锂离子电池负极锗酸盐复合材料的制备及电性能研究

发布时间：2018-05-10 08:35

  本文选题：锂离子电池 + 负极材料　； 参考：《华南理工大学》2014年硕士论文

【摘要】：本论文针对金属基锗类负极材料在应用过程中虽表现出较高的首次充放电比容量，但随后循环中所遭遇较快容量衰减的问题，运用了水热合成法、固相合成法两种方法分别合成了具有新型结构的纳米锗酸铜、锗酸锌负极材料，并分别将其与石墨烯和石墨进行复合。利用XRD、SEM、TEM、XPS、Raman等技术对这些材料的组成以及微观形貌进行表征，采用循环伏安法（CV）、电化学阻抗（EIS）和恒电流充放电等技术测试了各种复合材料的电性能。本论文主要开展了以下几方面的工作： 利用六角晶型结构的GeO2能够微溶于水的性质，将其与乙酸铜反应，成功制得了具有纳米线结构的锗酸铜，为进一步稳定其性能，在其制备过程中又加入了氧化石墨烯溶液，水热反应后制得了CuGeO3/石墨烯复合负极材料。该材料中石墨烯含量为37%的样品在200mA/g的电流密度下，首次可逆比容量高达1265mAh/g，，库伦效率达71.6%，随后每次循环中，库伦效率均接近100%，经过50周循环后，材料的可逆比容量仍保持为853mAh/g。 使用两步水热合成法成功制得纳米棒结构的Zn2GeO4与石墨烯的复合材料，并且合成了部分结晶的Zn2GeO4纳米棒并将其应用到负极材料中。复合材料中石墨烯的含量仅为10wt%左右，而在后续的大电流密度（0.8A/g）下循环时，仍旧表现出了十分稳定的电性能（循环50周，可逆比容量为514mAh/g）。在所有的循环以及倍率测试中，复合材料所表现出的库伦效率均接近于100%。考虑到材料的工业化用途，本实验采用固相合成法在1000℃下合成Zn2GeO4材料， 后续使用简单的球磨法将石墨与Zn2GeO4按照不同的比例进行混合以获取复合材料。该种复合材料能够在较大的电流密度下保持很好的循环性能，改善了石墨在大电流下循环时容量衰减较快的问题。最终得出，当Zn2GeO4的含量为20%时，复合材料得到最好的循环性能，并且循环50周后其可逆比容量接近于500mAh/g。
[Abstract]:In this paper, the hydrothermal synthesis method is used to solve the problem that the metal-based germanium anode material has a high first charge / discharge specific capacity, but the rapid capacity decay in the subsequent cycle, although the first charge / discharge specific capacity of the metal based germanium anode material is high. Nanocrystalline copper germanate and zinc germanate anode materials with novel structures were synthesized by solid state synthesis method and combined with graphene and graphite respectively. The composition and micromorphology of these composites were characterized by XRDX SEMX TM Tem Raman technique. The electrical properties of the composites were measured by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and constant current charge / discharge (CCS) techniques. The main work of this thesis is as follows: Copper germanate with nanowire structure was successfully prepared by using the water-soluble properties of hexagonal GeO2, which was reacted with copper acetate. In order to further stabilize its properties, graphene oxide solution was added in the preparation process. CuGeO3/ graphene composite anode material was prepared by hydrothermal reaction. Under the current density of 200mA/g, the first reversible specific capacity of the sample with 37% graphene content is 1265mAh/ g, and the Coulomb efficiency is 71.6g. In each cycle thereafter, the Coulomb efficiency is close to 100mg. After 50 weeks of cycle, the reversible specific capacity of the material remains at 853mAh.g. The composites of Zn2GeO4 and graphene with nanorod structure were successfully prepared by two-step hydrothermal synthesis, and partially crystallized Zn2GeO4 nanorods were synthesized and applied to negative electrode materials. The content of graphene in the composite is only about 10 wt%, but it still shows a very stable electrical property (the reversible specific capacity is 514 mg 路h / g) at the subsequent cycle with high current density (0.8 A / g). The Coulomb efficiency of the composite is close to 100 in all cycle and rate tests. Considering the industrial use of the materials, Zn2GeO4 materials were synthesized by solid state synthesis at 1000 鈩

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