高性能金属锂负极的人工SEI保护膜研究

Recently, rapid development of portable electronic devices and electrical vehicles sets an even higher demand of lithium secondary battery, which makes an upsurge of the study of lithium metal batteries with high capacity and long cycling life. However, the lithium dendrite and dead lithium formed during charging-discharging significantly deteriorate the cyclability as well as safety, and therefore the commercialization of lithium metal batteries. It is found that the main factor that determines the performance of lithium metal anode is the SEI layer and how to stabilize the SEI would be the key to promote the electrochemical property of lithium metal battery. Aimed at the above problems, this project intends to prepare Al2O3 and TiO2, which are ion conductor and electron insulator at the same time, as the artificial SEI protecting layer; meanwhile, void space is introduced into the electrode to accommodate the huge volume change and stress in the substrate during the plating and stripping process of lithium metal. Finally, the Al2O3(TiO2)|Li|Cu composite was prepared and its structure was tuned and optimized to maximum the capacity and cycling life. Based on the in-situ TEM and Raman observation, our study reveals the capacity degradation mechanism of the Al2O3(TiO2)|Li|Cu composite as the lithium metal anode, which would provide theoretical foundation of the development of lithium metal batteries with high power density, energy density and overall safety.

近年来，便携式电子设备及电动车的高速发展对锂二次电池的性能提出更高的要求，从而激发了新一代高比容、长循环寿命的锂金属电池负极材料的研究热潮。然而充放电过程中的“锂枝晶”和“死锂”问题，会带来金属锂电池循环性和安全性的不足，成为其商品化的瓶颈。研究表明，影响金属锂负极性能的主要因素是表面的SEI膜；如何使锂金属表面SEI膜更好 “稳定化”，是提高其电化学性能的关键。因此本项目选用锂离子导体、电子绝缘体Al2O3和TiO2作为锂金属的人工SEI膜，并在电极中引入孔隙，来缓冲金属锂沉积-溶解反应巨大的体积变化和内应力。最后制备出Al2O3(TiO2)|Li|Cu复合结构的负极，并对其进行结构调控和优化，从而获得高比容、长循环寿命。通过原位TEM和Raman观测，揭示Al2O3(TiO2)|Li|Cu复合结构的负极容量衰减机制，为新型锂金属电池在大功率、高容量以及整体安全性的重大突破提供研究基础。

近年来，便携式电子设备及电动车的高速发展对锂二次电池的性能提出更高的要求，从而激发了新一代高比容、长循环寿命的锂金属电池负极材料的研究热潮。然而充放电过程中的“锂枝晶”和“死锂”问题，会带来金属锂电池循环性和安全性的不足，成为其商品化的瓶颈。研究表明，影响金属锂负极性能的主要因素是表面的SEI膜；如何使锂金属表面SEI膜更好 “稳定化”，是提高其电化学性能的关键。围绕此问题，本项目选用锂离子导体、电子绝缘体Al2O3和TiO2作为锂金属的人工SEI膜，并在电极中引入孔隙，来缓冲金属锂沉积-溶解反应巨大的体积变化和内应力。最后制备出Al2O3(TiO2)|Li|Cu复合结构的负极，并对其进行结构调控和优化，从而获得高比容、长循环寿命。通过原位TEM和Raman观测，揭示Al2O3(TiO2)|Li|Cu复合结构的负极容量衰减机制，为新型锂金属电池在大功率、高容量以及整体安全性的重大突破提供研究基础。相关结果发表在相关领域国际知名杂志上，迄今为止，以通讯作者和第一作者发表高水平论文（影响因子大于十）10篇，包括2篇Energy Environ. Sci.，1篇Nat. Commun.，1篇Adv. Mater.，1篇Adv. Energy Mater.，1篇Nano Lett.，3篇Nano Energy等。