An All‐Prussian‐Blue‐Based Aqueous Sodium‐Ion Battery

Abstract Aqueous rechargeable sodium‐ion batteries have received great attention as an alternative to meet the growing demand of large‐scale electrochemical energy storage systems due to the earth‐abundant and low‐cost sodium resources. In this study, an all Prussian‐blue‐based aqueous sodium‐ion battery is constructed using copper and iron‐based Prussian blue analogues as cathode and anode, respectively, and neutral NaNO 3 solution as electrolyte. The battery delivers an average output voltage of 0.70 V, a specific capacity of 50 mAh g −1 , and good rate capability with ∼86 % capacity retention over 250 cycles at 5 C. Moreover, the cathode, anode, and electrolyte materials are inexpensive, environmentally friendly, and inherently safe, which is particularly attractive for large‐scale energy storage applications.