Hierarchical LiMnPO4 assembled from nanosheets via a solvothermal method as a high performance cathode material
Hierarchical LiMnPO4 assembled from nanosheets via a solvothermal method as a high performance cathode material
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DOI：
10.1039/c5ra14040d
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发表时间：
2015-09
期刊：
影响因子：
3.9
通讯作者：
Zhijian Zhang;Guo-rong Hu;Yanbing Cao;J. Duan;K. Du;Zhongdong Peng
中科院分区：
文献类型：
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作者：
Zhijian Zhang;Guo-rong Hu;Yanbing Cao;J. Duan;K. Du;Zhongdong Peng
采用溶剂热法成功地合成了一系列不同形貌的LiMnPO4纳米粒子。用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)对样品进行了表征。结果表明，不同Li：Mn：P摩尔比的前驱体复合裁剪可以控制合成产物的形貌、粒度和晶向。在3：1：1时，得到了含Li+的前驱体Li3PO4，而在2：1：1时，只检测到了Mn5(PO4)2[(PO3)OH]2·4H2O和MnHPO4·2.25H2O的前驱体。特别是，在2.5：1：1条件下，前驱体主要由含Mn2+的前驱体和少量的Li3PO4组成。从2：1：1到3：1：1，随着颗粒尺寸的减小，颗粒形态由片状演变为球形织构。在尿素的存在下，得到了高度均匀的具有层次化微纳米结构的LiMnPO4，该结构由几十纳米厚的纳米片组成。因此，这些具有开放多孔结构的独特的分级纳米粒子在LiMnPO4正极材料中扮演着重要的角色。当尿素的浓度为0.16molLiMnPO4/C时，暴露出(010)晶面的层次型LiMnPO4/C样品具有最好的电化学性能，在0.1C，0.2C，0.5C，1.0C，2.0C下的可逆容量分别为150.4,142.1,138.5,125.5,118.6 mA h g−1。此外，复合材料具有高倍率长循环稳定性，在2.0℃循环600次后，容量保持率高达92.4%，没有明显的电压衰减。
A series of LiMnPO4 nanoparticles with different morphologies have been successfully synthesized via a solvothermal method. The samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM). The results show that the morphology, particle size and crystal orientation are controllably synthesized by various precursor composite tailoring with various Li : Mn : P molar ratios. At 3 : 1 : 1, a Li+-containing precursor Li3PO4 is obtained while at 2 : 1 : 1, only a Mn2+-containing precursor involving Mn5(PO4)2[(PO3)OH]2·4H2O and MnHPO4·2.25H2O is detected. Especially, at 2.5 : 1 : 1, the precursor consists predominantly of a Mn2+-containing precursor with a minor amount of Li3PO4. From 2 : 1 : 1 to 3 : 1 : 1, the particle morphology evolves from sheet to spherical texture accompanied with the particle size reducing. In the presence of urea, highly uniform LiMnPO4 with a hierarchical micro-nanostructure is obtained, which is composed of nanosheets with a thickness of several tens of nanometers. Thus, these unique hierarchical nanoparticles with an open porous structure play an important role in the LiMnPO4 cathode material. At a concentration of 0.16 mol L−1 for urea, the hierarchical LiMnPO4/C sample assembled from nanosheets with the (010) facet exposed shows the best electrochemical performance, delivering higher reversible capacity of 150.4, 142.1, 138.5, 125.5, 118.6 mA h g−1 at 0.1, 0.2, 0.5, 1.0, 2.0C, respectively. Moreover, the composites show long cycle stability at high rate, displaying a capacity retention up to 92.4% with no apparent voltage fading after 600 cycles at 2.0C.