Conventional high-temperature (800 °C) synthesis of fluoride-substituted samples from LiF has been found to encounter the volatilization of fluorine and to limit the fluorine content, as reported in our earlier paper. In the present study, a fluoride-substituted spinel LiMn₂O₄ material was synthesized by using a solid-state reaction method with (NH₄)HF₂ as the fluorine source. The structure and the electrochemical properties of the synthesized samples were characterized by using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area analysis, Fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV) and charge-discharge tests. As indicated by XRD, all samples showed a spinel cubic structure with space group Fd3m. In comparison with the pure LiMn₂O₄, fluoride substitution leads to an increase in the lattice parameter, as well as the crystal size, and a decrease in the oxidation state of manganese. From N2-sorption, LiMn₂O_3.85F_0.15 was found to have the smallest specific surface area and the largest pore diameter compared to the LiMn₂O₄ and the LiMn₂O_3.95F_0.05 samples. Additionally, the majority of the pores in all samples were found to be located in the region of mesopores. The results of the electrochemical study showed that a fluoride substitution into LiMn₂O₄ improved the initial discharge capacity of the materials. Among the synthesized samples, LiMn₂O_3.85F_0.15 can be used as a starting material for producing better performing spinel-type cathode materials.

中文翻译：

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氟代尖晶石LiMn 2 O 4阴极材料的合成，表征及电化学性能

正如我们之前的论文所报道的那样，发现传统的由LiF进行的高温（800°C）合成的氟化物取代的样品会遇到氟的挥发并限制氟的含量。在本研究中，通过与（NH ₄）HF ₂的固态反应方法合成了氟化物取代的尖晶石LiMn ₂ O ₄材料。作为氟源。利用粉末X射线衍射（XRD），扫描电子显微镜（SEM），表面积分析，傅立叶变换红外光谱（FT-IR），循环伏安法（CV）和化学气相色谱法对合成样品的结构和电化学性能进行了表征。充放电测试。如XRD所示，所有样品均显示出具有Fd3m空间群的尖晶石立方结构。与纯LiMn ₂ O _4相比，氟化物取代导致晶格参数增加，以及晶体尺寸增大，并且锰的氧化态降低。由N2吸附产生的LiMn ₂ O _3.85 F _0.15与LiMn ₂ O ₄和LiMn ₂ O _3.95 F _0.05样品相比，发现具有最小的比表面积和最大的孔径。另外，发现所有样品中的大部分孔位于中孔区域。电化学研究的结果表明，氟化物被置换为LiMn ₂ O _4可以提高材料的初始放电容量。在合成样品中，可以使用LiMn ₂ O _3.85 F _0.15作为起始材料来生产性能更好的尖晶石型阴极材料。