Superior fast-charging performance and prolonged lifespan of sodium vanadium phosphate via compositionally complex...

The commercial viability of polyanionic Na₃V₂(PO₄)₃ (NVP) cathodes in sodium-ion batteries is critically hampered by its intrinsically low electronic conductivity and structural degradation upon prolonged cycling. Herein, we break the conventional equal-ratio multi-element doping paradigm and propose an asymmetric multi-element doping strategy at the vanadium site, yielding a composition of Na₃V_1.5Cr_0.4(Ti,Al,Mg,Y,Zr)_0.1(PO₄)₃ (HE-NVP). This design establishes a clear synergistic division of labor: Cr³⁺, with an ionic radius closely matched to V³⁺, serves as the primary electronic modulator to activate the reversible high-voltage V⁴⁺/V⁵⁺ redox pair, while the five co-dopants (Ti, Al, Mg, Y, Zr) collectively function as structural stabilizers and dynamic regulators, which effectively reduces the band gap, thereby enabling superior electronic conductivity and high-rate performance. Accordingly, HE-NVP delivers a high specific capacity of 116.2 mAh g^-1 at 0.5C and demonstrates outstanding long-term stability, with 89.54% capacity retention after 3500 cycles at 20C. This work demonstrates that decoupling the functional roles of dopants offers a versatile and effective route for maximizing the electrochemical performance of NASICON-type cathodes for next-generation sodium-ion batteries.