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(NO3)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, LiNxOy, Li2O, and Li3N. 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||LiFePO4 (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%.