Multifunctional dual Na3V2(PO4)(2)F-3 cathode for both lithium-ion and sodium-ion batteries

Na3V2(PO4)(2)F-3 with a NASICON-type structure is shown to be synthesised with the particle surface found to be coated with amorphous carbon with its thickness in the range of 25-32 nm. The crystallographic planes (hkl) are labelled according to Density Functional Theory (DFT) calculations towards the as-prepared Na3V2(PO4)(2)F-3. The performances of Na3V2(PO4)(2)F-3 have been investigated in lithium-and sodium-ion batteries, exhibiting a specific capacity of 147 mA h g(-1) with an average discharge plateau around 4 V vs. Li+/Li, and 111.5 mA h g(-1) with three discharge plateaus in sodium-ion batteries. A predominant Li ion insertion mechanism is verified by comparing the redox potentials from CV and charge/discharge curves. It is found that the main migration from/into the crystallographic sites of Na3V2(PO4)(2)F-3 of Li ions is favoured to obtain satisfactory properties by a two-step process, while the Na ions are found to require three steps. The stable and three-dimensional open framework of Na3V2(PO4)(2)F-3 is considered to be vital for the excellent C-rate and cycling performances, as well as the fast ion diffusion with a magnitude of 10(-11) cm(2) s(-1), which could demonstrate that Na3V2(PO4)(2)F-3 is a multifunctional dual cathode for both lithium and sodium ion batteries and capable to be a promising candidate in the construction of high-energy batteries.