基于贝壳状仿生界面层的金属锂负极保护策略研究

Li metal batteries are recently receiving extensive attentions from the academic and engineering communities due to their ultra-high energy density. They are strongly regarded as the next-generation energy storage systems for portable devices and electronic vehicles. However, Li metal batteries are still suffering from severe capacity decay and poor safety performance, which is mainly attributed from uncontrolled dendritic Li growth induced by the unstable interface between Li metal anode and electrolyte. Currently, there is still no effective strategy to stabilize the interfacial film between Li metal anode and electrolyte. The knowledge about growth mechanism and evolution behavior of Li dendrites is still rudimentary.. This project focuses on the composite Li metal anode in its working state. Based on the nucleation and deposition behavior of Li metal, we try to develop a multifunctional shell-like interfacial film with ultrathin thickness, high ionic conductivity and high mechanical strength. Firstly, the in-situ optical microscopy is adopted to find out the diffusion and deposition mechanism of Li metals at the interface of electrolyte and Li metal anode. Based on the evolution behaviors of Li deposits, a composite shell-like interfacial film with ultra-strong mechanical performance is developed to suppress dendrite growth and reduce the adverse reactions between Li metal anode and the corrosive organic electrolyte. This project will present a novel insight into dendrite-free and high Coulombic efficiency Li metal batteries, which is greatly beneficial for the practical applications of high-energy-density Li batteries in the next-generation energy storage systems.

金属锂电池以其高理论能量密度受到学术和产业界的极大关注，有望在便携式电子设备和电动汽车等领域实现应用。但目前金属锂电池还存在严重的容量衰减和安全隐患问题，金属锂与电解质间界面不稳定导致的枝晶生长是电池性能恶化的主要因素。目前，对负极金属锂枝晶的生长机制和演变规律缺乏清晰的认识，无法建立高效稳定的界面以抑制金属锂负极的枝晶生长。.本课题以工作状态下的复合金属锂负极作为研究对象，在充分理解锂金属形核、沉积行为的基础上，拟设计一种超薄、高离子导率和坚韧力学性能的类贝壳结构负极保护层。通过原位光学电镜可视化研究锂离子在电解质/金属锂界面处的锂离子扩散和沉积规律。在此基础上，结合生物质贝壳层的超强硬度和韧性，研究类贝壳结构的复合金属锂界面保护层，保护金属锂负极，抑制枝晶生长，降低副反应，以实现无枝晶生长和高利用率的金属锂电池，推动高能量密度锂电池在下一代储能器件中的应用。

锂离子二次电池以其高能量密度在能源储存技术中占据越来越重要的地位，但传统锂离子电池（尤其是石墨负极）的实际能量密度逐渐接近于其理论极限值，因此迫切需要寻找更加高效的电极材料以满足新兴高端储能器件的发展需求。金属锂电池以其高理论能量密度受到学术和产业界的极大关注，有望在便携式电子设备和电动汽车等领域实现实际应用。但是目前的金属锂电池还存在严重的容量衰减和安全隐患，金属锂与电解质的不稳定界面导致的枝晶生长是电池性能恶化的主要因素。.目前，对于负极金属锂枝晶的生长机制和演变规律还缺乏清晰的认识，对于高效稳定界面的建立还没有系统的设计方法论。基于这样的背景，本项目针对金属锂负极体系开展下列研究：（1）针对对金属锂负极界面行为认识不清晰的难题，结合原位光学显微镜、非原位扫描/透射电子显微镜等表征结果和电池电化学性能分析，获得界面处的锂离子沉积行为和界面演化机制；（2）针对金属锂负极界面不稳定问题，基于对界面行为的理解和认识，设计多种类贝壳的界面膜结构，有效提升了金属锂负极的循环利用率，并匹配多种正极体系，实现了金属锂电池循环寿命的提升；（3）针对金属锂负极枝晶大量生长的难题，提出利用骨架材料设计提升电池性能的策略，并在纽扣和软包电池体系实现了性能验证。