碱金属负极的枝晶控制与表界面问题研究

Next-generation rechargeable batteries with high energy densities are the most important cutting-edge science and technology. Among various candidates, rechargeable alkali metal batteries using alkali metal (Li, Na, K, etc.) as the anode are most promising. The major issues hindering the application of these rechargeable metal batteries include the uneven alkali metal plating/stripping and the side effects between alkali metal and electrolytes. In this project, we will apply in-situ and ex-situ characterization methods and techniques, as well as molecular dynamics based DFT computation, to systemically study the alkali metal dendrite suppression and interface protection on the alkali metal anodes in rechargeable metal batteries which using chalcogen elements (S, Se, etc.) as the cathodes. We will systematically investigate the electrochemical plating/stripping behaviors, the evolution of interfacial chemical composition and structures, and the electrochemical dynamics on the alkali metal anodes, which are modified in various ways, various discharge/charge modes, various electrolyte systems, and a wide temperature range. On this basis, we will propose novel methods to control the alkali metal plating/stripping, develop new techniques for surface protection of alkali metal anodes, and finally solve the cycling and safety problems facing rechargeable metal batteries. This project will lay a solid foundation for the key science and techniques of the next-generation rechargeable batteries with high energy density and will help China to keep the advanced level in international study for electrochemical energy storage.

下一代高能量密度电池是一种重要的前沿技术，其中以碱金属（锂、钠、钾等）作为负极的可充放金属电池最具应用前景。制约各类碱金属电池发展的主要问题是充放电过程中金属的不均匀析出、粉化及金属负极与电解质间的界面副反应和界面电阻。本项目将利用原位/非原位表征方法和技术，结合理论计算，重点研究在以硫、硒为正极的金属电池中，多种改性方法处理的锂、钠等碱金属负极在不同充放电模式、多种电解质体系及宽温度范围等条件下的电化学沉积/溶解过程，表界面化学组成与结构演化规律，以及固固界面和固液界面的电极过程动力学。在此基础上，提出并优化金属均匀沉积/溶解的方法，发展表面保护的碱金属负极技术以及能稳定界面特性的电解质，解决以碱金属为负极的可充放金属电池面临的循环性和安全性问题，为下一代高能量密度可充放金属电池关键技术发展奠定坚实的科学基础，确保我国继续在先进能源电化学研究中处于国际先进行列。

通过对本项目的实施，我们深入研究了碱金属负极（锂、钠、钾等）在不同电解质体系下电化学沉积和溶解过程、表界面化学组成与结构演化规律，以及电极过程动力学，借助理论计算方法，结合多种先进的原位/半原位表征技术，揭示了金属锂储能过程的微观结构演化规律，建立了金属锂沉积/析出的理论模型；在此基础上，提出了三维集流体结构优化设计、界面化学修饰、亲锂(钠/钾)位点改性等手段调控碱金属的电化学沉积行为，实现了无枝晶、长循环、高面容量碱金属负极的可控制备；针对液态碱金属负极易形成枝晶、短路引发燃烧等安全问题，开发多种高离子电导、低界面电阻的固体电解质/阻燃电解质，研究金属枝晶生长及金属/电解质界面上的化学组成、微观结构、离子输运与碱金属沉积/溶解的热力学与动力学特性；采用了界面梯度固化技术和原位凝胶化技术，为构筑一体化碱金属电池提出技术解决方案；通过构筑异质多层复合固体电解质、转化型纳米氟化界面等方法提升碱金属负极与固体电解质界面稳定性和电化学兼容性，开发出针对固态电池应用的安全有效碱金属负极，为下一代高效、安全、长寿命的高能量密度二次碱金属电池关键技术发展奠定坚实的科学基础。