Synergistic effects between dual salts and Li nitrate additive in ether electrolytes for Li-metal anode protection in Li secondary batteries

The practical applications of Li-metal batteries (LMBs) are limited by dendrite formation. Thus, a synergistic approach for enhancing the cycling performance of LMBs by combining dual salts with lithium nitrate as an additive in an ether-based electrolyte system is presented. The dual salts, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(oxalate)borate (LiBOB), and lithium nitrate (LiNO3), are dissolved in a dual ether-based solvent composed of 1,2-dimethoxyethane and 1,3-dioxane. The electrolyte shows high electrochemical stability of up to ∼ 4.6 V, circumventing the drawback of ether-based solvents, which are known to exhibit an oxidation potential of <4 V. Moreover, dendrite inhibition is enhanced by the formation of a robust and passivating solid-electrolyte interface (SEI). Additionally, the rate capability and cycling performance are enhanced up to 1000 cycles, with a 90.0% discharge capacity retention at 1C for the lithium iron phosphate (LFP)/Li battery. Furthermore, Li/Li symmetric cells exhibit a high stability with >2300 h of repeated stripping and plating at 0.5 mA cm−2, which is an enhancement of approximately 300% compared with the reference electrolyte. This study provides a promising strategy for the practical application of ether-based electrolytes for Li-metal anodes in rechargeable batteries at low salt concentrations.