CAS: Understanding the Role of External Constraint on Electrochemical (De)alloying Mechanisms

与传统的锂离子电池相比，固态电池提供了更多的能量和更高的安全性。然而，为了提高电池性能，必须了解和更好地控制固态电池中用于锂离子存储的材料的反应行为。多种金属可以在固态电池中与锂离子发生反应并储存锂离子，但是当它们完全被其他固体材料包围和约束时，它们的动态反应行为在很大程度上是未知的。本研究采用多种实验技术来揭示锂金属合金在不同程度的机械约束下的反应过程，并将其与电化学行为联系起来。通过这项研究创造的新知识对于推进当前最先进的储能技术非常重要。这项研究是由研究生研究人员进行的，他们正在接受能量存储材料科学方面的培训。此外，该项目还包括与一名K-12教师合作，开发与电池相关的材料科学课程，供他们在课堂上使用。金属与锂的电化学合金/合金通常具有高锂存储容量。由于合金材料在电化学反应过程中表现出较大的体积变化，不同长度尺度的力学约束可能对颗粒合金材料的转变行为起重要作用。然而，力学约束对合金/脱合金反应的影响尚不清楚。本研究的总体目标是了解外部机械约束如何影响和控制固态电池金属颗粒电化学合金化/脱合金过程中跨长度尺度的内部反应机制。由于它们的全固体性质，这些系统固有地表现出机械限制。该研究使用了原位和非原位成像方法，电化学循环过程中的实时应力测量以及其他电化学评估。总之，这些技术阐明了表面涂层和周围材料施加的约束如何影响金属颗粒与锂合金化和脱合金过程中的形态演变和电化学行为。这项研究提供了对固态合金/脱合金工艺的新认识，这对于开发这些材料作为固态电池的电极至关重要。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL DESCRIPTIONSolid-state batteries offer the potential for more energy and greater safety compared to conventional lithium-ion batteries. However, the reaction behavior of materials used for lithium ion storage within solid-state batteries must be understood and better controlled for improved battery performance. A variety of metals can react with and store lithium ions within solid-state batteries, but their dynamic reaction behavior when entirely surrounded by and constrained by other solid materials is largely unknown. This research uses a variety of experimental techniques designed to reveal reaction processes of lithium metal alloys under various degrees of mechanical constraint and relate this to electrochemical behavior. The new knowledge created through this research is important for advancing the current state-of-the-art in energy storage technologies. This research is being carried out by graduate student researchers, who are being trained in the science of materials for energy storage. Additionally, this project also includes a collaboration with a K-12 teacher to develop materials science curriculum related to batteries for use in their classroom. TECHNICAL DESCRIPTION Metals that electrochemically alloy/dealloy with lithium often exhibit high lithium storage capacity. Because of the large volume changes exhibited by alloy materials during electrochemical reactions, mechanical constraint at different length scales likely plays an important role in the transformation behavior of particulate alloy materials. However, the effect of mechanical constraint on alloy/dealloying reactions is not well understood. The overall objective of this research is to understand how external mechanical constraint affects and controls internal reaction mechanisms across length scales during electrochemical alloying/dealloying of metal particles for solid-state batteries. These systems inherently exhibit mechanical confinement due to their all-solid nature. This research uses in situ and ex situ imaging methods, real-time stress measurement during electrochemical cycling, and other electrochemical assessments. Together, these techniques clarify how constraint exerted by surface coating layers and surrounding materials affect morphological evolution and electrochemical behavior during alloying and dealloying of metal particles with lithium. This research provides new understanding of solid-state alloying/dealloying processes, which is critical for developing these materials as electrodes for solid-state batteries.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.