Zwitterion-Decorated Silica Nanoparticle Networks in Ionic Liquid Electrolytes

安全、可靠的电池是未来移动设备和可穿戴电子产品的关键。锂离子电池和钠离子电池都可以提供高工作电压和大能量密度，但目前使用的许多离子传输电解质材料都是易燃的，如果电池发生故障，可能会带来安全隐患。一类室温熔盐，被称为离子液体，可以消除可燃性问题，但一个基本的挑战仍然是如何促进目标阳离子（Li+, Na+）的选择性运动，而不是其他离子也存在于电解质中。该项目由美国国家科学基金会材料研究部固态与材料化学项目和聚合物项目支持，旨在通过创造涂有两性离子化学基团的无机氧化物材料来解决这一挑战。两性离子基团包含相等数量的带正电荷和带负电荷的原子，它们之间的距离仅为几个键长，已知它们与电解质离子以及彼此之间都有强烈的相互作用。该项目测试了两性离子修饰的氧化物纳米粒子网络可以选择性地增强离子液体电解质中Li+和Na+的传输的假设。这项研究为未来更安全的电池电解质的设计提供了必要的见解，并揭示了非水、离子密集电解质中两性离子相互作用的新基本信息。一个新的K-12外展活动也是这个项目的一部分。该活动将向大学预科学生介绍未来的能源存储技术，将他们与本研究的研究成果联系起来，并培养他们从事科学或工程职业的兴趣。本项目的主要目标是利用有机两性离子（ZI）官能团修饰的二氧化硅纳米结构网络选择性地增强离子液体电解质中Li+和Na+离子的传输。这类独特材料的两种不同表现形式将被研究：(1)ZI基团修饰的氧化物纳米粒子（ZIONs）， (2) ZI基团功能化的介孔氧化物网络（两性离子硅）。本研究的一个关键假设是，与液体电解质本身相比，在离子液体电解质中组装成连续三维网络的ZI基团功能化二氧化硅纳米结构可以显著改善选择性碱金属阳离子传输（Li+或Na+），同时还可以创建一个坚固的复合凝胶电解质层，可以防止泄漏。通过在空间上定义ZI基团/碱金属阳离子相互作用的区域，该区域位于ZIONs或两性离子二氧化硅的暴露表面，假设这种方法可以有效地最大化ZI单元在这些本质上更安全的电解质中增强Li+/Na+导电性的能力。该项目由美国国家科学基金会材料研究部的固态与材料化学项目和聚合物项目资助，包括具有不同ZI化学性质的锡离子和两性离子硅的合成，以及它们与离子液体电解质组合的相关离子传输指标的测量。此外，这项工作为不同群体的学生提供指导本科生和研究生的研究经验，支持他们未来在美国工业研发、学术界和国家实验室就业的目标。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。

Part 1: Non-technical SummarySafe, reliable batteries are critically needed for future mobile devices and wearable electronics. Both lithium and sodium ion-based batteries can provide high operating voltages and large energy densities, but many of the ion-transporting electrolyte materials used today are flammable and may present a safety hazard if the battery fails. A class of room temperature molten salts, known as ionic liquids, can eliminate flammability concerns, but a fundamental challenge remains in how to promote the selective motion of the targeted cations (Li+, Na+) over that of the other ions also present in the electrolyte. This project, supported by the Solid State and Materials Chemistry program and the Polymer program in the Division of Materials Research at NSF, aims to address this challenge by creating inorganic oxide materials that are coated with zwitterionic chemical groups. Zwitterionic groups contain an equal number of both positively- and negatively-charged atoms, separated by a distance of just a few bond lengths, which are known to interact strongly with electrolyte ions as well as with one another. This project tests the hypothesis that zwitterion-decorated oxide nanoparticle networks can selectively enhance Li+ and Na+ transport in ionic liquid-based electrolytes. The research generate needed insights into the design of safer future battery electrolytes and reveal new fundamental information about zwitterion-ion interactions in nonaqueous, ion-dense electrolytes. A new K-12 outreach activity is also developed as part of this project. The activity will inform pre-college students about future energy storage technologies, connect them to the research findings of this study, and foster their interest in pursuing a career in science or engineering.Part 2: Technical SummaryThe primary objective of this project is to selectively enhance the transport of Li+ and Na+ ions within ionic liquid electrolytes using organic zwitterionic (ZI) functional group-decorated silica nanostructured networks. Two different manifestations of this unique materials class will be pursued: (1) ZI group-decorated oxide nanoparticles (ZIONs), and (2) ZI group-functionalized mesoporous oxide networks (zwitterionosilicas). A key hypothesis of this study is that ZI group-functionalized silica nanostructures assembled into a continuous three-dimensional network within an ionic liquid electrolyte can enable a substantial improvement in selective alkali metal cation transport (Li+ or Na+) compared to that in the liquid electrolyte itself, while also creating a robust composite gel electrolyte layer that can prevent leakage. By spatially defining the region of ZI group/alkali metal cation interaction to be located along the exposed surfaces of the ZIONs or zwitterionosilicas, it is posited that this approach can effectively maximize the ability of ZI units to enhance Li+/Na+ conductivity within these inherently safer electrolytes. This project, funded by the Solid State and Materials Chemistry program and the Polymer program in the Division of Materials Research at NSF, encompasses the synthesis of ZIONs and zwitterionosilicas featuring different ZI chemistries and the measurement of relevant ion transport metrics for their combinations with ionic liquid electrolytes. Additionally, the work provides mentored undergraduate and graduate research experiences for a diverse group of students, supporting their goals of future employment in U.S. industrial research and development, academia, and national laboratories.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.