二元锂合金基纳米结构材料的可控构筑及储锂性能研究

Binary lithium alloys (for example, Li4.4Si, Li4.4Sn and Li3P) with pre-stored lithium exhibit several times higher capacity than lithium metal oxides (for example, LiCoO2, LiMn2O4 and LiNi1/3Co1/3Mn1/3O2). They can work as anode additives to compensate the lithium loss in the initial charge process of lithium-ion batteries (LIBs), and also can be used as anode materials and paired with lithium-free high-capacity cathode materials (for example, S, FeF3 and V2O5) to construct new high-energy LIB systems. This project is mainly focused on the development of binary lithium alloys with good ambient stability, high capacity, good rate capability and long cycle life via nanostructure engineering (for example, microstructure/nanostructure, nanocomposite and surface structure). The effect of component, structure and surface of these materials on the environmental stability and electrochemical performance will be investigated. Meanwhile, the importance of nanostructural design for improving the electrochemical performance of battery materials will be illustrated based on the experimental and theoretical results. The processes of electron conduction and lithium ion diffusion during the charge/discharge processes will be explored and the relationship between the nanostructure and the lithium-storage performance will be clarified. It is expected that this research would provide beneficial guidance and help to achieve high-performance binary lithium alloy battery materials.

二元锂合金LixMy（例如Li4.4Si、Li4.4Sn、Li3P等）具有数倍于锂过渡金属氧化物（例如：LiCoO2、LiMn2O4、LiNi1/3Co1/3Mn1/3O2等）的储锂比容量，可以作为负极添加剂补偿锂离子电池首次充电过程中的锂损失；也可以作为高容量负极材料与不含锂高容量电极材料（例如：S、FeF3、V2O5等）相匹配，构建高比能量锂离子电池新体系。本申请拟从材料微/纳米结构构筑、材料复合、材料表/界面设计等角度出发，研发一系列对环境条件稳定、容量高、倍率好和寿命长的二元锂合金基纳米结构材料，系统研究组分、复合结构、界面结构等对材料环境耐受性及电化学性能的影响，认识纳米结构设计在高性能电极材料中的作用，探索新型纳米结构材料在电化学反应过程中电子传导、锂离子扩散的机理，揭示微/纳米结构、材料复合化、表面修饰与储锂性能的构效关系，实现高性能二元锂合金纳米结构材料的可控制备与应用。

本研究主要围绕着二元锂合金基纳米结构材料的设计、制备和电化学性质展开研究，实现了多种高性能二元锂合金基纳米结构材料的可控制备与电化学性质研究。利用热熔反应法制备出多种锂合金基纳米结构材料，主要包括磷化锂/碳（Li3P/C）纳米复合材料和锂硼合金/锂(Li5B4/Li)纳米复合材料；利用室温合金化反应制备了多种锂合金基纳米结构材料，主要包括锂锡合金/锂（Li22Sn5/Li）纳米复合材料和锂锡合金/锡（LiSn/Sn）纳米复合材料；利用锂锡合金脱锂反应制备了纳米多孔锡箔材料。系统研究了这些材料的组分、复合结构、界面结构等对材料稳定性和电化学性质的影响。相关材料实现了优异的电化学性能，比如由所制备的Li22Sn5/Li纳米复合材料组成的对称电池在电流密度高达30 mA cm-2 和面容量高达5 mAh cm-2下能稳定循环200次，且保持循环过程中极低的过电位（20 mV）。面积容量为1.0 mAh cm-2的LiNi0.6Co0.2Mn0.2O2正极与所制备的Li22Sn5/Li纳米复合负极组装的电池在6 C 下（6.6 mA cm-2）容量保持率为74%。