Anionic Group Doping of Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 Stabilizes Its Structure and Improves Electrochemical Performance for Sodium Ion Storage

作者：Mingzu Liu, Min Li, Bolun Zhang, Houmou Li, Jiaxin Liang, Xinyu Hu, Haimei Liu, Zi‐Feng Ma · 发表于：ACS Sustainable Chemistry & Engineering · 年份：2023 · DOI：10.1021/acssuschemeng.3c06667 · 被引用次数：50 · 研究领域：Advancements in Battery Materials、Advanced Battery Materials and Technologies、Advanced Battery Technologies Research

Due to its low cost and high stability, the iron-based mixed polyanionic compound Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 is widely studied for use as a sodium-ion battery cathode material. However, its development is limited by a low electrical conductivity and restricted diffusion kinetics. In this work, we chose to replace the PO 4 3– group with the SiO 4 4– group to enhance the electronic conductivity and diffusion kinetics, while this structural substitution maintains the integrity of the material. Furthermore, this substitution at a nonactive site improves the electrochemical performance without reducing the theoretical capacity. Additionally, it stabilizes the crystal structure during the repeated charging and discharging process. As a result, this SiO 4 4– doped Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 exhibits improved electrochemical properties. For instance, it achieves a capacity of 119.4 mA h g –1 at a rate of 0.1 C and 60.7 mA h g –1 at 50 C after 5000 cycles with 84.2% of its capacity retained. Moreover, theoretical calculations revealed the doping form and occupancy of SiO 4 4– in the host material structure. It is believed that this work provides a new perspective on doping modification with anionic groups to improve the electrochemical performance of cathode materials for sodium ion storage.