NSF-DFG CONFINE: Lithium ion transport in self-assembled zwitterionic nanochannels containing ionic liquids

金属锂电池等下一代储能系统对于可再生能源和移动能源的更广泛使用至关重要。它们的成功依赖于先进电解液材料的开发，这种材料可以快速和选择性地传导目标离子(例如锂)，同时还提供强大的机械性能。自组装聚合物将导电离子限制在纳米尺度的区域内，同时提供坚固的结构，可能使这种材料成为可能。然而，到目前为止，这种类型的电解液只达到了有限的离子电导率水平。该项目旨在了解离子如何在自组装形成两性离子纳米级结构域的特殊聚合物中移动，这些结构域可以优先与离子液体一起膨胀。我们希望这些发现将为新的、性能更好的储能电解液的应用打开大门。本项目的目的是研究两亲性梳状共聚物自组装形成的两性离子(Zi)导电纳米通道中的锂离子传输。为了确保在环境温度下足够高的离子传导性，富锌通道将用控制量的非挥发性离子液体(IL)膨胀，其中含有溶解的锂盐。由此产生的材料被称为纳米结构电解质(NSE)。这项研究的主要目的是检验一种假设，即限制在带有弱相互作用ZI界面的纳米通道中将选择性地增强锂离子在NSE中的传输。该实验方案旨在系统地调节NSE中IL-溶胀的纳米通道尺寸(即导电域的通道直径)，以考察ZI侧基对锂离子传输的影响。限制的调节将通过仔细调整：(I)共聚物结构，(Ii)IL膨胀程度，和(Iii)结构域的刚性来实现。交流阻抗谱和直流极化测量将用来确定锂离子迁移数值，以表征离子在NSE中的整体传输。单个离子物种的扩散将使用7Li、19F和1H脉冲场梯度核磁共振波谱进行探测。首次将电泳谱应用于NSE中，直接测量选择性锂电导。NSE的物理特性将包括DSC、TEM、SAXS/WAXS和流变学。拟议中的具有Zi导电纳米通道的NSE有望为电解液材料设计提供一种有价值的新战略，以实现电化学能量存储系统中定向离子传输的增强。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。

Next generation energy storage systems such as lithium metal batteries are crucial for the broader use of renewable energy resources and mobile energy. Their success relies on the development of advanced electrolyte materials that quickly and selectively conduct the target ion (e.g. Li+) while also providing robust mechanical properties. Self-assembling polymers that confine the conducting ions into nanometer-scale domains while providing a robust structure can potentially enable such materials. This type of electrolyte, however, has achieved only limited ionic conductivity levels to date. This project aims to understand how ions travel within specialty polymers that self-assemble to form zwitterionic nanometer-scale domains that can be preferentially swollen with ionic liquids. We expect that these findings will open the door to new, better-performing electrolytes for energy storage applications.The aim of this project is to study Li+ ion transport within zwitterionic (ZI) conducting nanochannels formed by the self-assembly of amphiphilic comb copolymers. To ensure sufficiently high ionic conductivity at ambient temperatures, the ZI-rich channels will be swollen with controlled amounts of a nonvolatile ionic liquid (IL) containing a dissolved Li salt. The resulting materials are referred to as nanostructured electrolytes (NSEs). The primary objective of this study is to test the hypothesis that confinement into nanochannels decorated with weakly interacting ZI interfaces will selectively enhance Li+ ion transport within NSEs. The proposed experimental plan is designed to examine the effect of ZI side-groups on Li+ ion transport as the IL-swollen nanochannels size (i.e. channel diameter of the conducting domain) inside a NSE is systematically modulated. Modulation of confinement will be achieved by carefully tuning: (i) copolymer architecture, (ii) degree of IL swelling, and (iii) rigidity of the structural domain. Overall ion transport in NSEs will be characterized by AC impedance spectroscopy and DC polarization measurements used to determine Li+ transference number values. Diffusion of individual ion species will be probed using 7Li, 19F, and 1H pulsed field gradient NMR spectroscopy. Electrophoretic NMR (eNMR) spectroscopy will be applied to NSEs for the first time to measure selective Li+ conduction directly. Physical characterization of NSEs will include DSC, TEM, SAXS/WAXS, and rheology. The proposed NSEs featuring ZI conducting nanochannels are expected to provide a valuable new strategy for electrolyte materials design to realize an enhancement of targeted ion transport within electrochemical energy storage systems.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.