ABSTRACT The practical deployment of sodium metal batteries (SMBs) is severely plagued by an unstable solid electrolyte interphase and dendritic sodium growth. This work proposes a spatial confinement polymerization strategy utilizing an MgF 2 ‐functionalized glass fiber (MgF 2 /GF) skeleton to construct high‐performance gel polymer SMBs. Unlike corrosive soluble initiators, the immobilized MgF 2 Lewis acid triggers a heterogeneous “grafting‐from” polymerization of 1,3‐dioxolane precisely within separator pores and at interfaces. This spatial regulation yields a heterogeneous electrolyte and a conformal electrode‐electrolyte interface, extending the oxidative stability window to 4.44 V vs. Na/Na + . Beyond catalysis, the multifunctional MgF 2 /GF framework tailors both ion kinetics and interfacial chemistry by preferentially anchoring TFSI − to boost the Na + transference number to 0.75 and constructing a fluorine‐rich, sodiophilic interphase reinforced by in situ formed metallic Mg. This synergistic design effectively suppresses dendritic growth and alleviates concentration polarization. Na || Na cells demonstrate stable cycling for over 1000 h at 0.1 mA cm −2 , while Na || Na 3 V 2 (PO 4 ) 3 full cells retain 89.0% capacity after 1000 cycles at 2 C. Remarkably, practical pouch cells operate stably for over 3500 cycles. This work presents a scalable, separator‐centric engineering approach for safe and high‐energy‐density SMBs.
Chen et al. (Sun,) studied this question.