Nonvolatile Gel Electrolytes for Safer Lithium Ion Batteries

为了实现混合动力/电动汽车以及未来便携式或可穿戴电子设备的更安全电池，开发稳定、不易燃、高效的锂离子电解质用于高能量密度锂离子电池是一个重要的研究重点。该项目将研究一类由熔盐（离子液体）、锂离子和两性离子聚合物组成的新型凝胶电解质材料的适用性。这些材料的预期优势包括：超低挥发性，防泄漏设计，以及在室温下锂离子传输的良好选择性。这项工作的成果将对储能研究领域产生直接影响，并有望在不久的将来促进安全有效、高能量密度、不易燃的凝胶电解质锂离子电池的开发，用于实际应用。在这些凝胶体系中锂离子传输的基础知识将从这个项目中得到。此外，该项目将为本科和高中STEM中代表性不足的少数民族学生提供支持，让他们参与与储能主题相关的研究体验。更广泛的影响和推广活动将包括在PI的实验室提供每年夏季研究职位，并举办当地高中化学课参观和电解质活动日。本项目也由CBET分子分离项目资助，NSF 18-1417。该项目旨在建立基本的理解，并创建一个连贯的框架来描述决定未来锂离子电池的一种新型更安全电解质的不同物理和电化学特性的因素：两性离子（co）聚合物支撑，非挥发性锂阳离子导电离子液体凝胶电解质。这些目标将通过对各种两性离子-电解质离子分子间相互作用的全面光谱研究来实现。通过原位自由基聚合制备凝胶电解质，使用两种有前途的非挥发性电解质：锂基溶剂离子液体，以及传统的锂盐/离子液体溶液。两性离子-离子相互作用将使用核磁共振、红外光谱和拉曼光谱进行探测，而所有凝胶电解质的离子电导率和锂离子转移数值将分别使用交流阻抗光谱和直流极化测量进行实验测定。压缩应力-应变测试将用于确定这些凝胶电解质的弹性模量值。将采用线性扫描伏安法、循环伏安法和恒流充放电循环来考察凝胶的电化学稳定性和锂离子电池的可行性和性能。该项目的一个重要成果是将液态溶液电化学特性的知识与用作电解质材料的凝胶版本联系起来。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。

In order to realize safer batteries for hybrid/electric vehicles and also for future portable or wearable electronic devices, the development of stable, nonflammable, and efficient lithium ion-electrolytes for high energy density lithium-ion batteries is a high research priority. This project will examine the suitability of a new class of gel electrolyte materials that are composed of molten salts (ionic liquids), lithium ions, and zwitterionic polymers. Expected advantages of these materials include: ultralow volatility, a leak-proof design, and good selectivity for lithium ion transport at room temperature. The outcomes of this work will make an immediate impact in the field of energy storage research and are expected to facilitate the development of safe and effective, nonflammable gel electrolyte-containing lithium ion batteries with high energy densities for real-world applications in the near future. Fundamental knowledge on lithium ion transport in these gel systems will result from this project. In addition, this project will provide support for underrepresented minority students in STEM both at the undergraduate and high school levels to participate in a research experience related to energy storage themes. Broader impact and outreach activities will include providing an annual summer research position in the PI's laboratory and hosting a local high school chemistry class visit and electrolyte activity day. This project is also funded by the CBET Molecular Separations Program, NSF 18-1417.This project seeks to develop fundamental understanding and create a coherent framework to describe the factors that determine the varying physical and electrochemical characteristics of a novel class of safer electrolytes for future lithium ion batteries: zwitterionic (co)polymer-supported, nonvolatile lithium cation-conducting ionic liquid gel electrolytes. These objectives will be achieved through a comprehensive spectroscopic investigation of various zwitterion-electrolyte ion intermolecular interactions. Gel electrolytes created via in situ free radical polymerization using two promising classes of nonvolatile electrolytes will be examined: lithium-based solvate ionic liquids, as well as conventional lithium salt/ionic liquid solutions. Zwitterion-ion interactions will be probed using NMR, FTIR, and Raman spectroscopies, while ionic conductivity and lithium ion transference number values will be experimentally determined for all gel electrolytes using AC impedance spectroscopy and DC polarization measurements, respectively. Compressive stress-strain testing will be used to determine elastic modulus values of these gel electrolytes. Linear sweep voltammetry, cyclic voltammetry, and galvanostatic charge/discharge cycling will be conducted in order to interrogate gel electrochemical stability and lithium ion battery cell feasibility and performance. One important outcome of this project is linking knowledge of the liquid solution electrochemical properties to the gel version for use as an electrolyte material.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.