Ten times of LiNO3 solubility increase in co-solvents free ester-based carbonate electrolytes enables 450 Wh/kg lithium metal batteries

• A two-step method dissolves 0.1 M LiNO 3 into carbonate ester-based electrolytes. • MD simulation: negative enthalpy drives LiNO 3 dissolution without co-solvents. • Performance boost is exhibited in Li||Cu, Li||Li, Li||LiNi 0.83 Mn 0.06 Co 0.11 O 2 coin cells. • A pouch cell with 450 Wh kg -1 is fabricated. • Solvation structure–SEI/CEI–performance correlation is studied. LiNO 3 is a promising additive for high-energy-density lithium metal batteries (LMBs) via regulating the solid electrolyte interphase (SEI) layer. However, the extremely low solubility of LiNO 3 in carbonate ester-based electrolytes limits applications. In this study, a two-step physical method successfully dissolves 0.1 M LiNO 3 into carbonate ester-based electrolytes without co-solvents (∼10 × higher solubility than conventional systems), where EC disrupts Li⁺–NO 3 ⁻ interactions and the subsequent mixing with a preformed LiFSI/LiPF 6 –DMC/FEC electrolyte releases part of the coordinated species, increasing entropy, while the remaining solvents/anions stabilize Li⁺ - making the process both enthalpically and entropically favorable. This facile, scalable, cost-effective way is confirmed by theoretical simulation and experimental investigations. With the synergistic effect of 4-fluoro-1,3-dioxolan-2-one (FEC), the NO 3 - anions preferentially enter the Li + solvation layer. Therefore, the enhanced SEI layer with LiF, Li x C, and Li 2 O homogenizes lithium deposition. The robust cathode–electrolyte interphase (CEI) composed of NSO x F y and LiF supports high-voltage Ni-rich cathodes. Notably, Li||LiNi 0.83 Mn 0.06 Co 0.11 O 2 cells retain 82.5% capacity after 300 cycles at 1 C (1 C=200 mA g -1 ) with a 4.3 V cut-off voltage and an 85.5% capacity after 100 cycles at 1 C with a 4.5 V cut-off voltage. Importantly, a pouch cell with 450 Wh kg -1 energy density further demonstrates the practical potential in industry. Additionally, this strategy also demonstrates the potential application of LiNO 3 in some carbonated ester-based electrolytes for other alkali metal batteries.