Kinetics and structural changes of Li-rich layered oxide 0.5Li2MnO3·0.5LiNi(0.292)Co(0.375)Mn(0.333)O2 material investigated by a novel technique combining in situ XRD and a multipotential step.
Kinetics and structural changes of Li-rich layered oxide 0.5Li2MnO3·0.5LiNi(0.292)Co(0.375)Mn(0.333)O2 material investigated by a novel technique combining in situ XRD and a multipotential step.
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DOI：
10.1021/am503132t
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发表时间：
2014-07
影响因子：
9.5
通讯作者：
Chongheng Shen;Ling Huang;Zhou Lin;Shouyu Shen;Qin Wang;Hang Su;Fangbao Fu;Xiao-Mei Zheng
中科院分区：
文献类型：
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作者：
Chongheng Shen;Ling Huang;Zhou Lin;Shouyu Shen;Qin Wang;Hang Su;Fangbao Fu;Xiao-Mei Zheng
采用水溶液蒸发法制备了富锂层状氧化物0.5Li2MnO3·0.5LiNi0.292Co0.375Mn0.333O2。 X射线粉末衍射(XRD)表明合成的材料是由层状α-NaFeO2型LiMO2(M=Ni、Co、Mn)和单斜晶系Li2MnO3组成的固溶体。选定区域电子衍射图案中的超晶格点表明了这种富锂层状氧化物中TM层中锂离子与过渡金属(TM)离子的有序化。电化学性能测试表明，合成材料的首次放电容量为267.7 mAh/g，33次循环后容量保持率为88.5%。首次应用一种新的组合技术——多电位步骤原位 XRD（MPS 原位 XRD）测量来研究富锂层状氧化物。使用这种方法，可以同时获得动力学和结构变化之间的关系。原位 XRD 结果显示，在第一次充电过程中，c 参数从 3.70 V 下降至 4.30 V，并从 4.30 V 上升至 4.70 V，而 a 参数下降至 4.30 V 以上。在第一次放电过程中低于 3.90 V，发现 c 参数略有下降，同时 a 参数增加。在第一次充电过程中，锂离子扩散系数（DLi+）在4.55 V时降至最小值，这可能与Ni（2+）迁移有关，如Ni在Li（+）层中3b位点（Ni3b％）的占据和复杂的化学反应所表明的。值得注意的是，在第一次放电过程中，主体结构的局部域内可能会发生晶格畸变，这由 3.20 V 处的 (003) 衍射峰的轻微分裂表明。
Li-rich layered oxide 0.5Li2MnO3·0.5LiNi0.292Co0.375Mn0.333O2 was prepared by an aqueous solution-evaporation route. X-ray powder diffraction (XRD) showed that the as-synthesized material was a solid solution consisting of layered α-NaFeO2-type LiMO2 (M = Ni, Co, Mn) and monoclinic Li2MnO3. The superlattice spots in the selected area electron diffraction pattern indicated the ordering of lithium ions with transition metal (TM) ions in TM layers in this Li-rich layered oxide. Electrochemical performance testing showed that the as-synthesized material could deliver an initial discharge capacity of 267.7 mAh/g, with a capacity retention of 88.5% after 33 cycles. A new combination technique, multipotential step in situ XRD (MPS in situ XRD) measurement, was applied for the first time to investigate the Li-rich layered oxide. Using this approach, the relationships between kinetics and structural variations can be obtained simutaneously. In situ XRD results showed that the c parameter decreased from 3.70 to 4.30 V and increased from 4.30 to 4.70 V, whereas the a parameter underwent a decrease above 4.30 V during the first charge process. Below 3.90 V during the first discharge process, a slight decrease in the c parameter was found along with an increase in the a parameter. During the first charge process, the value of the coefficient of diffusion for lithium ions (DLi+) decreased to its mininum at 4.55 V, which might be associated with Ni(2+) migration, as indicated by both Ni occupancy in 3b sites (Ni3b%) in the Li(+) layers and complicated chemical reactions. Remarkably, a lattice distortion might occur within the local domain in the host stucture during the first discharge process, indicated by a slight splitting of the (003) diffraction peak at 3.20 V.