Electrolyte tuning with low concentrations of additive for dendrite suppression in lithium metal anodes

Abstract

Lithium (Li) metal is considered to be an ideal anode for high-energy density storage systems. However, its high reactivity and instability towards organic electrolytes leads to continuous consumption of electrolytes and Li metal, causing dendrite growth. This induces safety issues and low cyclability, which hinders its practical use. Although electrolyte additives are extensively utilized to address these issues, the practice remains challenging due to the least understanding of their interactions with electrolytic environments. Here, we report a novel electrolyte additive, gadolinium nitrate (Gd(NO₃)₃), with a low optimal concentration of 3 mM in a lithium bis(trifluoromethanesulfonyl)imide-lithium nitrate (LiTFSI-LiNO₃) ether-based electrolyte; this additive promotes plating/stripping of Li in nodular morphology, significantly suppressing dendrites and dead Li growth while improving the cycle life and overall stability of Li metal batteries. A significant reduction is observed in the Li-metal electrode overpotential under a current density of 2 mA cm⁻². When a Li metal battery was tested with LiFePO₄ (LFP) cathode at an active mass loading of 4 mg cm⁻², a capacity retention of 98.33% was observed after 400 cycles. Such stable cycling and enhanced performance are attributed to the formation of a chemically stable, mechanically robust, and ionically conductive solid electrolyte interphase (SEI) layer on the Li metal surface, which is enabled by the incorporation of Gd(NO₃)₃ compared to cells with pristine Li electrolytes.