固态锂金属电池的负极改性及纳米结构电极/电解质界面研究

For the application of military power supply with good safety and high energy density, it is highly required to investigate solid state battery technologies and their interface modification strategies in order to achieve long cycling life, safety and reliability. In this project, we intend to explore the nano-technologies to fabricate air-stable garnet LLZO solid electrolytes, and then to design and construct the nanostructured interfaces based on LLZO electrolytes. The nano-engineering in the solid state architecture is expected to overcome the propagation of Li metal dendrites. .We will develop the molten salt method and high energy ball-milling technology to synthesize nano-grains of LLZO, and to decrease the temperature for cation/anion doping, solid solution process and grain boundary wetting. These means are expected to improve the ionic conductivity of LLZO and achieve stable Li plating and stripping at anode. .We will modify the nanostructured interfaces between LLZO electrolytes and Li metal anodes, and construct two-dimensional, three-dimensional and porous solid electrolyte interfaces for better lithiophilicity and Li-injection, as well as soft heterogeneous interfaces based on interactive polymer. The detailed methods to decrease interface resistance and improve cycling energy efficiency will be studied. .We will investigate the chemical reaction, expansion rate, stress and microstructure of the interfaces between anode and LLZO especially during electrochemical process. We will also study the evolution of Li electrode and its interface and their influence on battery safety during cycling.

针对高安全性和高比能军事电源的重大需求，需迫切研究安全可靠的固态锂金属电池技术及其界面改性策略，本项目拟通过探索空气稳定的石榴石型氧系固态电解质（LLZO）的纳米化制备，并构建基于LLZO的纳米结构界面，以抑制负极锂金属枝晶的蔓延。通过熔盐法和高能球磨法等手段合成LLZO纳米颗粒，降低掺杂、固溶、晶界浸润的实现温度，提升其离子导电率和对于负极锂金属的稳定沉积/剥离。改性锂金属负极与石榴石型氧系固态电解质的纳米结构界面，构筑二维、三维多孔、基于交互聚合物的亲锂固态电解质界面，研究降低界面阻抗和提高循环能量效率的方法。研究石榴石型氧系固态电解质与负极界面的化学反应、膨胀率、界面应力和界面结构，研究金属锂电极和界面在电池循环过程中的演化对安全性的影响。

大规模电网静态储能和电动汽车移动储能对电池的能量密度、安全性和成本提出了更高的要求，本项目针对氧化物和聚合物固态电解质的界面设计展开研究，着重围绕用于固态锂金属电池的液态金属和共晶合金的界面结构设计、二维和三维聚合物填料的界面构筑、特种超薄缺陷涂层和MOF衍生涂层体系开发等方向取得了系列进展。（1）提出陶瓷基固态电解质界面的脆化-碎化机制，发展出碳酸锂亲附缔合的界面改性模式，避免了钝化层消除或电解质倍加呵护的额外复杂步骤，极大改善了陶瓷基固态电池在常规环境中的可操作性。提出“共晶合金诱导固固对流”模式改性LLZO/Li界面的思路，实现了固固界面在电化学过程中的高度愈合，成功驱动了转换反应型FeF3正极在陶瓷基固态电池体系中的高可逆循环。（2）提出“硬质”C-N聚合物介孔微球堆垛填充策略，加强了“软质”PEO基电解质对锂负极的形变抑制，通过与PEO-LiTFSI的多尺度成键交联，构建出具有“渗流效应”的丰富高导界面。研制出聚合增强型的锂氟转换全固态电池，实现了氟基正极循环过程中转换反应产物的空间限域和溶解抑制效应，突破了转换型全固态电池的高倍率和长循环性能瓶颈，为发展高安全、高能量密度的柔性氟基固态电池提供了技术方向。（3）提出锂金属电池负极的超薄缺陷聚合物涂层、MOF衍生多孔涂层、液态金属双向合金涂层的设计策略，调控出锂金属的纳米织构电镀和选择性包裹沉积模式，发现了鲁棒异质性可诱导锂镀层二维薄层化的新现象。通过设计合成内置亲锂种子的MOF衍生中空胶囊，提出可使锂金属接续诱导成核-限域生长的双调控机制，这一内注射式传质过程被透射电镜成像技术成功监控。