Intercalation engineering of layered vanadyl phosphates for high performance zinc-ion batteries

Aqueous zinc-ion batteries(ZIBs) have attracted great attention as the candidates for large-scale energy storage system,recently,because of their low cost,environment-friendly,high safety,and high theoretical energy densities.Among the numerous cathode materials,layered structure vanadium based polyanionic compounds,such as VOPO,exhibit high specific capacity for Zn ion storage.However,the low Zn ion diffusion coefficient and limited interlayer spacing make the cathodes low reversible capacity and inferior cycling stability.Herein,K ions were pre-intercalated into the VOPOlayers via ions exchange adopting VOPO·2 HO as the precursor.When evaluated as the cathode for ZIBs,an excellent cycle stability of 400 cycles under a current density of 500 mA gwas achieved by the obtained KVOPOelectrode,verifying the positive effect of intercalation engineering.Furtherly,a solid-solution reaction Zn ion storage mechanism was confirmed.This study provides a new insight to explore high performance cathode materials for ZIBs.