Robust Cross-Linked Na3V2O1.6(PO4)2F1.4@rGO&MWCNTs as High-Performance Cathode for Aqueous Zinc-Ion Batteries

Abstract

Aqueous zinc-ion batteries (AZIBs) are advantageous for grid-scale energy storage applications due to their high safety, cost-effectiveness, and environmental sustainability. However, developing high-rate and long-life cathodes for AZIBs remains a significant problem. Herein, a composite (Na₃V₂O_1.6(PO₄)₂F_1.4@rGO&MWCNTs) that integrates Na₃V₂O_1.6(PO₄)₂F_1.4 nanoparticles within a 3D conductive matrix comprising 2D reduced graphene oxide (rGO) and 1D multi-walled carbon nanotubes (MWCNTs) has been prepared through a microwave-assisted hydrothermal method followed by calcination, enhancing surface electronic conductivity to improve electrochemical performance. Na₃V₂O_1.6(PO₄)₂F_1.4@rGO&MWCNTs cathode exhibits a high capacity of 98.4 mAh g⁻¹ at 0.2 A g⁻¹ and maintains a capacity of 52.8 mAh g⁻¹ over 6,000 cycles at 5 A g⁻¹. The soft-pack battery demonstrates excellent cycling stability, maintaining stable performance over 1,000 cycles at a high current density. Remarkably, it exhibits robust mechanical stability, delivering a stable output voltage even under various mechanical stress conditions. The outstanding performance arises from enhanced conductivity, high pseudocapacitive contribution, improved Zn²⁺ diffusion coefficients, low charge transfer resistance, robust structural framework, and reversible Zn²⁺ insertion/extraction mechanism verified by in situ electrochemical impedance spectroscopy, distribution of relaxation time, cyclic voltammetry, galvanostatic intermittent titration techniques, ex situ X-ray diffraction, and ex situ X-ray photoelectron spectroscopy.