Protection of Li-metal anode by surface coating to enhance the cycling performance of Li-S batteries

锂硫电池的性能取决于正极和负极发生的界面过程。例如，在锂金属阳极上形成的表面层已知会影响电池的动力学、容量和整体性能。液体电解质和金属电极之间的界面反应限制了循环寿命、电压窗并导致电池退化。此外，锂金属的苔藓状和树枝状生长发生在重复的锂剥离/电镀过程中，造成热失控事件的风险，影响电池的安全性。分子气相沉积（MVD）是一种可以在各种基底上沉积非常薄（几纳米）和保形薄膜的涂层技术，包括与电化学应用相关的金属箔。这种薄膜的化学性质和厚度可以根据特定的基材和应用进行调整和定制。例如，在金属阳极的情况下，薄膜可以设计成这样一种方式，以减轻电极/电解质界面的寄生副反应，并适应体积变化，有助于保持电极的机械完整性。该项目的目的是利用MVD的能力和灵活性来生长符合复杂衬底（如锂金属阳极）的功能薄膜。特别是，重点将放在具有特殊设计功能的有机和混合有机无机聚合物的保护涂层的生产上。提出的研究成果是多方面的，包括(1)建立对定制表面涂层对锂金属阳极电化学和机械性能影响的基本理解，(2)开发高性能锂电池的功能涂层及其沉积方法，(3)扩大MVD技术在储能设备领域的应用，(4)提供解决方案并提高OXIS Ltd锂电池的循环寿命。

The performance of Lithium-Sulphur batteries is dependent on interfacial processes occurring at the positive and negative electrodes. For example, the surface layers that form on the Li-metal anodes are known to affect the kinetics, capacity and overall performance of batteries. Interfacial reactions between the liquid electrolyte and the metal electrodes limit cycle life, voltage window and cause battery degradation. Furthermore, mossy and dendritic growth of Li-metal occurs in the repetitive Li stripping/plating process creating the risk of thermal runaway events, compromising battery safety. Molecular vapor deposition (MVD) is a coating technique which can deposit very thin (few nm) and conformal films on a variety of substrates including those relevant in electrochemical applications such as metallic foils. The chemical nature and thickness of such films can be tuned and tailored for the specific substrate and application. For instance, in the case of metal anodes, the films can be designed in such a way to mitigate the parasitic side reaction at the electrode/electrolyte interface as well as accommodate the volumetric changes helping to maintain the mechanical integrity of the electrode. The aim of the project is to exploit the capability and flexibility of MVD to grow functional thin films that conform to complex substrates such as Li-metal anodes. In particular, the focus would be on the production of protecting coatings of organic and hybrid organic-inorganic polymers with ad-hoc designed functionalities. The outcomes of the proposed research are multiple and include (i) building a fundamental understanding of the effect of tailored surface coatings on electrochemical and mechanical properties of Li-metal anodes, (ii) to develop functional coatings and their deposition methodology for high performance Li-S batteries, (iii) to widen the applications of MVD techniques to the field of energy storage devices and (iv) provide solutions and improve cycle life of OXIS Ltd Li-S batteries.