Collaborative Proposal: Understanding and Tuning the Molecular Arrangement and Charge Storage Properties of Textured Graphene-Ionic Liquid Interfaces

随着对电力需求的不断增长，下一代能量存储设备（电池和超级电容器）必须被设计成能够支持比当前技术更高的能量密度。因此，必须探索新的电解质和电极材料，以允许更高的电解质填充密度。为了改善电极/电解质界面，该项目由美国国家科学基金会材料研究部固态和材料化学项目支持，旨在通过在纳米尺度上精确控制电极几何形状来了解离子液体的结构及其在电极界面上的排列。单层石墨烯是一种碳基材料，只有一个原子厚度，可以作为高度柔韧性的导电电极，用于制造本研究的纹理电极。研究小组研究了电极形态对离子液体电解质组织的影响及其对电荷存储的影响。除了探索这些基础科学问题外，该项目还支持来自不同背景的本科和研究生的教育和培训，在材料和表面科学的交叉领域，通过在UIUC和TAMU主要研究人员的实验室之间的协调合作环境中培训学生进行交叉研究，为美国能源部门劳动力的发展做出贡献。在美国国家科学基金会材料研究部固态和材料化学项目的支持下，主要研究人员（UIUC的Espinosa-Marzal和TAMU的Batteas）验证了一个基本假设，即通过控制表面形态和基材诱导电荷掺杂，以及离子液体的化学成分，可以精确调节石墨烯上液体的局部堆积密度。这反过来又有望更好地控制它们的电荷存储特性。为了填补所概述的知识空白，该团队进行了三个主要的研究方向。开发了从原子到纳米尺度精确控制电荷掺杂和形态的石墨烯表面制备新方法。此外，在电化学电池中，利用原子力显微镜研究了衬底形态和电荷掺杂对离子液体界面结构和双电层特性的影响。此外，利用局部和全局电化学阻抗谱分析了双电层与织构界面差分电容之间的关系。这些研究可以确定石墨烯粗糙度、电荷掺杂和离子液体成分对双电层及其电容的相对贡献。从该项目中获得的知识有望通过石墨烯结构的调制来控制液体的界面组装和存储电荷。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。

Non-technical summary With the ever-increasing need for electrical power on demand, next generation energy storage devices (batteries and supercapacitors) must be designed that can support higher energy densities than current technologies. Therefore, new electrolyte and electrode materials must be explored that allow for higher electrolyte packing densities. To improve electrode/electrolyte interfaces, this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, seeks to understand how the structure of ionic liquids and their arrangement at electrode interfaces may be tuned by precisely controlling electrode geometry on the nanoscale. Single-layer graphene, a carbon-based material, just one-atom thick, which can function as a conductive electrode that is highly flexible, is used to created textured electrodes for this study. The research team investigates the influence of the electrode morphology on the organization of the ionic liquid electrolyte and how it impacts charge storage. In addition to exploring these fundamental science questions, this project supports the education and training of undergraduate and graduate students from diverse backgrounds, at the intersection of materials and surface science, contributing to the development of the energy sector work force in the U.S., by training students in cross-cutting research in a coordinated collaborative environment between the labs of the principle investigators at UIUC and TAMU. Technical summaryWith this grant, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, the principle investigators (Espinosa-Marzal at UIUC and Batteas at TAMU) test the fundamental hypothesis that by controlling surface morphology and substrate-induced charge doping, along with the chemical composition of the ionic liquids, the local packing density of the liquid on graphene can be precisely modulated. This in turn is expected to afford better control over their charge storage properties. To fill the outlined knowledge gap, the team pursues three major lines of research. New methods to prepare graphene surfaces with precisely controlled charge doping and morphology from the atomic to the nanoscale are developed. In addition, the effects of substrate morphology and charge doping on the interfacial structure of ionic liquids and on the characteristics of the electrical double layer are investigated by Atomic Force Microscopy in an electrochemical cell. Furthermore, local and global electrochemical impedance spectroscopy are used to relate the electrical double layer to the differential capacitance of the textured interfaces. These studies allow determining the relative contributions of graphene roughness, charge doping and ionic liquid composition on the electrical double layer and its capacitance. The knowledge gained from this project is expected to enable control of the interfacial assembly of the liquids and stored charge through the modulation of the graphene texture.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.