Insights into the Mg storage property and mechanism based on the honeycomb-like structured Na3V2(PO4)(3)/C/G in anhydrous electrolyte

摘要

The high-voltage cathode material based on the sodium super ionic conductor (NASICON) structured Na3V2(PO4)(3) (NVP) has been found to be a potential candidate for Mg storage. In this work, to improve its electrochemical performance, we construct honeycomb-like structured NVP/C/G with faster electronic and ionic transport by a convenient and universal spray-drying method for the first time. After electrochemically desodiating two Na from the NVP/C/G (ED-NVP/C/G), the ED-NVP/C/G is tested in highly anhydrous Mg electrolyte, and the insights into its Mg storage property and mechanism are carefully studied. An initial capacity of 87 mAh g(-1) with a relatively high average discharge voltage of 2.47 V vs. Mg2+/Mg is obtained at 0.1 C. The X-ray diffraction (XRD) results show that the inserted Mg2+ ions tend to occupy the Na2 (at 18e sites) vacant sites. The investigation of kinetic process by galvanostatic intermittent titration technique (GITT) reveals that the Mg diffusion kinetics is faster during the demagnesiation process. The electrochemical reaction bases on two-phase transition mechanism, and the R-ct value shows a positive relationship to the formation of NaV2(PO4)(3) phase. Finally, a Mg full cell prototype based on the ED-NVP/C/G cathode with Mg metal anode is built. The rational structure design of NVP/C/G improves the electrochemical performance for Mg storage, and our work also gives new understanding into the Mg storage mechanism in the ED-NVP/C/G structure.