硅/新型石墨化碳负极材料的设计构筑及电化学性能研究

Silicon holds great promise as an anode material for next-generation lithium-ion batteries with higher energy density; its implication, however, has been limited by the structural degradation, instability and low initial Coulombic efficiency caused by huge volume change upon cycling. One effective strategy is to construct a layer of conductive shell with adaptable void space, which can effectively accommodate the volume change during cycling. This proposal aims to explore the design and preparation of highly graphitic carbon caging aerosol-assisted assembly of silicon particles in large scale, which will be achieved by in-situ growth using magnesiothermic reduction products as novel template and catalyst. Developing in situ/ex-situ microstructure characterization methods to elucidate the growth process of self-catalytic reaction and the mechanism of structure evolution during charge and discharge cycling. We will focus on investigating the mechanism of structural design of silicon, electrode/electrolyte interface engineering for alleviating volume expansion, especially in the high specific energy lithium ion batteries. Elaboration of the relationship in terms of microscopic structure, electrode/electrolyte interface properties, and lithium storage properties will be discussed systematically, to finally obtain the key technology for the synthesis of silicon anode materials and stable solid electrolyte interphase (SEI) layer on silicon surface. It is believed that the aforementioned technology could provide a theoretical guide and experimental support to develop the next generation superior volumetric energy density, long cycling silicon-based lithium ion batteries.

硅是极具潜力的下一代高能量密度锂离子电池负极材料，硅负极目前面临的主要挑战是充放电循环过程中体积膨胀带来的容量快速衰减以及低的库仑效率。构建一个可缓减体积膨胀空间的导电壳层是有效的解决策略，使硅材料可有效地适应充放电过程中的体积变化。本项目旨在研究一种基于气溶胶喷雾-自催化化学气相沉积法制备高度石墨化结构的新型碳限域包覆硅的新方法，拟采用镁热还原产物原位催化石墨化碳的生长从而实现结构可控的硅碳复合材料的宏量制备。借助原位/非原位及微区结构的表征方法深入阐明自催化反应机理以及循环过程中硅负极的结构演变机制，重点研究硅材料的结构设计、电极/电解液界面调控对于缓解体积膨胀的作用机制，尤其是在高比能锂离子电池中的行为，实现高效稳定硅负极的可控制备以及稳定SEI膜的形成，揭示材料微结构、表界面性质与电化学性能之间的构效关系。为发展下一代高体积能量密度、长寿命的硅基负极锂离子电池提供理论与实验指导。

硅具有高的理论比容量、储量丰富和低成本等优点，硅基负极材料是高比能锂离子电池的重要发展方向。然而，由于合金化反应储锂机制，硅在充放电过程中会发生较大的体积效应，进而引起低的库仑效率以及快速衰减的循环性能。本项目研究了一种基于气溶胶喷雾-自催化化学气相沉积法制备高度石墨化结构的碳材料包覆硅负极的新方法，利用镁热还原反应产物原位催化石墨化碳的生长实现硅碳复合材料的可控制备。在此基础上提出利用脱合金化过程原位生成的金属颗粒对碳的固定或原位生长的创新思想，结合界面修饰策略，构筑了一维纳米管状的硅碳复合材料。从功能材料制备出发，研究CO2化学固碳及高效转化利用，以Mg2Si为前驱体制备了具有类似于珊瑚的管状结构硅碳复合材料。碳均匀包覆及中空结构有效缓减了材料的体积膨胀，提高了硅的库仑效率及循环稳定性能，制备的复合材料表现出了高比容量、快的充放电速率和优异的循环稳定性能。进一步发展了具有高孔隙率、高热阻和对电解液具有良好浸润性的聚酰亚胺隔膜解决硅负极界面稳定性和容量衰减的新方法。借助原位/非原位结构表征方法和理论计算阐明了自催化反应机理、循环过程中硅负极的结构演变和性能衰减机制，深入研究了制备过程参数、界面修饰策略等与材料电化学性能间的构效关系。在材料开发的基础上，研究了硅碳材料为负极，商业化LiCoO2、LiFePO4及高镍三元材料等为正极的新型低成本高比能锂离子电池器件，组装的全电池具有高的首周库仑效率和能量密度。项目实现了高效稳定硅负极的可控制备、表/界面结构调控，为低成本宏量制备具有良好动力学特征的硅碳负极提供了新的解决方案，可为进一步研究和开发提供指导和理论依据。