Insights on "nitrate salt" in lithium anode for stabilized solid electrolyte interphase

A Li/KNO3 composite (LKNO), with KNO3 uniformly implanted in bulk metallic Li, is fabricated for battery anode via a facile mechanical kneading approach, which exhibits high Coulombic efficiency and prolonged cycle life. The mechanism behind the enhanced electrochemical performance of the "salt-in-metal" composite is investigated, where KNO3 in metallic Li composite electrode would be sustainably released into the electrolyte. The presence of NO3- stabilizes the solid electrolyte interphase by producing functional Li3N, LiNxOy, and Li2O species. K+ from KNO3 also helps to form an electrostatic shield after its adsorption on the electrode protrusions, which suppresses the dendritic growth of metallic Li. With the above advantages, uniform Li plating with dense and planar structure is realized for the LKNO electrode. These findings reveal a deep understanding of the effect of the "salt-in-metal" anode and provide new insights into the use of nitrate additives for high-energy-density Li metal batteries.