Organic molecules intercalated hydrated vanadium oxide with bifunctional of hydrophobicity and pillar in aqueous zinc-ion batteries

The issue of water molecule activity in aqueous zinc-ion batteries presents a significant challenge. During the charging and discharging process, the strong polarity of water molecules tends to cause the dissolution of cathode materials, which reduces the cycle stability and specific capacity, consequently limiting the practical application of zinc-ion batteries. In this work, hydroxypropyl β-cyclodextrin (HP-β-CD), a special stereo cyclic organic molecule with hydrophobic inner cavity and hydrophilic outer cavity, is used as the intercalator for hydrated vanadium oxide (VOH) to enlarge the layer spacing and enhance the hydrophobicity of the cathode material. The larger interlayer spacing (13.9 Å) of HP-β-CD-VOH is beneficial for improving ion mobility and the intrinsic electrochemical reaction kinetics. HP-β-CD- VOH delivers a discharge capacity of 336.7 mAh g⁻¹ at 0.2 A g⁻¹ and high-rate capability (242 mAh g⁻¹ at 5 A g⁻¹). Due to the hydrophobic property of HP-β-CD in the interlayer pillar, the vanadium dissolution effect of polar water molecules can be reduced during charge and discharge; HP-β-CD-VOH demonstrates sustained high efficiency and extended cycle longevity, maintaining a remarkable durability of 6000 cycles at a current density of 10 A g⁻¹. This study presents an effective strategy for developing high-performance aqueous zinc-ion battery cathode materials.

Graphical abstract