The Development of Recyclable Hybrid Solid Electrolytes for Battery Applications

在过去的20年里，可充电电池技术的指数级增长是由于对便携式电子产品的需求不断增长，但最近，电池已成为一种越来越重要的存储能量的手段，以推动可再生能源的使用，减少人类活动对环境的影响。自20世纪70年代至80年代发展以来，锂离子（Li-ion）电池一直主导着该领域，2019年诺贝尔化学奖授予了Goodenough、Whittingham和Yoshino。锂离子电池使电动汽车的发展和可再生能源（如太阳能和风能）的能源储存成为可能。然而，它们的重大缺陷是使用有机溶剂中的锂盐作为电池的电解质，这是高度易燃的，并且存在潜在的安全风险，例如火灾和爆炸。固体或半晶体电解质（SEs）已被证明可以提高锂离子电池的安全性，从而生产出所谓的全固态电池（ASSB）。这项博士研究包括开发可回收的混合固体电解质，用于固态电池系统，混合元素是聚合物/陶瓷的组合。一些聚合物能够有效地作为电解质发挥作用，并显示出日常设备使用所需的强大机械性能，即聚环氧乙烷（PEO）显示出相当大的灵活性和化学稳定性，使其成为SEs的优秀候选材料。然而，由于离子在材料中的传输受阻，它们无法满足实际电导率要求（~10-3 S cm-1），因此它们的商业化是不可行的。因此，聚合物电解质可以与陶瓷填料（如Al2O3或TiO2）结合，在不影响其机械强度的情况下大幅提高se的离子电导率。该项目探索了这种聚（缩醛）在混合电解质中的潜力，结合阻抗测量和介子自旋弛豫光谱研究，使用传统和原位固态核磁共振光谱相结合的方法评估了它们的离子传输机制。将评估聚合物的结构参数（如单体组成和聚合程度）对所得机械性能的影响，以使生产坚固的电解质成为可能。还将评估一系列不同的无机陶瓷，以确定最佳的聚（缩醛）：陶瓷组合。该领域的重点研究将是评估制备的混合电解质相对于当前基于peo的电解质的性能，以确定其在固体电解质群体中的地位。此外，计算技术，包括原子建模和DFT计算将被用来理解新的SE材料中的离子迁移率。该项目涵盖EPSRC的多个研究领域，包括能源应用材料、储能材料、高分子材料、材料工程（陶瓷）、计算化学、功能陶瓷和无机物等，研究主题为能源和制造业的未来，以及循环经济。

The exponential growth in rechargeable battery technologies over the last 20 years is due to the rising demand for portable electronics, but more recently, batteries have become an increasingly important means of storing energy, to drive the use of renewable energy resources and decrease the impact of human activity on the environment. Since their development in the 1970s-80s, lithium ion (Li-ion) batteries have dominated the field, exhibited by the award of the Nobel Prize in Chemistry in 2019 to Goodenough, Whittingham and Yoshino. Li-ion batteries have enabled the development of electric vehicles and the storage of energy from renewable sources, such as solar and wind power. Their significant downfall, however, is the use of lithium salts in organic solvents as the cell's electrolyte, which are highly flammable and pose potential safety risks, such as fires and explosions. An explored alternative to these dangerous solvents are solid or semi-crystalline electrolytes (SEs), which have shown to improve the safety of Li-ion batteries, producing what is known as an all-solid-state battery (ASSB). This PhD research encompasses the development of recyclable hybrid solid electrolytes for implementation into solid-state battery systems, with the hybrid element being a polymer/ceramic combination. Some polymers are capable of functioning effectively as electrolytes, and display the robust mechanical properties required for use in everyday devices, i.e., poly(ethylene oxide)s (PEO) displays considerable flexibility and chemical stability, making them excellent candidate materials for SEs. Yet, their commercialisation alone isn't feasible due to their inability to meet the practical conductivities required (~10-3 S cm-1) due to the frustrated transport of ions through the material. Therefore, polymer electrolytes can be combined with ceramic fillers such as Al2O3 or TiO2, drastically improving the ionic conductivity of the SEs, without affecting their mechanical strength. The project explores the potential of such poly(acetals) in hybrid electrolytes, assessing their ion transport mechanisms using a combination of conventional and in situ solid-state NMR spectroscopy, in conjunction with impedance measurements and muon spin relaxation spectroscopy studies. The effects of structural parameters of the polymers such as monomer composition and degree of polymerisation on the resultant mechanical properties will be assessed, to enable the production of robust electrolytes. A range of different inorganic ceramics will also be evaluated to determine the optimal poly(acetal):ceramic combination. Key research in this area will be to evaluate the performance of the hybrid electrolytes prepared relative to current PEO-based electrolytes, to determine their standing within the community of solid electrolytes. Additionally, computational techniques, including atomistic modelling and DFT calculations will be utilised to understand the ion mobility within the new SE materials. This project spans multiple EPSRC research areas including materials for energy applications, energy storage, polymer materials, materials engineering (ceramics), computational chemistry, and functional ceramics and inorganics, with the work falling under the themes of energy and manufacturing the future, as well as circular economy.