Prussian blue (PB) and its analogues (PBAs) are promising cathode materials for sodium ion batteries (SIBs) because of their wide diffusion tunnels for sodium ions. However, water molecules typically contained within PB structures have been hypothesized to undermine their stability and rate performance. Here we report that zeolite water molecules in PB structures may induce the formation of Na₂CO₃ as one of the main components in SEI layer on the surface of PB materials. From PB samples containing zeolite water synthesized via a solvothermal method at different temperatures, a specific capacity of 113 mAh g⁻¹ is demonstrated at 10 mA g⁻¹, with a capacity retention of 75% at 1000 mA g⁻¹. Cycling tests reveal a capacity loss of only 1.2% after 100 cycles at 200 mA g⁻¹. It is suggested that Na₂CO₃ contained in the SEI layer not only protects the electrode materials from side reactions with the electrolyte, but also facilitates quick charge transfer at the interfaces, leading to improved electrochemical performances.

普鲁士蓝（PB）及其类似物（PBA）是钠离子电池（SIB）的有希望的阴极材料，因为它们的钠离子扩散通道很宽。但是，已经假设通常包含在PB结构中的水分子会破坏其稳定性和速率性能。在这里，我们报道PB结构中的沸石水分子可能会诱导Na ₂ CO ₃的形成，这是PB材料表面SEI层中的主要成分之一。从包含通过溶剂热法在不同温度下合成的沸石水的PB样品中，在10 mA g ^-1下显示出113 mAh g ^-1的比容量，在1000 mA g ^-1下具有75％的容量保持率。循环测试显示，在200 mA g ^-1下进行100次循环后，容量损失仅为1.2％。建议SEI层中包含的Na ₂ CO ₃不仅保护电极材料免于与电解质的副反应，而且还促进了界面处电荷的快速转移，从而改善了电化学性能。