NaV6O15: A promising cathode material for insertion/extraction of Mg2+ with excellent cycling performance
Dongzheng Wu, Jing Zeng, Haiming Hua, Junnan Wu, Yang Yang, Jinbao Zhao
Abstract
The rechargeable magnesium batteries (RMBs) are getting more and more attention because of their high-energy density, high-security and low-cost. Nevertheless, the high charge density of Mg2+ makes the diffusion of Mg2+ in the conventional cathodes very slow, resulting in a lack of appropriate electrode materials for RMBs. In this work, we enlarge the layer spacing of V2O5 by introducing Na+ in the crystal structure to promote the diffusion kinetics of Mg2+. The NaV6O15 (NVO) synthesized by a facile method is studied as a cathode material for RMBs with the anhydrous pure Mg2+ electrolyte. As a result, the NVO not only exhibits high discharge capacity (119.2 mAh·g−1 after 100 cycles at the current density of 20 mA·g−1) and working voltage (above 1.6 V vs. Mg2+/Mg), but also expresses good rate capability. Besides, the ex-situ characterizations results reveal that the Mg2+ storage mechanism in NVO is based on the intercalation and de-intercalation. The density functional theory (DFT) calculation results further indicate that Mg2+ tends to occupy the semi-occupied sites of Na+ in the NVO. Moreover, the galvanostatic intermittent titration technique (GITT) demonstrates that NVO electrode has the fast diffusion kinetics of Mg2+ during discharge process ranging from 7.55 × 10–13 to 2.41 × 10–11 cm2·s−1. Our work proves that the NVO is a potential cathode material for RMBs.