▎ 摘　　要

Na3V2(PO4)(2)F-3 (NVPF) is one of the Na-containing superionic conducting crystals, but it has a disadvantage of low intrinsic electronic conductivity. To improve this issue, NVPF@C/G with a three-dimensional conductive structure from bio-carbon (buckwheat) and graphene is fabricated via a straightforward carbothermal reduction method. We use this material to construct cathodes for Na-ion batteries. The resulting NVPF@C/G delivers high initial (equal to 137.5 mAh g(-1) at 0.2 C) and stable long-term (equal to 110.5 mAh g(-1) after 100 cycles) capacity. At 10 C, the capacity of the NVPF@C/G-containing cathode is 80.6 mAh g(-1). Furthermore, a Na-ion full-cell containing our NVPF@C/G-based cathode and hard carbon anode shows outstanding cycling stability with the initial discharge capacity of 101.6 mAh g(-1). The discharge capacity of this full cell returns to 90.4 mAh g(-1) at 0.5 C after it is tested at various high rates. Such superior performances can be attributed to the 3D conductive network in NVPF@C/G, which can increase the conductivity and improve the kinetics of the Na3V2(PO4)(2)F-3. This work suggests that the buckwheat-derived carbon-coated Na3V2(PO4)(2)F-3 enwrapped in graphene can be a potential active material for high rate and long-cycle Na-ion batteries.