PNNL

Abstract

Sodium (Na) super ion conductor structured Na3V2(PO4)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).