Synthesis, Structure and Electrochemistry of Lithium Vanadium Phosphate Cathode Materials
Synthesis, Structure and Electrochemistry of Lithium Vanadium Phosphate Cathode Materials
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DOI：
10.1149/2.003112jes
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发表时间：
2011
影响因子：
3.9
通讯作者：
C. Allen;Q. Jia;C. Chinnasamy;S. Mukerjee;K. Abraham
中科院分区：
文献类型：
--
作者：
C. Allen;Q. Jia;C. Chinnasamy;S. Mukerjee;K. Abraham
锂离子电池正极材料α-LiVOPO4、β-LiVOPO4 和Li3V2(PO4)3 通过控制合成条件，由常见的前驱体混合物制备成各个相。这些相是由于其独特的晶体对称性和 V 氧化态而产生的。该合成涉及由 NH4VO3、NH4H2PO4、LiF 和己酸制备的前体混合物的分解，在不同条件下热处理时产生三种 LiwVxOy(PO4)z 产物。通过元素分析、X射线衍射（XRD）、X射线吸收光谱（XAS）和锂电池数据对材料进行了表征。还使用 XAS 探测局部钒环境，研究了正常和深度放电条件下的 Li 循环性能以及对 α-和 β-LiVOPO4 的结构影响。 XANES 和 EXAFS 证实，当插层不超过 1Li/VOPO4 时，两种结构会发生可逆变化。更深的放电表明两种结构受到更多破坏，包括 V=O 键长额外增加 0.25 A。 α-LiVOPO4 的 VO6 对称性范围更大，因此具有更灵活的调节主体，这与其相比 β-LiVOPO4 改进的低电压性能一致。
The Li-ion battery positive electrode materials, α-LiVOPO4, β-LiVOPO4, and Li3V2(PO4)3 have been prepared as individual phases from a common precursor mixture by controlling the synthesis conditions. These phases result because of their distinct crystal symmetries and V oxidation states. The synthesis involves the decomposition of a precursor mixture prepared from NH4VO3, NH4H2PO4, LiF and hexanoic acid which when heat-treated under different conditions produced the three LiwVxOy(PO4)z products. The materials were characterized by means of elemental analysis, X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) and Li cell data. The Li cycling performance and the accompanying structural effects on α- and β-LiVOPO4 were also studied under normal and deep discharge conditions using XAS to probe the local vanadium environment. XANES and EXAFS confirm reversible changes in the two structures when intercalation does not exceed 1Li/VOPO4. Deeper discharge revealed more disruption to both structures, including an additional 0.25 A increase to the V=O bond length. A greater range in the VO6 symmetry of α-LiVOPO4 resulted in a more flexible accommodating host, in agreement with its improved low voltage performance compared to β-LiVOPO4.