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

锂金属电池等下一代储能系统对于可再生能源和移动能源的广泛使用至关重要。他们的成功依赖于先进电解质材料的发展，这些材料可以快速和选择性地传导目标离子（例如Li+），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，这种类型的电解质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特殊聚合物中移动，这些聚合物自组装形成两性离子纳米级结构域，可以优先被离子液体膨胀。我们希望这些发现将为能量存储应用打开一扇新的、性能更好的电解质的大门。本项目的目的是研究由两亲性梳状共聚物自组装形成的两性离子（ZI）导电纳米通道内Li+离子的传输。为了确保在环境温度下具有足够高的离子电导率，富锌通道将被一定量的含有溶解的锂盐的非挥发性离子液体（IL）膨胀。由此产生的材料被称为纳米结构电解质（nse）。本研究的主要目的是验证这样一个假设，即约束在带有弱相互作用ZI界面的纳米通道中，将选择性地增强nse内Li+离子的输运。所提出的实验计划旨在研究当NSE内部il膨胀的纳米通道尺寸（即导电畴的通道直径）被系统调节时，ZI侧基对Li+离子传输的影响。约束的调制将通过仔细调整：(i)共聚物结构，（ii） IL膨胀程度，以及（iii）结构域的刚度来实现。nse中的整体离子传输将通过交流阻抗谱和直流极化测量来表征，用于确定Li+转移数值。使用7Li， 19F和1H脉冲场梯度核磁共振波谱来探测单个离子的扩散。电泳核磁共振（eNMR）光谱将首次应用于nse，直接测量Li+的选择性传导。nse的物理表征将包括DSC、TEM、SAXS/WAXS和流变学。所提出的具有ZI导电纳米通道的nse有望为电解质材料设计提供有价值的新策略，以实现电化学储能系统中靶向离子传输的增强。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。

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.