Alloying Indium Additive Enables Fast-Charging Lithium Metal Batteries

Energy-dense lithium metal batteries (LMBs) are limited by safety risks and electrode degradation from dendritic lithium plating. To reap the benefits of lithium metal’s high theoretical capacity (3780 mAh g –1 ), forming an ionically conductive and electronically insulating protective layer that prevents dendritic lithium plating is crucial. Here, we investigate the synergistic combination of a Li–In alloy and a nitrate-derived protective layer resulting from an In(NO 3 ) 3 electrolyte additive. The protective layer was chemically characterized with time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS), revealing the composition of the mechanically stable and ionically conductive Li–In alloy, LiN x O y, Li 2 O, and Li 3 N. Protected Li||Li cells exhibit dendrite-free cycling at 2 mA cm –2 for 495 cycles and 10 mA cm –2 for 175 cycles. Li||LiFePO 4 (LFP) cells retain a stable capacity of ∼130 mAh g –1 at C/2 for 250 cycles while achieving an average Coulombic efficiency of >99.97%.