Intramolecular Polarization-Mediated Solvation and Interphase Engineering for Low-Temperature High-Voltage Lithium...

Simultaneously achieving stable lithium metal batteries (LMBs) under cryogenic and high-voltage conditions remains a fundamental challenge due to uncontrolled interfacial chemistry at lithium anodes and nickel-rich cathodes. Here, we report an intramolecular polarization strategy that jointly regulates Li⁺ solvation dynamics, solid electrolyte interphase (SEI) formation, and cathode electrolyte interphase (CEI) stress dissipation. An intramolecularly polarized electrolyte featuring orthogonally arranged electron donor-acceptor moieties with a dipole moment (∼4.2 D) establishes a potential-dependent solvation screening effect, reducing Li⁺ desolvation energy to 38.1 kJ mol^-1, while enabling anodic stability beyond 5.3 V. The tailored solvation chemistry induces spontaneous formation of dual-gradient interphases composed of a LiF-rich SEI and a boroxane-incorporated CEI with an interface modulus ∼20 nN. Consequently, Li||Li symmetric cells exhibit stable cycling over 16 000 h with a minimal polarization of 8.3 mV. Full cells employing LiNi_0.8Co_0.1Mn_0.1O₂ cathodes retain 90% capacity after 1000 cycles at 4.5 V and maintain 80% at 4.9 V. 3 Ah pouch cells achieve a high energy density of 509 Wh kg^-1 at 30°C with 96.8% capacity retention after 80 cycles, while delivering 439.1 Wh kg^-1 at -30°C. This work establishes a molecular polarization paradigm for electrolyte and interphase engineering toward high-energy-density LMBs under extreme conditions.