Cooperative distortions in Prussian blue analogues

能源安全的一个关键方面是获得电网存储技术。普鲁士蓝类似物（PBAs）是电网存储中最有前途的正极材料之一。PBAs使用地球上丰富的元素，并使用K+离子技术进行操作。虽然PBAs可以显示有竞争力的能量存储密度（针对高K+离子含量进行优化）和非凡的可循环性（针对低K+离子含量进行优化），但最重要的挑战之一是通过适当的设计策略来协调这两个目标。该项目旨在利用合作的Jahn-Teller扭曲和空位分布的相互作用，作为在单一PBA材料中实现高能量存储和竞争性循环的机制。这样做将确定新的改进的pba基材料应用于下一代电网存储技术。该项目的主要目标包括：(i)建立粗粒度微观模型，以确定Jahn-Teller （JT）浓度、空位浓度、空位分布和远程对称破缺的相互作用；（ii）就主要PBA族的行为，实验证明该模型的准确性；（iii）应用（如可能的话）x射线自由电子激光（XFEL）技术来表征PBA正极材料中的局部JT /空位顺序；（四）新型pba基K+离子正极材料的开发。在我们所有的研究中，我们将利用三维差分对分布函数（3D-DPDF）方法，这是漫射散射方法的最新应用。同时，作为该项目的一部分，我们将进行第一次基于xfl的总散射测量。如果成功，该项目将在应用XFEL总散射测量来研究功能材料的局部结构方面形成一个重要的概念验证。该项目与物理科学和能源研究主题非常吻合。它不仅解决了能源安全和储存方面的关键目标，而且还寻求为英国参与欧洲XFEL设施开发更广泛的科学案例。该项目属于EPSRC物理科学和能源研究领域。

A key aspect of energy security is access to grid storage technologies. One of the most promising cathode materials for application in grid storage is the family of Prussian blue analogues (PBAs). PBAs use earth-abundant elements and operate using K+-ion technology. While PBAs can show competitive energy storage densities (optimised for high K+-ion contents) and extraordinary cyclability (optimised for low K+-ion contents) one of the most important challenges is reconciling these two targets via an appropriate design strategy. This project aims to exploit the interplay of cooperative Jahn-Teller distortions and vacancy distributions as a mechanism of achieving both high energy storage and competitive cyclability in a single PBA material. Doing so will identify new improved PBA-based materials for application in next-generation grid-storage technology. The main aims of the project include: (i) developing coarse-grained microscopic models for determining the interplay of Jahn-Teller (JT) concentration, vacancy concentration, vacancy distribution, and long-range symmetry breaking; (ii) experimental demonstration of the veracity of this model in terms of the behaviour of key PBA families; (iii) the application (if possible) of X-ray free-electron laser (XFEL) technologies to characterising local JT / vacancy order in PBA cathode materials; and (iv) the development of new PBA-based K+-ion cathode materials. In all our studies, we will exploit three-dimensional difference pair distribution function (3D-DPDF) methodologies, which are a recently-developed application of diffuse scattering methods. In tandem, we will be carrying out the very first XFEL-based total scattering measurements as part of this project. If successful, the project will form an important proof-of-concept in applying XFEL total scattering measurements to the study of local structure in functional materials. The project is well aligned to both the physical sciences and energy research themes. Not only does it address key objectives in terms of energy security and storage, but it also seeks to develop a broader science case for the UK's involvement in the European XFEL facility. This project falls within the EPSRC Physical Sciences and Energy research areas.