Directional Graphene Aerogel Electrodes to Overcome Limitations in Organic Electrochemical Systems

电网规模的储能有可能缓解风能或太阳能等可再生能源的可变性和不可预测性，同时还能提高电网的稳定性和国家基础设施的安全性。本研究项目研究了有机电化学氧化还原液流电池系统及其主要限制因素之一：导致整个系统效率下降的电极性能损失。在大多数电化学系统中，离子必须移动才能在电极中储存或释放电。如果离子传输缓慢，那么系统以高效率提供电力的能力就会受到影响。研究小组将研究电极材料的合成，电极形成机制的数学模拟，以及电极在液流电池应用中的电化学性能表征。所述电极材料具有多孔结构，其设计方便了液体电解质的输送，提高了整个电池系统的功率和效率。本研究的数学模拟部分有望有助于更广泛地了解流体在多孔结构中的运动方式。这些知识将在油气生产、地下水流体动力学和其他电化学反应器中发挥作用。该研究将整合到广泛的教育和推广活动中，包括通过研究生和本科生课程传播研究，大学预科暑期课程，以及YouTube上传播的实验演示和模拟结果的视频剪辑。本研究项目的目标是通过定向多孔石墨烯气凝胶（DGA）电极加速有机电化学系统中的离子传输并减少离子传输损失。研究将导致对定义粘性流动、孔隙度、孔隙形态、质量和离子传输之间关系的基本物理学的理解。该研究将补充现有的有机氧化还原电化学系统的研究，包括鉴定有前途的电化学氧化还原偶和合适的分离器。该项目涉及合成条件的分子动力学模拟、通过冷冻模板法合成DGA电极、材料性能评估以及在运行中的有机氧化还原液流电池（联苯阳极、硫化物/多硫化物阴极和三酸钠作为电荷载体）中进行电极演示之间的循环集成。分子动力学模拟将侧重于冻结条件对电极结构和离子（联苯自由基，硫化物和钠离子）在电解质对流存在下运输的影响。将在多种条件下合成DGA电极，与模拟结果进行比较，并在联苯/多硫氧化还原液流电池中实现。物理性能包括刚度、孔隙率和表面积，电极相关性能包括电化学表面积、电子和热导率以及有效渗透率。一种新的表征技术将直接测量有效液相离子电导率的变化，使用与用于测量固相离子电导率（例如离子交换膜）的标准四点探针测试相同的基本原理。新的诊断将测量液相离子电导率，有无多孔电极，有无对流通量。液相离子电导率将用传统的碳毡电极对氯化钠水溶液进行基准测试。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。

Grid-scale energy storage has the potential to alleviate the variability and unpredictability of renewable energy sources, such as wind or solar, while also improving electrical grid stability and national infrastructure security. This research project investigates organic electrochemical redox flow battery systems and one of their major limiting factors: electrode performance losses that contribute to a decrease in efficiency to the overall system. In most electrochemical systems, ions must move to store or release electricity in the electrode. If ionic transport is slow, then the system's ability to deliver power at high efficiency suffers. The research team will address the synthesis of the electrode material, mathematical simulations of the electrode formation mechanisms, and characterization of the electrochemical performance of the electrode in a flow battery application. The electrode material has a porous structure that is designed so that the transport of liquid electrolyte is facilitated and improves the power and efficiency of the whole battery system. The mathematical simulation component of this research is expected to contribute to a broader understanding of how fluids move in porous structure. Such knowledge will be useful in oil and gas production, groundwater hydrodynamics, and other electrochemical reactors. The research will be integrated into a broad range of educational and outreach activities that include research dissemination through graduate and undergraduate courses, a pre-college summer program, and video clips of experimental demonstrations and simulation results for YouTube dissemination. The goal of this research project is to accelerate ionic transport in organic electrochemical systems and to reduce ion transport loss via directionally-porous graphene aerogel (DGA) electrodes. Studies will lead to an understanding of the fundamental physics that define the relationship between viscous flow, porosity, pore morphology, and mass and ionic transport. The research will complement current research in organic redox electrochemical systems including identification of promising electrochemical redox couples and suitable separators. The project involves cyclic integration between molecular dynamics simulations of synthesis conditions, synthesis of DGA electrodes via freeze-templating, material property assessment, and electrode demonstration in an operating organic redox flow battery (biphenyl anode, sulfide/polysulfide cathode, and sodium triflate as charge carrier). Molecular dynamics simulations will focus on the effects of freezing conditions on electrode structure and ionic (biphenyl radical, sulfide, and sodium ion) transport in the presence of electrolyte convection. DGA electrodes will be synthesized under a variety of conditions for comparison with simulation results and implementation in a biphenyl/polysulfide redox flow battery. Physical properties including stiffness, porosity, and surface area, and electrode-relevant properties including electrochemical surface area, electronic and thermal conductivities, and effective permeability will be assessed. A novel characterization technique will directly measure changes in effective liquid-phase ionic conductivity using the same foundational principle underlying the standard four-point probe test used to measure solid-phase ionic conductivity (e.g. ion exchange membranes). The new diagnostic will measure liquid phase ionic conductivity, with and without a porous electrode, and with or without convective flux. Liquid phase ionic conductivity will be benchmarked against aqueous sodium chloride with a conventional carbon felt electrode.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.