富锂合金对金属锂枝晶的抑制机理研究及合金基柔性复合界面层的构筑

Lithium metal is the ‘Holy Grail’ negative electrode of rechargeable batteries, having the highest theoretical specific capacity and lowest electrochemical potential of all candidates. Alternative approaches that promise higher energy densities such as Li/O2 and Li/S batteries relies on the realization of a stable and safe lithium metal anode. Major problems associated with the lithium metal anode are the dendrites formation, and unstable SEI interface caused by huge volume change on cycling, which are challenging the practical application of lithium metal anode. This proposal intends to overcome these issues by an in-situ formed flexible interlayer on lithium metal, which composed by polymers and lithium-rich alloys that proved to suppress dendrite nucleation in our previous study. We will study the lithium adsorption, diffusion and nucleation properties on the lithium-rich alloys by DFT calculations and interface analysis. This would uncover the mechanism that governs the lithium non-dendritic deposition by the alloy phases. The polymer-alloy interlayer will be synthesized by a one-step process, for which the cyclic ether solvent is polymerized through a Lewis acid ring-opening reaction during the surface alloy process, enabling the interlayer with limited impedance between the polymer and alloy phases. This study will be beneficial to the development of devices using lithium metal as the negative electrode.

锂负极具有理论比容量高、电位低等优点，是实现锂硫电池、锂氧电池等高比能电池的必要条件。然而，金属锂在沉积过程中存在反应活性高、体积变化大及枝晶生长等问题，限制了其在实际电池中的应用。本项目基于申请人关于表面合金化策略抑制枝晶生长的工作积累，拟结合聚合物的高韧性和富锂合金对锂沉积的调控作用，在金属锂表面构筑致密、稳定的柔性复合界面层，抑制锂枝晶生长并缓释体积形变，大幅度提高金属锂负极的循环稳定性。通过密度泛函理论计算和界面化学分析，探索锂离子在富锂合金相的吸附、扩散、成核行为，解析其对锂沉积的调控机理；设计路易斯酸开环聚合环醚的方法，利用合金前驱物的路易斯酸特性，在合金化过程中原位合成聚合物，提高合金相与聚合物的微界面兼容性，降低界面阻抗；设计可靠的电化学滴定方法评价金属锂界面保护层的致密性、完整性。本项目将丰富锂负极界面化学研究，研究结果将有益于以金属锂为负极的器件开发。

锂负极具有理论比容量高、电位低等优点，是实现锂硫电池、锂氧电池等高比能电池的必要条件。然而，金属锂在沉积过程中存在反应活性高、体积变化大及枝晶生长等问题，限制了其在实际电池中的应用。本项目从富锂合金、聚合物分子工程、电解液添加剂、溶剂化结构调控等多个方面展开，研究了对锂金属电沉积行为的影响，解析了锂金属致密、无枝晶生长和稳定循环的关键问题。通过密度泛函理论计算和界面化学分析，探索锂离子在富锂合金相的吸附、扩散、成核行为，解析其对锂沉积的调控机理，制备了稳定的合金-聚合物复合界面层保护的金属锂负极，基于电化学滴定技术，建立了柔性复合界面膜可靠性评价方法。这些研究成果有益于以金属锂为负极的锂硫电池、固态锂电池等器件开发。