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

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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.