A Non-Expendable Leveler as Electrolyte Additive Enabling Homogenous Lithium Deposition.

Li metal anodes have been extensively studied owing to their unparalleled advantages in achieving high energy density. However, safety issues originating from dendritic Li growth are always a huge hindrance for applications in Li metal batteries (LMBs). In this study, a functional additive, 4,6-dimethyl-2-mercaptopyrimidine (DMP), which is a typical leveler in the copper electroplating industry, was selected to suppress Li dendrite formation. Various Li-metal-based batteries were systematically investigated and they showed stable performances, such as excellent cycling stability above 800 h at 3 mA cm in Li||Li cells and 400 cycles with high coulombic efficiencies (CEs >98%) at 1 mA cm in Li||Cu cells. Furthermore, a comprehensive verification of the protective mechanism induced by the DMP leveling agent showed that the leveler updated the Li solvation structure and occupied the inner Helmholtz plane of the Li anode. The planar DMP molecular layer absorbed on the surface of the Li metal could suppress side reactions and modified the Li deposition behavior via steric hindrance, inducing homogeneous Li deposition. Interestingly, the DMP leveler did not participate in the formation of the solid electrolyte interphase. This study can stimulate further ideas on non-depleting but effective levelers as electrolyte additives for high-performance LMBs. This article is protected by copyright. All rights reserved.