Graphene quantum dots-shielded Na-3(VO)(2)(PO4)(2)F@C nanocuboids as robust cathode for Na-ion battery

The natural abundance, environmental friendliness, low cost of sodium salts, and the electrochemical properties similarity between lithium-and sodium-ion batteries (LIBs, SIBs) make SIBs one of the most promising alternatives to current LIBs. In order to match with performances of LIBs, challenges in improving high-rate capability and long-term cycling stability of SIBs need to be addressed. In this work, we design and construct an excellent cathode material for SIB, i.e. carbon-coated, graphene quantum dots (GQDs) shielded Na-3(VO)(2)(PO4)(2)F nanocuboids (NVOPF@C), which possesses highly exposed crystalline a-b planes for rapid ion diffusion. The GQD as well as amorphous carbon layer shielding NVOPF nanocuboids not only can improve the charge transport and transfer kinetics, but also stabilize the open framework structure from the agglomeration. Impressively, NVOPF@C delivers an unexpectedly high capacity of 70 mA h g(-1) at ultra-high rate 45 C, with 81% retention after 2000 cycles. (C) 2016 Elsevier B.V. All rights reserved.