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Sodium-ion batteries (SIBs) are promising for large-scale energy storage, but their development is hindered by the lack of high-rate, long-life cathode materials. Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 (NFPP) offers structural stability and cost advantages but suffers from low electronic conductivity and sluggish Na + diffusion. Herein, a tungsten-doped NFPP (NFPP-W x ) is achieved via a scalable sol–gel method in which W substitution at Fe sites suppresses grain growth, increases surface area, and improves electrode–electrolyte contact. Combined density functional theory and systematic experimental analyses reveal that W-doping narrows the band gap from 2.639 to 0.696 eV, enhances electronic conductivity, and boosts the pseudocapacitive contribution. NFPP-W 0 . 03 delivers 105.6 mAh g –1 at 0.1C and demonstrates exceptional cycling stability, retaining 93.7% after 970 cycles at 2C, 89.3% after 4000 cycles at 50C, and 73.8% after 6000 cycles. A full cell paired with hard carbon exhibits 97.8 mAh g –1 at 0.1C and long-term stability. This work demonstrates W-doping as an effective strategy to engineer NFPP for high-rate, durable SIB cathodes.
Wang et al. (Wed,) studied this question.