RII Track-4: Pore-Scale Transport Phenomena in Li-O2 Battery Electrodes Characterized by Nano-Tomography

具有高比能量和功率的可充电电池是高性能和远程电动汽车以及许多便携式电源应用的关键。锂氧（Li-O2）电池作为下一代储能技术具有巨大的潜力。然而，目前锂氧电池可实现的比能量（即单位质量的能量）比其理论极限低十倍，而且它们目前的动力性能仍远低于电动汽车所需的加速性能。这两个限制部分是由于电极中氧的缓慢传质。提高比能需要电池电极中孔尺度材料传输的基础知识。为了填补这一知识空白，PI将与卡内基梅隆大学（CMU）的合作者合作，测量和重建Li-O2电池电极的孔隙尺度结构，并提出从根本上改善Li-O2电池电化学性能的标准。该奖学金的研究成果亦会整合到课程发展中，向年轻研究人员传授新理论和知识，培训本科生和研究生，并培养一支熟练和受过良好教育的专业劳动力，以促进本地工业和经济的发展。与Shawn Litster教授的合作以及CMU独特的x射线计算机断层扫描设备（XCFT）的访问，是重建高分辨率（~50 nm）孔尺度结构和后续Li-O2电池研究的关键。重构的定制电池电极三维纳米层析成像将1)与统计模型相结合，将孔隙尺度的形貌转移到电极水平的性质；2)结合流体动力学模型预测其电化学性能；3)有助于理解固体Li2O2在放电/充电过程中析出/耗竭引起的孔隙结构演化。该项目开发的新知识和理论以及新技术将使先进电极材料的研究和开发能够显着提高Li-O2电池的比能量和功率。其深远的科学意义将持续到本次奖学金之后，并促进高能量和功率密度的电化学技术，如燃料电池、锂离子电池、金属-空气电池、超级电容器和氧化还原液流电池。该项目的成功将开启PI和Litster教授之间的长期合作，以追求新知识并促进堪萨斯大学和CMU之间的更多合作研究。它还为一名研究生提供了一个极好的机会，每年夏天接受系统的科学研究，发起合作和传播研究成果的培训。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。

Nontechnical DescriptionRechargeable batteries with high specific energy and power are the key for high-performance and long-range electric vehicles as well as many portable power applications. The lithium-oxygen (Li-O2) battery has great potential as the next generation energy storage technology. However, the current achievable specific energy (i.e., energy per unit mass) for Li-O2 batteries is a factor of ten lower than its theoretical limit and their current power performance are still far below the acceleration performance required for electric vehicles. Both of these limitations are partially due to the sluggish mass transfer of oxygen in the electrode. Increasing the specific energy requires fundamental knowledge of pore-scale material transport in battery electrodes. To fill this knowledge gap, the PI will work with collaborators at Carnegie Mellon University (CMU) to measure and reconstruct the pore-scale structure of Li-O2 battery electrodes and propose criteria for fundamentally improving the electrochemical performance of Li-O2 batteries. Research findings from this Fellowship will also be integrated into curriculum development efforts to transmit the new theory and knowledge to young researchers, train undergraduate and graduate students, and nurture a skilled and educated professional workforce to grow local industry and economy.Technical DescriptionThe collaboration with Prof. Shawn Litster and access to the unique X-ray Computed Tomography Facility (XCFT) at CMU, made possible by this Fellowship, is the key to reconstructing high-resolution (~50 nm) pore-scale structure and for subsequent studies of Li-O2 batteries. The reconstructed three-dimensional nano-tomography of customized battery electrodes will 1) be integrated with statistical models to transfer pore-scale morphology to electrode-level properties; 2) be coupled with fluid dynamics models to predict its electrochemical performance; and 3) facilitate the understanding of pore structure evolution caused by the solid Li2O2 precipitation/depletion during discharge/charge. The new knowledge and theory, as well as the new techniques, developed in this project will enable research and development of advanced electrode materials to significantly improve the specific energy and power of Li-O2 batteries. The profound scientific significance will last beyond this Fellowship and promote electrochemical technologies with high energy and power density such as fuel cells, Li-ion batteries, metal-air batteries, super capacitors, and redox flow batteries. The success of this project will initiate a longstanding collaboration between the PI and Prof. Litster to pursue new knowledge and foster more collaborative research between the University of Kansas and CMU. It also provides an excellent opportunity for one graduate student to receive systematic training on conducting scientific research, initiating collaborations, and disseminating research findings each summer.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.