One Pot Synthesis of Ammonium Rich Nickel Hexacyanoferrate as Stable Cathode Material for Ammonium‐Ion Batteries

Abstract Rechargeable aqueous batteries based on ammonium‐ion (NH 4 + ) redox reactions shows great potential for large‐scale energy‐storage due to its plentiful supplies, environmental friendliness, intrinsic security, and sustainability. Prussian blue analogues (PBAs) are regarded to be one of the most promising electrode materials owning to high energy storage density, ease of synthesis, and excellent electrochemical performances. However, the synthesis of ammonium rich Prussian blue analogues is too complicated. Herein, a one pot synthesis of NH 4 + ‐rich nickel hexacyanoferrate (NNiHCF) is developed and the NH 4 + storage chemistry is investigated. NNiHCF cathode is coupled with an activated carbon (AC) anode and (NH 4 ) 2 SO 4 aqueous electrolyte to assemble ammonium‐ion batteries. The aqueous full cell demonstrates good electrochemical performance, such as 50.2 mAh g −1 at the current rate of 2 C, and 60 % capacity retention in 5000 cycles. Furthermore, the fundamental characteristics of the reversible redox reaction and the durable structure of NNiHCF are revealed by X‐ray diffraction (XRD) and electrochemical measurements. This work proposes a facile method for the synthesis of ammonium‐rich Prussian.