Engineering and Evaluating the End-Group Assisted Electrodeposition of Conformal Polymer Electrolytes for Ultrathin-Film Batteries

从个人电子产品到电动汽车，锂离子电池是许多设备的主要电源。虽然这种电池储存的能量稳步增加，但仍然存在一个限制，即它们无法在几分钟内安全充电或维持高功率输出。这种缓慢的主要瓶颈是锂离子在电池中的缓慢运动，这是由液体或聚合物电解质介导的。将正极和负极靠得更近将大大提高电池的运行速度。然而，为了避免这些电极之间的短路，需要超薄的固体电解质，这种电解质可以在极小的尺度上以均匀的方式制造而没有缺陷。该研究项目旨在通过开发聚合物结构和制造方法来解决这一技术需求和工程知识差距，从而使超薄聚合物电解质能够在保持电子绝缘和安全的同时实现快速离子运动。具体来说，本研究探索了电沉积作为一种本质上受表面限制的工艺，用于用聚合物电解质均匀涂覆复杂的电极结构。为了在电池相关的尺度上评估这些超薄聚合物薄膜，该研究项目进一步开发了高通量多尺度分析，利用光和颜色快速测量聚合物薄膜的电子和离子特性。此外，这笔拨款将为波士顿大学的一个本科生暑期研究项目引入微电池的纳米制造研究项目，将纳米制造和能源存储这两个传统上互不相关的领域结合起来。这项研究还将包括为本科材料科学课程开设一个新的固体材料离子扩散实验室。该项目解决了对新制造工艺的基本理解，以实现高能量密度和高功率密度的交叉薄膜电池。该项目解决了在三维（3-D）电极结构上缺乏超薄、保形和无缺陷聚合物电解质的合成和加工方法的问题。为了克服这一障碍，本研究计划寻求建立对具有电化学交联端基的聚合物电解质电沉积机制的基本理解。这种方法的基本原理是将由电化学反应端基控制的自限电沉积能力与由薄膜组成和分子结构决定的离子电导率等薄膜特性解耦。首先，系统地研究了带酚端基的聚环氧乙烷在平面和三维多孔电极上的氧化电沉积，揭示了电化学条件以及聚合物和酚端基的分子结构对薄膜生长和性能的影响。这些任务将测试一个假设，即电子绝缘聚合物的成功自限制电沉积需要快速交联速率和端基氧化时溶解度的同时降低。因此，这项研究将产生多尺度分子设计规则和加工窗口，从而导致聚合物电解质的保形电沉积，为克服交叉薄膜电池以及其他功能聚合物涂层的工程挑战创造基础知识。在研究计划的第二个轨道上，将通过开发高通量光学筛选方法来解决由溶液组成、沉积条件和所产生的薄膜性能之间的相互作用所带来的多维参数空间的分析挑战，从而在空间上解决覆盖、电子电阻率和离子电导率等关键指标在电池相关区域的亚微米分辨率。这些技术将为自限制聚合物电解质电沉积从分子到器件水平建立基本的结构-加工-性能关系，其综合评估将为一套新的多尺度电化学分析工具奠定基础。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。

Lithium-ion batteries are the primary power source for many devices from personal electronics to electric vehicles. While the energy stored in such batteries has steadily increased, a remaining limitation is their inability to safely charge in minutes or sustain a high-power output. The main bottleneck for this sluggishness is the slow movement of the lithium ions across the battery, which is mediated by either a liquid or polymeric electrolyte. Bringing the positive and negative electrodes much closer to each other would dramatically increase the speed at which batteries can operate. However, to avoid short circuits between these electrodes, ultra-thin solid electrolytes are needed that can be fabricated at extremely small scales in a uniform fashion without defects. This research project aims to address this technological need and engineering knowledge gap by developing polymer structures and manufacturing methodologies that enable the uniform fabrication of ultrathin polymer electrolytes capable of fast ion movement while maintaining electronic insulation and safety. Specifically, this research explores electrodeposition as an intrinsically surface-confined process for the uniform coating of complex electrode architectures with polymer electrolytes. To evaluate these ultrathin polymer films on battery-relevant scales, this research program further develops high-throughput multi-scale assays that use light and color to rapidly measure the electronic and ionic properties of the polymeric films. Additionally, this grant will introduce nanomanufacturing research projects in microbatteries to an undergraduate summer research program at BU, combining the traditionally disconnected fields of nanofabrication and energy storage. This research will also include the development of a new lab on ion-diffusion in solid materials for an undergraduate Materials Science course.This project addresses fundamental understanding of new manufacturing processes to enable interdigitated thin-film batteries with both high energy density and high-power density. The project addresses the lack of synthesis and processing methods of ultrathin, conformal, and defect-free polymer electrolytes on three-dimensional (3-D) electrode architectures. To overcome this barrier, this research program seeks to establish a fundamental understanding of the electrodeposition mechanism of polymer electrolytes with electrochemically crosslinkable end-groups. The rationale of this method is to decouple the capability for self-limiting electrodeposition, governed by the electrochemically reactive end-group, from film properties such as ionic conductivity that are determined by the film composition and molecular architecture. First, a systematic study will be conducted on the oxidative electrodeposition of poly(ethylene oxide) with phenolic end-groups on planar and three-dimensional porous electrodes to reveal the impact of the electrochemical conditions, as well as the molecular architecture of the polymer and the phenolic end-group, on the film growth and properties. These tasks will test the hypothesis that successful self-limiting electrodeposition of electronically insulating polymers requires a fast crosslinking rate and concurrent decrease of solubility upon end-group oxidation. Thus, this research will yield multiscale molecular design rules and processing windows that result in the conformal electrodeposition of polymeric electrolytes, creating foundational knowledge needed to overcome an engineering challenge for interdigitated thin-film batteries, as well as other functional polymer coatings. In a second track of the research program, the analytical challenge of the multi-dimensional parameter space posed by the interplay between solution composition, deposition conditions, and resulting film properties will be addressed by developing high-throughput optical screening methods to spatially resolve the key metrics of coverage, electronic resistivity, and ionic conductivity at submicron resolution over battery-relevant areas. These techniques will establish foundational structure-processing-property relationships for self-limiting polymer electrolyte electrodeposition from the molecular to the device level, and their comprehensive evaluation will build the basis of a new suite of multiscale electrochemical analysis tools.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.