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

LiNO₃ 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 LiNO₃ in carbonate ester-based electrolytes limits applications. In this study, a two-step physical method successfully dissolves 0.1 M LiNO₃ into carbonate ester-based electrolytes without co-solvents (∼10 × higher solubility than conventional systems), where EC disrupts Li⁺–NO₃⁻ interactions and the subsequent mixing with a preformed LiFSI/LiPF₆–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 NO₃^- anions preferentially enter the Li⁺ solvation layer. Therefore, the enhanced SEI layer with LiF, Li_xC, and Li₂O homogenizes lithium deposition. The robust cathode–electrolyte interphase (CEI) composed of NSO_xF_y and LiF supports high-voltage Ni-rich cathodes. Notably, Li||LiNi_0.83Mn_0.06Co_0.11O₂ 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 LiNO₃ in some carbonated ester-based electrolytes for other alkali metal batteries.