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，这些材料可以稳定地进行电化学循环。取代碳的最有吸引力的候选者是硅；它具有已知的最高容量，相对低成本，并且物质丰富。目前，硅的缺点是，在锂插入时，体积会膨胀约300%，导致循环过程中容量迅速衰减。采用纳米级材料和几何结构来实现高可靠性电极的创新方法正在被追求；已经取得了令人印象深刻的成果，但仍然缺乏基本的认识。为此，本项目专注于理解锂从硅中插入和提取的复杂现象，并开发新型纳米结构的硅基阳极，以解决硅阳极的这些关键技术问题。技术细节：本项目旨在通过紧密耦合的实验-理论研究，揭示控制从硅中插入和提取锂的复杂现象的潜在原理，特别是电化学表面反应、输运、力学响应和材料演化之间的复杂相互作用。结合理论电化学力学、有机-无机混合溶胶-凝胶合成、利用聚焦离子束系统对微观结构发展进行现场监测以及交流阻抗测量，可以系统地探索材料化学，以创建纳米结构的硅基阳极。通过提高循环稳定性、机械稳定性和库仑效率，这些核壳纳米结构被设计成具有无与伦比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（从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，紧密整合的研究为新一代科学家和工程师干部的教育提供了独特的环境，他们将成为各自学科领域的专家，并了解可持续能源的更广泛背景；因此，他们将有能力领导设计一个新的可持续能源的未来。

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.