Toward the Sustainable Lithium Metal Batteries with a New Electrolyte Solvation Chemistry

Abstract

Herein, a new solvation strategy enabled by Mg(NO3)2 is introduced, which can be dissolved directly as Mg2+ and NO3− ions in the electrolyte to change the Li+ ion solvation structure and greatly increase interfacial stability in Li-metal batteries (LMBs). This is the first report of introducing Mg(NO3)2 additives in an ester-based electrolyte composed of ternary salts and binary ester solvents to stabilize LMBs. In particular, it is found that NO3− efficiently forms a stable solid electrolyte interphase through an electrochemical reduction reaction, along with the other multiple anion components in the electrolyte. The interaction between Li+ and NO3− and coordination between Mg2+ and the solvent molecules greatly decreases the number of solvent molecules surrounding the Li+, which leads to facile Li+ desolvation during plating. In addition, Mg2+ ions are reduced to Mg via a spontaneous chemical reaction on the Li metal surface and subsequently form a lithiophilic Li–Mg alloy, suppressing lithium dendritic growth. The unique solvation chemistry of Mg(NO3)2 enables long cycling stability and high efficiency of the Li-metal anode and ensures an unprecedented lifespan for a practical pouch-type LMB with high-voltage Ni-rich NCMA73 cathode even under constrained conditions.