Optimizing Cycling Stability and Coulombic Efficiency of Nanostructured Si-Based Anode

非技术描述：传统的锂离子电池采用碳质阳极，但下一代锂离子电池的预期性能目标需要新的、更高容量的材料，这些材料可以以稳定的方式进行电化学循环。最有吸引力的替代碳的候选者是硅;它具有最高的已知容量，成本相对较低，并且物理上丰富。目前，硅的缺点是体积膨胀约为1000微米。300%发生在Li插入时，这导致循环期间的快速容量衰减。人们正在用纳米级材料和几何结构来追求实现高度可靠电极的创造性方法;已经取得了令人印象深刻的结果，但仍然缺乏基本的理解。 为此，该项目的重点是理解Li从Si中插入和提取的复杂现象，并开发新型纳米结构的Si基阳极，以解决Si阳极的这些关键技术问题。该项目旨在揭示控制Li插入和从Si中提取的复杂现象的基本原理，特别是电化学表面反应，运输，机械响应，和材料演变的基础上紧密耦合的实验-理论研究。结合理论电化学力学，混合有机-无机溶胶-凝胶合成，原位监测与聚焦离子束系统的微观结构的发展，和交流阻抗测量允许系统的探索材料化学的纳米结构的Si基阳极的创建。 通过增强循环稳定性、机械稳定性和库仑效率，这些核-壳纳米结构被设计为表现出卓越的锂离子电池阳极性能。 通过将研究发现与正在进行的和新的教育活动相结合，各级学生（K-12到研究生）将接触到可再生能源的兴奋，包括电动汽车的储能材料系统。跨学科，紧密结合的研究提供了一个独特的环境，为科学家和工程师的新干部谁将成为专家在各自的学科领域，也了解可持续能源的更广泛的背景下的教育;因此，他们将有能力领导一个新的可持续能源的未来设计。

NON-TECHNICAL DESCRIPTION: Traditional Li-ion batteries employ carbonaceous anodes, but projected performance targets for next-generation Li-ion batteries require new, higher capacity materials that can be electrochemically cycled in a stable manner. The most attractive candidate to replace carbon is silicon; it has the highest known capacity, is relatively low-cost, and is physically abundant. At present, the drawback with silicon is that a volume expansion on the order of ca. 300% occurs upon Li insertion that leads to rapid capacity fade during cycling. Creative approaches to realize highly-reliable electrodes are being pursued with nanometer-scale materials and geometric architectures; impressive results have been obtained, but a fundamental understanding is still lacking. To this end, this project focuses on understanding the complex phenomena of Li insertion and extraction from Si, and developing novel nanostructured Si-based anodes which can address these critical technical issues with Si anodes.TECHNICAL DETAILS: This project aims to uncover the underlying principles that govern the complex phenomena of Li insertion and extraction from Si, especially the complex interplay among electrochemical surface reactions, transport, mechanical response, and material evolution based on a tightly-coupled experimental-theoretical research. A combination of theoretical electrochemomechanics, hybrid organic-inorganic sol-gel synthesis, in situ monitoring of microstructural developments with a focused ion beam system, and AC impedance measurements allows a systematic exploration of materials chemistries for the creation of nanostructured Si-based anodes. By targeting enhanced cycling stability, mechanical stability, and coulombic efficiency, these core-shell nanostructures are designed to exhibit unsurpassed performance as Li-ion battery anodes. By coupling research discoveries with ongoing and new educational activities, students at all levels (K-12 through graduate) will be exposed to the excitement of renewable energy including energy storage material systems for electric vehicles. Interdisciplinary, tightly integrated research provides a unique environment for the education of a new cadre of scientists and engineers who will become experts in their disciplinary fields and also understand the broader context of sustainable energy; thus, they will be equipped to lead the design of a new sustainable energy future.