Enhanced Solid Electrolyte Interface (SEI) on Li Metal Surfaces through Catalytic Electrolyte Decomposition

Abstract

Lithium metal batteries have seen a rise in attention as the next generation battery is sought. Li metal is considered the “Holy grail” anode material with a high theoretical capacity of 3860 mAh g-1.[1] However, Li metal is unstable during cycling leading to issues with dendrite formation leading to cell short or “dead” Li, and increase in cell impedance due to the excess formation of SEI on the “dead” Li..[2–4] The SEI plays an important role in altering the ion transport which alters the structure evolution of the Li metal anode during repeated cycling. While the understanding of the fundamental properties of the SEI has advanced continuously in recent years, effectively tuning the SEI components, especially the inorganic constituents, is still challenging. In this work, tungsten oxide, WO 3, is found to promote the formation of inorganic salts e.g., LiF/Li2CO3 in SEI layers and thus enhancing the SEI properties allowing for the smoother plating of Li metal. Additionally, WO3 is reduced to W during electrochemical process, the addition of W within the SEI increases the electronic conductivity, reducing the formation of “dead” Li which otherwise is completely wrapped by insulating SEI layers. The possibility of WO3 to catalyze electrolyte decomposition through favored reaction pathway to produce more robust SEI layers is discussed, providing new insights to control the SEI formation on Li metal. Xu, W., Wang, J., Ding, F., Chen, X., Nasybulin, E., Zhang, Y. and Zhang, J.G., 2014. Energy & Environmental Science, 7(2), pp.513-537.Pei, A.; Zheng, G.; Shi, F.; Li, Y.; Cui, Y. Nano Lett 2017, 17, 1132–1139.Wu, B.; Lochala, J.; Taverne, T.; Xiao, J. Nano Energy 2017, 40, 34–41.Aurbach, D.; Zinigrad, E.; Cohen, Y.; Teller, H. J. Solid State Ionics 2002, 148, 405–416.