Spatially Confined in Situ Formed Sodiophilic-Conductive Network for High-Performance Sodium Metal Batteries

The sodium (Na) metal anode encounters issues such as volume expansion and dendrite growth during cycling. Herein, a novel three-dimensional flexible composite Na metal anode was constructed through the conversion-alloying reaction between Na and ultrafine Sb₂S₃ nanoparticles encapsulated within the electrospun carbon nanofibers (Sb₂S₃@CNFs). The formed sodiophilic Na₃Sb sites and the high Na⁺-conducting Na₂S matrix, coupled with CNFs, establish a spatially confined "sodiophilic-conductive" network, which effectively reduces the Na nucleation barrier, improves the Na⁺ diffusion kinetics, and suppresses the volume expansion, thereby inhibiting the Na dendrite growth. Consequently, the Na/Sb₂S₃@CNFs electrode exhibits a high Coulombic efficiency (99.94%), exceptional lifespan (up to 2800 h) at high current densities (up to 5 mA cm^-2), and high areal capacities (up to 5 mAh cm^-2) in symmetric cells. The coin-type full cells assembled with a Na₃V₂(PO₄)₃/C cathode demonstrate significant enhancement in electrochemical performance. The flexible pouch cell achieves an excellent energy density of 301 Wh kg^-1.