Layered Structures of Enriched V 5+ States of Vanadium Oxide as a Hybrid Cathode Material for Long-Cyclable Aqueous Zinc-Ion Batteries.

Recently, aqueous zinc-ion batteries (AZIBs) have garnered much attraction because of their ecofriendly nature, cost effectiveness, and reliability. However, there are still many challenges in developing suitable cathode materials for practical usage in ZIBs. In this work, we have synthesized a layered V 5+ -rich vanadium oxide (V 6 O 13 ) flaky structure that provided the electrolyte with a large active surface area. In addition to that, the mixed (V 4+/ V 5+ ) valence states of V have significantly improved the ionic diffusion of Zn 2+ , thereby improving the V 6 O 13 electrical conductivity. Therefore, the AZIBs based on the layered structure V 6 O 13 cathode with 1 M ZnSO 4 electrolyte exhibited a very high specific capacity of 394 mAh g -1  @ 0.1 A g -1 without the addition of any additives or electrode modification. The rate capability and cycle life are investigated at the current density of 2 A g -1 , where the capacity retention was found to be around 94% along with a coulombic efficiency of 96% for over 100 cycles. Such a material with high electrochemical performance can be used for portable electronic devices and electric vehicular applications.