Impact of Ion Transport and Dissociation on Polymer Electrolyte Battery Rate Capability

在先进的电动和混合动力交通应用中，需要固体聚合物电解质来实现电池容量的变革性增长。然而，目前的聚合物电解质受到离子传输速率低的困扰，最常见的特征是电导率。这个基础工程科学项目将评估一个假设，即电导率本身并不是电池倍率能力的一个很好的衡量标准，聚合物电解质中的离子传输也是一个同样重要的组成部分。这样的理解将使下一代电动汽车电池固体电解质的智能设计成为可能。新型聚合物电解质将研究不典型应用于电解质的实验技术。该技术提供了实时离子浓度和离子形态的直接测量，这两者对于准确和完整地表征电池中聚合物电解质的性能都很重要。该项目的研究人员分别将工程和化学方面的互补专业知识结合起来，通过尖端的时间分辨测量和专门用于探测这些系统中结构-性能关系的新型合成聚电解质，将这些专业知识用于进一步了解离子传输和电池性能。在教育和推广活动方面，该项目包括与本研究相关的动手电池活动，这些活动将在经济条件较差的中学进行。参与这项研究的学生将获得新的精密聚电解质系统的合成开发和锂电池商业开发所需的技能培训。这项研究的目标是开发聚合物电解质传输的完整图景，以及它与电池性能的关系。具体目标是：(1)使用几种互补技术全面表征聚合物电解质系统中的输运，(2)研究离子形态和电解质结构对输运行为的作用，(3)确定聚合物电解质电池的极限电流，并比较基于对输运的完全理解的速率预测。利用表面增强拉曼光谱来评估解离状态和x射线散射来检查离子结构的连通性，将实现对传输基础的物理洞察。这项工作将在目前标准的聚合物电解质——含双三氟甲烷磺酰亚胺锂（LiTFSI）盐的聚环氧乙烷（PEO）上进行。纳米结构的影响将使用机械强度强的peo嵌段共聚物和LiTFSI来检测。用掺合PEO的精密聚电解质得出阴离子连通性对解离态的影响及其与阳离子结构的可通约性。最后，通过连续级模拟对聚合物电解质电池的极限电流进行了测量和预测。该项目包括对锂电池聚合物电解质传输的全面评估，这可能会改变理解限制这些电池放电速率的范式。利用前沿技术和新材料的结合，将获得关于运输的物理基础的知识。一个经过验证的聚合物电解质电池模型将被开发并公开提供。它将帮助电池界确定下一代固体电解质的目标传输特性。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。

Solid, polymer electrolytes are needed to enable transformative increases in battery capacity for advanced electric and hybrid-electric transportation applications. However, the current polymer electrolytes suffer from low ion transport rates, most commonly characterized by conductivity. This fundamental engineering science project will evaluate the hypothesis that conductivity alone is not a good metric for battery rate capability and that an equally critical component is ion transport in the polymer electrolytes. Such understanding will allow intelligent design of the next generation of solid electrolytes for electric vehicle batteries. Novel polymer electrolytes will be studied with experimental techniques not typically applied to electrolytes. The techniques provide direct measurement of ion concentration in real time and ion speciation, both of which are important for accurate and complete characterization of polymer electrolyte performance in a battery. The investigators of this project combine complementary expertise in engineering and chemistry, respectively, which will be used to further the understanding of ion-transport and battery performance through cutting-edge, time-resolved measurements and new synthetic polyelectrolytes tailored to probe structure-property relationships in these systems. For educational and outreach activities, this project includes hands-on battery activities related to this research that will be presented at economically disadvantaged middle schools. Students involved in this research will be trained with skills needed in the synthetic development of new precision polyelectrolyte systems and commercial development of lithium batteries. The goal of this research is to develop a complete picture of transport in polymer electrolytes and how it connects to battery performance. The specific aims are (1) to fully characterize transport in a systematic set of polymer electrolytes using several complementary techniques, (2) to investigate the role of ion speciation and electrolyte structure on transport behavior, and (3) to determine limiting currents for polymer-electrolyte batteries and compare to rate predictions based on a complete understanding of transport. Physical insight into the underpinnings of transport will be achieved using surface-enhanced Raman spectroscopy to evaluate dissociation state and x-ray scattering to examine the connectivity of ionic structure. This work will be conducted on the current standard polymer electrolyte, poly(ethylene oxide) (PEO) containing lithium bis-trifluoromethanesulfonimide (LiTFSI) salt. The effect of nanostructure will be examined using a mechanically strong PEO-containing block copolymer with LiTFSI. Precision polyelectrolytes blended with PEO will be used to draw conclusions about the effect of anion connectivity on dissociation state and its commensurability with the cation structure. Finally, limiting currents of polymer electrolyte batteries will be measured and predicted with continuum-level simulations. This project encompasses a thorough evaluation of transport in polymer electrolytes for lithium batteries which could shift the paradigm in understanding what limits the discharge rate in these batteries. Knowledge will be gained of the physical underpinnings of transport using a combination of frontier techniques and novel materials. A validated polymer electrolyte battery model will be developed and made publicly available. It will assist the battery community in determining target transport properties for the next generation of solid electrolytes.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.