Construction of 2D sandwich-like Na₂V₆O₁₆·3H₂O@MXene heterostructure for advanced aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) have attained enormous attention in the last few years. The cathode materials of aqueous zinc ion batteries play a vital effect in their electrochemical and battery properties. In this manuscript, Sandwich-like MXene@Na₂V₆O₁₆·3H₂O (NVO@MXene) heterostructure was successfully prepared by the combination and cooperation of the layer lattice structure of Na₂V₆O₁₆·3H₂O and the high conductivity of MXene. When used as the cathode material for AZIBs, NVO@MXene demonstrates preeminent rate capability and excellent reversible capacity of 175 mAh/g after 3000 cycles at 5 A/g with a retention rate of 88.9 % of initial discharge capacity. The outstanding battery performance can be attributed to the MXene layers with high conductivity for accelerating the ion diffusion rate and reducing the agglomeration of Na₂V₆O₁₆·3H₂O nanowires during the (dis)charge process. Meanwhile, the stable layered structure of Na₁₆V₆O₆·3H₂O with wide interlamellar spacing (d = 7.9 Å) is also favorable for the s fast intercalation/deintercalation of Zn²⁺. Finally, ex-situ X-ray diffraction and X-ray photoelectron spectroscopy were applied to study and reveal the energy storage mechanism of this novel material for aqueous zinc ion batteries.