Zn ²⁺-Intercalated V ₂O ₅· nH ₂O derived from V ₂CT _x MXene for hyper-stable zinc-ion storage

Abstract

The intercalated Zn ²⁺ and abundant interfaces between the conductive V ₂CT _x and Zn _x V ₂O ₅· nH ₂O can weaken the electrostatic interactions and maintain a large lattice channel during cycling, thus reducing the activation energy of charge transfer.

Abstract

Aqueous zinc-ion batteries (ZIBs) are considered as desirable large-scale energy storage systems because of their environment friendliness and low cost. However, the development of ZIBs with stable performance still faces many obstacles before becoming viable for commercial applications. Herein, Zn _x V ₂O ₅· nH ₂O nanobelts with uniform size derived from highly conductive V ₂CT _x MXene (VC–ZVO) are designed and synthesized as cathodes for ZIBs via simultaneous ion intercalation and oxidation. Thanks to the pre-intercalated Zn ²⁺ and the ubiquitous interfaces between ZVO and the conductive network composed of the remaining V ₂CT _x and carbon, the charge redistribution in the active/conductive heterostructure leads to weakening of electrostatic interactions, quick zinc-ion insertion/extraction, and structural stability. Accordingly, the VC–ZVO electrode shows ultrastable cycling performance and high rate capacities for ZIBs, presenting no fading capacity at 0.1 A g ⁻¹ and 96.4% capacity retention over 8000 cycles at 10 A g ⁻¹. Further studies on the electrochemical kinetics and reaction mechanism elucidate faster Zn ²⁺ diffusion and the high reversibility of VC–ZVO ZIBs. The revelation of the origin of the improved Zn ²⁺-storage provides distinctive ideas for the enhancement of V-based electrodes and the development of a new type of cathode.