Stabilizing sodium metal battery with synergy effects of sodiophilic matrix and fluorine-rich interface

Sodium (Na) metal anode plays a pivotal role in realizing long-term cycling stability in the promsing Na-based batteries. However, the uncontrollable plating-stripping process and unstable solid electrolyte interphase (SEI) layer can induce the electrodes degradation, which hinders its potential applications. In this work, the synergistic effects of composite Na metal anode and fluorine-rich electrolyte are introduced to investagate the Na+ plating-stripping process and its potential use in Na metal batteries (SMBs). The composite anode was fabricated via alloying and capillary action between the sodiophilic carbon matrix and molten Na metal forming an integrated structure, which effectively improved the interconnection between Na and carbon scaffold to the uniform deposition. Combining with fluorine-rich electrolyte, stable SEI layer consisting of ion-permeable NaF and mechanically durable organic components were obtained. When coupled with Na3V2(PO4)3 cathode with a high mass loading of ~ 9 mg cm-2, the ultra-stable cycling behaviour (capacity retention of >90% over 1000 cycles) and outstanding rate performance (capacity retention of >80% at 15C) are observed due to the improved Na deposition process and interface stability. This work demonstrates that the synergy effects of composite metal anode and electrolyte modification can be the effective strategy to fabricate the highly stable SMBs.