Self-assembled monolayer regulates lithium nucleation and growth for stable lithium metal anodes

Abstract

As the “holy grail” anode material for next-generation lithium batteries, the application of lithium metal has been long hindered due to the uncontrolled dendrites. Organic polymer coatings have shown advantages in regulating the ion diffusion and reducing the surface energy of the substrate, with which large lithium nucleis and better cycle stability can be obtained, whereas the electronic insulation property of the thick polymer is adverse for lithium deposition. Hence, self-assembled monolayers (SAMs) are anchored onto the surface of planar copper via a spontaneous thiol-to-copper reaction to obtain the modified current collectors with lower surface energy. The electron/ion transfer and lithiophilicity of the planar copper are adjusted by changing the length of the alkyl length and the ending groups. Therefore, lithium nucleation and growth behaviors are regulated, and large dough-like nucleis are generated on the planar copper grafted with 3-mercaptopropionic acid (Cu-MPA), displaying a nucleation overpotential of 17.6 mV and a reversible Coulombic efficiency of 98.4 % over 250 cycles (0.5 mA cm−2, 1 mAh cm−2). This strategy provides a new avenue to achieve a stable Cu/Li interface and lithium metal anodes since the very beginning of the lithium nucleation.