Hydrogen Bonding Stabilizing Sodium Metal Interfaces: Toward Ultralong-Life, High-Rate, and Heatless...

Severe interfacial instability limits the practical deployment of succinonitrile (SN)-based deep eutectic solvent (DES) in sodium metal batteries (SMBs). Although fluoroethylene carbonate (FEC) has demonstrated effectiveness in mitigating side reactions, the fundamental understanding of FEC-SN interaction mechanisms and the chemical evolution of solid electrolyte interphase (SEI) remain largely unexplored. Here, it is revealed that the C─F···H─C hydrogen bonding between FEC and SN plays a pivotal role in enhancing the stability of SN with sodium metal (Na). Moreover, FEC competitively coordinates with Na⁺ against SN, effectively suppressing SN's coordination tendency while promoting the decomposition of both FEC and anion at the electrode-electrolyte interface. Therefore, the fabricated quasi-solid-state polymer electrolyte (QSPE) based on SN-DES-FEC exhibits excellent electrochemical stability. The quasi-solid-state Na||Na₃V₂(PO₄)₃ (NVP) cells maintain stable operation even at an ultrahigh rate of 120 C (16.17 mA cm^-2), and demonstrate a breakthrough long-term cycling stability even at 50 C (30 °C) within 20 000 cycles, and 3 C (0 °C) within 3000 cycles. More importantly, the pouch cells demonstrate superior safety under mechanical deformation and shear, with only 33% of temperature rise of the conventional liquid batteries during overcharging. This work represents a significant step toward enabling SMBs to operate effectively under high-power and harsh working conditions.