A Simple Way to Stabilize Li and Na Metallic Electrodes Surfaces

Abstract

Post Li-ion technologies such as Li-air, lithium sulphur or all-solid-state batteries have in common the use of lithium metal as negative electrode. Known from decades, dissolution and deposition of lithium induce the growth of inactive lithium moss or more critically the dendritic growth that can lead to short circuit phenomenon. Therefore, researchers try to tackle this problem by adding functional layers at the Li surface that may generate an improvement in capacity, lifetime and performances at high current rates.There are different ways to protect lithium such as ALD inorganic coating1,2, grafting of organic materials3,4,5, polymers6 or deposition of inorganic alloys7,8. In this work, by dip coating (a simple and cheap process) a lithium foil into a solution of glyme with phosphorus trichloride (DME-PCl3), we succeeded in obtaining a thin and protective phosphorus-based layer.Through electrochemical characterization techniques (EIS, GITT in 2 or 3 electrodes) and surface characterization techniques (SEM, and more importantly XPS), we were able to determine its morphology and chemical composition, its influence on the lithium plating and stripping processes and the mechanism of lithium diffusion through the protective layer. Cycling results in lithium symmetric cells but also full cells (Li-ion, Li-S) will be presented.Finally, since our results were very promising with lithium, we extended this type of protection to sodium since the reactivity of this metal with electrolyte is ever more pronounced. With the same methodology, we will demonstrate that our protection nicely improves the use of Na metal in liquid cells. 1 A. C. Kozen and al., Next-generation lithium metal anode engineering via Atomic Layer Deposition, acsnano, 2015, 9, 6, 5884-5892 2 C-F Lin, and al., ALD protection of Li-metal anode surfaces – Quantifying and preventing chemical and electrochemical corrosion in organic solvent, Adv. Mater. Interfaces, 2016, 3, 1600426 3 F. Marchioni and al., Protection of lithium metal surfaces using chlorosilanes, Langmuir, 2007, 23, 11598 - 11602 4 S. Neuhold and al., Effect of surface preparation and R-group size on the stabilization of lithium metal anode with silanes, Journal of Power Sources, 2012, 206, 295 -300 5 S. Neuhold and al., Enhancement in cycle life of metallic lithium electrodes protected with Fp-silanes, Journal of Power Sources, 2014, 254, 241-248 6 Y. Liu and al., Lithium-coated polymeric matrix as a minimum volume-change and dentrite-free lithium metal anode, Nature communications, 2016, 7, 10992 7 X. Liang and al., A facile surface chemistry route to a stabilized lithium metal anode, Nature Energy, 2017, 2, 17119 8 L-L. Kong and al., Lithium-Magnesium alloy as a stable anode for Lithium-sulfur battery, Adv. Funct. Mater., 2019, 29, 1808756 9 L. Lin and al., Lithium phosphide/lithium chloride coating on lithium for advanced lithium metal anode, J. Mater. Chem. A, 2018, 6, 15859