Lithium metal is being extensively studied as an anode to replace graphite due to its high capacity and the lowest negative electrochemical potential. Current research focus is to mitigate lithium dendrite growth and to increase coulomb efficiency during electrochemical cycling by using various surface coatings, electrolyte additives. In addition, a 3D host can be beneficial due to the reduced volume change.

We have recently focused on designing interfacial chemistries that enable dendrite free cycling. In this regard, we report the synthesis of lithium methyl carbonate, a known compound in common anode SEI, via a simple one step reaction. This reaction is used to coat Li or Cu with a protection layer of pure LMC, which is supported by the cryo-TEM observations.¹ This coating layer is shown to enable dendrite free Li cycling in a symmetric Li||Li cell even at a current density of 3 mA cm^-2.² Moreover, FIB-SEM shows this LMC coating layer loses thickness once it is transferred into EC/DMC, which reveals that it dynamically dissolves into the carbonate electrolyte. In order to enhance the sustainability of the LMC coating layer in commercial electrolytes, LMC powder is used to pre-saturate the organic electrolyte. As a consequence of the two strategies, the Li cycling CE in a commercial carbonate electrolyte is significantly improved from 90.5% to 96.1%. These findings provide new insights on designing effective protection layers and managing sustainable SEI formation for stable Li cycling. Recently, we have extended the one step reaction approach to the formation of a polymer gel electrolyte which enables the Li/Li cell cycled for 1000 hours without increase of resistance at a current density of 5 mA cm⁻². Finally, we will discuss recent progress on a novel 3D electrode design that enables dendrite free and high coulombic efficiency of Li metal cycling in carbonate electrolytes.

Acknowledgements

This work was supported by the Office of Vehicle Technologies of the U.S. Department of Energy through the Advanced Battery Materials Research Program (Battery 500 Consortium) under Contract DE-EE0007764. Part of the work used the UCSD-MTI Battery Fabrication Facility and the UCSD-Arbin Battery Testing Facility.