Nano-NaVPO4F enwrapped in reduced graphene oxide as a cathode material for long-cycle and high-rate sodium-ion batteries

Nano-NaVPO4F enwrapped in reduced graphene oxide is obtained via the modified freeze-drying method. In the composite, reduced graphene oxide constitutes a 3D conductive framework, and NaVPO4F particles less than 100 nm are uniformly enwrapped in the graphene sheets. The composite exhibits not only excellent cycle stability but also extraordinary rate capability in sodium-ion batteries. The corresponding discharge capacities at 10, 20, 50, and 100 C are 113.9, 112.1, 106.9, and 86.6 mAh g(-1), respectively. In particularly, it delivers an initial discharge specific capacity of 110.6 mAh g(-1) while obtains 100.0 mAh g(-1) with the capacity retention of 90.4% at 10 C after 3000 cycles. Such superior performance can be ascribed to the uniform nanometer-sized particles and the 3D conductive graphene framework. This work implies that graphene-modified NaVPO4F can be a promising cathode material for long-cycle and high-rate sodium-ion batteries. (C) 2019 Elsevier B.V. All rights reserved.