Novel K-V-Fe Prussian blue analogues nanocubes for high-performance aqueous ammonium ion batteries

The development of aqueous ammonium ion batteries is currently in its infancy. Searching for suitable electrode materials is one of the most important jobs in preparing high-performance batteries. In this work, we report a one-step hydrothermal method to successfully synthesize novel K-V-Fe Prussian blue analogues nanocubes (PBAs NCs) by using oxalic acid as the reducing agent. The obtained electrode materials effectively combine the high electrochemical activity of vanadium-contained ions with the excellent structural stability of Prussian blue frame, thus ensuring their high capacity for electrochemical energy storage and excellent cycling stability. The optimal K-V-Fe PBAs NCs can achieve a high specific capacity of 92.85 mAh·g−1 at a current density of 2 A·g−1, outstanding cycling stability with a capacity retention of 91.44% (84.9 mAh·g−1) after 2000 cycles at 2 A·g−1 and good rate capability with a specific capacity of 46.2 mAh·g−1 at 5 A·g−1. This strategy of combine vanadium element with open three-dimensional framework provides a new way for selecting and improving electrode materials suitable for electrochemical energy storage. And the present K-V-Fe PBAs NCs will be a promising candidate for aqueous rechargeable ammonium-ion batteries due to their high capacity, reasonable cost and excellent cycling stability.