Separator-free and concentrated LiNO3 electrolyte cells enable uniform lithium electrodeposition

Abstract

Imaging of lithium electrodepositions revealed that in the absence of a compressed porous separator, achieved via a plastic washer, dendrite-free lithium was deposited from glyme solutions of 1 M LiNO₃. When the 1 M LiNO₃ in glyme was coupled with a 1 M LiFSI salt, high coulombic efficiencies were also attainable in both Li|Cu and anode-free LFP|Cu cells. However, dendrite resurgence was observed in cycled lithium coin cell electrodes when a porous separator was utilized. This was attributed to the restriction of Li⁺ flux to the electrode surface induced by the porous and tortuous structure of the polymer separator. At these pores, localized current densities, which exceeded the applied current density, and a non-uniform Li⁺ flux resulted in dendritic lithium growth. Replacement of the separator by a washer normalized the current distribution and provided for non-dendritic lithium deposits in coin cells.