High‐Energy and Long‐Life Na 3 V 2 (PO 4 ) 2 F 3 Cathodes via Multielement V‐Site Modulation of Local M–O/F Bonding

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Abstract
Sodium‐ion batteries are promising for sustainable energy storage, but their energy density still lags behind lithium‐ion systems. Na 3 V 2 (PO 4 ) 2 F 3 (NVPF) is an attractive high‐voltage polyanionic cathode, but fluorine loss generates low‐voltage Na 3 V 2 (PO 4 ) 3 impurities that lower energy density and aggravate lattice deformation during cycling. Here, we report a multielement V‐site charge modulation strategy, realized in Na 3‐δ V 1.9 Zr 0.02 Ti 0.02 Cr 0.02 Fe 0.02 Al 0.02 (PO 4 ) 2 F 3 (ME‐NVPF). The deliberate combination of high‐valence Zr 4+ , Ti 4+ , and same‐valence Cr 3+ , Fe 3+ , Al 3+ cations creates a heterogeneous M–O/F bonding network with multi‐directional electrostatic interactions enhancing lattice‐F retention that completely eliminates NVP impurities, lowers the Na + migration barrier, and reduces unit‐cell volume variation to merely 2.87%. Consequently, ME‐NVPF delivers a record‐high energy density of 477 Wh kg −1 , sustains 11 000 cycles, operates across −40 to 80°C, and is further validated in 600 mAh‐level pouch cells. This work establishes multielement compositional regulation as an effective strategy for designing high‐energy, long‐life, and all‐temperature polyanionic cathodes.
Funding Information
  • China Three Gorges Corporation (WWKY 2021‐0027)
  • National Natural Science Foundation of China (52202121)

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