CAREER: Understanding the Influence of the Framework on Alkali Ion Diffusion in Polyanionic Intercalcation Electrodes

从蜂窝电话到便携式计算机，近年来的许多重大技术进步都依赖于在极小的电池中存储大量能量的能力。这些电池通过从电化学活性主体材料可逆地插入和移除Li离子来操作。这项工作的目标，由材料研究部内的固态和材料化学计划支持，是建立一个更深入的了解在这些主机的原子水平上发生了什么，因为锂离子移动通过其晶体结构。这一基本知识对于提高电池的充电（放电）速率以及延长其使用寿命至关重要。与此同时，这项工作旨在利用这一认识来确定新的地球丰富的钠离子电池电极材料，以降低生产电动汽车和电网的大规模储能系统的成本。该项目还侧重于鼓励位于洛杉矶地区的美洲原住民社区的中学生增加他们对STEM学科的参与。实践教学演示和实验用于揭开电力和能源科学的神秘面纱，让学生从小就参与科学。技术摘要聚阴离子过渡金属化合物（如磷酸盐、硫酸盐和硅酸盐）对能量储存至关重要，因为它们在分解时不释放氧，这会加剧电池故障期间的热失控，因此比基于氧化物的电极安全得多。虽然大量的工作一直致力于优化这些材料的电化学性能，但对这些材料中锂离子传输的机制缺乏基本的了解。不同于最先进的氧化物，有效地表现出各向同性的变化，在其氧亚晶格，聚阴离子电极响应的去除或插入锂通过其刚性的含氧阴离子亚基的合作旋转。这项工作的重点是调查的机制，碱金属离子的扩散聚阴离子插层主机使用高分辨率的X射线和中子衍射技术，以表征这些材料的框架如何变化的充电和放电。了解这些密集堆积的固体如何促进带正电荷的离子通过其晶格的运动，对于加速设计下一代电池材料至关重要，这些材料可以基于Na等较大离子的传输来运行。

Non-Technical AbstractFrom cellular phones to portable computers, many major technological advances in recent years have relied on the ability to store massive amounts of energy within extremely small batteries. These batteries operate by reversibly inserting and removing Li-ions from electrochemically active host materials. The goal of this work, supported by the Solid State and Materials Chemistry program within the Division of Materials Research, is to build a deeper understanding of what happens at the atomic level of these hosts as Li-ions move through their crystal structures. This fundamental knowledge is crucial for increasing the rate at which batteries can be (dis)charged as well as prolonging their operational lifetime. In parallel, this work seeks to use this understanding to identify new Earth-abundant electrode materials for Na-ion batteries in order to reduce the cost of producing large-scale energy storage systems for electric vehicles and the grid. This project also focuses on encouraging middle school students in the Native American communities located within the Los Angeles area to increase their participation in STEM disciplines. Hands-on teaching demonstrations and experiments are used to demystify the often puzzling world of electricity and energy sciences to engage students in science from an early age.Technical AbstractPolyanionic transition metal compounds (like phosphates, sulfates, and silicates) are of critical importance to energy storage because they do not release oxygen on decomposition, which can exacerbate thermal runaway during cell failure, and are therefore considerably safer than oxide-based electrodes. While a large body of work has been dedicated to optimizing the electrochemical performance of these materials, there is a fundamental lack of understanding about the mechanism for Li-ion transport in these materials. Unlike state-of-the-art oxides, which effectively exhibit isotropic changes in their oxygen sublattice, polyanionic electrodes respond to the removal or insertion of Li through cooperative rotations of their rigid oxoanionic subunits. This work is focused on investigating the mechanism of alkali-ion diffusion in polyanionic intercalation hosts using high-resolution X-ray and neutron diffraction techniques in order to characterize how the framework of these materials changes on charge and discharge. Understanding how these densely packed solids facilitate the motion of positively charged ions through their lattices is critical for accelerating the design of next-generation materials for batteries that can operate based on the transport of larger ions like Na.