Zheng Zhuo, Hua Wei-Bo, Yu Chong, Zhong Yan-Jun, Xu Bin-Bin, Wang Jia-Zhao, Zhong Ben-He, Zhang Zhi-Ye
College of Chemical Engineering, Sichuan University, No. 24 South Section 1, Yihuan Road, Chengdu, 610065, China.
Dalton Trans. 2015 Aug 28;44(32):14255-64. doi: 10.1039/c5dt01678a.
A series of xLi1.5Ni0.25Mn0.75O2.5·(1 - x)Li0.5Ni0.25Mn0.75O2 (0 ≤ x ≤ 1) cathode materials have been synthesized. These compounds exhibit dramatic differences in structure, morphology and charge/discharge characteristics. As the x increases, the morphology shows an amazing trend: starting with an octahedral shape (x = 0), transforming to an octahedral/plate shape (0.1 ≤ x ≤ 0.9) in which both the spinel phase and the layered phase can be indexed in the XRD patterns, and ending up with a plate shape (x = 1.0). The particular layered-spinel composites xLi1.5Ni0.25Mn0.75O2.5·(1 - x)Li0.5Ni0.25Mn0.75O2 (0.1 ≤ x ≤ 0.9) exhibit better cycling stability than that of pristine spinel Li0.5Ni0.25Mn0.75O2 (x = 0) and layered Li1.5Ni0.25Mn0.75O2.5 (x = 1.0) materials. This improved cycling performance of these layered-spinel composites can be ascribed to the heterogeneous intergrowth of some layered phases and spinel phases in the parent structure as detected by TEM. Among these materials, Li0.5Ni0.25Mn0.75O2 and Li1.5Ni0.25Mn0.75O2.5 barely deliver the specific capacities of 90 mA h g(-1) and 117 mA h g(-1) at 5 C and show the capacity retentions of about 83% and 86% at 0.2 C after 50 cycles, respectively, while the layered-spinel 0.8Li1.5Ni0.25Mn0.75O2.5·0.2Li0.5Ni0.25Mn0.75O2 cathode shows the best rate capability of 162 mA h g(-1) at 5 C and the best cycling stability of 98% after 50 cycles at 0.2 C.
已合成了一系列xLi1.5Ni0.25Mn0.75O2.5·(1 - x)Li0.5Ni0.25Mn0.75O2（0≤x≤1）的阴极材料。这些化合物在结构、形态和充放电特性方面表现出显著差异。随着x的增加，形态呈现出惊人的趋势：从八面体形状（x = 0）开始，转变为八面体/板状（0.1≤x≤0.9），其中在XRD图谱中尖晶石相和层状相均可索引，最终变为板状（x = 1.0）。特定的层状 - 尖晶石复合材料xLi1.5Ni0.25Mn0.75O2.5·(1 - x)Li0.5Ni0.25Mn0.75O2（0.1≤x≤0.9）表现出比原始尖晶石Li0.5Ni0.25Mn0.75O2（x = 0）和层状Li1.5Ni0.25Mn0.75O2.5（x = 1.0）材料更好的循环稳定性。这些层状 - 尖晶石复合材料循环性能的改善可归因于通过TEM检测到的母体结构中一些层状相和尖晶石相的异质共生。在这些材料中，Li0.5Ni0.25Mn0.75O2和Li1.5Ni0.25Mn0.75O2.5在5C时几乎无法提供90 mA h g(-1)和117 mA h g(-1)的比容量，并且在0.2C下50次循环后分别显示出约83%和86%的容量保持率，而层状 - 尖晶石0.8Li1.5Ni0.25Mn0.75O2.5·0.2Li0.5Ni0.25Mn0.75O2阴极在5C时表现出最佳倍率性能，为162 mA h g(-1)，在0.2C下50次循环后表现出最佳循环稳定性，为98%。
