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首页> 外文期刊>Advanced energy materials >Electrochemical and Structural Investigation of Calcium Substituted Monoclinic Li_3V_2(PO_4)_3 Anode Materials for Li-Ion Batteries
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Electrochemical and Structural Investigation of Calcium Substituted Monoclinic Li_3V_2(PO_4)_3 Anode Materials for Li-Ion Batteries

机译：锂离子电池用钙替代单斜晶Li_3V_2（PO_4）_3负极材料的电化学和结构研究

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摘要

In this work, the effect of Li+ substitution in Li3V2(PO4)(3) with a large divalent ion (Ca2+) toward lithium insertion is studied. A series of materials, with formula Li3-2xCaxV2(PO4)(3)/C (x = 0, 0.5, 1, and 1.5) is synthesized and studied in the potential region 3-0.01 V versus Li+/Li. Synchrotron diffraction demonstrates that Li3V2(PO4)(3)/C has a monoclinic structure (space group P2(1)), while Ca1.5V2(PO4)(3)/C possesses a rhombohedral structure (space group R-3c). The intermediate compounds, Li2Ca0.5V2(PO4)(3)/C and LiCaV2(PO4)(3)/C, are composed of two main phases, including monoclinic Li3V2(PO4)(3)/C and rhombohedral Ca1.5V2(PO4)(3)/C. Cyclic voltammetry reveals five reduction and oxidation peaks on Li3V2(PO4)(3)/C and Li2Ca0.5V2(PO4)(3)/C electrodes. In contrast, LiCaV2(PO4)(3)/C and Ca1.5V2(PO4)(3)/C have no obvious oxidation and reduction peaks but a box-type voltammogram. This feature is the signature for capacitive-like mechanism, which involves fast electron transfer on the surface of the electrode. Li3V2(PO4)(3)/C undergoes two solid-solution and a short two-phase reaction during lithiation and delithiation processes, whereas Ca1.5V2(PO4)(3)/C only goes through capacitive-like mechanism. In operando X-ray absorption spectroscopy confirms that, in both Li3V2(PO4)(3)/C and Ca1.5V2(PO4)(3)/C, V ions are reduced during the insertion of the first three Li ions. This study demonstrates that the electrochemical characteristic of polyanionic phosphates can be easily tuned by replacing Li+ with larger divalent cations.
机译：在这项工作中，研究了Li3V2（PO4）（3）中具有大二价离子（Ca2 +）的Li +取代对锂插入的影响。合成了一系列材料，分子式为Li3-2xCaxV2（PO4）（3）/ C（x = 0、0.5、1和1.5），并在相对于Li + / Li的3-0.01 V电位区域中进行了研究。同步加速器衍射表明Li3V2（PO4）（3）/ C具有单斜晶结构（空间群P2（1）/ n），而Ca1.5V2（PO4）（3）/ C具有菱面体结构（空间群R-3c ）。中间化合物Li2Ca0.5V2（PO4）（3）/ C和LiCaV2（PO4）（3）/ C由两个主要相组成，包括单斜晶Li3V2（PO4）（3）/ C和菱形Ca1.5V2（ PO4）（3）/ C。循环伏安法揭示了Li3V2（PO4）（3）/ C和Li2Ca0.5V2（PO4）（3）/ C电极上的五个还原和氧化峰。相比之下，LiCaV2（PO4）（3）/ C和Ca1.5V2（PO4）（3）/ C没有明显的氧化和还原峰，但具有箱形伏安图。此功能是类电容机制的标志，该机制涉及电极表面上的快速电子转移。 Li3V2（PO4）（3）/ C在锂化和脱锂过程中经历两次固溶和短暂的两相反应，而Ca1.5V2（PO4）（3）/ C仅经历类似电容的机制。在操作中，X射线吸收光谱证实，在Li3V2（PO4）（3）/ C和Ca1.5V2（PO4）（3）/ C中，在插入前三个Li离子期间V离子都会还原。这项研究表明，通过用较大的二价阳离子取代Li +，可以轻松地调节聚阴离子磷酸酯的电化学特性。

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