First Principles Design of Ionomers for Facile Ion Transport

colbycurrent锂电池使用一种纳米多孔聚丙烯膜作为电极之间的隔膜，薄膜中填充了溶解在高介电常数溶剂中的锂盐。该技术存在安全性问题，而且无论选择哪种负离子，其移动速度都比Li+快5-10倍，导致负离子在电极处积聚，从而显著降低电池效率、电池最大功率和充电时间。替代膜的明显选择是一种单离子导电聚合物（离子聚体），它将所有阴离子共价地结合在聚合物上，没有溶剂会从电池中泄漏出来，并且可以很容易地制成薄膜。不幸的是，对于实际应用来说，最好的离聚体膜的Li+离子电导率太小了100倍。PI领导着一个由doe资助的五PI团队，试图为锂电池膜设计优质的离聚体，但也面临着非常广阔的设计空间，30个极性基团可以作为侧链添加，20个阴离子可以附着在聚合物上。与至少五种低Tg的主干结合，就有数千种可能的组合。此外，他是一个七pi陆军MURI的共同pi，旨在合成用于致动器的离聚体膜，该膜在阳离子选择方面也具有灵活性。本研究的智力价值有两个方面：(1)提出的研究将提出值得合成的阴离子，极性基团，骨干组合，并直接帮助上述两个小组的7名合成学生。(2)从头计算可以快速应用于不同极性介质中的各种阴离子和阳离子，从而可以详细了解离子相互作用和极性基团的溶剂化，这将推动我们与哥伦比亚大学Sanat Kumar的建模工作。我们提出的研究的更广泛影响有三个方面。(1)了解如何设计离子聚体以改善离子传导，不仅将影响先进的锂电池和致动器，而且对其他电池膜（如运输F-的商业膜）和燃料电池的膜电极组件也至关重要。所有的离子导电膜都存在一个问题，那就是只有一小部分反离子参与传导，而我们提出的研究直接解决了提高导电离子含量的问题。(2)能源领域的材料发展有望在美国未来的经济和生活方式中发挥非常重要的作用。(3)至少在未来十年内，美国工业界和学术界对这一“能源材料”领域的研究生都将有巨大的需求。宾夕法尼亚州立大学拥有优秀的本科生，研究激励他们进入研究生院（在过去的14年里，PI小组的25名本科生中有15名继续攻读科学和工程研究生院），许多本科生对“能源材料”感兴趣，包括目前的reu资助学生Daniel King，他是一名材料科学与工程大三学生，连续三年获得我们系的本科生研究奖学金。

0933391ColbyCurrent lithium batteries use a nanoporous polypropylene membrane filled with lithium salts dissolved in high dielectric constant solvents as the separator between electrodes. This technology has problems with safety and regardless of the choice of anion, which moves 5-10X faster than Li+, resulting in anion build-up at electrodes that significantly reduces battery efficiency, maximum battery power and recharge time. The obvious choice for a replacement membrane is a single-ion conducting polymer (ionomer) that has all anions covalently bonded to the polymer, has no solvent to leak out of the battery and can easily be made into a thin film. Unfortunately, the best ionomer membranes have Li+ ion conductivities 100X too small for practical applications. The PI leads a five-PI DOE-funded team that is attempting to design superior ionomers for lithium battery membranes, but also is facing a very broad design space, with 30 polar groups that could be added as side chains and 20 anions that could be attached to polymers. Combined with at least five backbones that have low Tg, there are thousands of possible combinations. Furthermore, he is a co-PI on a seven-PI Army MURI aiming to synthesize ionomer membranes for actuators, which additionally have flexibility in the choice of cation. The intellectual merits of this research are two-fold: (1) The proposed research will suggest anion, polar side group, backbone combinations worthy of synthesis and directly aid the seven synthesis students on the two teams mentioned above. (2) Ab initio calculations can be rapidly applied to a wide variety of anions and cations in different polar media, enabling a detailed understanding of ion interactions and solvation by polar groups, which should propel our modeling efforts with Sanat Kumar at Columbia. The broader impacts of our proposed research are three-fold. (1) The understanding of how to design ionomers for improved ion-conduction will not only impact advanced lithium batteries and actuators, but is also vital for other battery membranes (such as commercial ones transporting F-) and the membrane electrode assemblies for fuel cells. All ion-conducting membranes suffer from the fact that only a tiny fraction of counter-ions participate in conduction, and the proposed research directly addresses boosting the conducting ion content. (2) Materials development in the energy field is expected to play a very important role in the future of the United States economy and way of life. (3) Graduate students trained in this "energy materials" arena will be in enormous demand in both US industry and academia for at least the next ten years. Penn State has superb undergraduates and research motivates them to attend graduate school (15 of 25 undergraduate researchers in the PI's group over the past 14 years have gone on to graduate school in science and engineering) with many current undergraduates interested in "energy materials", including current REU-funded student Daniel King, a Materials Science and Engineering junior who has won our department's Undergraduate Research Fellowship for three consecutive years.