ABSTRACT High‐voltage sodium metal batteries (SMBs) under wide temperature are fundamentally contingent upon the electrochemical stability of electrode‐electrolyte interfaces. Although carboxylate esters offer a pathway to superior low‐temperature performance, their inherent low oxidative stability presents a major impediment. Herein, a synergistic electrolyte engineering strategy of employing ethyl acetate (EA) with vinylene carbonate (VC) as multifunctional additives is initially pioneered. Despite its weak coordination with Na + , the introduced VC serves as an effective regulator that restructures the solvation shell and preferentially decomposes in synergy with PF 6 − anions, thereby constructing a robust cathode electrolyte interphase (CEI). As confirmed by X‐ray spectroscopies and electronic microscopes, this ultrathin but gradient architecture comprises a flexible but fluorine‐rich organic outer layer and a mechanically robust with ionically conductive inner layer enriched with NaF/Na 3 PO 4 , extending the stability of high‐voltage O3‐type NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NFM) cathode and suppressing transition metal dissolution. Consequently, the NFM||Na cells achieve exceptional performance, demonstrating a capacity retention of 74.6% after 200 cycles under 4.5 V. Even decreasing the surrounding temperature to –20°C, a high capacity retention of 91.3% is achieved, and the NFM||hard carbon full cells maintain the Coulombic efficiency as high as 99.3% over 100 cycles, enabling high‐voltage operation and wide‐temperature tolerance for high‐energy‐density SMBs.
Li et al. (Sun,) studied this question.