EAGER: Suppressing Lithium Dendrite Growth by Functionally Graded Materials

目前的锂离子电池使用活性材料、导电添加剂和粘结剂的混合物，这些材料在能量密度、功率效率和耐用性方面已经迅速达到其功能的极限。这一早期概念探索性研究资助(AGIRE)项目致力于发展对新制造工艺的基本科学理解，并解决下一代可充电电池开发的瓶颈。该技术还可应用于其他新设计材料的制造，如自立式和无粘结剂复合材料。更广泛的影响可能是非常大的，这种方法可能是变革性的，因为这种方法直接应用于汽车、电子、农业设备、航空航天和国防工业。因此，该项目直接影响到美国的经济福利和国家安全。除了支持研究生，该项目还将为各种学生带来学习最先进制造工艺的教育机会，包括女性、残疾人和科学、技术、工程和数学(STEM)领域代表性不足的少数族裔。堪萨斯城一年一度的Maker Fire(为期两天的展览和科学展览，2017年吸引了来自几乎所有50个州的1.7万多名年龄从蹒跚学步的孩子到祖父母)等社交活动将被用来传播和分享研究成果，并为普通公众带来教育。虽然锂是最轻的金属(0.534 g/cm~3)，在标准氢电极上具有最低的负还原电位(-3.05V)，但与锂离子电池中的碳负极(比容量为372mAh/g)相比，金属锂具有极高的理论比容量(3829mAh/g)。尽管锂金属二次电池前景看好，但它的发展一直受到锂枝晶生长等瓶颈的阻碍。为了解决这一问题，电场增强超声喷雾热解(EFAUSP)工艺将能够制备能够抑制Li枝晶生长的功能梯度材料(FGM)。然而，到目前为止，在了解喷雾在EFAUSP过程中的产生、传输和沉积的协同效应方面存在着知识差距。例如，带有喷雾的湍流射流具有一系列涡流，这些涡流决定了沉积液滴或颗粒的分布，并最终决定了沉积模式。这项研究将为实现功能梯度材料的制备提供全面的湍流-喷雾相互作用的知识。此外，将开发新的知识和工具来研究什么是控制和抑制Li树枝晶生长的最佳功能梯度材料，这将对电池行业产生重大影响。这项具有潜在变革性的工作是使可充电金属锂电池商业化的关键一步。此外，在这项工作中获得的基本知识将使一种简单、低成本和可扩展的制造技术的开发成为可能，这将使电池制造发生革命性变化。这项技术将通过其对能源、交通、便携式设备行业和其他领域的影响对社会产生重大影响。该奖项反映了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。

Current lithium-ion batteries use a mixture of active materials, conductive additives, and binders, which have been quickly reaching the limit of their functionality in terms of energy density, power efficiency, and durability. This EArly-concept Grant for Exploratory Research (EAGER) project addresses developing a fundamental scientific understanding of a new manufacturing process as well as addressing the bottleneck in the development of the next generation of rechargeable batteries. The technology can also be applied to the fabrication of other newly designed materials, such as free-standing and binder-free composites. The broader impacts are potentially very large, and the approach could be transformative, as the approach has direct application in the automotive, electronics, agricultural equipment, aerospace, and defense industries. As such, the project directly impacts economic welfare and national security of the United States. In addition to supporting graduate students, the project will bring education opportunities for learning state-of-the-art fabrication processes to a diverse array of students, including women, the disabled, and underrepresented minorities in science, technology, engineering, and math (STEM). Social events like the annual Maker Faire at Kansas City (a two-day exhibit and science show, that drew more than 17,000 visitors ranging in age from toddlers to grandparents from nearly all 50 states in 2017) will be utilized to disseminate and share the research findings, as well as bring education to the general public. While being the lightest metals (0.534 g/cm3) and possessing the lowest negative reduction potential (-3.05 V) against a standard hydrogen electrode, lithium metal is merited with extremely high theoretical specific capacity (3,829 mAh/g) as compared to carbon anode in lithium-ion batteries (with a specific capacity of 372 mAh/g). Although promising, the development of rechargeable lithium metal batteries has been impeded by such bottlenecks as Li dendrite growth. To address this issue, the Electric-Field-Augmented Ultrasonic Spray Pyrolysis (EFAUSP) process will enable the fabrication of functionally graded materials (FGMs), which can suppress Li dendrite growth. However, to date, there exists a knowledge gap in understanding the synergistic effects of the spray's generation, transport, and deposition in the EFAUSP process. For example, the turbulent jet with sprays possesses a series of eddies that determine the distribution of deposition droplets or particles and, eventually, deposition pattern. The research will provide comprehensive knowledge of the turbulence-spray interactions to realize the fabrication of FGMs. In addition, new knowledge and tools will be developed to examine what the best FGMs are for controlling and suppressing Li dendrite growth, which will have a significant impact on the battery industry. This potentially transformative work is a crucial step on the path to making rechargeable lithium metal batteries commercially available. Moreover, the fundamental knowledge gained in the work will allow the development of a simple, low-cost, and scalable fabrication technology that could revolutionize battery fabrication. This technology will have a significant impact on society through its effects on energy, transportation, the portable device industry, and other areas.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.