Zwitterion-Decorated Silica Nanoparticle Networks in Ionic Liquid Electrolytes

第1部分：非技术概述未来的移动设备和可穿戴电子产品迫切需要可靠的电池。锂离子电池和钠离子电池都可以提供高工作电压和高能量密度，但当今使用的许多离子传输电解液材料是易燃的，如果电池发生故障，可能会带来安全风险。一类被称为离子液体的室温熔盐可以消除易燃性问题，但一个根本的挑战仍然是如何促进目标阳离子(Li+，Na+)的选择性运动，而不是也存在于电解液中的其他离子。该项目由NSF材料研究部的固态和材料化学计划和聚合物计划支持，旨在通过创造覆盖有两性离子化学基团的无机氧化物材料来应对这一挑战。两性离子基团包含相同数量的带正电和带负电的原子，彼此之间只有几个键长的距离，众所周知，这些原子与电解质离子以及彼此之间都有很强的相互作用。该项目测试了两性离子修饰的氧化物纳米颗粒网络可以选择性地增强锂离子和钠离子在离子液体电解液中的传输的假设。这项研究为设计更安全的未来电池电解液提供了必要的见解，并揭示了关于非水、离子密度电解液中两性离子-离子相互作用的新的基本信息。作为该项目的一部分，还制定了一项新的K-12外联活动。该活动将使大学预科学生了解未来的储能技术，将他们与本研究的研究成果联系起来，并培养他们对从事科学或工程职业的兴趣。第二部分：技术概述本项目的主要目标是使用有机两性离子(ZI)官能团修饰的二氧化硅纳米结构网络选择性地增强Li+和Na+离子在离子液体电解液中的传输。这类独特的材料有两种不同的表现形式：(1)Zi基团修饰的氧化物纳米颗粒(Zion)和(2)Zi基团功能化的介孔氧化物网络(两性离子硅酸盐)。这项研究的一个关键假设是，在离子液体电解液中组装成连续三维网络的ZI基团功能化的二氧化硅纳米结构，与液体电解液本身相比，可以显著改善选择性碱金属阳离子传输(Li+或Na+)，同时还可以形成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位于Zion或两性离子硅酸盐的暴露表面，该方法被认为可以有效地最大化ZI单元在这些固有安全的电解液中增强Li+/Na+电导的能力。该项目由NSF材料研究部的固态和材料化学计划和聚合物计划资助，包括合成具有不同ZI化学特征的Zion和两性硅酸钾，并测量它们与离子液体电解液结合时的相关离子传输度量。此外，这项工作还为不同的学生群体提供了本科生和研究生的指导研究经验，支持他们未来在美国工业研发、学术界和国家实验室的就业目标。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。

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.