Determining Bulk and Surface Degradation Mechanisms in Potassium Ion Batteries

非技术综述：开发不依赖锂的新型电池将使可再生能源得到更便宜和更广泛的采用。钾是一种特别有吸引力的替代锂的选择，因为它具有很高的自然丰度和理想的电化学性质。然而，简单地用Li原子交换K原子会导致钾离子电池(KIB)类似物的性能严重下降。在NSF材料研究部固态和材料化学项目的支持下，Marbella教授和她的研究小组收集了开发KIBS所需的基本信息。他们使用核磁共振波谱在分子水平上研究电池的每个组件，包括电极、电解液和电极/电解液界面。具体地说，这个研究项目测试了一种假设，即与Li相比，K的原子尺寸更大，会导致独特的降解机制，最终导致电池故障。该研究项目旨在确定KIBS中本体和界面降解模式与电化学行为之间的关系。这为重新设计最适合KIB技术的材料提供了洞察力。这项工作的更广泛影响包括专门为对攻读研究生教育感兴趣的人数不足的本科生妇女创建的研究机会和讲习班。这项研究项目还与教育活动紧密结合在一起，通过分别与巴纳德学院(哥伦比亚大学附属的所有女性文科学院)和为布朗克斯的新移民设立的埃利斯预备高中合作，在本科和高中层面吸引未被充分代表和处于不利地位的学生参与储能研究项目。技术总结：识别和分析Beyond-Li离子电池中整体和表面降解模式之间的复杂相互作用对于实现广泛采用电化学储能的经济有效的解决方案至关重要。该项目由美国国家科学基金会材料研究部的固态和材料化学计划支持，利用核磁共振的高化学和元素特异性来确定钾离子电池(KIBS)潜在高容量磷化锡阳极失效的化学机制。大原子尺寸的K在磷化锡钾化过程中产生高度无序和机械不稳定的结构，在电化学循环过程中容易失去电子连接性和寄生副反应。大体上，在K插入/移除时发生的相变很难用传统的材料表征工具(例如，衍射)来测量，这些工具需要长程有序来进行结构分配。相比之下，核磁共振可以直接探测阳极中的局部磷和锡环境，以确定促进可逆K合金化反应的特定化合物。此外，与K插入相关的体积膨胀暴露了电解液消耗的新鲜表面，提出了能够破译电解液反应性的策略的必要性。核磁共振用于在分子水平上描述产生独特电解液分解产物的电解液溶剂化结构。核磁共振分析允许创建一些第一个分子水平的描述符来描述KIBS中的整体相变和界面反应性。这项研究计划与教育活动紧密结合在一起，通过分别与巴纳德学院(哥伦比亚大学附属的所有女性文科学院)和布朗克斯埃利斯新移民预备高中的合作伙伴关系，在本科和高中层面吸引未被充分代表和贫困学生参与能源储存研究项目。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical summary:The development of new types of batteries that do not rely on lithium will enable cheaper and more widespread adoption of renewable energy. Potassium is a particularly attractive option to replace lithium because it has high natural abundance and desirable electrochemical properties. However, simply swapping Li atoms for K leads to severe performance decline in potassium ion battery (KIB) analogues. With this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, Prof. Marbella and her research group gather fundamental information required to develop KIBs. They use nuclear magnetic resonance (NMR) spectroscopy to study each component of the battery at the molecular-level, including the electrode, the electrolyte, and the electrode/electrolyte interface. Specifically, this research program tests the hypothesis that the larger atomic size of K compared to Li leads to unique degradation mechanisms that ultimately contribute to battery failure. The research project aims to identify the relationship between bulk and interfacial degradation modes and electrochemical behavior in KIBs. This provides insight that generate pathways to redesign materials that are optimal for KIB technologies. Broader impacts of this work include research opportunities and workshops created specifically for underrepresented undergraduate women interested in pursuing graduate education. This research project is also closely integrated with educational activities that engage underrepresented and underprivileged students in energy storage research projects at the undergraduate and high school level through partnerships with Barnard College (all women liberal arts college affiliated with Columbia University) and Ellis Preparatory High School for recent immigrants in the Bronx, respectively.Technical summary:Identifying and parsing the complex interplay between bulk and surface degradation modes in beyond-Li ion batteries is critical to realizing cost-effective solutions for the widespread adoption of electrochemical energy storage. This project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, leverages the high chemical and elemental specificity of nuclear magnetic resonance (NMR) to identify the chemical mechanisms underpinning failure in potentially high capacity tin phosphide anodes for potassium ion batteries (KIBs). The large atomic size of K generates highly disordered and mechanically unstable structures during potassiation of tin phosphides that are susceptible to a loss of electrical connectivity and parasitic side reactions during electrochemical cycling. In the bulk, phase transformations that occur upon K insertion/removal are difficult to measure with traditional materials characterization tools (e.g., diffraction) that require long-range order for structural assignment. In contrast, NMR can directly probe local P and Sn environments in the anodes to identify specific compounds that facilitate reversible K alloying reactions. Further, the volume expansion associated with K insertion exposes fresh surface for electrolyte consumption, presenting the need for strategies that can decipher electrolyte reactivity. NMR is used to describe, at the molecular-level, electrolyte solvation structures that generate unique electrolyte decomposition products. NMR analyses allows the creation of some of the first molecular-level descriptors of bulk phase transformations and interfacial reactivity in KIBs. This research plan is closely integrated with educational activities that engage underrepresented and underprivileged students in energy storage research projects at the undergraduate and high school level through partnerships with Barnard College (all women liberal arts college affiliated with Columbia University) and Ellis Preparatory High School for recent immigrants in the Bronx, respectively.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.