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

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 LiNi0.8Mn0.1Co0.1O2 (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 Li2S-modified NMC811 via atomic layer deposition (ALD). Thus, this study is inspiring for developing high-energy Li||NMC lithium metal batteries.

Automated summary

A new strategy of using molecular layer deposition to grow a polymeric lithicone coating on lithium metal anodes was proposed to overcome the challenges of continuous formation of solid electrolyte interphase (SEI) and lithium dendritic growth. The lithicone coating effectively prevented the formation of SEI and lithium dendrites, resulting in long cycling lifetime and enhanced performance of Li||NMC full cells.