CAREER: Sustainable Solutions for Li-ion Batteries through Cycle-Life Improvements in Nanostructured, 'Green' Cathodes

PI名称：Subramanian，Arunkumar建议ID：1453966电动汽车是减少化石燃料消耗和温室气体排放以满足可持续交通需求的一种替代方案。电动汽车需要充电电池来平衡电能存储和电力输送需求，这些电池必须具有足够的寿命，以降低成本并实现真正的碳足迹减少。此外，电池应该用可持续材料制造，以最大限度地减少对环境的影响。为此，这项研究试图通过提高锂锰氧化物混合物的可持续材料制成的电极的寿命来促进锂离子(Li-ion)电池技术的可持续性。这项研究计划的一个独特方面是研究由单根“纳米线”制成的电池材料，以更好地了解缩短锂离子电池寿命的基本过程。如果成功，这项研究将推进储能技术，以满足未来的清洁能源需求，特别是在交通运输领域。与该奖项相关的教育和推广计划将把研究成果的影响扩展到弗吉尼亚州里士满地区更广泛的STEM教育生态系统。教育活动包括通过纳米研究员研究所和数学科学创新中心(MSIC)的夏季地区总督学校倡议以及里士满工程少数民族地区计划(RAPME)提供的K-12外展计划。这些计划将向学生介绍作为未来科学家和工程师在可持续能源领域产生社会影响的令人兴奋的机会。这一职业奖项的总体技术目标是通过对由可持续锂/锰氧化物复合材料制成的单一嵌入纳米线阴极的重点分析，从根本上了解锂离子电池的内在存储容量。为此，第一个研究目标是测量单个α相二氧化锰(MnO2)纳米线阴极的锂存储容量，其分辨率优于每个主体分子0.03个锂原子。将单根MnO2纳米线进行不同深度的电化学循环，以揭示晶体变化与容量保持之间的关系。第二个目标验证了这样的假设，即在可逆离子插层过程中，通过最小化其主体晶体内发生的结构和电子电导变化，这些插层阴极的本征电容衰减将得到改善。这将通过使用受控的锂掺杂和进一步的氨处理来实现，以通过减轻Jahn-Teller扭曲来稳定主体晶体的2x2隧道结构。实验上，锂/二氧化锰纳米线电池将与纳米机电谐振器集成，通过电化学诱导的质量变化来量化纳米线的锂容量。在这根纳米线上，将以特定的充放电循环次数对其进行四种电化学相关测量：(1)用于表征其微观结构的透射电子显微镜成像，(2)电子电导测量，(3)用于研究纳米机械软化的接触式AFM，以及(4)使用基于原位电子显微镜的动态共振测量的充电容量测量。由于循环容量衰减是不同的电极材料体系以及不同的离子嵌入体系所共有的一种关键失效模式，由此产生的新的科学知识和其他先进的实验能力将有可能超越锂-MnO2体系，并改变未来电化学储能系统的电极设计策略。

PI Name: Subramanian, ArunkumarProposal ID: 1453966Electric vehicles are one alternative for reducing fossil fuel consumption and greenhouse gas production for sustainable transportation needs. Electric vehicles require rechargeable batteries that balance the electrical energy storage and power delivery needs, and these batteries must have a life span sufficient to reduce cost and achieve true carbon footprint reduction. Furthermore, batteries should be manufactured from sustainable materials to minimize environmental impact. Towards these ends, this research seeks to advance the sustainability of lithium-ion (Li-ion) battery technology through life-span improvements of electrodes made from sustainable materials based on lithium-manganese oxide mixtures. A unique aspect of the research plan is to study battery materials made from single "nanowires" to better understand the fundamental processes that reduce lithium-ion battery lifespan. If successful, this research will advance energy storage technology for future clean energy needs, particularly in the transportation sector. The education and outreach programs associated with this award will extend the impact of the research outcomes into the broader, STEM educational ecosystem in the Richmond, Virginia region. Educational activities include K-12 outreach programs delivered through the ?NanoFellows Institute and Summer Regional Governor's School initiatives at the Math Science Innovation Center (MSiC), and through the Richmond Area Program for Minorities in Engineering (RAPME). These initiatives will introduce students to exciting opportunities that exist for delivering societal impact as future scientists and engineers to the area of sustainable energy.The overall technical goal of this CAREER award is to gain a fundamental understanding of intrinsic storage capacity in Li-ion batteries through a focused analysis on single intercalation nanowire cathodes made from sustainable lithium/manganese oxide composites. Towards this end, the first research objective is to measure the lithium storage capacity of a single alpha-phase manganese dioxide (MnO2) nanowire cathode with a resolution better than 0.03 Li atoms per host molecule. Single MnO2 nanowires will be subjected to different electrochemical cycling depths in order to reveal the correlation between crystal changes and capacity retention. The second objective test the hypothesis that the intrinsic capacity fading in these intercalation cathodes will be improved by minimizing the structural and electronic conductivity changes, which occur within their host crystal during reversible ionic intercalation. This will be achieved by the use of controlled lithia-doping and further ammonia treatment to stabilize the 2x2 tunnel structure of the host crystal through alleviation of Jahn-Teller distortions. Experimentally, lithium/manganese dioxide nanowire cells will be integrated with nanoelectromechanical resonators to quantify the lithium capacity of the nanowire through its electrochemically-induced mass changes. Four electrochemically-correlated measurements will be performed on this single nanowire at specific charge-discharge cycle numbers that are spread over its cycle-life: (1) TEM imaging to characterize the microstructure, (2) electronic conductivity measurements, (3) contact-mode AFM to study nanomechanical softening, and (4) charge capacity measurement using in-situ electron microscopy-based dynamic resonance measurements. Since capacity fading with progressive cycling is a key failure mode that is common to diverse electrode material systems as well as to different ionic intercalation systems, the new scientific knowledge and other advanced experimental capabilities, which will emerge from this effort, have the potential to go beyond the lithium-MnO2 system and to transform the electrode design strategies for future electrochemical energy storage systems.