超薄二维铝纳米片的高效可控制备及其储锂机制研究

Due to their advantages of high specific capacity, high conductivity, and abundant in resources, Aluminum (Al) based anodes have the advantages in increasing the energy density of lithium ion batteries. However, the volume expansion and pulverization of Al during charging-discharging process leads to the capacity decay, and bad cycling stability. The key to solve this problem is to design and controllable prepare nanoscale Al materials. Ultra-thin two-dimension (2D) nanosheets, with typical thickness less than 5 nm and bending/folding structure in plane, can accommodate the volume expansion and show good cycling stability. However, there are few reports about ultra-thin 2D Al nanosheets because of the difficulty in controllable preparation. This project aims to develop anodes based on ultra-thin 2D Al nanosheets for high performance lithium ion batteries. Firstly, the method for the high-efficient and controllable preparation of ultra-thin 2D Al nanosheets will be developed. Next, the growth mechanism and controlling factors of ultra-thin 2D Al nanosheets under different technique conditions will be studied. Then, the relationship between the morphology/structure of ultra-thin 2D Al nanosheets and the electrochemical performance will be investigated. Finally, the morphological and structural change during the lithium insertion process will be detected and the internal mechanism of the accommodation of volume expansion will be clarified. The studies of this project will provide a viable way for the design and development of new anode materials for novel energy storage systems, such as sodium ion batteries, potassium ion batteries and dual ion batteries.

廉价铝金属负极具有比容量高、导电性好、资源丰富等优势，在提升锂离子电池的能量密度方面具有优势。但是，铝在充放电过程中的体积膨胀粉化问题会导致其容量迅速衰减，循环稳定性降低。解决问题的关键在于设计和可控制备可缓解体积膨胀的纳米结构。超薄二维纳米片具有小于5 nm的典型厚度和平面卷曲褶皱结构，可缓解/容纳体积膨胀，从而实现优异循环稳定性。目前基于铝超薄纳米片负极的研究非常有限，主要瓶颈在于其可控制备困难。本项目拟高效可控制备超薄二维铝纳米片负极材料，并理解和掌握超薄二维铝纳米片的生成原理及其控制因素；然后，建立超薄二维铝纳米片的形貌、结构与电化学性能的构效关系；最后，通过表征电池反应过程中超薄二维铝纳米片的形貌和结构变化，阐明超薄二维铝纳米片在储锂过程中容纳体积膨胀的内在机制。本项目的完成将为钠离子电池、钾离子电池以及双离子电池等新型储能器件负极材料的设计研究提供新思路。

本项目针对铝负极膨胀粉化的问题，开展了基于超薄二维铝纳米片的可控制备技术和电化学性能研究工作。一方面，超薄二维铝纳米片的可控制备技术为自创的单金属辊压法，具有设备工艺简单、制造成本低等优点。本项目通过实验探明了有机隔离层的性状、辊轧制备工艺以及后处理工艺对超薄二维铝纳米片的形貌、结构及表面成份的影响，并阐明了其形成原理和控制因素。通过上述单金属辊压技术获得了厚度范围为3-5nm，片层大小约1 μm的超薄二维铝纳米片。另一方面，针对超薄二维铝纳米片的电化学性质，由于其具有小于5 nm的典型厚度和平面卷曲褶皱结构，可缓解/容纳体积膨胀，因此超薄二维铝纳米片相对原始铝金属具有更优异循环稳定性。进一步地，我们使用类似方法获得了厚度小于5nm的超薄二维锡纳米片，该纳米片具有比锡纳米颗粒更优异的循环稳定性。铝和锡的超薄二维纳米结构的相关研究为开发高性能基于铝，锡负极的锂离子电池提供了有效途径。