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

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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.