Ether-Water Co-Solvent Electrolytes Enhanced Vanadium Oxide Cathode Cyclic Behaviors for Zinc Batteries

Vanadium-based compounds are fantastic cathodes for aqueous zinc metal batteries due to the high specific capacity and excellent rate capability. Nevertheless, the practical application has been hampered by the dissolution of vanadium in traditional aqueous electrolytes owing to the strong polarity of water molecules. Herein, we propose a hybrid electrolyte made of Zn(ClO₄)₂ salt in tetraethylene glycol dimethyl ether (G4) and H₂O solvents to upgrade the cycle life of Zn//K_0.486V₂O₅ battery. The G4 jointly solvates with Zn²⁺ ions and replaces a portion of the H₂O molecules in the Zn²⁺ solvation sheath. It forms a strong bond with H₂O, reducing its activity, and significantly inhibiting vanadium dissolution and water-induced parasitic reaction. Consequently, the optimized electrolyte with H₂O and G4 volume ratio of 5 : 5 enhances the cycling stability of Zn//K_0.486V₂O₅ battery, enabling it to reach up to 600 cycles. In addition, the battery demonstrates a satisfactory reversible capacity of 475.7 mAh g^-1 and excellent rate performance attributed to the moderate ionic conductivity (28.8 mS cm^-1) of the hybrid electrolyte. Last but not least, in the optimized electrolyte, the symmetric Zn//Zn cells deliver a long cycling performance of 400 h, while the asymmetric Zn//Cu cells shows a high average coulombic efficiency of 97.4 %.