Organic/inorganic cation co-intercalated ammonium vanadate cathode for high-performance aqueous zinc-ion batteries

Ammonium vanadate cathode materials are attractive cathodes for aqueous zinc-ion batteries due to their open crystal structures and superior theoretical capacity. However, the sluggish electrochemical activity and inevitable dissolution of vanadium hindered their application. Conventional intercalation strategy adopting metal ions could improve the charge transfer process through the expansion of interlayer space, whereas, incorporation of metal ions may also bring forth strong electrostatic repulsion, influencing the intercalation process of Zn2 +. In comparison, organic molecular with larger molecular size, structural flexibility, mean charge redistribution may contribute to a more balanced electrostatic force within the structure, giving rise to better structural stability. Herein, we designed an organic/inorganic (C5H14ON+/Mn2+) cations co-intercalated NH4V4O10, denoted as MnCh-NVO, and the as-synthesized cathode demonstrated a discharge capacity of 519 mA h/g at 1 A/g and stable cycling after 1000 cycles at 5 A/g. In comparison with bulk ammonium vanadate, characterization demonstrated that MnCh-NVO exhibited higher ion diffusion coefficient, which is a magnitude higher than that of bulk NH4V4O10. Furthermore, ex-situ tests manifested the high reversible zinc insertion/de-insertion process of MnCh-NVO, proving the effectiveness of this strategy. Generally, the co-intercalated MnCh-NVO possessed a balanced electrostatic force, expanded Zn2+ accommodation space, and improved charge transfer kinetics. Furthermore, this work provides an effective strategy for developing high performance cathodes of zinc ion batteries.