Amylopectin-Assisted Fabrication of in Situ Carbon-Coated Na₃V₂(PO₄)₂F₃ Nanosheets for Ultra-Fast Sodium Storage

Na3V2(PO4)2F3 is one of the most studied polyanion type cathode materials for sodium-ion batteries (SIBs) and offers great promises. However, the inferior rate capability induced by its sluggish diffusion of electrons and ions greatly limits the practical application of electrode materials in SIBs. Herein, we develop an efficient method to fabricate in situ carbon-coated Na3V2(PO4)2F3 nanosheets by using cost-effective amylopectin. The amylopectin not only could induce the nucleation of Na3V2(PO4)2F3 along its backbone to form a 2D nanostructure, but also act as a source of amorphous carbon for in situ coating on the active material surface. The composite exhibits extraordinary rate capability (104 mA h g-1 at 40 C, 51 mA h g-1 at 150 C) and desirable cycling stability. Such satisfactory achievements, especially the superior rate performance, should be ascribed to its unique 2D nanostructure which shortens the Na+ diffusion length, and the in situ carbon coating endows the composites with effective electron transport. Even applied to full cells, the obtained devices still display an exceptionally high energy density (94.8 W h kg-1), high power density (7295 W kg-1), and excellent cyclic stability.