高性能碳纳米纤维/金属氧化物复合膜"柔性"锂离子电池负极的设计、制备及性能调控研究

With the ever-growing demand for large-scale energy storage applications such as renewable energy and electric transportation, great improvement in high-energy and power-density, cycle life of lithium-ion batteries (LIBs) is urgently needed. There is a general consensus that the breakthrough in performance of LIBs necessarily requires the design and preparation of high-performance binder-free and self-standing flexible electrodes. This project will aim at design and prepare of a series of high-capacity and high-rate, long cycle life, and flexible anode for LIBs by tuning its composition, structure, morphology, size, and/or crystallinity. Based on the obtained experimental results, we will further clarify the reaction mechanism as well as the structure-properties relationship. Furthermore, our proposed free-standing anode will be fabricated using a facile and simple controllable molding process to avoid the use of the binder and metal current collector, and the obtained all-in-one electrode would overcome the instability and low electronic conductivity of the conventional electrode and thus would improve the reliability and performance homogeneity of LIBs. Our project explore a new avenue to design and construct high-performance and low-cost LIBs anode, which may provide a scientific basis for improving the LIBs performance and promoting their research and development.

高性能储能用锂离子电池的研究和开发对解决可再生能源存储和电动汽车续航里程短等问题具有重要的科学意义和实用价值，设计和制备具有高效储能特性、无粘接剂、自支撑的柔性电极是突破其发展和应用瓶颈的有效途径。本项目充分借助和发挥具有优异机械和导电特性的碳纳米纤维和高容量金属氧化物之间的协同作用，挖掘和拓展新颖静电纺丝技术，探索碳纳米纤维/金属氧化物柔性负极的设计、制备和表征方法,通过对电极材料组成和结构设计、纺丝工艺优化、碳纳米纤维导电性能和机械性能调控、电池性能表征等，设计和制备出一系列组分和结构可调，形貌、大小和结晶度可控的高容量、高倍率、长寿命锂离子电池柔性负极，揭示其构效关系和反应机理。此复合电极一体成型，省去了复杂的粉末电极制备过程，可降低成本，提高可靠性。本项目提出的设计和构筑高性能低成本锂离子电池柔性负极的新途径以及一体化设计思想，将为促进储能用锂离子电池的研究和开发提供科学依据。

随着人们环保意识的逐渐增强，环境友好型电动汽车已经成为汽车未来的发展方向。锂离子电池最有可能成为电动汽车的动力电源。然而，商业化的锂离子电池的能量密度和功率密度不能满足要求。解决这一问题的有效办法是寻找高容量、高功率密度的电极材料代替商业化的电极材料。随着研究的不断深入，基于转换反应的电极材料逐渐引起人们关注。这类电极材料可实现多电子转移，提供更高的容量和能量密度。然而，这类电极材料在充放电过程中都存在体积膨胀和导电性差等问题，导致电化学性能较差，阻碍进一步应用。我们通过联合静电纺丝技术和水热方法，成功地将Fe3O4纳米粒子修饰到的TiO2纳米纤维表面，从而得到具有次级复合结构的Fe3O4/TiO2复合材料。由于不同组分及结构的协同效应的存在，复合材料继承了具有高比容量和高导电性的Fe3O4以及具有优异的循环稳定性的TiO2的特性，从而使得复合材料表现出优异的电化学性能；我们又设计合成了三维大孔石墨烯与Fe3O4的复合材料。实验结果表明，这种结构的复合材料也可以有效解决Fe3O4负极材料存在的问题。该材料作为锂离子电池负极材料展现出优异的循环和倍率性能。在4 A g-1的电流密度下，循环470圈后还可以保持980 mAh g-1的可逆容量。并且在20 A g-1的电流密度下，仍然有293 mAh g-1的放电容量，展现了良好的倍率性能，为Fe3O4负极材料的研究提供新的思路。