Synthesis and electrochemical properties of hydrangea-like (NH4)2V4O9/V5O12·6H2O cathode for zinc-ion battery

Energy density, power density, as well as the cost of aqueous zinc-ion batteries (AZIBs), are largely determined by the cathode material. Among the various cathodic candidates, vanadium-based materials with various oxidation states of vanadium cations and open frameworks have emerged as highly promising options. In this work, a heterogeneous with hydrangea-like (NH 4 ) 2 V 4 O 9 /V 5 O 12 ·6H 2 O as cathode materials for AZIBs. The hydrogen bonds formed by NH 4 + of (NH 4 ) 2 V 4 O 9 , in conjunction with the lattice water in V 5 O 12 ·6H 2 O, sufficiently strengthen the cohesion of the layered structure and expand the interlayer space. As a result, accelerating the diffusion of Zn 2+ ultimately leads to an enhanced overall discharge capacity. Remarkably, the hydrangea-like (NH 4 ) 2 V 4 O 9 /V 5 O 12 ·6H 2 O electrode at a current density of 100 mA g −1 shows a high reversible capacity of 209 mAh g −1 after 150 cycles and higher rate capability (172 mAh g −1 at 500 mA g −1 ). The outstanding electrochemical performance can be attributed to the unique structure of the cathode material and accelerated diffusion coefficient of Zn 2+ .