三维有序大孔径介孔SiOx/C复合微球的可控制备及其锂电池性能

SiOx has been considered to be one of the most promising anode materials with high specific capacity for practical application. However, some inherent problems, such as their poor electron conductivity, the large volumetric expansion upon lithiation, and the formation of inert Li2O and silicate products, greatly limited their application as anode materials. To solve these problems, this project will provide a novel concept to design the mesoporous SiOx/C anode materials with three-dimensionally ordered large-pore structures for lithium batteries. The three-dimensionally ordered large-pore mesoporous structures could efficiently accommodate the volume expansion of SiOx with a high content. The in-situ formed grid SiC coating on the mesopore wall via magnesiothermic reduction could maintain the structural stability of SiOx/C microspheres. An efficient method for prelithiating SiOx/C anodes based on the facile self-discharge mechanism will also be developed through using the safe and cheap Li-contained cathode materials as the lithium sources. On the basis of the controllable synthesis of mesoporous SiOx/C microspheres with high electrochemical performances, the corresponding fundamental science will be researched thoroughly. The main research contents are including: the control mechanisms of three-dimensionally ordered large-pore mesoporous structures; the structure-performance relationships of the three-dimensionally ordered large-pore mesoporous structures. The intrinsic structure benefits of the three-dimensionally ordered large-poremesoporous structures could provide new implications for designing advanced SiOx-based anode materials for lithium batteries.

SiOx材料是一种非常有应用潜力的高比容量锂电池负极材料。然而，由于SiOx具有电导率差、放电时体积膨胀大、惰性产物Li2O及锂硅酸盐易生成等缺陷，使得以其为负极材料的锂电池存在可逆容量低、首次库伦效率低和循环性能差等核心问题。因此，本项目拟构筑一类新颖的、具有三维有序结构和较大介孔孔径的SiOx/C复合材料来解决上述问题。通过利用其大孔径的三维有序介孔结构来充分容纳SiOx放电过程中的体积膨胀；通过镁催化原位形成坚硬的SiC框架以提高材料的稳定性，同时优化SiOx物相状态；以安全便宜的含锂正极材料为锂化剂，利用简单高效的自放电方法对SiOx进行预锂化处理，从而制备高性能SiOx基复合负极材料。在此基础上，阐明三维有序大孔结构的形成机制，发展简单高效的电极材料预锂化技术，建立SiOx基负极材料结构与电化学性能的构效关系，进一步确立硅基负极与高容量硫正极的匹配性原则。

金属锂由于其高理论容量（3860 mAh g-1）和低电化学电位（-3.04 V vs 标准氢电极），被认为是下一代电池技术最理想的候选材料之一。然而，目前锂金属负极存在i）锂金属的电沉积过程在热力学上倾向生成枝晶状锂ii）不可控的锂枝晶容易刺穿隔膜，造成电池内部短路引发安全问题iii）锂金属负极循环过程中会发生巨大的体积变化，使得SEI膜无法稳定覆盖其表面，导致SEI膜要持续形成、电解液被不断消耗，从而降低电池的库伦效率和循环寿命等几个关键问题。这些严重阻碍了锂金属电池（包括全固态锂金属、锂硫和锂空电池等）的产业化应用。.针对这些问题，本项目利用两亲性嵌段共聚物和阳离子表面活性剂在水/油溶液中的协同自组装，通过“软模板法”，成功制备了一系列具有大孔径的新型介孔复合结构，探索了材料结构的形成机理以及其在锂/钠离子及锂金属电池中的电化学性能。主要进展包括：成功合成了一种氮掺杂的双壳层空心碳球（N-DHMCSs），得到高能量密度的锂离子电池；设计并制备了高吡咯/吡啶氮掺杂的介孔核-微孔壳碳球，提高样品赝电容贡献率，得到高能量密度的钠离子电池；通过在商业碳布（CFC）上原位生长和碳化ZIF-67纳米片，制备了三维多孔Co3O4嵌入和氮掺杂的多孔碳纳米片阵列（CFC/Co3O4-NC），可显著缓解锂金属体积膨胀；进一步将“三明治”多孔结构普鲁士蓝/氧化石墨烯修饰在隔膜表面，从而实现锂离子快速均匀传输等。.这些研究为实现锂/钠离子电池及锂金属电池的长循环寿命和高倍率性能提供了理论基础。同时，在Advanced Energy Materials、Energy Storage Materials、Journal of Materials Chemistry A等期刊发表论文22篇，培养博士研究生5名、硕士研究生3名。