Tackling issues of lithium metal anodes with a novel polymeric lithicone coating

Abstract

The LiTEA MLD coating showed exceptional protective effects on Li electrodes during long-term Li-stripping/plating cycles, i.e.,remarkable suppression of Li dendrites and SEI formation. • A novel polymeric lithium-containing triethanolamine is developed via molecular layer deposition. • This polymeric lithicone is electronically insulating and ionically conductive. • This lithicone as a surface coating can well protect lithium metal from corrosion and lithium dendritic growth. • Lithium metal anodes protected by this lithicone can greatly boost battery cells’ performance. • This study provides a new solution to tackle the issues of lithium metal anodes. Lithium metal (Li) has been hindered from as anodes in commercial batteries for over 50 years, due to two main issues: continuous formation of solid electrolyte interphase (SEI) and lithium dendritic growth. In this work, we report a new strategy to tackle these issues, i.e., using molecular layer deposition (MLD) to grow an ionically conducting but electrically insulating polymeric lithicone coating, an Li-containing triethanolamine (LiTEA). Our electrochemical tests revealed that this LiTEA coating could serve as an exceptional protection layer over Li anodes. Consequently, the LiTEA-coated Li electrodes could achieve a superior cyclability of > 10000 Li stripping/plating cycles at a current density of 5 mA cm −2 and a long cyclability of > 5500 cycles at 2 mA cm −2 in Li||Li symmetric cells without failures, under a fixed areal capacity of 1 mAh cm −2 . Characterizations using scanning electron microscopy and X-ray photoelectron microscopy verified that Li + ions could be easily extracted through and deposited under the LiTEA coating during the stripping/plating processes. Consequently, this LiTEA coating significantly inhibited the formation of SEI and Li dendrites. This underlies the long cycling lifetime of the LiTEA-coated Li||Li cells. Coupling with the nickel-rich LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) cathodes, more encouragingly, the LiTEA-coated Li anodes could remarkably extend the cyclability and sustainable capacity of the resultant Li||NMC full cells. We also demonstrated that the performance of Li||NMC cells could be further improved through combining an LiTEA-coated Li anode with an Li 2 S-modified NMC811 via atomic layer deposition (ALD). Thus, this study is inspiring for developing high-energy Li||NMC lithium metal batteries.

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