2-Dimensional Zeolite Nanosheet Tiled Ion Separators for Approaching Ideal Performance in Redox Flow Batteries

氧化还原液流电池(RFB)是一种大规模的储能系统，能够使用间歇性的可再生能源，如太阳能和风能，当能源被消耗时，这些能源可能并不总是可用的。与其他电池技术不同，RFB可以在大型储油罐的流体中储存大量能量。然后，流体流过电池以插入(即充电)或从系统中提取能量(即放电)。要实现这项技术的广泛部署，必须在储能能力、功率输出和材料成本方面做出重大改进。这一基础研究项目将通过解决离子分离膜组件中的关键障碍来帮助解决这些需求，离子分离膜组件的性能影响发电和储能的整体能效和系统寿命。现有的离子分离器是以聚合物为基础的，存在选择性不足和材料不稳定的固有缺点，降低了RFB的效率和使用寿命。同样，以陶瓷等无机氧化物为基础的膜也存在耐用性和效率问题。本项目旨在展示一种新的沸石纳米材料基膜，它可以接近理想的离子分离器性能，并有助于释放水基RFB的潜力，实现经济高效的能量存储。这一基础研究项目的发现将促进对纳米材料合成和新膜中离子传输行为的了解。该计划的多学科研究活动将为在新兴能源技术和关键材料开发的前沿领域培训下一代科学家和工程师提供极好的机会。该项目将专注于一种新的二维沸石纳米片状平铺式离子分离膜(ZNTM)。该项目将为二维纳米材料的合成和新结构的亚纳米孔二维纳米薄膜的离子传输行为提供基础知识。无缺陷分子筛膜，例如单晶，理论上能够在RFB操作中以高选择性和优异的材料稳定性传导质子。然而，传统的混合基质沸石膜结构不能有效地实现这些良好的性能，因为金属离子通过缩短晶间间隙而产生过多的交叉，并且在相对较大的膜厚度下具有较高的电阻。该项目将解决二维离子筛晶体的合成和性能调整方面的主要挑战，并通过新型的ZNTM结构有效地利用其独特的性能。基础研究旨在确定合成纳米厚沸石纳米片的条件，这些条件具有可控的表面化学、几何和尺寸性质(即足够大的宽厚长宽比)和沿较好方向的通道取向。为了建立一种制备超薄2D ZNTM离子分离器的有效方法，将进行系统的实验。我们将广泛考察离子分离器的离子选择性、导电性和材料稳定性，以了解它们与沸石纳米片和ZNTM的微观结构和表面化学的关系。具有经过验证的离子选择性和最小电阻的ZNTM将在全电池RFB操作中进行评估，包括电池能效、功率密度、热稳定性和寿命方面的性能。新膜的评估将集中在工业上重要的全钒和离子铬RFB化学物质上。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Redox flow batteries (RFBs) are large-scale energy storage systems that enable the use of intermittent renewable energy resources, such as solar and wind power, which may not always be available when energy is being consumed. Unlike other battery technologies, RFBs can store significant amounts of energy in fluids in large reservoirs. The fluids are then flowed through cells to insert (i.e. charging) or to extract energy (i.e. discharging) from the system. Significant improvements in energy storage capacity, power output and material costs are necessary to enable wide-scale deployment of this technology. This fundamental research project will help solve these needs by addressing key barriers in the ion separation membrane component whose performance impacts overall energy efficiency and system lifetime for power generation and energy storage. The existing ion separators are polymer-based, which have inherent shortcomings of inadequate selectivity and material instability that reduce the RFB efficiency and operation life. Similarly, membranes based on inorganic oxides such as ceramics have issues with durability and efficiency. This project aims to demonstrate a new zeolite nanomaterial-based membrane that can approach ideal performance as an ion separator and help unlock the potential of aqueous RFBs for cost-effective energy storage. The findings of this basic research project will advance knowledge on nanomaterial synthesis and ion transport behavior in the new membranes. The multidisciplinary research activities of this program will offer excellent opportunities for training next generation scientists and engineers in the frontiers of emerging energy technologies and critical material development.This project will focus on a new 2-dimensional zeolite nanosheet tiled ion separation membrane (ZNTM). This project will yield fundamental knowledge on 2D nanomaterial synthesis and ion transport behavior in the new structure of subnanometer-pore 2D nanosheet membranes. Defect-free zeolite membranes, e.g. single crystals, are theoretically capable of conducting protons with high selectivity and exceptional material stability in RFB operations. However, these favorable properties cannot be effectively realized by the conventional mixed matrix zeolite membrane structures because of excessive metal ion crossover through shortcutting intercrystalline spaces and high resistance from a relatively large thickness of membrane. The project will address the chief challenges in synthesizing and property tailoring of 2D ionic sieve crystals and effectively utilize their unique properties by the novel ZNTM structure. Fundamental studies are directed to identify the conditions for synthesizing nanometer-thick zeolite nanosheets with controlled surface chemistry, geometric and dimensional properties (i.e. adequately large width-to-thickness aspect ratios), and channel orientation in preferable direction. Systematic experiments will be carried out to establish an effective methodology for fabricating the ultrathin 2D ZNTM ion separators. The ion selectivity, conductivity, and material stability of the ion separators will be extensively examined to understand their dependences on the microstructure and surface chemistry of the zeolite nanosheets and ZNTM. The ZNTM with verified ion selectivity and minimized electric resistance will be evaluated for full cell RFB operation including performance in battery energy efficiency, power density, thermal stability, and lifetime. The evaluations of the new membranes will be concentrated on the industrially important all-vanadium and ion-chromium RFB chemistries.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.