Ion Transport in Prussian Blue Cathode Materials for Na-Ion Batteries

大规模收集可再生能源需要创新的储能解决方案。钠离子电池（NIB）形式的电化学能量存储为电网规模存储提供了一种有前途的低成本，清洁和安全的选择。NIB材料目前面临的一个核心挑战是，由于Na离子的离子半径大于Li离子，离子传输通常会减慢，从而降低充电速率和功率密度。为了提高现有电池材料的充电速率并寻找表现出快速离子传输的新材料，对离子传输的原子尺度过程的充分理解是必不可少的。然而，这种深深植根于材料的缺陷化学的知识迄今为止对于许多NIB材料是缺乏的。关于缺陷化学的信息也将阐明实验观察到的几种阴极材料的电化学性能随着水含量的增加而降低的现象。在这个项目中，将在普鲁士蓝中探索离子传输，普鲁士蓝是具有开放框架结构的NIB阴极的模型材料。这些材料是具有快速离子传输的阴极材料的良好候选者。离子传输将在原子和宏观水平上进行研究，采用强大的多学科方法，包括计算技术以及电化学调查和固态核磁共振（NMR）光谱研究。将分析插入的Na离子的传输机制，并阐明水对Na离子传输的影响。这将有助于使普鲁士蓝基材料中的离子传输对水的影响更加稳健，并在未来系统地寻找具有快速离子传输的新阴极材料。

Large-scale harvesting of renewable forms of energy requires innovative energy storage solutions. Electrochemical energy storage in the form of Na-ion batteries (NIBs) offers a promising low-cost, clean, and safe choice for grid-scale storage. A central challenge that NIB materials currently face is that due to the larger ionic radius of the Na-ion compared to the Li-ion, ionic transport is often slowed down, decreasing charging rates and power densities. To improve the charging rates of established battery materials and search for new materials exhibiting fast ion transport, a sound understanding of the atomic-scale processes underlying ionic transport is indispensable. Such knowledge, deeply rooted in the defect chemistry of the materials, however, to date is lacking for many NIB materials. Information on the defect chemistry will also shed light on an experimentally observed phenomenon of decreasing electrochemical performance of several cathode materials with increasing water content. In this project, ionic transport will be explored in Prussian Blue, a model material for NIB cathodes with open-framework structures. These materials are good candidates for cathode materials with fast ion transport. Ionic transport will be investigated both at the atomic and at the macroscopic level with a powerful multi-disciplinary approach encompassing computational techniques as well as electrochemical investigations and solid-state nuclear magnetic resonance (NMR) spectroscopic studies. The transport mechanism of the inserted Na-ions will be analysed and the impact of water on the Na-ion transport will be elucidated. This will contribute to rendering ion transport in Prussian Blue-based materials more robust against the influence of water and searching systematically for new cathode materials with fast ion transport in the future.