Ultra-Stable Zinc Nitroprusside Cathode Operating at High Potentials for Inexpensive, Simpler-to-Scale Sodium-Ion Batteries.

Driven by the demand for low-cost and environmentally sustainable energy storage technologies, sodium-ion batteries (NIBs) have emerged as a promising alternative to lithium-ion batteries. Among the various cathode candidates, Prussian blue analogs (PBAs) stand out due to their tunable chemistry, open-framework structure, and low production costs. However, conventional PBAs typically exhibit limited rate performance, leading to poor capacity retention and reduced cycle life. In this work, we present a straightforward coprecipitation synthesis of a novel zinc nitroprusside, Zn-[Fe-(CN)5NO], in which zinc incorporation enhances the structural stability of the large-channel framework, directly addressing the intrinsic limitations of traditional PBAs. The material exhibited remarkable structural stability under high-voltage operation (4.5 V), delivering excellent rate performance with 79% capacity retention after 500 cycles at 91 mA g-1 (1C), alongside a maximum discharge capacity of 69.4 mA h g-1 at 9.1 mA g-1 (0.1C). This study advances the development of stable, cost-effective cathode materials for NIBs. It highlights the potential of zinc-stabilized frameworks in enabling both high electrochemical performance and long-term cycling stability, representing a step toward wider adoption of NIB technology.