Chemical Synthesis of 3D Graphene‐Like Cages for Sodium‐Ion Batteries Applications

Sodium (Na) super ion conductor structured Na 3 V 2 (PO 4 ) 3 (NVP) is extensively explored as cathode material for sodium‐ion batteries (SIBs) due to its large interstitial channels for Na + migration. The synthesis of 3D graphene‐like structure coated on NVP nanoflakes arrays via a one‐pot, solid‐state reaction in molten hydrocarbon is reported. The NVP nanoflakes are uniformly coated by the in situ generated 3D graphene‐like layers with the thickness of 3 nm. As a cathode material, graphene covered NVP nanoflakes exhibit excellent electrochemical performances, including close to theoretical reversible capacity (115.2 mA h g −1 at 1 C), superior rate capability (75.9 mA h g −1 at 200 C), and excellent cyclic stability (62.5% of capacity retention over 30000 cycles at 50 C). Furthermore, the 3D graphene‐like cages after removing NVP also serve as a good anode material and deliver a specific capacity of 242.5 mA h g −1 at 0.1 A g −1 . The full SIB using these two cathode and anode materials delivers a high specific capacity (109.2 mA h g −1 at 0.1 A g −1 ) and good cycling stability (77.1% capacity retention over 200 cycles at 0.1 A g −1 ).