Dataset for Development of Analytical Techniques for Lithium-Sulfur Batteries

Dataset supports: Liam Michael Furness (2020) Thesis. Development of Analytical Techniques for Lithium-Sulfur Batteries. University of Southampton. The aim of this study is to develop analytical techniques that can be used to better understand the lithium-sulfur (Li-S) battery system. The first technique involves the determination of the total atomic sulfur content and the average polysulfide chain length of a polysulfide solution. These experiments elucidated the 2-phase boundaries and eutonic point, giving an accurate representation of the ternary (lithium sulfide-sulfur-electrolyte) phase diagram. The 2-phase boundary describes the maximum solubility of a polysulfide solution in contact with either solid lithium sulfide or solid sulfur. On the other hand, the eutonic point describes the maximum solubility of a polysulfide solution in contact with both solid lithium sulfide and solid sulfur, thus the concentration of polysulfide species at the eutonic point is the maximum that can be achieved. The saturation concentration of polysulfide species will depend on the nature of the solvent and the lithium salt, and these variables can be tuned to improve the Li-S battery performance. This was observed when increasing the electrolyte salt concentration which limited the polysulfide solubility and in turn improved the cyclability of the Li-S battery. Therefore, the composition of the ternary phase diagram can be implemented to explain changes in Li-S battery galvanostatic cycling performance. The second technique, electrochemical impedance spectroscopy, will give further insight to the Li-S battery system. This technique, initially developed from Lasia et al. to determine the electroactive surface area of catalysts, has been applied to the cathode formulations for Li-S batteries in this study.1 Starting with the impedance of the basic components in a Li-S battery to understand features on the Nyquist plot. The complexity of cell setup was increased until the impedance of a full Li-S battery was achieved. This method allows determination of the specific surface area of different Li-S battery cathode formulations whilst also studying how the specific surface area of an electrode changes during galvanostatic cycling.

本数据集支撑Liam Michael Furness于2020年完成的学位论文《锂硫（Lithium-Sulfur, Li-S）电池分析技术开发》，作者所属机构为南安普顿大学（University of Southampton）。本研究旨在开发可用于更深入解析锂硫电池体系的分析技术。
第一项技术用于测定多硫化物（polysulfide）溶液的总原子硫含量与平均多硫化物链长。通过该系列实验明确了两相边界与低共熔点，精准表征了硫化锂-硫-电解液三元（ternary）相图。其中，两相边界指与固态硫化锂或固态硫接触的多硫化物溶液的最大溶解度；低共熔点则指同时与固态硫化锂及固态硫接触的多硫化物溶液的最大溶解度，即该点处多硫化物物种的浓度可达理论峰值。
多硫化物物种的饱和浓度取决于溶剂与锂盐的性质，可通过调控这些变量优化锂硫电池性能。研究发现，提高电解液盐浓度可限制多硫化物溶解度，进而改善锂硫电池的循环性能。因此，可借助三元相图的组分特征解释锂硫电池恒电流循环性能的变化规律。
第二项技术为电化学阻抗谱（electrochemical impedance spectroscopy），可进一步揭示锂硫电池体系的内在机制。该技术最初由Lasia等人开发[1]，用于测定催化剂的电活性表面积，本研究将其应用于锂硫电池的正极配方研究。实验首先从锂硫电池基础组分的阻抗入手，解析奈奎斯特（Nyquist）图中的特征信号；随后逐步提升电池组装复杂度，直至获得完整锂硫电池的阻抗谱。该方法可实现不同锂硫电池正极配方的比表面积测定，同时可探究电极比表面积在恒电流循环过程中的变化规律。