Unlocking the Potential of Sparingly Soluble LiNO 3 in Carbonate Electrolytes With Pyridine as a Carrier Cosolvent for 450 Wh Kg −1 High‐Voltage Lithium Metal Batteries

ABSTRACT LiNO 3 is a highly effective electrolyte additive for ether‐based lithium metal batteries, but its extremely poor solubility in carbonate electrolytes has long restricted its application in high‐voltage high‐energy‐density systems. In this study, we develop a pyridine carrier cosolvent strategy to efficiently dissolve LiNO 3 in carbonate electrolytes. Pyridine coordinates with Li + to enter the solvation shell, weakening Li + ‐carbonate interactions to promote LiNO 3 dissolution and enable NO 3 − participation in interphase formation. The coordination effect also suppresses the intrinsic high reactivity of pyridine, realizing its controllable interfacial decomposition. The synergistic decomposition of pyridine and LiNO 3 constructs compact, inorganic‐dominated, rigid‐flexible interpenetrating electrode‐electrolyte interphases rich in Li 3 N, LiN x O y , and LiF with high mechanical strength. Benefiting from the optimized interphases, Li||Cu cells deliver a Coulombic efficiency (CE) of 97.3% at 2 mA cm −2 , and 4.5 V Li||NCM90 cells show outstanding cycling stability under practical thin‐lithium and lean‐electrolyte conditions. Remarkably, 5.6 Ah pouch cells achieve an energy density up to 453 Wh kg −1 with 95.5% capacity retention after 50 cycles. This work offers a facile approach for utilizing sparingly soluble functional additives and promotes the development of high‐voltage, high‐energy‐density lithium metal batteries.