Development of Solid Electrolytes Using a Combined in-Operando XPS-Theroetical Approach

锂离子电池系统正开始接近其性能的理论极限，因此，新的锂离子技术的发展越来越依赖于对表面化学及其对电化学响应的影响的深入了解。为了使可再生能源技术得到更广泛的应用，继续开发安全、可扩展和可靠的能源储存方法是切合实际的。电池系统是界面器件，界面上发生的化学过程对电池的整体性能和容量至关重要。X射线光电子能谱(XPS)等技术对于加深我们对表面和界面化学的理解越来越重要。XPS有助于跟踪电极材料在充放电循环过程中氧化状态的变化，并巧妙地检测化学环境的变化和界面上新物种的形成。电池的循环导致负极上形成固体-电解液界面(SEI)。这种电子绝缘的离子导电膜由电解液分解产物组成，其对电池性能的影响因组成而异，可能限制或增强整体功能。表面敏感技术能够表征电池中间相，而XPS是表面敏感的，因为光电子只能从表面区域逃逸，而不会损失能量和特定的化学和电子信息。术中研究允许通过观察和比较观察到的XPS峰的移动来了解固态电池中中间相的生长、组成和形成动力学。漂移可归因于氧化状态的变化、化学环境的变化、由于存在外加电势的样品掺杂而引起的能级变化。当与其他表面敏感技术一起使用时，可以获得关于样品的广泛信息。FTIR和拉曼光谱等技术可以用来进一步了解阴极上发生的化学物质以及充电或放电时形成的物质的性质。将实验数据与计算研究进行比较，将能够评估峰移动的原因，因为可以获得态密度和XPS光谱的理论数据，并将其与使用电池循环的术中和尸检研究的实验结果进行比较。DFT可以对材料的化学性质提供关键的见解，并可用于评估作为电池材料的可行性。分子动力学模拟还将展示对中间相形成动力学的关键见解。该项目的初始目标是比较和复制现有固体电解液的结果，从锂钛酸镧和锂氧化镧开始，使用这项新技术，重点是避免XPS数据中的伪影，并复制准确的电化学数据，提供有关容量、容量衰减、氧化还原电位和其他电池数据的信息。从关注充放电速率开始，由于这会改变形成的化合物和电池的整体性能，因此可以提高对电池动力学和相间形成的理解，并将结果应用于开发新的电解液材料。然后可以研究现有固体电解质的变化对电池性能的影响，例如卤化作用的影响，并将其应用于新材料的生产，如硫化物和复合固体电解质材料。

Lithium-ion battery systems are beginning to approach the theoretical limits of their performance and as a result, developments in new Li-ion technologies are becoming increasingly more dependent on gaining a deeper understanding of surface chemistry and its impact on electrochemical response. For renewable energy technologies to become more widely available, it is pertinent that safe, scalable, and reliable methods of energy storage continue to be developed. Battery systems are interface devices and the chemical processes occurring at the interfaces are crucial to overall performance and capacity of the battery.Techniques like x-ray photoelectron spectroscopy (XPS) are increasingly crucial for advancing our understanding of surface and interface chemistry. XPS facilitates the tracking of electrode material oxidation state changes during charge and discharge cycles, and it adeptly detects alterations in chemical environments and the formation of new species at interfaces.Cycling of the battery induces the development of a solid-electrolyte interface (SEI) on the anode. This electronically insulating yet ion-conductive film consists of electrolyte decomposition products, and its impact on cell performance varies based on composition, potentially limiting, or enhancing overall functionality. Surface sensitive techniques are capable of characterising battery interphases, and XPS is surface sensitive as photoelectrons can only escape the sample from the surface region without losing energy and specific chemical and electronic information.In-Operando studies allow for understanding of the growth, composition, and kinetics of forming interphases in solid-state batteries through observation and comparison of shifts in observed XPS peaks. Shifts can be attributed to changes in oxidation state, changes in chemical environment, changes to the energy levels due to sample doping of presence of an applied potential. When used alongside other surface- sensitive techniques, a broad range of information can be obtained about a sample. Techniques such as FTIR and Raman spectroscopy can be used to further understanding of the chemistry occurring at the cathode and the nature of and species formed upon charging or discharging.Comparison of experimental data to computational studies will allow for evaluation of the causes of peak shifts, as theoretical data for the density of states and XPS spectra can be obtained and compare this to what experimental findings through use of in-Operando and post-mortem studies of battery cycling. DFT can give key insights into chemical properties of materials and can be used to assess viability as battery materials. Molecular dynamics simulations will also show key insights into the kinetics of formation of interphases.Initial aims of the project are to compare and reproduce results of existing solid electrolytes, starting with lithium lanthanum titanium oxide and lithium lanthanum zirconium oxide, with this new technique, focusing on avoidance of artefacts in the XPS data and reproduction of accurate electrochemical data, which gives information about capacity, capacity fading, redox potential, and other battery data.From focusing on charge and discharge rates, as this alters the compounds formed and the overall performance of the cell, understanding of dynamics of the cell and interphase formation can be improved, and the results can be applied to developing new electrolyte materials. The effects of alterations to existing solid electrolytes, for example to effect of halogenation, on the performance of the cell can then be studied and applied to production of new materials such as sulfides and composite solid-electrolyte materials.