Structure and electrochemical behaviors of spherical Li1+xNi0.5Mn0.5O2+δ synthesized by rheological phase reaction method
Structure and electrochemical behaviors of spherical Li1+xNi0.5Mn0.5O2+δ synthesized by rheological phase reaction method
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DOI：
10.1016/j.electacta.2014.10.151
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发表时间：
2014-12
影响因子：
6.6
通讯作者：
Xixi Shi;Chiwei Wang;Yantao Zhang;Qian Liu;Hong Li;Dawei Song;Lianqi Zhang
中科院分区：
文献类型：
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作者：
Xixi Shi;Chiwei Wang;Yantao Zhang;Qian Liu;Hong Li;Dawei Song;Lianqi Zhang
采用流变相反应法制备了球形层状Li1+xNi0.5Mn0.5O2+δ(x=0，0.1，0.2)材料。X-射线衍射谱表明，所制备的材料具有R-3m空间群的α-NaFeO2结构。不同锂含量的材料在结构、颗粒形态、电化学性质和安全特性等方面存在明显差异。当x=0.1和0.2时，过剩锂存在于过渡金属层中，形成类Li2MnO_3结构。随着锂含量从1.0增加到1.2，首次放电容量和库仑效率降低，容量保持性提高。当x=0.2时，在2.5~4.5nV的电压窗口内循环时，Mn离子对容量有贡献，在20 mA/−时，其放电容量约为200mAHg/−，100次循环后容量无衰减。差示扫描量热分析表明，Li1+xNi0.5Mn0.5O2+δ的生热随x的增加而增加。
Spherical layered Li1+xNi0.5Mn0.5O2+δ(x = 0, 0.1 and 0.2) materials are synthesized by rheological phase reaction method. X-ray diffraction patterns reveal that the prepared materials have the α-NaFeO2structure with R-3m space group. The materials with different lithium contents show distinct differences in structure, particle morphology, electrochemical property and safety characteristics. When x = 0.1 and 0.2, excess lithium resides in the transition metal layer to form Li2MnO3-like structure. With lithium content increasing from 1.0 to 1.2, the initial discharge capacity and Coulombic efficiency are decreased, while capacity maintenance is improved. Mn ions are electrochemically activated in the charge–discharge process and has a contribution to the capacity when cycling in a voltage window of 2.5–4.5 V for x = 0.2, leading to a high discharge capacity of near 200 mAh g−1and the excellent cycling performance (with no capacity decay after 100 cycles) at 20 mA g−1. Electrochemical impedance spectroscopy shows that the appropriate excess of lithium can decrease charge transfer resistance obviously in the initial several cycles. The differential scanning calorimetric indicates that the generated heat of Li1+xNi0.5Mn0.5O2+δis increased with the increase of x.