正极材料Li[Ni_(1/3)Li_(1/9)Mn_(5/9)]O_2的结构和充放电过程研究

Understanding the structure and cycle behavior of Li[Ni_(1/3)Li_(1/9)Mn_(5/9)]O_2 positive electrode material

应用X射线衍射,选区电子衍射和同步X射线衍射等方法,对锂离子电池正极材料Li[Ni1/3Li1/9Mn5/9]O2的结构和充放电行为进行了研究.结果表明Li[Ni1/3Li1/9Mn5/9]O2可标定为单相α-NaFeO2,并具有3ahex.×3ahex.×3chex.超结构特征.电池充电时,伴随锂离子的脱出,相邻氧原子层间的静电斥力逐渐增大,当电压为3.8V时应力达到最大.接近4.6V时,晶胞常数c急剧下降,绝大多数Li+从材料的锂层拔出,Ni2+发生氧化.4.6～4.8V之间c增大,a变化很小,说明过渡金属层中的Li+拔出,而过渡金属离子的氧化状态未改变.

The structure and cycle behavior of Li[Ni1/3Li1/9Mn5/9]O2 were studied by means of XRD,SAED and synchrotron X-ray diffraction,respectively.The results show that Li[Ni1/3Li1/9Mn5/9]O2 can be indexed based on the α-NaFeO2 single phase and confirmed to be in good agreement with 3ahex.×3ahex.×chex.superstructure.When the cell was charged to 3.8 V with lithium de-intercalation,the electrostatic repulsion between adjacent oxygen layers gradually increased and became largest near 3.8 V.At 4.6 V the rapid decrease of lattice constant c revealed that the most of the Li+ extracted from the Li-layer,accompanying with the oxidation of Ni2+ ions.When the charge voltage located between 4.6 and 4.8 V,c axis increased while a axis remained almost constant.The fact suggested that some Li+ de-intercalated from the transition metal layer,but the transition metal oxidation states did not change at 4.6-4.8 V.