Dual-Guest Intercalated Vanadium Oxides with a Robust Channel for Efficient Zn Ion Diffusion and Storage

Aqueous zinc-ion batteries (AZIBs) have drawn extensive attention for their high theoretical capacity, low redox potential, and reliable safety. Although layered vanadium oxides are prospective cathodes for AZIBs, they still suffer from fast capacity decay and poor rate capability, resulting from small interlayer spacing and severe structural collapse. Herein, a dual-guest of zinc ions and n-butylamine cointercalation strategy was proposed to solve the above two issues simultaneously. The inserted zinc ions form strong Zn–O bonds between the layers, acting as "pillars" and effectively maintaining the stability of the structure in the repeated insertion/extraction of the Zn2+ process. The preinsertion of n-butylamine preserves a suitable interlayer distance for Zn2+ diffusion, facilitating the reversible insertion/extraction of Zn2+. The density functional theory (DFT) results show that the cointercalated sample (ZBVO) has a more favorable Zn2+ diffusion path with a lower migration barrier. Benefiting from the robust channel synergistically constructed by the two guests, ZBVO displays outstanding electrochemical performances, especially for capacity and long cyclic stability: ZBVO delivers a high specific capacity of 417.1 mAh g–1 at 0.1 A g–1. Moreover, it also shows an enhanced specific capacity of 261.8 mAh g–1 at 5 A g–1 after 1000 cycles and good long cycling stability (ultrahigh capacity retention of 93% over 5000 cycles at 10 A g–1). This work provides guidance for designing high-performance vanadium-based cathodes of AZIBs.