Zn3V2O7(OH)2·2H2O/MXene cathode with fast ion diffusion for highly durable zinc ion batteries

Abstract

V-based materials are considered promising candidates as cathode materials for zinc ion batteries (ZIBs). However, the inherent low conductivity of V-based compounds leads to the sluggish diffusion kinetics of Zn²⁺ and serious cycling capacity degradation of ZIBs. Herein, 1D Zn₃V₂O₇(OH)₂·2H₂O (ZVO) nanowires were grown on monodisperse 2D Ti₃C₂T_x MXene nanosheets via a facile microwave-assisted method. The introduction of Ti₃C₂T_x MXenes effectively improved the conductivity and hydrophilicity of ZVO. Furthermore, the Zn²⁺ diffusion coefficient of ZVO/Ti₃C₂T_x composites was enhanced to 10⁻⁷–10⁻⁸ cm² s⁻¹, which was superior to that of pure ZVO nanowires (10⁻⁸–10⁻¹⁰ cm² s⁻¹) and other previously reported typical V-based cathodes. The ZIBs based on the ZVO/Ti₃C₂T_x cathode possessed an excellent discharge specific capacity of 215.2 mAh g⁻¹ at 0.1 A g⁻¹ and cycling stability (84% retention over 14 000 cycles at 10 A g⁻¹). Moreover, the flexible Zn//ZVO/Ti₃C₂T_x ZIBs using a gel electrolyte still exhibited good cycling stability and rate performance.