High Capacity Main Group Anodes for Advanced Lithium-ion and Sodium-ion Batteries

• Author / Creator

  Xie, Hezhen

• Nowadays, rechargeable batteries play an ever more important role in our society as an energy storage medium for a wide range of applications from tiny electronic devices to grid-level energy storage. Among the different types of batteries, lithium-ion batteries (LIBs) have achieved significant advances during the last three decades and currently dominate the market. However, to meet the needs for emerging energy storage scenarios, such as electrical vehicles, improvement of battery performance in terms of energy density, cycling life, and safety is still required. In addition to LIBs, sodium-ion batteries (SIBs) are of great interest due to the abundance and wide geographical distribution of Na resources, especially for grid-scale battery applications. SIBs lag, however, far behind LIBs in terms of research and development and suffer from sluggish kinetics, poor cycling stability, and lower energy density. The development of high-performance LIBs mainly relies on improving the electrode materials. Therefore, studying the electrode materials for LIBs and SIBs is essential. This thesis focuses on understanding and developing high capacity alloying anode materials for the next-generation high-performance LIBs and SIBs.
  This thesis starts with an introduction to the motivation, working principles, and evaluation criteria of LIBs and SIBs. We begin with the research background of high capacity alloying anodes, including Sn, Sb, and Si based anodes. The three research projects are described as follows.
  In the first project, three series of ternary Sn–Bi–Sb alloy electrodes, as well as elemental Sn, Bi, and Sb electrodes, were prepared by magnetron sputtering, and their electrochemical performance as anodes for SIBs was examined. Alloying was used as the method to modify the morphology and electrochemical charge/discharge behavior in order to improve the cyclability of pure Sn and Sb electrodes. The prepared alloys were found to outperform the pure elements in terms of cycling stability and rate capability. The best performing alloy, composed of 80 at% Sb, 10 at% Sn, and 10 at% Bi, shows negligible capacity degradation after 100 charge/discharge cycles. The improved performance is ascribed to the increased resistance toward internal stresses and modification of Sb chemical potential induced by the dissolution of Sn and Bi atoms in the Sb lattice.
  The second project was to investigate the sodiation–desodiaton mechanism of β-SnSb, which is a highly stable anode material for SIBs but is poorly understood with respect to its reaction mechanism with Na. By combining in-situ TEM, ex-situ X-ray diffraction, and electroanalytical methods, it was found that sodiation of β-SnSb leads to the formation of Na3Sb and Na15Sn4 in sequence and that upon desodiaton, β-SnSb reforms. The amorphous-nanocrystalline microstructure during the sodiation–desodiaton and the intrinsic mechanical toughness of the β-SnSb account for the good cycling stability of β-SnSb.
  In the third project, the effect of the Ni adhesion layer and C/TiO2 surface coatings on the formation of both the c-Li3.75Si phase and the solid electrolyte interphase (SEI) in Si-based anodes was investigated. The adhesion layer and surface coatings were found to suppress the formation of c-Li3.75Si, resulting in improved capacity retentions and Coulombic efficiency. In addition, surface coatings were found to influence the growth rate and composition of SEI.
  The thesis concludes with a summary of each chapter and directions for future studies.

• Subjects / Keywords

  • Silicon Anode
  • Alloy Anode
  • High Capacity Anode
  • In Situ TEM
  • Sodium-ion Batteries
  • Lithium-ion Batteries

• Graduation date

  Fall 2019

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-xsd7-y002

• License

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