Boosting Ion Transport Kinetics in Sulfolane-Modified Aqueous Electrolytes for High-Performance Zinc-Ion Batteries with V₂C MXene Cathodes

The advancement of zinc-ion batteries (ZIBs) is propelled by their inherent safety, cost-effectiveness, and environmental sustainability. This study investigates the role of sulfolane (SL), a polar aprotic solvent with a high dielectric constant, as an electrolyte additive to enhance ion transport and electrochemical performance in V₂C MXene cathodes for high-performance ZIBs. The addition of 1% SL optimizes Zn-ion transport by increasing ionic conductivity, suppressing electrolyte decomposition, and mitigating zinc dendrite formation. Galvanostatic Intermittent Titration Technique (GITT) analysis reveals a reduction in Zn²⁺ diffusion coefficient from 1.54 × 10⁻⁷ cm²/s in 2 m ZnSO₄ to 1.07 × 10⁻⁹ cm² s⁻¹ in the SL-modified system, indicating a more confined Zn²⁺ transport environment. Electrochemical Impedance Spectroscopy (EIS) further demonstrates a substantial decrease in activation energy from 123.78 to 65.08 kJ mol⁻¹, signifying improved charge transfer kinetics. Ex situ XRD confirms that SL stabilizes the phase transformation of V₂C to Zn₀.₂₉V₂O₅, enhancing structural integrity. The modified system achieves an impressive specific capacity of 545 mAh g⁻¹ at 0.5 A g⁻¹ and exhibits exceptional cycling stability, retaining 91% capacity over 7000 cycles at 20 A g⁻¹. These findings underscore the potential of sulfolane as a key additive for advancing V₂C MXene-based ZIBs.