_(3)PO_(4)包覆前后的LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)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Li_(3)PO_(4)成功包覆在LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)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Li_(3)PO_(4)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)Li_(3)PO_(4)包覆样品的89.2%。而且在5C高倍率,2%(质量分数)Li_(3)PO_(4)包覆LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)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)Li_(3)PO_(4)包覆LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)的容量保持率比未包覆样品分别高出7.1%和9.9%。

Ni-rich LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) cathode materials are coated by the different contents of Li_(3)PO_(4) Li+-conductor via the typical Sol-Gel method.The crystal structure and micro-morphology of Li_(3)PO_(4) coated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) 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 Li_(3)PO_(4) is successfully covered on the surface of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2).In addition,the results of initial charging-discharging,rate capacity and cycling tests for the four samples demonstrate the cathodes after Li_(3)PO_(4) 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 Li_(3)PO_(4) coating content increases to 2 wt%.Moreover,the 2wt%Li_(3)PO_(4) coated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) 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%Li_(3)PO_(4) coated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) 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.