Effect of Zn-substitution induced structural regulation on sodium storage performance of Fe-based Prussian blue

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2022-04, Vol.433, p.133739, Article 133739
• Main Authors: Zhang, Lu-Lu, Chen, Zhao-Yao, Fu, Xin-Yuan, Yan, Bo, Tao, Hua-Chao, Yang, Xue-Lin
• Format: Article
• Language: English
• Subjects: Cathode material; Fe-based Prussian blue; Sodium ion battery; Structural regulation; Zn-substitution
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2021.133739

[Display omitted] •The Fe-PB structure has been regulated by Zn substitution for the first time.•FeZn-PB has higher Na content, less vacancies and lower crystal water.•Zn-substitution accelerates electrons and sodium ions migration.•Zn-substitution enhances the activity of both low-spin Fe and high-spin Fe.•FeZn-PB has high capacity and superior cycle stability. Fe-based Prussian blue (Fe-PB) has attracted wide attention as cathode materials for sodium-ion batteries due to its open frame structure, abundant iron ore resources, and simple preparation. Nevertheless, the poor cycle performance caused by the [Fe(CN)6] defects and crystal water hinders its practical application. Herein, the Fe-PB structure is regulated by Zn-substitution, and the effect of Zn-substitution induced structural regulation on sodium storage performance of Fe-PB is systematically investigated. The density functional theory calculation results confirm that Zn-substitution can reduce the bandgap and decrease the energy barrier of Na+ ions migration. Our experiment results further confirm the Zn-substituted Fe-PB composite (FeZn-PB) has a typical monoclinic structure with higher Na content, fewer [Fe(CN)6] vacancies and lower crystal water. Moreover, Zn-substitution accelerates electrons and sodium ions migration and enhances the activity of both low-spin Fe and high-spin Fe. As a cathode material for sodium-ion batteries, the FeZn-PB electrode has a higher capacity and better cycle stability than Fe-PB. Especially, FeZn-PB delivers an initial capacity as high as 145.0 mAh g−1 with a capacity contribution of 60.5 mAh g−1 from low-spin Fe at 20 mA g−1. Even at a high current density of 1 A g−1, FeZn-PB still delivers a high initial capacity of 98.5 mAh g−1 with a very low capacity decay rate per cycle of only 0.05% over 500 cycles.