Mo-Doped Na[sub.4]Fe[sub.3][sub.2]P[sub.2]O[sub.7]/C Composites for High-Rate and Long-Life Sodium-Ion Batteries

• Published in: Materials Vol. 17; no. 11
• Main Authors: Chen, Tongtong, Han, Xianying, Jie, Mengling, Guo, Zhiwu, Li, Jiangang, He, Xiangming
• Format: Journal Article
• Language: English
• Published: MDPI AG 01.06.2024
• Subjects: Batteries; Electrochemistry; China
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma17112679

Na[sub.4]Fe[sub.3](PO[sub.4])[sub.2]P[sub.2]O[sub.7]/C (NFPP) is a promising cathode material for sodium-ion batteries, but its electrochemical performance is heavily impeded by its low electronic conductivity. To address this, pure-phase Mo[sup.6+]-doped Na[sub.4]Fe[sub.3−x]Mo[sub.x](PO[sub.4])[sub.2]P[sub.2]O[sub.7]/C (Mox-NFPP, x = 0, 0.05, 0.10, 0.15) with the Pn21a space group is successfully synthesized through spray drying and annealing methods. Density functional theory (DFT) calculations reveal that Mo[sup.6+] doping facilitates the transition of electrons from the valence to the conduction band, thus enhancing the intrinsic electron conductivity of Mox-NFPP. With an optimal Mo[sup.6+] doping level of x = 0.10, Mo0.10-NFPP exhibits lower charge transfer resistance, higher sodium-ion diffusion coefficients, and superior rate performance. As a result, the Mo0.10-NFPP cathode offers an initial discharge capacity of up to 123.9 mAh g[sup.−1] at 0.1 C, nearly reaching its theoretical capacity. Even at a high rate of 10 C, it delivers a high discharge capacity of 86.09 mAh g[sup.−1], maintaining 96.18% of its capacity after 500 cycles. This research presents a new and straightforward strategy to enhance the electrochemical performance of NFPP cathode materials for sodium-ion batteries.