新型功能化补锂隔膜的制备及应用基础研究

As the extension of continuing voyage ability (for electric vehicles) and standby time (for consumer electronics) becomes an imperative requirement, the developing trend of Li-ion batteries is to improve the energy density. Li-ion battery with high energy density of 300 Wh/kg can be achieved by using NCM and Si as electrode, which is approved both in academic and industrial fields. Since Si based anode suffers from large volumetric changes during charging and discharging process, which leads to the break and formation of unstable solid electrolyte interphase (SEI) layer. The continuous formation of SEI layer incessantly on the fresh Si surface consumes Li ions and electrolytes, resulting in low initial coulombic efficiency and low specific capacity. In this project, we creatively propose the technical route of novel functionalized prelithiation separator. Improve the ICE and initial capacity by introducing additional Li ions through prelithiation method. The simultaneous anionic and cationic redox of iron-based anti-fluorite oxides and the kinetics of transportation of Li ions in the process of prelithiation will be investigated systematically and the prelithiation models of full batteries will be built. The results of this project will provide theoretical basis and technical support for the development and industrial application of NCM-Si based high energy density Li-ion batteries.

通过提高电池的能量密度来增加电动汽车的续航里程及电子设备的待机时间是锂离子电池发展的必然趋势。以高镍三元正极搭配硅基负极是目前学术界和产业界公认的实现300 Wh/kg能量密度的主要技术路线。然而由于硅基材料在充放电过程中体积变化巨大，不断破坏和重建SEI膜，消耗系统中锂离子，导致电池的首次库伦效率和初始容量较低，因而难以实现产业化应用。本项目创造性的提出新型功能化补锂隔膜的制备技术路线，拟通过预锂化技术向电池系统补充额外的锂离子，提高电池的首效和初始容量，进而提高电池的能量密度。系统研究反萤石结构高容量补锂正极充电过程过渡金属阳离子、氧阴离子同时变价机制及功能化补锂隔膜补锂过程中锂离子脱嵌和传输动力学机制，建立全电池体系中补锂模型，为基于高镍三元正极-硅基负极的高能量密度锂离子电池的发展和产业化提供重要的理论基础和技术支持。

通过提高电池的能量密度来增加电动汽车的续航里程及电子设备的待机时间是锂离子电池发展的重要趋势。以高镍三元正极搭配硅基负极是目前学术界和产业界公认的实现300 Wh/kg能量密度的技术路线。然而由于硅基材料在充放电过程中体积变化巨大，不断破坏和重建SEI膜，消耗系统中锂离子，导致电池的首次库伦效率和初始容量较低，因而难以实现产业化应用。针对以上问题，本项目开展了预锂化技术的相关工作，开发了多种补锂技术实现了在高能量密度锂离子全电池和镍钴锰三元和磷酸铁锂正极材料的再生修复中的应用。研究了反萤石结构Li5FeO4、氢氧化锂和草酸锂等作为锂源，通过热力学补锂和化学补锂形式对正极材料晶体结构的修复；开发了适用于大面积生产的功能化补锂隔膜，厘清了多种补锂剂的脱嵌锂和传输动力学机制，实现了在高比能硅基电池中的应用，电池的首次库伦效率和能量密度得到了较大的提升。本项目的研究结果为基于高镍三元正极-硅基负极的高能量密度锂离子电池的发展提供了重要的理论基础和技术支持。