Dual-Phase Engineered Iron-Based Polyanion Cathodes for Fast and Durable Sodium-Ion Batteries.
basic_science · Level V
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- Record sourced from PubMed, PMID 40772675.
- Also identified by DOI 10.1021/acsnano.5c06271.
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Abstract
Iron-based polyanion material Na<sub>2</sub>Fe<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> has gained attention for sodium-ion batteries due to its excellent electrochemical performance and low cost. However, Na<sub>2</sub>Fe<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> suffers from residual FeSO<sub>4</sub> formation during synthesis, which limits its capacity and rate performance. Herein, we introduce a dual-phase engineering strategy by incorporating NaF during synthesis that effectively eliminates FeSO<sub>4</sub> residues and enables the formation of a dual-phase composite: Na<sub>2.56</sub>Fe<sub>1.72</sub>(SO<sub>4</sub>)<sub>3</sub> (primary phase) and Na<sub>3</sub>Fe<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>F (secondary phase). This dual-phase structure not only eliminates excess FeSO<sub>4</sub> but also enhances Na<sup>+</sup> diffusion by introducing abundant phase boundaries, leading to a superior electrochemical performance. The optimized Na<sub>2.375</sub>Fe<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>F<sub>0.375</sub> (NF-0.375) cathode achieves a high discharge capacity of 112 mAh g<sup>-1</sup> at 0.1 C, an exceptional rate capability of 82.9 mAh g<sup>-1</sup> at 30 C, and outstanding long-term stability, retaining 80% capacity after 10,000 cycles at 30 C. This dual-phase design provides a pathway for optimizing polyanion cathodes and accelerates the development of fast and durable SIBs for large-scale electric energy storage systems.