Metal Fluoride Open Frameworks for Next-generation K-ion Battery Cathodes

最近的环境问题提高了我们对低碳未来的认识，要求立即采取行动，实现可持续能源解决方案。最新的地缘政治事件和能源价格上涨进一步刺激了全球能源独立和安全感，呼吁大力扩展和部署本土可再生能源，如风能，太阳能，潮汐能等，所有这些都需要高效的电网存储系统进行整合。正是在这种背景下，电池，特别是锂离子电池（LIB）成为人们关注的焦点。虽然LIB一直主导着移动应用市场，如便携式电子产品和电动汽车，但它们也占当前全球电网存储市场的90%。然而，锂在地壳中的稀缺性以及不均匀的地理分布意味着锂离子技术在可负担性和确保能源独立性的能力方面不是可持续的净零解决方案。相比之下，源自相同碱金属家族的K离子化学在其经济可行性、战略相关性和循环稳定性方面显示出几个关键优势，将K离子电池（KIB）置于未来发展的优先新电池技术之列。本项目旨在解决目前KIB阴极开发的瓶颈问题，并将设计一个新的金属库，氟化物开放框架（MeFOF）材料，其在成本和耐久性方面都可以满足阴极应用的标准。这些材料的设计策略源于碱金属氟化物化学的结构多样性和化学灵活性，并通过其机械化学合成的最新进展得到证实。它们的晶体结构是由角共享的金属氟化物八面体连接，并表现出各种开放通道图案与理想的腔体大小主机大K离子。这些独特的基序不仅构成了一个库的有利的拓扑结构，方便的K离子的运输，但也构成了一个强大的和灵活的支架可逆的K离子accommodation.In这项工作中，重点将放在阐明的影响，材料的空腔大小，结构的灵活性，和化学取代对它们的电化学性能。通过研究MeFOFs的结构-性能关系，不仅将建立其设计原则和优化以促进KIB商业化，而且还将开发一种基于实验室的新型仪器，用于通过对分布函数技术进行先进的原子结构表征，以加快具有复杂结构特性的新型功能材料的开发，具有超越能量存储的更广泛的意义。

Recent environmental concern has raised our awareness of a low-carbon future, demanding immediate action towards sustainable energy solutions. Latest geopolitical events and rising energy prices have further stimulated a global sense of energy independence and security, calling for drastic expansion and deployment of homegrown renewable energy, such as wind, solar, tidal power etc, all of which require efficient grid storage systems for integration. It is in this context that batteries, particularly lithium-ion batteries (LIBs), come to the spotlight. Whilst LIBs have been dominating the market for mobility applications, such as portable electronics and electric vehicles, they also make up 90% of the current global grid storage market. However, Li's scarcity in Earth's crust with an uneven geographical distribution means that the Li-ion technology is not a sustainable net-zero solution in terms of affordability and ability to secure energy independence. In contrast, originating from the same alkali-metal family, K-ion chemistry shows several key advantages in its economic viability, strategic relevance, and cycling stability, placing K-ion batteries (KIBs) among the prioritised new battery technologies for future development, especially for stationary applications.This project aims to solve the bottleneck problem in the current KIB development on cathodes and will design a library of new metal fluoride open framework (MeFOF) materials that can meet the criteria for cathode application in both cost and durability. The design strategy of these materials stems from the structure diversity and chemical flexibility of the alkali-metal-fluoride chemistry and is corroborated by the recent progress in their mechanochemical synthesis. Their crystal structures are supported by corner-shared metal-fluoride-octahedra linkages and exhibit a variety of open-channel motifs with desirable cavity sizes to host large K ions. These unique motifs not only constitute a library of advantageous topologies for facile K ion transport, but also compose a robust and flexible scaffold for reversible K ion accommodation.In this work, an emphasis will be laid on elucidating the impact of the materials' cavity sizes, structural flexibility, and chemical substitution on their electrochemical performances. Through an investigation of MeFOFs' structure-property relationships, not only will their design principle and optimisation be established to facilitate KIB commercialisation, but a novel laboratory-based instrumentation for advanced atomic structure characterisation via pair distribution function technique will also be developed to expedite the development of novel functional materials that have complex structural properties, with a broader implication beyond energy storage.