锂离子电池三维多孔等级结构化硅碳纳米杂化负极的研究

The properties of materials depend upon their composition and structure, and can be engineered or modified by specifically designed processing. The elaborate assembly of nanoscopic active components for lithium-ion anodes into macroscopic materials and complete exertion of their unique properties in practical applications are significantly important for developing high-performance lithium-ion batteries used in many fields ranging from electric vehicles to energy storage for many types of intermittent renewable energy sources. This project will target potential utilization of nanoscale assembly techniques in lithium-ion batteries, propose to assemble a kind of new silicon-carbon nanohybrids with a three-dimensional hierarchical porous structure at the molecular level or nanoscale, and realize the low-cost large-scale synthesis of these silicon-carbon hybrid anodes for lithium-ion batteries while simultaneously endowing them with uniform, stable, and tunable structures from both the macro and micro perspectives. The project will systematically investigate the effects of component, structure, and morphology of these nanohybrids on their electrochemical properties, disclose the correlation between size, dimensionality, structure, and electrochemical properties of the silicon component in these nanohybrids, and establish the structure-property relationships of these three-dimensional hierarchical porous silicon-carbon nanohybrids. A series of optimizations on components and structures of nanohybrids will be further carried out to not only effectively accommodate the large volume change of silicon during lithium ion insertion and extraction processes, but also greatly improve electron and ion transport in the electrodes. Finally, the above studies will induce the demonstration of a kind of high performance silicon-carbon nanohybrid-based lithium-ion anode prototype with both high specific capacity (>2000 mAh/g) and excellent cycling stability (>500 cycles) at high charge/discharge current densities, which may build a substantial scientific platform for applied study of next-generation low-cost high-performance lithium-ion anodes composed of silicon and carbon nanomaterials.

将纳米级锂离子电池活性电极材料组装成具有特定结构的宏观体并使其特性在宏观应用中得以充分发挥对发展高性能锂离子电池具有极其重要的意义。本项目探索纳米组装技术在锂离子电池领域的应用，提出从分子水平和纳米尺度上组装一类全新的三维多孔等级结构化硅碳纳米杂化材料，实现在宏观和微观上结构均一、稳定和可调控的锂离子电池硅碳纳米杂化负极的低成本规模化制备；系统研究和深入探讨这类硅碳纳米杂化负极的组分、形态和结构对其性能的影响，阐明硅组分的尺寸、形态和结构与其性能间的关系，建立三维多孔等级结构与其性能间的相关关系；通过对三维多孔等级结构的优化，在有效缓解硅材料体积变化效应的同时，改善电子和锂离子在电极中的输运，开发一种在高倍率充放电条件下具有高比容量（>2000 mAh/g）和高循环稳定性（>500次）的硅－碳纳米杂化电极结构原型，为新一代低成本高性能锂离子电池硅基负极的实用化研究奠定科学基础。

如何解决硅在充放电过程中其体积变化导致的结构、表界面及电荷传输等不稳定性问题一直是锂离子电池硅负极研究领域的难点。本项目探索了纳米组装技术在硅负极领域的应用，结合化学溶液法和化学气相沉积法从分子水平和纳米尺度上组装了系列全新的三维多孔等级结构化碳硅纳米杂化材料，包括石墨烯包裹的硅纳米线、石墨烯分层次包裹的硅纳米线、石墨烯/碳纳米管/硅纳米线三元杂化材料、管中线结构碳硅纳米杂化材料、织构化碳硅杂化纳米线阵列，实现了该类杂化材料在宏观和微观上的结构调控;研究了杂化材料的充放电行为及其在电化学反应过程中的结构及表界面衍变，建立了碳硅两相间的高效结合机制；基于对该类材料结构衍变的分析及电化学储锂性能的系统研究，阐明了该类材料三维多孔等级结构化对其电化学储锂性能的影响，建立了材料结构性能间的相关关系；基于项目发展的一维/二维杂化、自适应壳层构筑、管中线结构化及纳米级系统工程等新型设计策略和组装方法，通过对材料组分、结构及形态的系统优化，制备了多种具有高比容量和优异循环稳定性的碳硅纳米杂化结构材料及电极原型。上述原创性研究为进一步发展高性能实用性锂离子电池硅负极奠定了基础。本项目于2014年12月底顺利完成，截至2015年2月，已在Nano Lett.，Adv. Mater.，ACS Nano，Small，Nanoscale等杂志共计发表SCI论文8篇，包括综述论文2篇，影响因子大于10的论文3篇，已被引用150余次，其中关于自适应壳层构筑的论文已被引用60余次，关于管中线结构化和纳米系统工程的论文被J. Power Sources主编Yang-Kook Sun教授在国际著名刊物Mater. Today上重点介绍；申请国家发明专利2项；1名研究生获2013年度国家奖学金。