Enhanced electrochemical performance of ammonium vanadate (NH4V4O10) cathode for rechargeable aqueous zinc-ion batteries by altering pH regulators

Ammonium vanadate (NH4V4O10: NVO) as cathode for rechargeable aqueous zinc-ion batteries (AZIBs) have drawn extensive concern due to its high specific capacity and long cycle life. The controllable synthesis of high-performance NH4V4O10 is greatly desirable for the development of AZIBs but still remains a significant challenge. In this work, sulfuric acid, hydrochloric acid, and nitric acid were used as pH regulators to prepare NVO via a simple one-step hydrothermal route. The resulting NVO product (NVO-1) based on sulfuric acid pH regulator has the optimal overall performance for its favorable structure stability originated from the high crystallinity and wonderful 3D cross-linked nanowire morphology, contributing to fast electron transfer in the (de)intercalation process of Zn2+. Consequently, NVO-1 electrode exhibits excellent rate capability and cyclic stability, delivering high reversible capacities of 418.9 and 257.1 mAh g- 1 at current densities of 0.1 and 2 A g- 1, respectively, and demonstrating a discharge capacity of 105.7 mAh g- 1 as well as superior long-term durability with an ultra-high capacity retention of 119.7 % at a large current density of 5 A g- 1 after 2000 cycles. Investigation on the electrochemical kinetics reveals that surface capacitive behavior plays a significant role in the highly reversible Zn2+ storage in NVO electrode.