1. Preparation and Electrochemical Performance of Na 2−x Li x FePO 4 F/C Composite Cathode Materials with Different Lithium/Sodium Ratios.
- Author
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Wang, Lei, Tian, Hualing, Yao, Xiang, Cai, Yanjun, Gao, Ziwei, and Su, Zhi
- Subjects
ELECTROCHEMICAL electrodes ,COMPOSITE materials ,ELECTRODE performance ,LITHIUM ,SODIUM ions ,SODIUM - Abstract
With their advantages of abundant raw material reserves, safety, and low toxicity and cost, sodium-ion batteries (SIBs) have gained increasing attention in recent years. Thanks to a high theoretical specific capacity (124 mAh g
−1 ), a high operating voltage (about 3.2 V), and a very stable three-dimensional layered structure, sodium ferric fluorophosphate (Na2 FePO4 F, NFPF) has emerged as a strong candidate to be used as a cathode material for SIBs. However, applications are currently limited due to the low electronic conductivity and slow ion diffusion rate of NFPF, which result in a low actual specific capacity and a high rate performance. In this study, the authors used a high-temperature solid-phase technique to produce Na2−x Lix FePO4 F/C (0 ≤ x ≤ 2) and evaluated the impact on electrode performance of materials with different Na+ and Li+ contents (values of x). Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were also used to analyze the material's crystal structure and nanostructure. The results show that the material had the best room-temperature performance when x = 0.5. At a charge–discharge rate of 0.1 C, the first discharge-specific capacity of the resulting Na1.5 Li0.5 FePO4 F/C cathode material was 122.9 mAh g−1 (the theoretical capacity was 124 mAh g−1 ), and after 100 cycles, it remained at 118 mAh g−1 , representing a capacity retention rate of 96.2% and a Coulomb efficiency of 98%. The findings of this study demonstrate that combining lithium and sodium ions improves the electrochemical performance of electrode materials. [ABSTRACT FROM AUTHOR]- Published
- 2024
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