The Development of Recyclable Hybrid Solid Electrolytes for Battery Applications

可充电电池技术在过去20年中呈指数级增长，这是由于对便携式电子产品的需求不断上升，但最近，电池已成为一种越来越重要的存储能源的手段，以推动可再生能源的使用，并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)电池一直在该领域占据主导地位，2019年诺贝尔化学奖授予古德足够、惠廷汉和吉野。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液，这种电解液高度易燃，并构成潜在的安全风险，如火灾和爆炸。这些危险溶剂的一种已探索的替代品是固体或半结晶电解液(SE)，它们已被证明可以提高锂离子电池的安全性，产生被称为全固态电池(ASSB)的产品。这项博士研究包括开发用于固态电池系统的可回收混合固体电解质，混合元件是聚合物/陶瓷组合。一些聚合物能够有效地用作电解液，并显示出日常设备所需的强大机械性能，例如，聚氧乙烯(PEO)S(PEO)表现出相当大的柔韧性和化学稳定性，使其成为SE的极佳候选材料。然而，由于离子在材料中的传输受阻，它们无法满足所需的实际电导率(~10-3 S厘米-1)，因此单靠它们的商业化是不可行的。因此，聚合物电解质可以与氧化铝或二氧化钛等陶瓷填料结合，在不影响机械强度的情况下极大地提高SES的离子导电性。该项目探索了这类聚(缩醛)在混合电解质中的潜力，结合常规和现场固态核磁共振光谱，结合阻抗测量和Muon自旋弛豫光谱研究，评估了它们的离子传输机制。将评估聚合物的结构参数(如单体组成和聚合度)对所得机械性能的影响，以使生产出坚固的电解液。还将对一系列不同的无机陶瓷进行评估，以确定最佳的聚(缩醛)：陶瓷组合。这一领域的关键研究将是评估所制备的混合电解质相对于当前基于PEO的电解质的性能，以确定它们在固体电解质中的地位。此外，计算技术，包括原子模拟和密度泛函计算，将被用来理解新的SE材料中的离子迁移率。该项目横跨EPSRC的多个研究领域，包括能源应用材料、储能材料、聚合物材料、材料工程(陶瓷)、计算化学、功能陶瓷和无机物，其工作主题为能源和制造未来，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.